AECL-4764

iSI

OF PARTSOLE SAMPLING PROBES

I!

D.E. MINNS, R.K. GHAi,

D.R. JOHNSON and F.H. KETCHESON

Whiieshei! Nuclear Research EstabiishtY>enV

Pinawo, Monl ioba

" - December 1974 t.

A NEW TECHNIQUE FOR MEASURING THE EFFICIENCYOF PARTICLE SAMPLING PROBESIN FLOWING LIQUID SYSTEMS

D. E. Minns

R. K. Ghai*

D. R. Johnson**

F. H. Ketcheson**

* Postdoctoral Felicw

.- ft*

" ^ 5 - 5 "* >5r

A-^3 -r^»- -

^«w "^•"Sii

Nouvelle technique pour mesurer l'efficacité des sondesd,'_gchanti 11 on nage des particules dans les

systèmes oit coulent des liquides

par

D.E. Minns, R.K. Ghai*, D.R. Johnson**,et F.H. Ketcheson**

* Boursier post-Doctorat** Etudiants coop., campus de Regina, Université

de la Saskatchewan

Résumé

On décrit, dans ce rapport, une nouvelle techniquepour déterminer l'efficacité de l'échantillonnage des parti-cules solides. Cette technique est très perfectionnée carelle permet de mesurer l'efficacité des échantillonnagesavec une précision de ±b% dans n'importe quelle concentration,allant même jusqu'à une seule particule.

Cette technique est fondée sur la détection d'une seuleparticule radioactive circulant dans una boucle d'essai.Dans chaque cycle, la particule peut soit pénétrer dans unevoie d'échantillonnage via la sonde des échantillons, soitpoursuivre sa course dans le courant principal. Le choixqu'elle fait est enregistré pour de nombreux cycles et lesdonnées ainsi recueillies sont étudiées statistiquement pourdéterminer l'efficacité de la sonde».

L'Energie atomique du Canada, LimitéeL'Etablissement de Recherches Nucléaires de Whiteshell

Pinawa, Manitoba, ROE 1L0

Décembre 1974

AE0L-47S4

A NEW TECHNIQUE FOR MEASURING THE EFFICIENCYOF PARTICLE SAMPLING PROBESIN FLOWING LIQUID SYSTEMS

by

D. E. Minns, R. K. Ghai* D. R. Johnson**and F. H. Ketcheson**

ABSTRACT

This report describes a new and improved technique for detec

raining sampling efficiencies of solid particles. This technique is a

considerable improvement since it can measure sampling efficiencies

accurately (± 5%) for any concentration down to a siagia particle.

The technique is based on detection of a siagle radioactive

particle as it circulates in a test loop. For each cycle, the particle

has the choice of moving into a sample line through the saiaple probe or

continuing in the main stress. Each choice is recorded for many cycles

and treated statistically to derive the efficiency of the probe.

*- Postdootoral Fellow•'•'••** ; Cos-op j Vadents, Segina Campus, University of Sas

/ ..; Atomic Energy of Canada Liaited

Bhifeesfcell Mttclear Eeseareli aGt'^

Pinawa, Hsnitaba., KiEi 1L0

, 1074

... A V/ .\

CONTENTS

Page

1.

2.

3. ^

A

5.

G.

INTRODUCTION

EARLIER STUDIES OF PARTICULATE SAMPLING

EXPERIMENTAL DETAILS

3.1 PRINCIPLE OF THE TECHNIQUE3.2 DESIGN AND COKSTRUCTION OF THE LOOP3.3 TEST PARTICLES3.4 LOCATIONS WHICH TRAP'PARTICLES

' ERROR ANALYSIS

4.1 RANDOMNESS OF PARTICLE MOTION4.2 TRROR IN FLOW MEASUREMENT4.3 ERROR IN ESTIMATE OF JUNCTION EFFICIENCY

CONCLUSION

REFERENCES

1

2

3

3467

8

8910

10

11

ACKNOWLEDGEMENTS 12

NOMENCLATURE , 13

FIGURES - 14

•** * 4r ^ —' ^ —- ^ ~** "s-

1. INTRODUCTION

The sampling of a flowing fluid containing solid particulate

material is prone to inaccuracy. In most industrial situations, accuracy

is not required, as long as the samples are reproducible; operating

experience serves to 'calibrate' the instrument and give meaning to the data.

