Eleven Points to Consider Before Buying a Silo Protection System

Silo protection is an important plant investment decision, and not all systems give you the safety you need. Here are some key points you need to think about before settling on an SPS supplier.

1. From whom are you considering buying a system?
Do your homework! Many companies selling silo protection systems have a poor understanding of what the silo protection application involves. Their approach is just a box-ticking exercise to offer something that looks like a silo protection system. It is not stretching the truth to say that most suppliers only source a ‘bag of bits’ of equipment and build a panel to accompany it. Therefore, the first questions you should ask a supplier when considering their silo protection system are:

What is their company background? Do they manufacture anything or just buy from other suppliers? Do they have experience in this area of over pressurisation? Is the information readily available in print or on a website? Dedicated silo protection companies will provide materials explaining what causes silo pressurisation and how to prevent it, with advice to help avoid the common mistakes.

Can the company you are considering also offer back-up and service support in the future? Do they have engineers who can diagnose faults and explain what to avoid to keep your silos safe? It is no good dealing with a small one- or two-person operation which is on holiday for eight weeks a year or cannot be contacted in an emergency.

Hycontrol has been an instrument manufacturer for over thirty-five years, designing pressure, level and temperature systems. We understand the cement delivery process in precise detail. We know flow rates, discharge pressures, filter flow rates, the exhaust rates of pressure relief valves. In short, we know what you need to protect your silos.

2. How harsh will the environment be on the system?
Many companies supply a ‘bag of bits’ of components intended for general industry automation applications. Such equipment is generally not suitable for the dusty, demanding environments of a typical cement application. As anyone who has spent time working in the industry knows, insufficiently robust equipment will not last long. Choosing systems like this will compound maintenance issues and multiply expenditure over time.

Hycontrol has been supplying the quarry industry for over three decades and our rugged equipment that is designed specifically for this environment, with sensors that clean themselves.

3. What logic control does the system need?
Automatic shut-off systems are essential to protect a silo because human reactions are too slow to deal with a pressure spike, which can happen in milliseconds. Many silo protection systems use a simple panel with a few warning lights that show if the high-level alarms are activated.  Some of these panels appear to indicate fault diagnosis; however, this can be misleading, as what they show is if the signal is on or off and not whether the probe is fully functional.

Most site managers do not fully understand the tanker delivery process or the ramifications if it goes wrong. They do not know that a silo can blow or split from an increase of just 1 or 2 psi, or that a pressure relief valve should open at the same pressure as a child’s balloon (0.7 psi). Site managers have also generally had little-to-no training on shut-off timings for pressure sensors and level alarms. These settings can vary greatly and are critical if not correct.

Hycontrol systems offer complete clarity of information, informing you of high-level events, high-pressure events, and PRV lifts, which are all recorded and logged. This information is valuable for preventative maintenance and will indicate system failures such as filter blockage of driver errors.

4. How do you avoid working at height risks?
A significant consideration for any site with silos is the risks arising from working at height. To ensure a silo is adequately protected, the safety equipment mounted on its roof must undergo a test before each fill takes place. Unfortunately, this means working at height in all weather conditions is unavoidable - vastly increasing the danger of accidents resulting from slips, trips and falls. Most operators are wary of climbing a high silo on a sunny day, let alone in the middle of winter! With a growing percentage of the workforce now over the age of 65, the risk from this strenuous activity will only increase.

Hycontrol silo protection systems hugely reduce the need for working at height, keeping it to a minimum by utilising Ground Level Test (GLT) technology. GLT checks all the essential safety equipment with a single button-push at ground level, removing the need to climb silos regularly.

5. What do a smoke detector and a good silo safety system have in common?
As with choosing a smoke detector for your home, it is sensible to make sure the system you are buying for safety protection works, i.e. it has a test button function. As mentioned, Hycontrol systems perform a comprehensive Ground Level Test (GLT) function with a single button-push. Many competing systems have a ‘lamp’ test which manufacturers have tried to pass off as an operational test. This is not the case, and it is vital to know the difference. A lamp test will, as the name suggests, show you that the alarm lights on the panel are working – but this is not a test of the sensor’s functionality. As such, these tests cannot be relied upon to confirm that safe operation is possible! If you are considering purchasing a non-testable system, then you need to ask yourself a serious question: how will you know it is working when you need it?

