agricultural engineering v12

8/3/2019 Agricultural Engineering v12

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UDK 631 (05) YU ISSN 0354-8457Vol. 12 No. 1-4

AGRICULTURAL ENGINEERINGReports for Southeastern Europe

Agr. Engng Vol. 12 (2006), No. 1-4, p. 1-53, Novi Sad, May 2007


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JournalAGRICULTURAL ENGINEERING

PublisherYUGOSLAV SCIENTIFIC SOCIETY OF AGRICULTURAL ENGINEERING,

Jugoslovensko nauno drutvo za poljoprivrednu tehnikuTrg Dositeja Obradovia 8, SRB- 21121 Novi Sad, Serbia

Tel. +381 21 6350366, Fax +381 21 459989E-mail: [email protected], [email protected]

CopublishersVOJVODINIAN SOCIETY OF AGRICULTURAL ENGINEERING (VDPT), Novi Sad

DEPARTMENTN FOR AGRICULTURAL ENGINEERING, Agricultural faculty, Novi SadINSTITUTE FOR MECHANIZATION AND DESIGN ENGINEERING,Faculty of Engineering,

Novi SadJournal is founded by VDPT, Novi Sad

The Journal is financially supported by the Ministry of Science and Environment Protection of theRepublic of Serbia and the Society of Agricultural Engineering of Vojvodina (VDPT).

Editor in ChiefProf. dr Milan Martinov

EditorProf. dr Nikola uki

Technical EditorMr Aleksandar Sedlar

UDC NumbersRadmila Kevrean

CIP Kategorizacija u publikacijiBiblioteka Matice srpske, Novi Sad631AGRICULTURAL ENGINEERING: Reports for Southeastern Europe / editor in chief Milan Martinov Vol 1,no.1/2 (sept. 1995) Novi Sad. Yugoslav Scientific Society of Agricultural Engineering,1995-. Ilustr.- 23 cmTromeseno.ISSN 0354-8457COBISS.SR-ID 111736839

Editorial board

Prof. Dr. Mirko Babi, Department of Agricultural Engineering, Agricultural Faculty, Novi Sad,Yugoslavia

Prof. Ing. Jozef Bajla CSc, Slovak Agricultural University, Faculty of Agricultural Engineering, Nitra,SlovakiaProf. Dr. Rajko Bernik, Biotehnical faculty, Ljubljana, Slovenia.Prof dr Milan evi, Institute for Agricultural Engineering, Agricultural Faculty, Beograd-Zemun,

YugoslaviaProf. Dr. Zoltan Lang, SzIE University, Budapest, HungaryProf. Dr. Nikola uki, Department of Agricultural Engineering, Agricultural Faculty, Novi Sad,

YugoslaviaProf. dr Milan Martinov, Institute for Mechanization and Design Engineering, Faculty of

Engineering, Novi Sad, YugoslaviaProf. Dr. Jovan Crnobarac, Department for Field and Vegetable crops, Agricultural Faculty, Novi

Sad, Yugoslavia.Prof. Dr. Nicolay Mihalilov, University of Rousse, BulgariaProf. Dr. Victor Ros, Technical University, Cluj Napoca, RomaniaProf. Dr. Peter Schulze Lammers, Institut fr Landtechnik der Rheinischen Fridrich-Wilhelms

Universitt, Bonn, GermanyProf. dr Milo Tei, Institute for Mechanization, Faculty of Engineering, Novi Sad, YugoslaviaProf. Dr. Joachim Mller, Wageningen University and Research Centre, Farm Technology Group,

Wageningen, The NederlandsProf. Dr. Kamil Okyay Sindir, Ege University, Bornova, Izmir, Turkey

Any statements or views expressed in the papers published in this journal are those of the authors.The editors and the Society takes no responsibility for the accuracy of such statements or views.In the interests of factual reporting, occasional reference to manufacturers, trade names andproprietary products may be inevitable. No endorsement of named products is intended nor is anycriticism implied of similar products which are not mentioned.All submitted manuscripts and other correspondence should be sent to the editor at the aboveaddress.Journal is published four times a year. For subscription please contact the Editor.

Printed by Grafoprodukt, Novi Sad


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Agr. Engng12(2006) 1-4, 153

CONTENTS

Luis S. Pereira, Isabel AlvesEvapotranspirationand crop water requirementsReview0354-8457 (2006)12:1-4, p. 01-15

1

Ivanka Georgieva, V. K. GebovSystems and methods applied in controlling the technological process at the fodder productionOriginal paper0354-8457 (2006)12:1-4, p. 16-21

16

N. uki, A. Sedlar, R. BugarinFirst inspections of mist blowers in SerbiaOriginal paper0354-8457 (2006)12:1-4, p. 22-29

22

A. Sedlar, N. uki, R. BugarinEstablishing sprayer inspection in Serbia

Professional paper0354-8457 (2006)12:1-4, p. 33-38

30

S. Y. Ovcharov, V. K. GebovHigh precision extrapolation method in dynamic dosing systems based on weight measuring principlesOriginal paper0354-8457 (2006)12:1-4, p. 39-44

39

Dear readers,

following newest trends Agricultural Engineering Reposts for Southeastern Europe, will continue, since 2007, tobe published as electronic journal. Until now has not be decided which web site will be used for publishing of

electronic form of the journal. It will be whether the site of Faculty of Agriculture, Novi Sad, http://polj.ns.ac.yu/, orthe site of Vojvodina Society of Agricultural Engineering, www.poljoprivrednatehnika.org.yu.

The authors are kindly asked to sent their papers now using E-mail o Editor in Chief, Prof. Dr. Milan Martinov,[email protected], or Technical Editor, MSc Aleksandar Sedlar, [email protected].

For the paper submission authors should follow the instructions of CIGR ejournal:http://cigr-ejournal.tamu.edu/submission_instructions.html.

April, 2007

Editor in Chief

Prof. Dr. Milan Martinov


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Agr. Engng12(2006)14, 153

BIBLID: 03548457 (2006)12:14, p. 0115 UDC: 631.432.21:633/635EVAPOTRANSPIRATION AND CROP WATER REQUIREMENTS

L. S. Pereira, Isabel Alves1

SUMMARY

Crop water requirements(CWR) are defined as the depth of water[mm] needed tomeet the water consumed through evapotranspiration (ETc) by a diseasefree crop,

growing in large fields under nonrestricting soil conditions including soil water andfertility, and achieving full production potential under the given growingenvironment. This article summarizes the essential definitions and methodologiesfor estimating crop water and irrigation requirements.

Key words: crop water requirements, evapotranspiration

INTRODUCTIONCrop water requirements (CWR) are defined as the depth of water [mm] needed to

meet the water consumed through evapotranspiration (ETc) by a diseasefree crop, growing

in large fields under nonrestricting soil conditions including soil water and fertility, andachieving full production potential under the given growing environment. Defining crop

evapotranspiration (ETc) as the rate of evapotranspiration [mm d1] of a given crop as

influenced by its growth stages, environmental conditions and crop management to achievethe potential crop production, then the CWR is the sum ofETc for the entire crop growth

period. When management or environmental conditions deviate from the optimal, then thatrate of evapotranspiration has to be adjusted to the prevailing conditions and is called actualcrop evapotranspiration (ETa). Both CWRand ETc concepts apply to either irrigated or

rained crops.For irrigated crops, the concept ofCWRhas to be complemented by that of irrigation

water requirement (IWR), which is the net depth of water [mm] that is required to beapplied to a crop to fully satisfy its specific crop water requirement. The IWR is the fractionofCWRnot satisfied by rainfall, soil water storage and groundwater contribution. When it isnecessary to add a leaching fraction to assure appropriate leaching of salts in the soilprofile, this depth of water is also included in IWR. In practice, IWRhas to be converted intogross irrigation requirements to take into consideration the efficiency of the irrigationsystems utilized.

DISCUSSION

Crop Evapotranspiration

The rate of evapotranspiration ET[mm d1] can be computed with the PenmanMonteith(PM) equation:

( ) ( )( )as

aaspn

rr1

reecGR1ET

++

+

= (1)

1 Prof. Dr. Luis S. Pereira, Isabel Alves, Departamento de Engenharia Rural, InstitutoSuperior de Agronomia, Tapada da Ajuda, 1340-017 Lisboa, Portugal, [email protected]


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where is the latent heat of vaporization [kg m3], RnG is the net balance of energy

available at the surface [MJ m2 d1], (es ea) represents the vapor pressure deficit (VPD)of air at the reference (weather measurement) height [kPa], represents mean air density

[kg m3], cp represents specific heat of air at constant pressure [kJ kg1 C1], represents

the slope of the saturation vapor pressuretemperature relationship at mean air temperature

[kPa C1], is the psychometric constant [kPa C1], rs is the bulk surface resistance [s m1],

and ra is the aerodynamic resistance [s m1].

The PM Eq. (1) can be utilized for the direct calculation of crop evapotranspiration sincethe surface and aerodynamic resistances are cropspecific. However, data for these cropcharacteristics are scarce for most crops.