However, for experimental purposes and the comparison of information between

systems, both accuracy and reproducibility are required.

The three major sources of particulate sampling error are:

r

1. The particulate concentration profile in the processline gives a non-representative concentration at thesampling probe.

1. ""-- ?f-or collection efficiency of some sample probesresults from the particles failing to follow the fluidstreamlines because of their size and density. Errorsup to 50% have been recorded in gas/solid systems*1 .

3. The error due to deposition or release of participatesfrom sample line and cooler was found to be up to 10%for interchange with sample lines and 25% for "the cooler , ,for a high temperature water sampler system used by Wages 2 •

The technique presented here is for evaluation of the efficiency-

of probes for estimating the aveiage -particulate concentration in the pro-

cess line." Therefore, it evaluates the combined error frosrFjrticuiate

concentration profile and collection nefficiency. ^-f - " .

" ~ , ~" - A single iqh-exchange bead_^(300-1500.urn size)1 labelled irith -T

60Co was used in developing this technique.-The effects' of -particle size,

density, concentration and shape, flows, and probe geonetty, are toM^";

studied using this technique,-and will be discussed in subsequent reports. -

- 2 -

2. EARLIER STUDIES OF PARTICULATE SAMPLING

No data have been found in the literature pertaining directly

to probe efficiencies in liquid systems. The few studies of sampling which

have been made have basically used the systems shown in Figure 1 to collect

the samples so the data are prone to all the errors associated with sampling.

Separation of the contribution of the various errors to the total is very

difficult. • ' , • - • . .

The only effort to identify errors associated with the sampling ::,-:-.\

probe itself ws.s made by Sehme.l -1' for the uranine/air system. He invest!- .*•

gated errors resulting from the poor application of isokinetic probes. He

resolved the various errors by dismantling the sampling system and washing

with water after each test. Sehmal does not mention the experimental error

involved in his procedure.

Wages(2) used a similar technique to study deposition in sample

lines from high temperature pressurized water systems. He also dismantled

his equipment after each test and cleaned off any deposits with acid. Wages'

data are reproducible only to + 50% (90% confidence). Errors of this magni-

tude might be expected in Sehmelrs esti™nte of probe efficiency since he

used a similar technique,

Trinkel, Henzel, and Schuck'3^ compared samples from probe

types (a) and (b) (Figure 1) with samples obtained isokinetically from the

BLW-KAHL reactor in Germany. They used a sampling technique similar to that of

Wages, but instead of cleaning the sampling system after each test, they

ran their sampling system on bypass for 5 hours before.taking measurements .

and assumed the system .was at equilibrium. Their efforts to compare tlie , • -

three probes ware inconclusive as their data showed the same r epr oduc ib,ility I-

as obtained by Wages, y

- 3 -

..,.-..; Our technique overcomes the uncertainties of these earlier

techniques and allows £he\ measurement;jof. sample probe efficiencies in

liquid systems to ±^3%:(90% confidence^ ^ ;

,3. EXPERIMENTAL DETAILS

3.1 PRINCIPLE OF THE TECHNIQUE

The technique is based on detection of a single radioactive particle

as it circulates it tbe test loop. The loop has a sample line bypassing the

main circuit (Figure 2) and is designed sc that^a. small particle (300 -f15G0 y.m

diameter") will circulate for jthe duration of each experiment without becoming

trapped.

To'satisfy statistical requirements% ea£h experiment meecis about

1000 cycles*/ Bar each cycle, the particle hss the' choice of entering either

the matin line or the sample lineT "Each line USE itB own radiation detector

i and counter which records the pressace of *h$s particle as-a. single ecmtt.

