atex powder - are atex powder storage silos disasters waiting to happen?

8/20/2019 ATEX powder - Are ATEX powder storage silos disasters waiting to happen?

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by Mark Stevenson and Nigel Allen, Hycontrol

S T O R A G E

Level measurement specialists Hycontrol

have long had a background in the

control of our, grain, starch and

animal feed, and have been designingspecialist silo protection systems for

over 20 years. As such, they have

extensive experience of the potential

problems that exist on sites, especially

those handling products such as our,

sugar, grains and starch. According to Hycontrol’s MD Nigel

Allen, many ATEX-rated powder storage silos are disasters

waiting to happen, putting lives at risk and posing serious threats

to the environment.

“Our ndings are worrying to say the least and the photos

taken by our installation engineers speak for themselves,”

says Mr Allen. “Companies just don’t seem to understand theconsequences of poorly maintained protection systems. It’s

quite frightening that operators accept pressure blowouts via the

pressure relief valve (PRV), erroneously thinking that ‘It’s ok -

the PRV is doing its job’. This couldn’t be further from the truth

- PRVs are there as a last resort.”

“If the silo protection system is working correctly and is

tted with an automatic shut-off feature to prevent over-lling,

the PRV should never be used. If a PRV blows then there’s an

inherent problem with the system or the lling protocol and

corrective action must be taken.”

“Material in and around a PRV is a tell-tale sign that there’s

something wrong and a catastrophic blow-out is waiting to

happen,” he continues. “The material blown out from the

silos will almost certainly solidify over time and this will, at

best, prevent the PRV from working correctly and, at worst,

completely clog it up. Unfortunately many maintenance

engineers just don’t realise the potential dangers that lurk

beneath. They often think that simply cleaning off the material

on and around the PRV is good enough. They don’t realise that if

the PRV doesn’t lift next time an ‘event’ occurs the over-pressure

could easily rupture the silo or eject the lter housing from the

top. On an ATEX-rated silo the over-pressure could be sufcient

to simulate an explosion and open the protective blast panels,

resulting in costly loss of product and silo contents being left

open to the elements.”With regard to lter housings, Hycontrol engineers have

witnessed another worrying practice at a number of sites where

companies t chains to prevent the housing being blown off the

top of the silo, almost accepting blowouts as being inevitable.

What Causes Over-Pressurisation Problems?

Silo protection systems are designed to prevent the damaging

and potentially dangerous

consequences of silo over-lling or over-pressurisation whenpowdered material is being transferred pneumatically from road

tankers to silos. Unfortunately, perched out on the top of silos,

such protection systems are all too often ‘out of sight, out of mind’

- until a major problem occurs!

Problems during the lling process usually arise through an

inherent problem with the silo protection system or with the

air ltration system on top of the silo. Problems can also occur

through tanker driver/operator error. Delivery tankers are pressure-

tested vessels typically capable of withstanding up to two-bar (29

psi) pressure. Storage silos, on the other hand, are only designed to

withstand the weight of material stored in them and can rupture at

pressures as low as 1-2 psi above atmospheric pressure.The consequences of over-lling or over-pressurisation include:

• Serious or fatal injury to workers and the public

• Catastrophic silo damage

• Loss of material and production plus

• Harmful environmental pollution

• Damage to company reputation

A key issue with many silo protection systems is that without

adequate ground level testing capabilities, operators don’t know

if they will work when needed. Working at height restrictions

limit silo top inspections and maintenance, especially in adverse

weather conditions. However, the main problem is: what can

engineers actually do when they are at the top of the silo? How do

you physically test a relief valve or pressure transmitter unless you

remove them?

Even if the protection system does do its intended job and

prevents a major incident, companies rarely investigate the root

cause of the problem so that remedial work can be carried out to

prevent the situation re-occurring. High-level events and high-

pressure events are routinely not recorded and often conveniently

dismissed. Hycontrol have clear evidence that in practice there are

more near misses than realised and that the situation is a ticking

time bomb.

Filter housings on top of silos are designed to vent the silo

during lling, whilst preventing dust escaping into the atmosphere.