The transfer of heat and vapor from the evaporative surface into the air in the turbulent

layer above a canopy is determined by the aerodynamic resistance ra[s m1] between the

surface and the reference level above the canopy:

z2

oh

h

om

m

auk

zdz

lnzdz

lnr

= (2)

where zm is the height of wind velocity measurements [m], zh is the height of air

temperature and humidity measurements [m], d is the zero plane displacement height [m],zom is the roughness length relative to momentum transfer[m], zoh is the roughness length

relative to heat and vapor transfer[m], uzis the wind velocity at height zm[m s1] and kis

the von Karman constant (= 0.41).Equation (2) assumes that the evaporative surface may be represented as a big leaf

inside the canopy. However, exchanges in the top layer of the canopy, between heights d +zom and the crop height h [m] are important as sources of vapor fluxes. Adopting d + zom

as the level of the evaporative surface can lead to overestimation ofra and underestimation

ofrs. Thus, in alternative ra can be computed from the top of the canopy:

z2

h

om

m

auk

dhdzln

zdzln

r

= (3)

Both parameters dand zom depend upon the crop height, h, and canopy architecture.

Information exists relating d and zom to h. Most of these relationships are cropspecific.

More general functions also consider the leaf area index, LAI, or the plant area index(Pereira and Alves, 2005).

The height zohis estimated as a fraction ofzom, commonly zoh = 0.1 zom for short and

fully developed canopies. The factor 0.2 is often preferred for tall and partialcover crops.However, there is relatively small impact on ETcalculations from selecting a zoh/zom ratio

between 0.1 and 0.2.

The surface resistance, rs[s m1], for fullcover canopies is often expressed by

efflsLAI/rr= (4)

where rl is the bulk stomata resistance of a wellilluminated leaf [s m1], and LAIeff is the

effective leaf area index [ ], usually taken as 0.5 LAI. rlusually increases as a crop matures


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and begins to ripen. Typical values forrland rs are listed e.g. by Allen et al. (1996). The use

of these equations for prediction of crop water requirements is difficult due to differencesamong varieties and crop management practices. Information on stomata conductance orstomata resistance available in the literature is mainly oriented to physiological orecophysiological studies, rather than practical agricultural management. Information on bulkstomata resistances is still scarce.

Resistances rland rs are influenced by climate and water availability. rs increases when

soil water availability limits ET, the VPD increases and ra is higher. rs decreases when

energy available at the surface increases. In general, rs varies according to:

( )( )GR

VPDc11rr

n

pas

++

= (5)

where is the Bowen ratio (the ratio between the sensible and latent heat fluxes). In thisequation plays the role of a waterstress indicator (Alves and Pereira, 1999). Thisequation illustrates that weather variables interact and their influences are interdependent,thus adding to the difficulties in appropriately selecting rs.

These difficulties create challenges in applying the PM equation or other multilayerresistance equations to estimate ETfrom agricultural crop canopies. Current research workis focused on improving our ability to apply the PM equation or multilayerETmodels tospecific agricultural crops; this work often utilizes relatively complex computer models.Meanwhile, the PM equation is used to compute the reference evapotranspiration and todetermine ETcwith crop coefficients.

Crop coefficients

Crop evapotranspiration, ETc [mm], can be calculated by multiplying the reference

evapotranspiration, ETo [mm], by a dimensionless crop coefficient, Kc:

occ ETKET = (6)

The reference crop is a hypothetical crop with an assumed height of 0.12 m having asurface resistance of 70 s m1 and an albedo of 0.23, closely resembling an extense surfaceof green grass of uniform height, actively growing and adequately watered. The reference

evapotranspiration ETo [mm d1] can then be easily computed with the PM Eq.(1) since theaerodynamic and surface resistance terms can be parameterized, resulting in the FAOPenmanMonteith (FAOPM) equation:

)u34.01(

)ee(u273T

900)GR(408.0

ET2

as2n

o ++

+

+= (7)

where, in addition to variables defined for Eq. (1), T is mean daily air temperature [C] andu2is wind speed [m s

1], both at 2 m height. (For hourly calculations see Allen et al., 2006)The reference crop corresponding to a living, agricultural crop (i.e., a coldseason

clipped grass) incorporates the majority of the weather effects into ETo estimates.

Therefore, since ETo represents an index of climatic demand on evaporation, the Kcvaries

predominately with the specific crop characteristics and little with climate. This enables thetransfer of standard values forKcbetween locations and climates.

Kc

represents an integration of the effects of three primary characteristics that

distinguish the crop from the reference: crop height (affecting roughness and aerodynamicresistance); cropsoil surface resistance (related to leaf area, fraction of ground coveredby vegetation, leaf age and condition, degree of stomata control, and soil surface wetness);


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and albedo of the cropsoil surface (influenced by the fraction of ground covered byvegetation and soil surface wetness).

Two Kcapproaches are considered. The first uses a timeaveraged Kcto include multi

day effects of evaporation from the soil. The second concerns the basal crop coefficient anda separate calculation of evaporation from the soil.

The crop coefficient curve represents the changes in Kcover the length of the growing

season (Fig. 1). Its shape relates to changes in the vegetation and ground cover during plantdevelopment and maturation that affect the ratio ETc/ETo. Shortly after planting of annuals,

or the initiation of new leaves for perennials, the value for Kc is often small. The Kc

increases from that initial value, Kcini, at the beginning of rapid plant development and

reaches a maximum, Kcmid, at the time of maximum or near maximum plant development,

the midseason period. During the late season period, as leaves begin to senesce, the Kc

begins to decrease until it reaches a lower value, Kcend, at the end of the growing period.

Time of Season, days

Kc

Kc midKc end

Kc ini

0.2

0.4

0.6

0.8

1.0

1.2

0.0

Fig. 1: Generalized crop coefficient curve from planting or initiation to harvesting or

dormancy (from Allen et al., 1998)

The form for the equation used in the dual Kcapproach is:

ecbsc KKKK += (8)

where Ks is the stress reduction coefficient [0 1], Kcb is the basal crop coefficient [0

~1.4], and Ke is the soil water evaporation coefficient [0 ~1.4]. Kcb represents the ratio

ETc/ETo when the soil surface layer is dry but the average soil water content of the root

zone is adequate to sustain full plant transpiration, thus representing the baseline potentialKc in the absence of evaporation from the soil (Fig. 2). Ks reduces the value ofKcb when

the soil water content is not adequate.


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0 20 40 60 80 1000

0.2

0.4

0.6

0.8

1

1.2

1.4

Days after Planting or Greenup

Kc

Kcb

Ke

cbK Ke+

Fig. 2: Crop coefficient definitions showing the basal crop coefficient Kcb, which

approximates canopy transpiration, the soil evaporation coefficient, Ke,

Because Eq. (8) requires the calculation of a daily soil water balance for the surface soillayer, a simplification is required for routine application. The timeaveraged Kc is then

adopted:

ecbc KKK += (9)

where ecb KK + represents the sum of the basal Kcb and timeaveraged effects of

evaporation from the soil, Ke. Typical shapes for the Kcb, Ke and Kcb + Ke curves are

shown in Fig. 2. When summed, the values for Kcb

and for Ke

represent the total crop

coefficient, Kc. The timeaveraged Kc is used for planning, irrigation system design, and

typical irrigation management. The dual Kc is best where effects of daytoday variation in

soil surface wetness are important to estimate the resulting impacts on daily ETc, soil

moisture profile, and deep percolation.

The single crop coefficient approach

A simple procedure may be used to construct the Kccurve (Fig. 3):

Divide the growing period into four general growth stages that describe crop phonologyor development, and determine the lengths [days] of these stages. The four crop growthperiods are:

Initial: for annual crops, duration is from planting date to approximately 10% groundcover. For perennials, the planting date is replaced by the "greenup" date, when initiation ofnew leaves occurs.

Crop Development: from 10% ground cover to effective full cover,which often occurs at

the initiation of flowering or when LAIreaches 3.


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Crop

Dev.Initial

PeriodPeriodPeriodPeriod

Mid SeasonLate

Season

Time of Season, days

Kc

Planting /Greenup

0.2

0.4

0.6

0.8

1.0

1.2

0.0

Kc ini

Kc mid

Kc end

Fig. 3: Crop coefficient (Kc) curve and crop development stages definitions (from Allen et

al., 1998)

Mid Season: from effective cover to start of maturity, which is often indicated by thebeginning of the ageing, yellowing or senescence of leaves, leaf drop, or the browning offruit.

Late Season: from start of maturity to harvest or full senescence. For some perennialvegetation in frostfree climates, crops may grow year round so that the date of terminationmay be taken as the same as the date of "planting".

Identify the three Kcvalues that correspond to Kcini, Kcmid and Kcend.

Connect straight line segments through each of the four growth stage periods.The length of crop growth stages are cropspecific and change duration with crop

variety, planting date, cultivation practices and weather conditions, mainly air temperature.The length of crop growth stages may be predicted using cumulative degreebasedequations or plant growth models.

The lengths of the initial and development periods may be relatively short for deciduoustrees and shrubs that develop new leaves in the spring at relatively fast rates. The K

cini

should then reflect the ground condition prior to leaf initiation, including the amount of grassor weed cover, soil wetness, tree density, and mulch density. The length of the lateseasonperiod may be relatively short for vegetation killed by frost or for crops harvested beforesenescence. The value forKcendshould reflect thesoil surface condition and that of the

vegetation following plant death or harvest. Indicative lengths of growth stages are given inFAO Guides. However, local observations or information should be used to incorporateeffects of plant variety, climate and cultural practices.