At th<» end of the experiment ? the amplisig efficiency r*Bave* *a5 *e determined -

frbiis the tafio of the liquid flows and the ratio ~ofT>aefounts in t:he two linee.

where Ng is the mean number ot times the bead enters the saaple. line asA

- S T is" the totaJUnti^fceT-o^cyclee. Pg i& the voxuaetrie (IMF i» -tfc* Maple

line and Rf 3,s e^e tot^ flew,

- I€ jthe^articj* l>ecoate« trapped during an experiment It coft b*

rontinued without aff*ctin« th« r£«ulta.

However, it is inconvenient if trapping is frequent since the operator

must keep a continuous watch on the experiment. To reduce this effort,

the loop was designed to decrease the chance of trapping particles.

Locations which showed a high trapping occurrence are discussed later.

3.2 DESIGN AND CONSTRUCTION OF THE LOOP

A schematic diagram of the experimental set-up used in these

experiments is given in Figure 2.

The tubes and fittings are of clear polyvinyl chloride (PVC),

supplied by Johnston Industrial Plastics. The *T' junctions were made from

acrylic resin because it is easy to machine and has good Optical properties

for photography.

Initially, an attempt was made to fabricate the loop from 6 mm

I.D. glass tube with ground glass joints. However, the joints forced apart

under pressure, and when under vacuum they leaked air. These joints also

caused large flow disturbances which trapped particles. The use of PVC and

acrylic resin eliminated these problems to a large extent. •

Flow rates were measured using ventu'ri flow meters machined

from rods of acrylic resin. The venturi-meters were used with differential

manometers. Pitot tubes were also tried but they had a slow response to -

flow changes, tended to trap particles, and were difficult to seal.

The various materials used in the loop were bonded using the

solvents given in the following table. Strong joiats were made by using

a solution of acrylic resin chips dissolved in methyl-ethyl-ketone.

- 5 -

TABLE 1

SOLVENTS FOR BONDING PLASTICS

BOND . SOLVENT

PVC - PVC VC - 1*

Acrylic - Acrylic Chloroform

PVC - Acrylic Methyl-ethyl-ketone (MEK)

PVC - Tygon VC - 1*

* Supplied by Johnston Industrial Plastic Limited

Two types of pumps were used. A peristaltic pump was used

for small flow rates (maximum 5 x 10~3 rar/min) and a centrifugal pump

for large flow rates Csi2.::iirm 0,1 ra3/iain), Both of these pumps were

supplied by Fisher Scientific Company.

The peristaltic pump imparts a pulsating flow to the*

These pulses were dampened oat by placing a closed surge tank befcwofcn the

pump and the test section as shown 3n Figure" 2.

A tee (Figure 3) imnersed in an open, surge, tank iresisd

upstream ox the pucip .provides a place t;o Inject: particlai. intc the cy£to

Lengths cf 3 E J I.D. Tygon tubing or £lo«jr6Sl3i-or? T.Sii-e Cron a

rod of acrylic resin vere u^ed fct local- fi«y control 5 a rht_lt.'jp. SIi.--rt

lengths of 6 mm Tygoa tuTjinc W'S' if-'.sucocu clarp:. '? rc crvca ;Li,i.i3i> • »it

they had to be clsmpcd so tign.cty to obi r-r- tha. dteslred f'i. J .r^J-.s* rl,-,r

they trapped, the porcicl^s.

- 6 -

Geiger Miiller radiation probes were used to detect the presence

uf the active particle. The signal from the probe is converted into a

voltage output by a contamination rate meter and then boosted by a differen-

tiator/integrator circuit coupled to a transistor to drive a mechanical

counter. The mechanical counter records one count each time a particle

passes the radiation probe. A schematic of the elect" Lc circuitry of this

counter is given in Figure A.

The radiation probes were placed lengthwise along the tube

walls. This probe position WO..J satisfactory except when the bead was

circulating at high linear velocities»(^ 4 m/s in 19 mm diameter pipe).

