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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,
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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.
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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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