Values forKcini, Kcmid and Kcend are listed in Appendix 1 (page 4547) for various

agricultural crops. Usually there is close similarity in Kcwithin the same crop group, since

the plant height, leaf area, ground coverage and water management are usually similar.The Kc values in Appendix 1 represent potential water use by healthy, diseasefree,

and densely planted stands of vegetation, with adequate levels of soil water. When standdensity, height, or leaf area are less than that attained under perfect or normal conditions,Kcshould be reduced by as much as 0.3 0.5 for poor stands, according to the amount of

effective leaf area relative to healthy vegetation with normal planting densities.The Kcini values in Appendix 1 are only approximate because they vary widely with soil

wetting conditions and because ETduring the initial stage for annual crops is predominately


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in the form of evaporation from the soil. Therefore, estimates for Kcini must consider the

frequency of irrigation and rainfall that wet the soil surface.Evaporation from bare soil, Es [mm d

1], can be characterized as occurring in twostages (Fig. 4). During stage 1, termed the "energylimited" stage and having a duration t1[days], moisture is transported to the soil surface at a rate sufficient to supply the potential

rate of evaporation, Eso [mm d1], which is governed by energy availability at the soil

surface. Eso can be estimated from

oso ET15.1E = (10)

where ETo is averaged for the initial period [mm d1].

EvaporationRa

te,mmd

-1

Depth of Soil Water Evaporated, D , mme

Stage 1Drying

Stage 2Drying

REW TEWD e

Fig. 4: Two stages model for soil evaporation (from Allen et al., 1998).TEW and REW standfor total and readily evaporable water, respectively

Stage 2 is termed the "soil waterlimited" stage, where hydraulic transport of subsurfacewater to the soil surface is smaller, thus making Es < Eso. A portion of the evaporation

occurs from below the soil surface, and energy is supplied by transport of heat into the soilprofile. Es decreases as soil moisture decreases and can be assumed to be linearly

proportional to the depth of water remaining in the evaporation layer.When the time interval [days] between two successive wettings is tw > t1, Kcini is

approached as:

( )( )

ow

sow

cETt

TEW

REWTEW

REWEtt

REWTEWTEW

K

+

=

1

exp1

ini

(11)

where REWis the readily evaporable water, corresponding to the depth of evaporationwhen stage 1 drying is complete [mm], TEWis the total evaporable water, i.e. the maximum


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evaporation depth when soil evaporation effectively ceases [mm]. From the concept of stage

1 drying resultst1

= REW/E

so.When tw< t1, the entire process resides within stage 1, then

osoinic ETEK = (12)

Where furrow or trickle irrigation is practiced, and only a portion of the soil surface iswetted, Kcini in Eq. (11) and (12) should be reduced in proportion to the average fraction of

wetted soil surface, fw (ranging from 0, when no rain or irrigation occur, to 1). Indicative

values for fware shown in Table 1. The infiltration depth from irrigation, Iw [mm], shouldalso be adjusted:

ww f/II = (13)

where Iis the total irrigation depth [mm].

Table 1: Indicative values of the average fraction of wetted soil surface, fw.

Irrigation method fw

Rain, sprinkling, basin and border irrigation 1.0Furrow irrigation 0.4 to 0.6Irrigation with alternate furrows 0.3 to 0.4Trickle irrigation 0.2 to 0.5

REWis higher for mediumtextured soils and is lower for coarse soils. Maximum valuesforREW(REWmax) may be predicted according to soil texture:

%50Cl%,80Safor)Cl(08.08REW

%50Clfor)Cl(06.011REW

%80Safor)Sa(15.020REW

max

max

max

>=

>=

(14)

where Sa and Cl are the fractions of sand and clay in the soil [%].

The TEWvalue is governed by the depth of soil contributing to evaporation, ze [100 to150 mm]. The soil waterholding properties within this evaporative layer, the presence of ahydraulically limiting layer beneath it, the unsaturated hydraulic conductivity, the conductionof sensible heat into the soil, and any root extraction of water from the evaporative layer allinfluence TEW. An approximation to TEWmaxis:

( )WPFCemax 5.0zTEW = (ETo 5 mm d1) (15)

( )5

ET5.0zTEW oWPFCemax = (ETo < 5 mm d

1) (16)

where FC and WP are the soil water content at field capacity and wilting point [mm mm1].Typical values forFCand WPare given in Table 2.

The average total water available for evaporation, Da [mm], during each drying cycle iscomputed from the average depth [mm] added to the evaporative layer at each wetting:

winimeana nWPD += (17)


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where Winiis the available soil water[mm] in the evaporation layer at the time of planting,

nwis the number of wetting events and Pmean is the average depth [mm] of water added to

the evaporating layer at each wetting event. Pmean can be obtained with:

Table 2: Typical soil water characteristics for different soil types (Allen et al., 1998).

Soil water characteristicsAmount of water that can

be depleted by evaporationfor ze=0.10 m

FC WP (FCWP) Stage 1REW

stages 1 and 2TEW*

Soil type

(USA SoilTexture

Classification) m3/m3 m3/m3 m3/m3 mm mm

SandLoamy sandSandy loamLoamSilt loamSiltSilt clay loamSalty clayClay

0.07 0.170.11 0.190.18 0.280.20 0.300.22 0.360.28 0.360.30 0.370.30 0.420.32 0.40

0.02 0.070.03 0.100.06 0.160.07 0.170.09 0.210.12 0.220.17 0.240.17 0.290.20 0.24

0.05 0.110.06 0.120.11 0.150.13 0.180.13 0.190.16 0.200.13 0.180.13 0.190.12 0.20

2 74 86 108 108 118 118 118 128 12

6 129 14

15 2016 2218 2522 2622 2722 2822 29

( ) wwnmean nIPP += (18)

but where each value ofPn and Iwmust be limited to Pn TEWmax and Iw TEWmax. The

values forTEWand REWin Eq. (11) are calculated from TEWmax and REWmax as:

( )amax D,TEWminTEW = (19)

and

= 1,

TEW

DminWREREW

max

amax (20)

When Eqs. 14 to 16 are used, appropriate checking of results is required. An updateand extension of calculation procedures is presented by Allen et al. (2005a)

Kcadjustment for climate

The Kcmid and Kcend values in Appendix 1 represent Kcb + Ke for irrigation

management and precipitation frequencies typical of a subhumid climate where RHmin =

45% and u2= 2 m s1.

Under humid and calm conditions, the Kcfor "fullcover" agricultural crops generally do

not exceed 1.0 by more than about 0.05, because "fullcover" agricultural crops and thereference crop behave similarly regarding absorption of shortwave radiation, the primary

energy source for evaporation under humid and calm conditions. Because the VPD is smallunder humid conditions, differences in ET caused by differences in ra between the

agricultural and the reference crop are also small, especially with lowtomoderate windspeeds. Thus the values ofKcare less dependent on differences between the aerodynamic


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components ofETcand ETo. On the contrary, under arid conditions, the effect of differences

in ra between the agricultural and the reference crop on ETc become more pronouncedbecause the VPD is often large. Hence, Kcwill be larger under arid conditions, mainly for tall

crops. Because the Kcmid and Kcend in Appendix 1 represent conditions where RHmin

45% and u2 2 m s1, when climatic conditions deviate from these values, the tabled

values need to be adjusted:

( ) ( ) ( )[ ]3.0

min2tabcc 3

h45RH004.02u04.0KK

+= (21)

where (Kc)tab represents the Kcmid orKcend taken from Appendix 1, u2 is the average

daily wind speed at 2 m height [m s1], RHmin is the average daily minimum relative

humidity [%], and h is the average plant height [m], all averages referring to the midseasonor the lateseason period. Indicative values for h are listed in Appendix 1, but it shouldbetter be obtained from field observations. When crops are allowed to senesce and dry in

the field (Kcend < 0.45), no adjustment is necessary.Kcadjustment for nonpristine conditions

The values ofKc in Appendix 1 reflect typical crop and water management practices.

When local water management and harvest timing deviate from those typical, thenadjustments should be made to Kcmid and Kcend.

When stand density, height or leaf area of the crop are less than that attained underappropriate crop and irrigation management conditions, the value forKcis reduced by 0.1 to

0.5, according to the amount of effective (green) leaf area relative to that of healthyvegetation having normal plant density:

cmtablecc AKK = (22)

where Acm is the adjustment factor [0 0.5] that can be approximated through a greencover ratio of the type

normalactualcm LAI/LAI1A = (23)

where the LAI refers to the midseason period. As referred further, other procedures,including remote sensing, may be used to estimate the Kc values for nonpristine

conditions.

The dual crop coefficient approach

The basal crop coefficient, Kcb (Eq. 8) represents primarily the transpiration component

of ET. Its use provides for separate adjustment for wet soil evaporation immediatelyfollowing rain or irrigation events. This results in more accurate estimates of ETc when

computed on a daily basis. Recommended values for Kcb are listed in Appendix 1,which

must be adjusted for climate using a similar equation to Eq. (21).The computation of the soil water evaporation coefficient Ke is based on the fact that

evaporation from the soil is governed by the amount of energy available at the soil surface,which depends, in turn, on the portion of total energy that has been consumed by planttranspiration. K

edecays after a wetting depending on the cumulative amount of water

evaporated from the surface soil layer. Thus Ke can be calculated from


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( )cbmaxcre KKKK = (24)

where Kr is the evaporation reduction coefficient [01] and Kcmax is the maximum valuefor Kc following rain or irrigation. However, Ke is limited by the fraction of wetted soil

exposed to sunlight, few[0.011]:

maxcewe KfK (25)

Kcmax represents an upper limit on ET from any cropped surface [1.05 to 1.35]. It

should change with climate similarly to Kc(Eq. 21), thus:

( ) ( )[ ] 05.0K,3

h45RH004.02u04.02.1maxK cb

3.0

min2maxc +

+= (26)

u2, RHmin and h may refer to the midseason period or, when more detailed

computations are applied, be averaged for shorter periods (e.g., five days). h for the initialperiod can be considered the same as for the grass reference crop (h = 0.12 m).