'At such velocities, detection signals x ere too low for measurements. The

problem was circumvented by introducing a large vertical PVC pipe (50.8 mm

diameter) at the detection point. First, a system in which the outcoming

flow from the tube was fed to the bottom of the pipe was tried. This system

did not work for glass or steel beads because the net upward fluid velocity was

found to be less than the settling velocity of the beads. A system in which

the outcoming flow was fed to the top of the pipe worked satisfactorily.

In order to increase the detection sensitivity, two probes were

used instead of one on each pipe. The probes were placed diametrically

opposite along the pipe wall. The radiation level of the beads required

for successful detection was found to be 5 to 50 mR/h at a distance of one

inch.

3.3 TEST PARTICLES , .,. . :

The requirements for the test particles are:

1. sufficient physical strength to withstand the passage throughthe pumpj

2. ability to be activated to 5 to 50 mR/h at a distance of cue inch.

3. availability in different sizes with a uniform shape.

- 7 -

Spherical particles (sizes 300-1500 um) of macrorecticular

ion-exchange, resin, soft glass, and steel were tested. Ion-exchange

resin beav.s, Amberlite 200 and Amberlite 252, manufactured by Rohm and

Haas, were used. Amberlite 252 is black and more convenient to use because

it is easier to see. Both resins were activated by immersion in a 50Co

solution for about one day. Small ion-exchange resin beads were better

than large beads since they maintained their activity and physical

strength for up to ten days. The larger ion-exchange beads

split in the radioactive solution. The glass and steel beads were neutron

activated by placing them in the WR-1 reactor.

3.4 LOCATIONS WHICH TRAP PARTICLES

The particles had a tendency to be entrapped in:

v a l v e s ' . •" : •.•.-• :" •. '.:•.'''.'-""•,'".• ." -•:...••'•'•.•'••••

any rough edges protruding into the flow3 particularly iutube fittings such as elbows, connecxors, and U bends

manometer faps•whers ths particles were swepc in "by thR Clowturbulence and became lodged.

The frequency of particles being trapped was reduced by;

using lengths of 3 IBHI I.D. Tygcn tubing . '-

•using flow resxstors made of acrylic resin iristeed of valves forflow control

carefully filing-down -J!3 rough ecgs.i of tubes and suba sittings.

keeping the ir.anofr.3ter ts,r.= vertically upwards so-that Is. fctfcparticle entered ii: fell out sigain uadei c"^o t>>zr.a. <.»/ ravi-

4. ERROR ANALYSIS

The total experimental error in the estimate of sampling

efficiency is a combination of the errors in random motion of the particle

and errors from the measurement of flow rates.

4.1 RANDOMNESS OF PARTICLE MOTION

For the data to be valid, the test particle must have a random

chance of entering the sample junction concomitant with its probability

of being sampled. To determine this randomness, a 1000 cycle test was

repeated 7 times and the data statistically analyzed. The tests were

conducted using a 'T1 junction and with a flow rate of 55 g/s upstream

of the sample junction and 15 g/s through the sample line. These data gave:

245

o| = 392.5 (6 d.f.)

where Og is the standard deviation

d.f. denotes degree of freedom.

It is shown*1*' that for a random event with a probability, P, standard

deviation or is given by:

a£ = NP ( 1 - P)

.. 9 -

Adapting this to our experiments:

N = N™ = total number of cycles (1000)

P = ~ = 0.245 (6 d.f.)T

Therefore, a* = 185 (6 d,f.)

2If the particle is moving randomly, 0"g should not be significantly different

from ar •

Using the F

F = 1- = 2.12; FC6,6) = 5.82 (5% significance)

Since F is not larger than F (6,6), the variances are not significantly

different, which suggest the particle is moving randomly.

4•2 ERROR IN FLOW MEASUREMENT

A flow rate of mean 12.5 g/s uas reset and c- libraued four

times for vsach venturi meter, The calibration gave tha.ssme standard

deviation for each meter- of;

cf = 0.14 <3 d.f.) g/s.