Normally these are tted with some form of self-cleaning systemto keep lters clear, typically mechanical shakers or reverse jet

systems. Although lter manufacturers give recommended check

routines and lter replacement schedules, in practice it would

appear these guidelines are regularly ignored. A range of issues,

Are ATEX powder storage silos disasters waiting to happen? ATEX powder

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including blockages and the tting of unsuitable or wrongly

sized lters, can cause faulty operation. Most powders form hard

compounds when mixed with water from the atmosphere, further

exacerbating the problems at the top of the silo.

Effective Silo Protection

Other industrial areas are further ahead in dealing with this issue.

For example, the Mineral Products Association (MPA) publishes

comprehensive guidelines for silo protection systems in UK

quarries and cement works. But worryingly there are little or no

such recommendations for powder silos used in a broader range of

industries, including food and beverage, grain, starch, sugar, and

animal feed. The primary principles are the same for protecting any

pneumatically-lled silo, yet the issue is being routinely overlooked.

Even with guidelines in place, the benchmark for the

effectiveness of any silo safety protection system can only relate to

the last time all the components were fully tested.

Optimum Solution

The only effective solution is to take an integrated approach

to silo protection design whereby the PRV, pressure sensor and

high level alarm can be tested at

ground level, prior to each ll.Only when all these safety devices

have passed the checks should the

safety interlock allow the silo inlet

valve to open and the delivery to

commence.

As an added benet, an effective

protection system can serve as a

powerful predictive maintenance

diagnostic tool by recording critical

near-miss events that occur during

the lling process. This information

allows managers to carry out effective

predictive maintenance by means

of a logical step-by-step root cause

analysis (RCA) process to understand

why the problems are arising. For

example, high pressure and PRV lift

events may be due to lter problems,

prompting questions such as:

• Are the lters the correct size?

• Is the lter-cleaning regime fully

operational?

• Have the lter bags/

cartridges been changed

as per manufacturers’

recommendations?

In parallel, the logs will also

indicate if the tanker drivers are

routinely over-pressurising during

the ll process.

In summary, the optimised

silo protection system should

incorporate:

• Pressure sensor, high alarm

level sensor and PRV testing

(essential)

• Simple one-button press to testall components

• Silo lling auto shut-off control

• Pneumatic cleaning of pressure

sensor

• Recording of the number of events on incidents of over-pressure

(time / date stamp)

• Recording of the number of events of PRV lift and opening

(time / date stamp)

• Recording of the number of events of high level probe

activation (time / date stamp)

• Filter ON / OFF output option to check lter status

• Filter air supply monitoring alarm option

There is strong empirical evidence that many silos are disasters

waiting to happen. The practical reality is that powder storage silos

can split or rupture at pressures as low as one or two psi above

atmospheric pressure. Malfunctioning lter housings can and have

been ejected at similar pressures.

Simply relying on cursory visual inspections of silo protection

equipment is woefully inadequate. Therefore it is imperative that

any installed safety system must be capable of providing reliable

protection that can be easily veried by testing critical components

before each and every delivery - without having to climb to the top

of the silo. This approach will provide total silo safety; protecting

assets, the environment and most importantly site personnel and

the public.

August 2015 | 67

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Iowa State University’s Northwest Research Farm now has

its rst grain storage system, thanks to GSI, which donated

a 10 500 bushel grain bin, and its local dealer, C-S Agrow

Service, of Calumet, Iowa, which donated the labour to

install it.

Josh Sievers, manager of ISU Northwest Research

Farm explains “the deal came about following last year’s

harvest where a lot of wet grain had been wasted, he and

his colleagues were driving past their local GSI dealer and

decided to head in and try to strike up a deal. The local GSI

made a request to their headquarters. GSI has gained some

publicity and the farm has ended up with a 10 500 bushel

grain bin on their site at the end of it”.

Mr Sievers cannot express his gratitude to GSI enough,

exclaiming, “It was like the stars had aligned and the red

carpet had been rolled out.”

The new bin will enable the research facility, based in

O’Brien County, to store and dry corn more efciently at

harvest than continuing to transport it to a nearby commercial

elevator.