The method used to estimate evaporation from soil is similar to the one used tocompute Kcini, where the evaporation rate is at the maximum rate until the depth of water

evaporated, De [mm], equals REW(Fig. 4). When De > REW, the evaporation process is in

stage 2, and its rate decreases in proportion to the remaining water. Therefore, Kr(Eq. 24)

may be calculated as:

1Kr= for WREDe (27a)

REWTEW

DTEWK er

= for REWDe > (27b)

REWand TEWmay be estimated with Eq. 14 through 20. De, the current depth of water

depleted from the fewfraction of wetted soil exposed to sunlight, is computed from the daily

water balance of the upper 100 to 200 mm of the soil

( ) isiew

oe

w

iii1ieie Tf

ETK

f

IROPDD +

+= (28)

limited to [0 DeiTEW], where the subscript i refers to the day of estimation, Pi is the

precipitation [mm], RO iis runoff [mm] [0 ROi Pi], Ii is the net irrigation depth [mm] that

infiltrates the soil (Eq. 13), (Ke ETo / few)i is the evaporation from the few fraction of the

exposed soil surface [mm], and Tsi is the transpiration from the fw fraction of the

evaporating soil layer [mm]. To initiate the water balance, Dei= 0 immediately following a

heavy rain or irrigation, orDei= TEWif a long time has passed since the last wetting. When

Pi< 0.2 ETo, it may be ignored. For most applications RO i= 0 and for the majority of crops,

except for very shallowrooted crops, Tsican be neglected.

When the complete soil surface is fully wetted (e.g., by precipitation or sprinkler

irrigation), few= (1fc), where fcis the average fraction of ground covered by vegetation [0


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12

0.99]. For irrigation systems where only a fraction of the soil surface is wetted, few is

calculated as:( )wcew f,f1minf = (29)

When not observed, fccan be estimated daily fromh5.01

mincmaxc

minccbc KK

KKf

+

= (30)

Kcmin is the minimum Kc for dry, bare soil [0.15 0.20]. The exponent "1+0.5h"

represents the effect of plant height on shading the soil and in increasing the Kcb given a

specific value forfc. (Kcb Kcmin) 0.01 for numerical stability.

Kcb values are reduced when the soil water content in the root zone is too low to

sustain transpiration at potential levels. The reduction is made through the water stresscoefficient, Ks [0 1]:

WPpWPsK

= ( < p) (31)

where is actual average soil water content in the root zone [mm mm1] and p is the

threshold below which transpiration is decreased due to water stress [mm mm1]. Bydefinition, Ks = 1.0 for > p. The threshold p is:

( ) ( )WPFCp p1 = (32)where p is the depletion fraction for no stress [0 1]. Indicative values can be found inAppendix 1. The determination ofKs requires a daily balance of soil water content. Further

and updated information is provided by Allen et al. (2005b).

Kc for nonpristine and unknown conditions

For vegetation where the Kcis not known, but where estimates of the fraction of ground

surface covered by vegetation can be made, Kcbmid can be approximated as:

( )h1

1

effcmincfullcbmincmidcb fKKKK+

+= (33)

where fceffis the effective fraction of ground covered by vegetation [0.01 1], and Kcbfullis the maximum value forKcb for vegetation having complete ground cover:

( )[ ] ( ) ( )3.0

min2fullcb 3

h45RH004.02u04.02.1,h1.00.1minK

++= (34)

For small, isolated stand sizes, Kcbfull may need to be increased beyond the value

given by the equation above. Kcb fullmay be reduced for vegetation that has a high degree

of stomatal control.


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IRRIGATION WATER REQUIREMENTS

The soil water balance is calculated for the effective rooting depth as:

ir

iiiciwii1ii z1000

GWDPETIROP +++= (35)

where, in addition to the symbols used before, DPirepresents deep percolation [mm], GWi

is groundwater contribution [mm], and zr iis the rooting depth [m], all referred to day i. DPis

often estimated as DPi= 0 when iFCand DPi= 1000 (i FC) zr iotherwise. GWisestimated from soil hydraulic properties and the water table depth. zr i can be predicted

assuming a linear variation from planting to maximum rooting. Maximum root depths formost common crops are presented in Appendix 1.

The latest date for scheduling irrigation to avoid water stress is when i= p(Eq. 32).

However, irrigation is often scheduled when the "managementallowed depletion", MAD, is

attained. Generally, MAD p whenplant water stress is intentional. Then,

( )( ) WPWPFCMADi MAD1 +== (36)

Table 3: Indicative values of irrigation efficiencies.

System Efficiency (%)Irrigation methods

Surface irrigation, precision levelling furrow 65 85 border 70 85 basin 70 90

Surface, traditional furrow 40 70 border 45 70 basin 45 70 basin, rice fields 25 50

Sprinkler solid set 65 85 handmove lateral 65 80 sideroll wheel move 65 80 traveller sprinkler 55 70 lateral move systems, center pivot 65 85

Microirrigation trickle, 3 emitters per plant 85 95 trickle, < 3 emitters per plant 80 90 bubblers and sprayers 85 95 line source emitters 70 90

Distribution and transport systems pipe 95 100

lined canals 60 90 nonlined canals 55 85

The net irrigation depth to be applied will be


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( )iFCiriw z1000I = , (37)

which summed for the entire season leads to the irrigation water requirement (IWR):

LR1

SGWPETIWR ec

= (38)

where Pe is the effective precipitation (gross precipitation less all runoff and deep

percolation), GW is groundwater contribution, S is the change in soil water storage in theroot zone between planting and harvesting, and LR is the leaching requirement (thepercentage of irrigation water that must pass through the root zone to keep the salinity of thesoil below a specified value). The soil water balance is currently computed through cropwater simulation models, which allow the selection of best irrigation scheduling alternatives.

The gross irrigation water requirement is computed as

Eff

IWRGIWR= (39)

where Eff is the efficiency of the irrigation system. Indicative values of the efficiencies arepresented in Table 3.

CONCLUSION

This article summarizes the essential definitions and methodologies for estimating cropwater and irrigation requirements. The concept of reference evapotranspiration is assumedrelative to a crop canopy such as grass but with constant crop characteristics. Thehypotheses on which this approach is based are discussed relative to crop surface andaerodynamic resistances to heat and vapor fluxes. The crop evapotranspiration is definedusing crop coefficients applied to the reference evapotranspiration, which reflect the canopydifferences between the crop and the reference crop. Both time averaged and dual cropcoefficients are explained, the first when the coefficients relative to crop transpiration andevaporation from the soil are summed and averaged for the crop stage periods, the laterwhen a daily calculation of transpiration and evaporation coefficients is adopted. Finally, theessential information on the soil water balance to estimate crop irrigation requirements is

provided. Several figures and tables are included to support both the text and calculationprocedures.

REFERENCES

1. Allen, R.G., Pruitt, W.O., Businger, J.A., Fritschen, L.J., Jensen, M.E., Quinn, F.H.,1996. Evaporation and Transpiration. In: Wooton TP, Cecilio CB, Fowler LC, Hui SL,Heggen RJ (eds.) ASCE Handbook of Hydrology, pp. 125252, ASCE, New York.

2. Allen R.G., Pereira L.S., Raes D., Smith M., 1998. Crop Evapotranspiration. Guidelinesfor Computing Crop Water Requirements. FAO Irrig. Drain. Pap. 56, FAO, Rome, 300pp.

3. Allen, R.G., Pruitt, W.O., Raes, D., Smith, M., Pereira L.S., 2005a. EstimatingEvaporation from Bare Soil and the Crop Coefficient for the Initial Period UsingCommon Soils Information. J. Irrig. Drain. Engng. 131(1): 1423.

4. Allen, R.G., Pereira L.S., Smith, M., Raes, D., Wright, J.L., 2005b. FAO56 Dual CropCoefficient Method for Estimating Evaporation from Soil and Application Extensions. J.Irrig. Drain. Engng. 131(1): 213.

5. Allen R.G., Pruitt W.O., Wright J.L., Howell T.A., Ventura F., Snyder R., Itenfisu D.,Steduto P., Berengena J., Yrisarry J.B., Smith M., Pereira L.S., Raes D., Perrier A.,Alves I., Walter I., Elliott R., 2005. A recommendation on standardized surface


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resistance for hourly calculation of reference ETo by the FAO56 PenmanMonteithmethod.Agric. Water Manage. (in press).

6. Alves, I., 1995. Modeling crop evapotranspiration. Aerodynamic and surfaceresistances. Ph. D thesis, Instituto Superior de Agronomia, Lisboa [in Portuguese]

7. Alves I, Pereira LS, 2000. Modelling surface resistance from climatic variables? Agric.Water Manag. 42: 371385.

8. Pereira L.S., Allen R.G., 1999. Crop Water Requirements. In: HN van Lier, LS Pereira,FR Steiner (Eds.) CIGR Handbook of Agricultural Engineering, Vol. I: Land and WaterEngineering, ASAE, St. Joseph, MI: 213262.

9. Pereira L.S., Alves I., 2005. Crop water requirements. In: D. Hillel (ed.) Encyclopedia ofSoils in the Environment. Elsevier, London and New York, Vol. 1, pp. 322334.

10. Pereira LS, van den Broek B, Kabat P, Allen RG (Eds.) (1995) CropWater SimulationModels in Practice. Wageningen Press, Wageningen, 339 pp.

11. Pereira L.S., Smith M., Allen R.G., 1998. Mthode Pratique de Calcul des Besoins enEau. In: JR Tiercelin (Ed.) Trait dIrrigation, Lavoisier, Technique & Documentation,Paris: 206231.