Using Student's t tast s the 90%,cor.fidancc band for flow "iicctircncut i.o

± 0,4 g/s. - . . . , , . -

- 10 -

4..3 ERROR IN ESTIMATE OF JUNCTION EFFICIENCY

Rather than combining the errors of Ilow rate and particle

motion, the error in tne junction efficiency was measured directly. Six

replication tests were carried out under the same conditions as the tests

for randomness using the sama 'T' type sample probe. No other probe

geometries have been tested and it is possible that they would have different

errors. These data gave:

e = 0.88 (5 d.f.)ave

a = 0.018

Using Student's t test, the 90% confidence band for junction

efficiency is ± 0.04 (approximately 5%).

5. CONCLUSION

A new technique has been developed to measure sample probe

efficiencies in liquids. It is a considerable improvement ove r the earlier

techniques since:

probe collection eff"ciencies are measured to ± 5%

the collection efficiency for any concentration down to asingle particle can be measured.

Previous techniques for measuring probe collection efficiencies

in liquids have had precision or' only ± 50% and are then only suitable for

use with this accuracy for particulate concentrations > 100 ug/kg.

- 11 -

This new technique will be used to study sampling as functions

of:

particle size, density, concentration, and shape

liquid velocity, density and viscosity

probe geometry and location

The aim is to develop a consistent sampling procedure and a reliable

sample probe design.

6. REFERENCES

1. Sehmel, G. A., "Particle Sampling Bias Introduced by Aniso-kinetic Sampling and Deposition within the .sampling Line".American Industrial Hygiene Association Journal, November -December 1970, p. 758.

2. Wages, S.R,, "Corrosion Product Sampling from Aqueous HighTemperature DynaFdc Systems", Knols Atomic Power Lab-SKAP-P-3935 (1971).

3. Trinltel, A., Henzel, S., and Schuck, V., "Sampling Techniquefor Feedwater and Saturated Steam in a Boiling .Water Reactor",Reaktortagung, Hamburg, April 1972, p. 598.

4. Levinson, H. C . "Chance, Luck, and Statistics",, Dover 19&3sp. 237.

5. Katrella, M. G.s "Experimental Statistics", Rational Bureauof Standardss Handbook 91, U.S. Department of Coinaiarce (1966),pp. 4 - S to 4 - 9.

- 12 -

ACKNOWLEDGEMENTS

The development of this technique would not have been possible

without the help and advice of many people at WNRE too numerous to mention

individually. Their efforts are greatly appreciated. ot"^td± thanks

are due to the staff of the workshop and Instrument Development Branch

for their invaluable contributions to the mechanical and electronic

aspects of che work.

- 13 -

NOMENCLATURE

£ave probe collection efficiency for estimating the averageparticulate concentration in the process line

in T' testZ

r

liquid flow rat- at inlet to test section

liquid flow rate through sample linemean value of the number of times a particle moves along thesample line

total number of cycles

probability of an event occurring

a standard deviation

2 •• —

Og variance of N<;• . • • . _ : : ;

variance oh the number of times an event of:raadom probabilityP occurs in a total of N events

- 14 -

FLOW

YZA XZZAFLOW

(a) (b)

FLOW

SAMPLE PROBE

FLOW

- 15 -

1. PUMP2. FEED TANK3. SURGE TANK4. RADIATION PROBES5. FLOW DIVIDER

6. VENTUR! - METERS7. FLOW RESISTOR

4 6

FIGURE ""a;" v : \ , ; > , -SCHEMATIC DIAGRAM "OF THE- EXPERIMENTAL -S£T»UP

- 16 -

TO PUMP FROM PUMP

r

XZZZL

FIGURE 3 FEED TANK AND TEE FOR INJECTING

BEADS

- 17 -

LOOP

DIFFERENTIATOR / INTEGRATORCSRCUIT

is? •

" CUV _ ^ * ,

Additionalmay

ScientificAtomic Bfterefjf Qi^V-^inaaQ Irmi^ed

Chalk. Riv^r, Oi^loicio, «- , .« . , - .. - ^ ^ « =-

ige - $LQO pej