According to Mr Sievers, “While the farm primarily

functions as a research facility, it is also a production farm

which has its own nancial targets to reach, this new bin will

make things easier. The donated storage bin can hold a thirdof our entire crop, not to mention it is highly automated and

very safety conscious.”

In addition to the 30-foot bin, the new storage system

includes GSI grain bin accessories provided by C-S Agrow

at cost to ISU, including outside stairs, unloading auger,

aeration oor, stirring equipment, a fan and heater. The

dealer’s sister company, The Concrete Guys, donated labour

to pour the bin’s concrete pad. GSI, based in Assumption,

IL, is a leading global provider of on-farm and commercial

grain storage bins, material handling systems, and grain

conditioning and drying equipment.

“We are extremely grateful for these donations, without

which this project would not have been possible,” says Mr

Sievers. “This bin will not only allow us to dry and store

grain on the farm, but also allow an earlier start on corn

harvest without having to pay for off-farm drying and shrink

charges. This new system will be put to good use for years to

come.”

Bryan Halverson, sales manager for C-S Agrow, said it

took six workers three days to complete the project, which

is located about 1.5 miles south of Calumet. “The ISU

Northwest Research Farms plays a key role in advancing

agriculture for Iowa farmers,” says Mr Halverson. “As GSI’s

largest dealer in the state, we’re proud give back to the

community by providing this grain storage system to support

their research efforts.”

Mr Siever says “The Northwest Research Farm which

conducts research in a wide range of agricultural areasincluding pest treatment applications, water quality, and

soil quality amongst other things, currently has no plans

to expand further in the short-term but are always open to

opportunities which might arise in the future.”

Storage project

GSI donates new grain storage system for Iowa State

University Northwest research farm

ISU NorthWest Research Farm grain bin when nearly completed


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Storage News

BinMaster of Lincoln, Nebraska, USA and Eye-

Grain of Denmark have announced their strategic

alliance that will bring a new line of temperature,

moisture and CO2 sensors to the North and South American

grain storage markets. BinMaster will be manufacturing

and marketing the revolutionary Crop-Protector™ line

of sensor systems for monitoring stored grain under this

exclusive agreement. This builds on the success of the

Crop-Protector™ line of products in Europe, Africa, andAsia sold under the igrain brand name in international

markets.

Crop-Protector™ solutions include state-of-the-art digital

temperature and moisture monitoring cables for installation

in bins and silos that are highly accurate and have a

long service life. Portable sensor lances with handheld

readouts are a cost-effective solution for monitoring at

storage, piles or occasional temperature data sampling.

The Crop-Protector™ CO2 sensor developed in 2009 was

the rst product of its kind on the market. Now in its third

generation, it is a fast-growing new technology that detects

carbon dioxide, which is an indication of undesirablebiologic activity and infestation in stored grain. The Crop-

Protector™ line also includes an advanced, easy-to-use

Aeration Control System that includes rugged, professional

weather stations required for accurate ambient weather

information. The Dash Board Manager software can

be operated on-site or via Cloud-based software and is

designed to keep crops in optimum condition.

“Crop-Protector™ grain conditioning systems are already

proven in grain storage facilities in many international

markets,” according to Peer Hansen, biochemist and director

of marketing and sales for Eye-Grain. “BinMaster’s ISO

9001:2008 (quality management) manufacturing and

experienced staff will ensure that grain facilities get topquality products and personal service in the North and

South American markets.” The innovations created by Peer

Hansen and the current Eye-Grain products have served the

post-harvest grain storage industry from farm level to major

industrial customers worldwide since 2003.

The Crop-Protector™ monitoring and control solutions

will be offered by BinMaster as complete systems

including communication hubs, wall-mounted touch

screens, and software for a turnkey solution with

continuous monitoring of stored grain conditions,

automated alerts, and other options. “Temperature and

moisture monitoring systems are a perfect complementto BinMaster’s line of level controls and inventory

monitoring systems,” stated Scott McLain, CEO of

BinMaster. “Eye-Grain delivers the quality and innovation

customers expect from BinMaster.”

BinMaster and Eye-Grain announce strategic alliance



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