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Agr. Engng12 (2006) 14, 153

BIBLID: 03548457 (2006)12: 14, p. 1621 UDC: 006:631.3: 621.313.333: 636.086.3

SYSTEMS AND METHODS APPLIED IN CONTROLING THETECHNOLOGICAL PROCESS AT THE FODDER PRODUCTION

Ivanka Georgieva, V. K. Gebov1

SUMMARY

In modern systems for fodder production new techniques for control of the processare increasingly initiated, which makes possible the realization of new technologicaltasks. At the development of the tense metrical weighing system a differentapproach had been chosen, which includes constructing a net MPI (Multi pointinterface) of the PLCSiemens and microprocessor modules (based on hcs12),which have in their structure tense metrical transducers of Analog device AD7730. There is a method for frequently maintenance of 3ph asynchronousmotors, which are able to control at the same time only one inverter, connected to

the PLC through USS protocol.Key words: automation, networks of the Siemens, tense sensors, astatically regulator

of the dosing

INTRODUCTION

In modern systems for fodder production, new techniques for control of the process areincreasingly initiated, which makes possible the new technological tasks.

Defining the main problems, connected to the technological process of the production,proposing methods to overcome them, as well as the optimization of processes for controlare really a complicated task for the people, who develop such kinds of systems. Theultimate aim that we chase in this article is to mould and found out a system, based on themodern achievements at control field, which gives the possibility to accomplish the finalparameters of the quality production: exactness at dosing, homogeneity of mixing and higherproductivity with lower energetic consumption.

1 Ivanka Georgieva, Vladimir Krumov Gebov, South -West University Neofit Rilski, Chair"Electronic and communication techniques and technologies Blagoevgrad, Bulgaria 2700Blagoevgrad, [email protected]


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Fig. 1: Technological process of the produce of he fodder factory, controlling by PC, withsoftware growth on base WinCC flexible (2004) Siemens.

Fig. 2: Organization control system. 1PC; 2 PLC Siemens, CPU224XP, 3 Profibus

DP module, 4 p HCS12& transducer AD7730, 5 weigh scale, 6 inverter Sinamics


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RESULTS AND DISCUSSIONS

Organization of the system for control

The system for control is shown on Fig. 2. At its construction is used PLC Siemens,S7200 and CPU 224XP.The master interface is accomplished by PC, based on WinCCflexible 2004, which affords great interactivity, ergodicity and flexibility at the maintenanceof the system. WinCC flexible 2004 also affords creating screens, graphics, menus,buttons etc. in a way that is easier for the programmer. The history of the process, alarmsand the consistence of the controlled variables are saved in database (ACCESS) or in fileswith enlargement *.csv (EXCEL). There is a possibility for creating own functions andscripts, except the available systems, which gives extra chance for enriching theapplications, as well as for sharing the mathematical and systematical resources betweenPLC and PC.

There are two special characteristics, which distinguish the construction of the systemfrom the other existing:

The main factor at dosing of components and micro components, which defines thequality of the dosing process, is the exactness of measurement the weight by the electronic

machines. The conventional approach, advanced by Siemens, is to develop a tense metricalcontrol with conventional module for PLC Siemens. This approach requires lengtheningthe cables of the tense sensors, their laying through the cable devices near the high voltcables, which supposes induction of the electromagnetic disturbances, connected to thefrequency of the net, as well as those who are accidental. The high sensibility of the tensemetrical bridges supposes measurement of very low values of the output voltages, as wellas usage of other means for increasing the measurement quality, such as: stabilization ofthe mass of the analogical supplement of the transformer, connection to the mass ofscreening the tense system` cables, special topology of the scheme of the analogicaltransformer, as well as other different methods of software and hardware filtration. Theincreasing of the value of filtration leads to signal warping of the tense sensors, but mostly toslowing down the signal, which is the main reason for additional mistakes of the dosingsystem.

To overcome all these peculiarities at the development of the tense metrical weighingsystem a different approach had been chosen, which includes constructing a net MPI (Multipoint interface) of the microprocessor modules and PLC(digital interface for the controllingchannel),which have in their structure tense metrical transformers of Analog device AD7730. The main advantage of the applied approach consists in following: stretching thedistance between the tense sensors of the electronic weighing scale does not effect over themetrological characteristics of the measuring process. In case that the distance between thecontrol panel, where usually is situated the PLC, and the electronic scales could sometimesreach a few kilometers, and this fact does not have any influence over the quality of thetense measurement and the process of dosing.

There is a method for frequently maintenance of 3ph asynchronous motors (Fig. 3),which are able to control at the same time only one inverter, connected to the PLC throughUSS protocol [3]. In this case is applied again the digital interface of the controlling channelPLC inverter Sinamics, at which by two conducted line could be maintained till 32inverters, as well as unlimited access to all parameters of the inverter, which increases theintelligence of the interactivity, increases also the abilities for maintenance and control of thewhole system.


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Fig. 3: Algorithm, controlling system flying inverter: one inverter 8 motors.

At Fig. 4 is shown maintenance of the system with one inverter to eight motors. The

consequence of activating and deactivating of the devices on the scheme is special for thiscase: circuit closer inverter circuit closerinverter. Firstly, this guarantees protection ofthe inverter, and secondly it is a result of the requirements set from the 5value speeddiagram of the dosing process [1].

Fig. 4: Electronic system for dynamic sneak dosing

1 Inverter; M1M8 eight 3ph asynchronous motors; S1S8 eight dosing sneak; 2 Weigh scale with tense sensors;

Dosing system

Main problems, connected to the process micro components dosing:Organization of the tense metrical system, which includes choice of tense metrical

sensors, transformers and interfaces.Organization of the dosing process of main and micro components, which aim is to

achieve technological criteria for exactness.The quantity of the bulky product, which moves through the auger for unit per hour,

should be defined by the following formula:

= SLdt

dm, (1)


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where is the compactness of the product; S section of the auger; L pitch of the auger;

frequency of rolling the auger.The law for changing the force F (t), which influences over the electronic scale, containspseudo stationary component, equal to the product of the mass of the substance in thepacket and of the acceleration of gravity (m (t)*g) and absolutely dynamic component,conditioned by the falling of the portion mass dm/dt over the scale from height h, which

finishes /.1/ with speed Vfc.= gh2 for time =(2h/g). Because of the dependence of the

measured force of the tense metrical system combined with counting the influence of the

falling post will be reached the following: gh2dt

)t(dmg)t(m)t(F += (2)

As we replace the dependence (1) in (2), we get the following:

gh2SLg)t(m)t(F += (3)The probably errors, appearing under the influence of different factors, could be

separated in two columns: determinate and conventional. At [2] is offered a method forovercoming the negative effect of the determinate factors by using the transformation of

Furrier and the exploitation of the curve of weight changing.This method presumes an extended research, complicated computing procedures andbecause of this fact, it could be difficult applied to wide range of tasks. We could supposethat the main errors are as a result of the deviations at the dosage that are based onaccidental factors. We tried to create a method that could be applied to wider field ofapplications.

Influence of the factor time

From the moment of the effect of the force applied to the tense sensors of the electronicscale till the moment of stopping the dosing auger a defined time goes up and could becalculated by the following formula:

=t +tint+ tcrawl +tinv+tinv_stop, (4)where are:

t time delay because of Sigma Delta () modulation of AD7730, defined by thecomputing digital filter;

tint time for maintenance of the net interruption at the microprocess modules with PLC;

tcrawl time delay of the crawling integration , organized in microprocess system hcs12;tinv time for maintenance of the USS protocol between the inverters Sinamics and

PLC;tinv_stop time for stopping the inverterIf an error appears, it will be calculated in the following way:

( )2

SLtSLttt Stop_invcrawlint)t(F

+++= (5)

I could be make the following conclusions: Stopping the process of dosing could be accomplished by anticipate(F) of the

weight, defined by the dependency (5); F depend on the comp activity of the product, which is very important for different

kinds of products with different comp activity ; F depends on the frequency of rolling the auger( the frequency applied in the

inverter) Conclusion: The synthesis of a nonstationary regulator for maintenance the stopping of the

dosing process should be separated in different augers, respectively the products.


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Constructing and supporting of recipes and database

Siemens supports the structure, the organization and the conservation of the recipes,thanks to the new product WinCC flexible [3]. There is a high flexibility of data transition ofthe reports for the different recipes: PLC, Storage medium, External data medium.

Data archiving in WinCC flexible is shown at Fig. 5.Data logging is used to capture, process and log process data from industrial

equipment. The collected process data can then analyzed to extract important business andtechnical information regarding the operational state of the equipment.

Fig. 5: Method of the archiving process data value on HMI device

ACSESS and Crosstab Queries are used for searching and rearranging of thedatabase, accomplished by WinCC flexible. This method enables free searching andrearranging of the tables by the following criteria: date and time of beginning, recipe, groupindex, and kind of the product. The accomplishment of global and local sums is part of thefunctions that ACSESS owns. All macros and modules increase the interactivity and make iteasier for the final consumer. The applying of this method enables development of thesystem and its connecting to the whole marketingmanager program for batch maintenanceof the production, according to the requirements of ISO 9001.

Results:

This system for dosing affords an opportunity for remote tense metricalmeasurement, as well as for higher sensibility of the measurement;

There is also a resource for frequently maintenance of a group of motors, that takepart in the dosing process; This system has already been created and incorporated in the fodder factory that

belongs to the pigbreeding farm in Brushlen, Ruse.

CONCLUSIONS

The applying of methods for digital conveyance of information from the terminal devicesand sensors to HMI device, nets that already exist from type USS, FreePort, Profibus,affords an opportunity for increasing the quality of the dosing process, when it concernsfodder production. The synthesis of a nonstationary regulator for maintenance of thedosing process should not depend on the separate augers, respectively products, andshould be connected to the times of transmission and transformation of the information,created in the controlmeasurement system.

REFERENCES

1. Ovcharov, S., Gebov, V., High precision extrapolation method in dynamic dosing

systems based on weight measuring principles, Conference ELECTRONICS20042. Ivanka Georgieva, Ilia Smilianov, Vladimir Gebov, Communication network ASi ,

Faculty of Mathematics& Natural Science FMNS 20053. www.siemens.com


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Agr. Engng12(2006) 14, 153

BIBLID: 03548457 (2006)12: 14, p. 2229 UDC: 620.95:631.57 (497.113)

FIRST INSPECTIONS OF MISTBLOWERS IN SERBIA

N. uki, A. Sedlar, R. Bugarin1

Summary

During 2006, first inspections of mistblower machines were conducted in Serbia.The inspection is not yet mandatory for mistblowers in Serbia, but it will be by thebeginning of 2007. During 2005 and 2006, Faculty of Agriculture in Novi Sad haspurchased modern equipment from AAMS (Belgium) for inspection of mistblowers,while also developing some original solutions.The equipment was used for inspections in compliance with EN 13790. Theinspections were conducted on machine owners demands as a result ofintroduction of HACCP quality control system in processing industry. The inspectionresults showed that the machines, despite being relatively new, (6 years old) failed

to meet set criteria.Most common cause of failure was clogged nozzle, caused by inadequatemaintenance. In some cases, pump capacity did not match the nominal value,deviating more than 20 % from the nominal capacity. Suggested in this paper arerecommendations for removal of specified inadequacies.Due to future mandatory inspection in Serbia, it would be interesting to shareexperiences with colleagues from the countries which have been practicingmandatory inspection for a longer period. Thus detected inadequacies could beremoved in an optimal way, reducing space for manipulations by machine owners,who try to avoid the corrective procedure.Of special interest is future initiation of inspection of new mistblowers. Inspectorsshall be facing dilemma whether new machines should meet standards morestringent than the machines already in use. Another question is how manufacturers,who opt for inspection of newly produced machines, can receive Certificate ofQuality, which is valid in all EU countries.

Key words: mistblowers, inspections, Certificate of QualityINTRODUCTION

Regular inspection of working condition of devices for application of pesticides is anecessary measure in modern agricultural production, which uses pesticides on a largescale (Sedlar, 2006). In order to provide for production of ecosafe food, environmentprotection, and decrease of production costs, it is necessary to ensure controlled applicationof pesticides (uki, 2005). Such application is possible only with machines in perfectworking condition (Langenakens 1999).

In June 2006, at the Faculty of Agriculture in Novi Sad, within the Department ofAgricultural Engineering, Central laboratory was established for inspection of machines forpesticide application. Basic purpose of this Laboratory is to allow inspection of workingcondition of both new and used sprayers, mistblowers and other machines for application ofpesticides. In addition, the idea for this Laboratory is to coordinate and assist establishmentand operation of local regional laboratories for inspection, helping them hire and trainpersonnel, acquire and complete machine inspection equipment and homologize

documentation. The Central laboratory has professional personnel and modern equipment ,

1Prof. Dr. Nikola uki, MSc Aleksandar Sedlar, Dr. Rajko Bugarin, Faculty of Agriculture,

University of Novi Sad , Serbia, [email protected].


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which is necessary for inspection of sprayers and mistblowers in compliance with Europeannorm EN 13790. Laboratory experts have initiated working condition inspection for machinesfor pesticide application which is already mandatory in over 20 European countries (Liegos iLeskoek, 2004). Eight years ago, according to the Law on plants protection, FederalMinistry of Agriculture of former FRY passed a Policy on services rendered in the area ofplants protection, with an important novelty for users of plant protection machines, namely,the mandatory machine inspection every two years followed by inspection of workingcondition. Unfortunately, the stated parts of the Law and Policy so far have not been dulyrespected (Bugarin, 2000). During 2007, new Law on usage of pesticides should enter intoforce which is compliant with the European directive 91/414/ EEC and which introducesmandatory machine inspection.

One of the first tasks for the newly established Central laboratory was the testing of 4Munckhof type 105 tractorhauled mistblowers which are used for orchard protection. Themistblowers are used for protection of sour cherries, which are exported to France for furtherprocessing, i.e. for production of cherry liquor pralines. Cherries are processed according toHACCP (Hazard Analysis Control Critical Point) system. Since January 2006, in ourprocessing and food industry HACCP is mandatory system of food safety and quality

control. European market is closed for products, which are not manufactured according toHACCP system. One of prerequisites for later HACCPcompliant processing of agriculturalproducts is inspection of machines for pesticides application (Sedlar, 2006). In modernEuropean countries, factories, which buy agricultural products, demand of manufacturers tosubmit certificate of inspection for the machine, which was used for application of pesticides.All these facts motivated introduction of working condition inspection for mistblowers.

MATERIAL AND METHODS

The inspected mistblowers were hauled, manufactured in 2000 and with tank capacity of1000 lit. Inspected were the working state and number of revolutions of crank shaft, tank(visual inspection), tubing, filters and valves, pump throughput, nozzle, left and right sidenozzle distribution pattern and, finally, manometer. All of these tests were conducted incompliance with EN 13790 standards.

RESULTS AND DISCUSSION

Crankshaft inspection

Inspected were the working condition and number of revolutions of the connecting crank(Fig. 1).

Fig. 1: Connecting shaft


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Crankshafts were visually inspected in all four aggregates, and it was established thatthey have the required protective coating and that it is setup correctly. Number ofrevolutions was checked for the connecting shaft and it was established that it provides 540o/min to the crankshaft.

Visual inspection of storage tank, tubing and filters

Visual inspection of storage tanks in all four mistblowers showed that the main tank andthe tank for technical water are in good condition. The deficiency of storage tanks is thattheir liquid level indicator does not have a floater. Instead, it is glued to the tank. Inspectionof level indicator proved its correctness and its visibility from tractor cabin and from the spotwhere the tank is filled.

Inspection of all filters on the misting machines showed that their mesh structure isadequate and that they are in good condition.

During visual tubing inspection, 5 seconds after stopping and pressure shutdown, noleakage was detected in any of inspected mistblowers, thus the tubing is in good condition.

Pump throughput inspection

Pump throughput was inspected using pump throughput gauge shown in Fig.2. It wasmeasured at working pressure of 11 bar.

Fig. 2: Pump throughput gauge

Throughput measured in the first mistblower was 52,72 l/min, which is 21,40 % belownominal throughput which is 64 l/min. Throughput measured in the second mistblower wassimilar to the first one, i.e. 52,88 l/min, which is 21,03 % less than nominal throughput.

Throughput measured in the third mistblower was 43,10 l/min, which is 48,49 % lessthan nominal throughput, while throughput of the fourth misting machine was 41,50 l/min,which is 54,21 % less than nominal throughput.

According to EN 13790 the allowed deviation is 10 %, which means that the inspectedpump requires maintenance (change of membranes, valves, thorough cleaning...).

Inspection of nozzles

Inspection of nozzle throughput

Nozzle throughput was measured at working pressures of 11, 13 and 14 bar for the

duration of 1 minute. The mistblowers were fitted with nozzles made of synthetics andceramics, type Whirl AMTP223 and AMTP230 Albuz (green and blue inserts) . Twospecial devices shown in Fig.3 measured capacity of the mistblowers.


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Fig. 3: Measuring nozzle throughput

A stopwatch was used for measuring nozzle throughput. Mistblowers is fitted with sevennozzles on the left and right side. Measured values are shown in Table 1.

Table 1: Nozzles throughput

Mistblower No. ALeftside nozzles Rightside nozzlesNozzle

No. Throughput deviation(%)

Throughput (l/min) Throughput (l/min) Throughput deviation(%)

1 Decrease 4,41 2,533 1,666 Decrease 37,132 Decrease 6,94 2,466 2,733 Increase 3,133 Increase 0,60 2,666 2,600 Decrease 1,884 Increase 0,60 2,666 2,600 Decrease 1,885 Decrease 16,55 4,266 3,066 Decrease 16,236 Decrease 7,10 3,400 3,666 Increase 0,167 Increase 20,21 4,400 3,200 Decrease 12,56

Mistblower No. B

Leftside nozzles Leftside nozzlesNozzleNo. Throughput deviation(%)

Throughput (l/min) Throughput (l/min) Throughput deviation(%)

1 Decrease 19,24 2,14 2,81 Increase 6,042 Increase 3,39 2,74 1,80 Decrease 32,073 Increase 11,69 2,96 2,81 Increase 6,044 Increase 3,39 2,74 2,77 Increase 4,535 Decrease 5,74 3,45 3,97 Increase 8,476 Increase 4,37 3,82 4,61 Increase 25,967 Increase 4,37 3,82 4,80 Increase31,15

Mistblower No. CLeftside nozzles Leftside nozzlesNozzle


Throughputdeviation (%)


Throughput deviation(%)

1 Increase 2,43 2,95 2,77 Decrease 3,822 Increase 9,37 3,15 3,12 Increase 8,333 Increase 6,59 3,07 2,4 Decrease 16,664 Increase 4,16 3 2,62 Decrease 9,03

5 Increase 4,16 3 2,74 Decrease 4,866 Increase 2,77 2,96 2,55 Decrease 11,467 Increase 5,55 3,04 3 Increase 4,16


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Mistblower No. DLeftside nozzles Leftside nozzlesNozzle




Throughput deviation(%)

1 Decrease 15 2,55 2,88 Decrease 42 Decrease 22,66 2,32 2,51 Decrease 16,333 Increase 15 3,45 2,92 Decrease 2,664 Decrease 15 2,55 2,88 Decrease 45 Decrease 27,66 2,17 2,88 Decrease 467

Increase 11,33Decrease 22,66

3,342,32

2,963,19

Decrease 1,33Increase 6,33

Mistiblowers A and B were inspected in Irig. As recommended by Norm 13790,inspection was done at pressures that are most often used by machine owner, which in thiscase was 11 bar.

Four front nozzles on the left and right side, as seen from the ground, are green codedand their throughput at 11 bar pressure is 2,65 l/min. Aft three nozzles are blue coded andtheir nominal throughput is 3,66 l/min

Mistblowers C and D were inspected at a farming estate in Nova Crvenka. Since theyusually operate at 13 and 14 bar, they were also inspected at these pressures.All nozzles on mistblower C are green coded and their working pressure was 13 bar.

Nominal throughput at this pressure is 2,88 l/min.All nozzles on mistblower D are also green coded and their working pressure was 14

bar. Nominal throughput at this pressure is 3,00 l/min.The above listed values are taken from the throughput table for whirl nozzles Albuz.

Nozzles were assigned numbers from the ground up.Analysis of Tab.1 shows that each of the misting machines A and B had 2 nozzles

whose throughput increased above the allowed 15 %. New ones should immediately replacethese nozzles. In misting machine D, one nozzle was detected with throughput increased by15 %. As this is on the edge of tolerance, the nozzle should be replaced by a new one.

However, much larger problem is a number of nozzles with throughput diminished incomparison with the table value. Diminished capacity is due to inadequate nozzlemaintenance, which resulted in clogging. All these nozzles should be taken off and washedthoroughly in lukewarm water. The washing should be done using brush for nozzle cleaning,

rather than using sharp objects, which are likely to cause damage to the nozzles. Beside thenozzles, filters which are placed in the nozzle holder, should also be washed in lukewarmwater.

Measurement of left and rightside nozzle distribution pattern

For the measurement of right and leftside nozzle distribution, the data for nozzlethroughputs were processed in MsExcel producing distribution histogram shown in Fig. 4.

Nozzle throughput on the left side is prefixed by minus sign () for efficient presentation.According to EN 13790, mistblowers distribution is acceptable if the difference inthroughputs of left and right side nozzles does not exceed 10 %. Statistical processing ofdata revealed that an average nozzle throughput for mistblowers A, equals 3,20 l/min onthe left side, and 2,79 l/min on the right side. Comparing these two values shows that thedifference in average nozzle throughputs for the left and right side is 15 %, which exceedsthe allowed 10 %. Similar was found in mistblower C, where leftside nozzle throughputaverage was 3,00 l/min, and for the rightside nozzle 2,7 l/min. Comparing these twovalues shows that the difference in average nozzle throughput for the two sides is 11 %,

which also exceeds the allowed 10 %.


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-5 -4,5 -4 -3,5 -3 -2,5 -2 -1,5 -1 -0,5 0 0,5 1 1,5 2 2,5 3 3,5 4 4,5 5

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kapacitet rasprskivaa sa leve i desne strane (l/min)

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d) mistblower D

Fig. 4: Mistblowers distribution histogram

In mistblowers B and D the leftside nozzle throughput is 3,10 l/min, i.e. 2,67 l/min,while for the rightside nozzles the corresponding values are 3,37 and 2,88 l/min. Whencompared, these two values show an average difference in nozzle throughput of 8 %, formistblower B, and 7 % by mistblowersC, which is below the allowed 10 %.

Manotest

Manotest means inspection of working condition and correctness of manometer. Beforethe inspection, diameter radius was measured and it was established at 100 mm, which ismore than the mandatory 63 mm as required by EN 13790.

Manometer scale is graduated from 0 to 20 bar in 0,2 bar increments, while from 20 to

60 bar the increments are 10 bar, which is compliant with EN 13790.Control manometer, calibrated according to EN 8371, was used for measuring

correctness of manometer (Fig.5).

Fig 5: Inspection of manometer correctness


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Measurement for mistblowers A, B and D was done at 5 and 10 bar. While the controlmanometer indicated these pressures, the inspected manometers of misting machines Aand D indicated pressures of 5 bar and 10 bar. The result shows that these manometers arecorrect. Manometer of mistblower B indicated pressures of 5,5 bar and 10,5 bar. Theinspected manometer showed error of 0,5 bar and that deviation was constant with pressurechange. The deviation is caused by the pointer failing to reset to 0 bar position.

In mistblower C, measurement was performed at pressures of 5, 10 and 15 bar. Whilethe control manometer indicated these pressures, the inspected manometer indicatedpressures of 5,2 bar, 10,3 bar and 15,4 bar. The inspected manometer showed a 4 % errorat 5 bar and the error decreases with pressure increase, so that at 15 bar pressure, theerror equals 2,6 %. Detected manometer deviation is within allowed deviation according toEN 13790.

CONCLUSIONS

Inspected mistblowers are in reasonably good condition. However, certain correctionsare required in order to receive Certificate of Quality in compliance with EN 13790.

First, it is necessary to determine the reason for diminished pump throughput in all

mistblowers. For mistblowers A and B the decrease equals 21.4 % and 21.0 %, while formachines C and D the decrease is doubled and equals 48.5 %, i.e. 54.2 %. For that reasonit is necessary to inspect pump pistons and valves. All sealers on the pump should bechecked and replaced if worn out. Upon inspection and performed corrections, pumpthroughput shall be inspected again.

All nozzles with throughput increased over the limit, need replacement. Such nozzlesare few only 5. Alarming is the fact about numerous nozzles with diminished throughput.This is due to inadequate maintenance of mistblowers. In order to solve this problem, liquidsupply tubing needs to be inspected, working of filter in nozzle holder needs checking andnozzles should be washed thoroughly in lukewarm water. Once the corrections are done,nozzle throughput is to be inspected again.

For future inspections, it is important to stress out that in order to obtain precise andvalid results of nozzle distribution inspection, all working parts in the system must bethoroughly clean and prepared.

Due to future mandatory inspection in Serbia, it would be interesting to shareexperiences with colleagues from the countries, which have been practicing mandatory

inspection for a longer period. Thus detected inadequacies could be removed in an optimalway, reducing space for manipulations by machine owners, who try to avoid the correctiveprocedure.

Of special interest is inspection of new misting machines. Inspectors shall be facingdilemma whether new machines should meet standards more stringent than the machinesalready in use. Another question is how can manufacturers who opt for inspection of newlyproduced machines, receive Certificate of Quality, which is valid in all European countries.

REFERENCES

1. Bugarin, R., uki, N., Ponjian, O., Sedlar, A.: Atestiranje maina u sklopu primenezakona i pravilnika o zatiti bilja. Savremena poljoprivredna tehnika br. 34, strana 5361, 2000

2. uki, N, Sedlar, A, Bugarin, R: Znaaj redovne kontrole prskalica, Revija Agronomskasaznanja, godite XV, br. 4, str. 1820, 2005.

3. Langenakens, J, Pieters M. 1999. Organization and Results of The CompulsoryInspection of Spryers in Belgium, 7th International Congress on AgriculturalMechanization and Energy 26 27 May, Adana Turkey, p. 5053.

4. Leskoek, G, et all 2004. An overview of the situation in the field of devices used for theapplication of plant protection products un Slovenia; First European Workshop on:


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Standardized Procedure for the Inspection of Sprayers in Europe, 27 29 April,Braunschweig Germany.

5. Liegeois, E. 2004. Thematic strategy on the Sustainable Use of pesticides: a plan ofaction to improve good plant protection practices throughout Europe; First EuropeanWorkshop on: Standardized Procedure for the Inspection of Sprayers in Europe,Braunschweig Germany.

6. Sedlar, A, uki, N, Bugarin, R.: Redovna kontrola prskalica kao uslov kontrolisaneaplikacije, Biljni lekara, XXXIV, Br. 2, str. 147152, 2006.

7. Sedlar A. 2006. Analiza metoda za testiranje prskalica, Magistarski rad, Univerzitet uNovom Sadu, Poljoprivredni fakultet, Novi Sad.


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Agr. Engng12(2006) 14, 153

BIBLID: 03548457 (2006)12: 14, p. 3038 UDC: 631.348:006.015.5(497.11)

ESTABLISHING SPRAYER INSPECTION IN SERBIA

A. Sedlar, N. uki, R. Bugarin1

SUMMARY

In Serbia, since 1999, there is an article within the ,,Policy on services rendered inplant protection which regulates mandatory inspection of sprayers and mistblowersin use. Due to transitional problems, which have been troubling Serbia during thelast seven years, the inspection has not yet seen proper implementation in practice.By the beginning of the 2007 year, a new plant protection law is to come into power,to regulate the field of pesticide application. This law is compliant with the EUdirective 91/414/EEC, and shall also include the article on mandatory inspection ofsprayers and mistblowers.In order for the inspection to be applied in practice after the law has been enacted,

experts of the Faculty of Agriculture have been campaigning for the last three yearsto educate agricultural producers and establish technical and organizationalprerequisites for the beginning of the inspection.In lieu with the above mentioned, a Procedure for sprayer inspection has beenproposed, which is compliant with EN 13790. Also proposed is the regionalmanagement which should conduct the inspection. In the course of making thisproposal, all positive experiences from the countries, which already haveestablished such inspection, were taken into account.What is still missing for efficient work on analysis of the number of sprayers andtheir state of readiness in Serbia, is the work on a joint project with the colleaguesfrom the European countries which already have established regular inspectionpractice. Such joint effort not only would advance the completely agriculturalproduction in Serbia, but would also help lower users fear of inspection and thusfacilitate the introduction of mandatory inspection into practice

Key words:sprayer, mandatory inspection, procedure for sprayer inspection

INTRODUCTIONAmongst various methods of plant protection, surely the most widespread one is the

chemical protection. Chemical protection is performed using equipment for pesticideapplication, whereby the equipment must meet several conditions:

it should apply sufficient quantity of protective agent on the plant, which shouldremain in place for the required period

protective agent should penetrate to reach all plant parts protective agent should be applied so as to cover the largest possible area protective agent should be spread evenlyThese conditions imply that the equipment for pesticide application is extremely

important, since it accounts for more than 50% of inadequate applications of protectiveagent, lowering agent efficiency and causing pollution.

All this leads to conclusion that the only way towards controlled application of pesticidesis regular inspection of sprayers, which of all machines and devices are the mostfrequently used for pesticide application.

1MSc Aleksandar Sedlar, Prof. Dr. Nikola uki, Ass. Prof. Dr. Rajko Bugarin, Faculty of

Agriculture, University of Novi Sad, Serbia, [email protected].


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Quality performance means capability of maintaining spraying standards while evenlydistributing pesticide over the treated area. Knowing the small ratios in which modernpesticides mix with water (several ml per liter), the reliability and quality performance ofsprayers becomes even more important.

In order to achieve maximum precision of application and thus allow full protection, thesprayers not only must have modern construction and impeccable performance, but alsomust have adequate exploitation potential.

Exploitation potential of tractor sprayers is defined as their ability to continuously andreliably perform through all operational stages during pesticide application. It comprises bothquantitative and qualitative parameters.

The quantitative parameters are: pump throughput, nozzle throughput, throughput ofdevices for hydraulic mixing, adjustment of the three throughputs, the range of operatingspeeds, tank volume, etc.

The qualitative parameters are: precision of feed and throughput, consistent distributionof protective agent, consistency of spray droplets

Applying optimal pesticide quantities while using proven machinery, strengthens theconsumers confidence in fruits, vegetables and crop farming products, while guaranteeing

that quantities of pesticides remain below the allowed maximum (MAQ) as required for thespecific pesticide or treated plant.This procedure is favorable to soil and water, which gradually become less polluted.

This proves that mandatory inspection of sprayers, as emphasized by Langenakens (1995),contributes to healthier environment.

DISCUSSIONS

In order to successfully implement the regular inspection of sprayers in domesticconditions, it is necessary that all factors relevant to this task, perform their share of duties:

Machine users should inspect, prepare and ready machines for protection, enhancethe maintenance and get informed about the testing procedure;

Certified laboratories, together with the manufacturers they contract for technicaland business cooperation, should recruit and train personnel, purchase andcomplete the testing equipment, homologize documentation;

The central laboratory prepares instructions for inspection of technical correctnessof spraying machines and devices and delivers it to manufacturers, it alsoorganizes and conducts machinetesting training courses for manufacturers,training for operators of equipment for chemical protection on farms, or training fora group of individual farmers (agricultural cooperatives);

The Ministry of Agriculture legally mandates the inspection and coordinates formingof regional inspection stations, the Ministry also constantly improves regulations formachine inspection and plants protection;

The public media (the press, radio, TV) are also involved, informing readers andviewers, especially the machine users, of the necessity and benefits of regularinspection of machines for plant protection, providing useful information on theorganization of inspection, etc.

For the last three years, the experts of the Department for agricultural engineering of theFaculty of Agriculture in Novi Sad, have been conducting a widespread campaign aimed ateducating agricultural producers and creating technical and organizational requisites for thebeginning of the inspection.

Considering the above mentioned, a proposal has been made entitled the Procedure for

sprayer inspection, which is compliant with EN 13790, as well as the proposal for theregional management which is to conduct the inspection. In the course of making thisproposal, all positive experiences from the countries, which already have established suchinspection, were taken into account.


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Proposal ofProcedure for sprayer inspection The Proposal was made using ISO standards (subject area: Equipment for plant

protection), Policy on rendering services in plant protection (Slubeni glasnik SRJ, 1999.)and regulation EN 13790 which was fundamental. In addition, analysis has been conductedregarding procedures, which are used in other EU countries. All positive experiences havebeen taken into account with the intention of producing a proposal for a simple and efficientprocedure.

The proposal was done in an electronic form, in order to simplify the inspection processin the field as well as to allow the required data to be derived at any moment by simplyselecting a parameter from Segment I (Review of a typical setup). This means that, forinstance, by simply entering the name of machine owner, it is easy to derive the data on theinspection performed and the inspection results.

The proposal of Procedure for sprayer inspection requires inspection of all sprayercomponents and comprises four segments:

I Review of a typical setup

Review of a typical setup is the first segment, which comprises six articles. The firstarticle is 1.1 General, and it contains data on the sprayer owner, manufacturer and type ofsprayer and vintage. The next five articles specify the sprayer in more detail.

II General Specification

General specifications the second segment of the procedure, which comprises thefollowing specifications:

Tank specification Pump specification Specification of spraying wings (booms) Specification of tubing Specification of filters Equipment Specification of the system for volume regulation Specification of special devices Volume of protective agent residues Specification of nozzles

III Inspection methods for hydraulic sprayers

Inspection methods for hydraulic sprayers as the third segment of the Procedure, itdefines methods for testing particular sprayer components, as well as the standards theyshould meet. The sprayer components undergoing tests are pump, manometer and nozzles.All other components such as the tank, hoses, filters, valves, etc. undergo visual inspection.The capacity of pump is tested by throughput gauge, shown in Fig. 1. Pump is considered tobe in order if the deviation from the nominal capacity does not exceed 10 %.

The tested analogous manometer must satisfy standards defined by EN 13790, i.e.must have a minimum diameter of 63 mm and a clearly visible scale. The scale must besubdivided into 0.2 bar segments for manometers measuring up to 5 bar, or 1 and 2 barsegments, for manometers measuring up to, and more than 20 bar. Manometer isconsidered correct if the deviation of the measured pressure, when working with pressuresover 2 bar, falls within the limits of 10 % as compared to the referential manometer. Thus

when working with pressures of up to 2 bar, the allowed deviation is 0.2 bar.


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Fig. 1: Pump throughput gauge (AAMSBelgium)

Manometers are tested using manotester shown in Fig. 2.

Fig. 2: Manotester (AAMSBelgium)

Inspection of nozzle requires testing their capacity and transversal distribution ofpesticides. To test capacity of nozzle an electronic throughput gauge is used, as shown inFig.3.

Fig. 3: Electronic nozzle throughput gauge (AAMSBelgium)

Inspection of transversal distribution is performed with a mechanical spray scannershown in Fig. 4.

Fig. 4: Mechanical spray scanner


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Inspection results are presented in tabular form and by a diagram. The allowed CV(Coefficient of Variation) is 10 %, which is compliant with EN 13790.

IV Inspection report

Inspection report is the segment, which contains data on time of inspection, names ofinspectors and the laboratory conducting the inspection, as well as the number of Inspectionlog and number of the issued Certificate of Quality.

The data, which are given in the Review of a typical setup and General specification,are logged in the "SPRAYER INSPECTION LOG". The log also contains the results ofinspection.

After the inspection of sprayer is finished, three copies of inspection log are printed out.In addition, every sprayer that passes inspection is awarded the "CERTIFICATE OFQUALITY" which is issued by the"Central laboratory".

The party that ordered the inspection (owner or user of sprayer) receives one copy ofthe log, while the institution, which conducted inspection and the central laboratory, keepsthe other two copies. The inspected sprayer is also marked with the "Label" which statesthe date of inspection. Should the results of inspection be unsatisfactory, the Inspector

informs the ordered of inspection results by issuing him the Inspection log. In this case, thelog also features a chapter entitled "Note" in which the Inspector suggests the detectedfaults in the sprayer to the inspection ordered, also suggesting ways to correct the errors inorder to become eligible for the "Certificate of quality".

Organization of sprayer inspection in Serbia forming the regional management

Analysis of sprayer inspection in other EU countries reveals the differences amongthese countries, regarding both the organization of inspection, and the sprayer componentsbeing subjected to inspection.

Generally speaking, the inspection in all EU countries is conducted in two principalways:

using mobile teams which conduct inspections touring the country with theequipment

through a network of laboratories dispersed throughout country (Germany, Holland,Slovakia)

The first way of inspection organization is adopted in Norway and Belgium. In December2000, Norwegian authorities decided to make inspection mandatory as of January 1, 2006.Department of Agricultural Engineering of the Faculty of Agriculture in Norway, alsoproduced a mobile inspection unit, i.e. one trailer Fig. 5a, which is following inspectors in thefield and which contains the equipment for inspection (Bjugstad, N, Hermansen, P, 2004).Similar situation is in Belgium, their inspectors using a van Fig. 5b which carries theinspection equipment.

a) Inspection trailerNorway b) Van Belgium

Fig. 5: Mobile inspection units


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The other way of organizing inspection is prevailing in the majority of EU countries and itfeatures a Central laboratory, which organ

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