Any system can demonstrate full operational effectiveness at installation, but what about the day after that? Hycontrol’s system carries out a full-function test of all the critical components in just six seconds, saving maintenance time and removing the risk of faulty safety sensors. Hycontrol has pioneered full testability for silo protection systems. As part of the GLT routine, the following essential components are all thoroughly tested within six seconds:
  1. The pressure sensor is fully tested and cleaned
  2. The pressure relief valve cycles open and closed
  3. Functionality test of the level probe
  4. Checks the air pressure to the filter unit
Hycontrol’s system is unique because it gives a full, reliable test before each operation, guaranteeing safety and functionality.

6. Are there hidden maintenance and upkeep costs?
Consider the costs of maintaining and testing the system you are looking to buy. For example: in most cases, to properly check a pressure sensor and pressure relief valve, you would have to remove them from the top of the silo, take them to your workshop and bench-test with appropriate equipment. As such, a check could take two hours; understandably, it would be deemed impracticable and ignored during maintenance. Historically, this avoidance of testing is why so many systems in the industry do not work.

There are two options: have a non-testable system and hope it works, or opt for a Hycontrol system with a Ground Level Test facility. A GLT-enabled system will test itself in just six seconds with a single button-push on the control panel. Within a short period – perhaps as little as 12 months – the system will have paid for itself, offset against potentially incurred maintenance costs.

7. Is the system simple to operate if you have staff changes?
Consider the level of knowledge required of your staff to operate a system and maintain safety levels. For example: with staff changes, sickness or holiday cover, would the employees on your site know how to manage or test the system you have installed? Is it likely that they would neglect essential checks, putting the silo and the site at risk? Because of this, the system you opt for needs to be simple to operate, comprehensive and requiring minimal training for newcomers.

The Hycontrol option is to test everything with one simple key turn or button push. It is that simple – and to make sure, our system WILL NOT let you fill the silo without running the test cycle to confirm the safety system is fit for duty. If any component of the system should fail the test, the control panel will report the issue. Until rectified, a filling will not be allowed. Effectively, this forces compliance with safety procedures.

8. Can you rely on the pressure sensor operating with a cement build-up?
Often, pressure sensors working in a dusty cement environment endure years of neglect. As a result, there will inevitably be a build-up of product on the sensitive front face of the sensor, many of which have delicate, flexible rubber diaphragms. This build-up will compromise the effectiveness of pressure monitoring during a fill, ultimately putting the silo at risk. Diaphragms tear, ports get blocked, and sensors are often never tested after installation.

A potentially worse situation arises from a literal hand-testing of the sensor. Site operators will sometimes check the device by forcing the pressure pad to move with their hand, applying an equivalent force which is ten times too high. This action provides no real test benefit and a false sense of security. It may even damage the sensor

The patented, purpose-designed Hycontrol pressure sensor overcomes product build-up by self-cleaning with a burst of compressed air during the test cycle before each delivery. This blast is highly effective at cleaning the sensitive front face and also creates a back pressure over the sensor operating range to confirm it is 100% operational. We recommend you consider this carefully when weighing Hycontrol’s SPS against competing systems – the pressure sensor is inarguably the most critical element in the safety system. Competing models lack the self-cleaning capacity of the Hycontrol model, generating the need for additional maintenance.

9. Will you be wasting money on compressed air?
In some systems, the air supply to the filters runs continuously, which can be extremely costly. Often the air supply is not correctly controlled to the filter or baghouse, causing a potential blockage and pressure build-up.

The Hycontrol system overcomes these issues by turning the air supply on and off, leaving it on for 30 minutes after the fill finishes to remove post-delivery cartridge contamination. Therefore, the filters are only on when needed, reducing costs and giving optimum efficiency.

10. Do you want a safety system or just a tick-box checklist?
With the competing priorities that site managers face, it is easy to understand why silo pressure safety is an ‘out of sight, out of mind’ problem, and why addressing it is very much just a box-ticking exercise for some. However, as we have seen, this laissez-faire attitude is very likely to lead to costly complications and possibly even physical danger further down the road.

Hycontrol creates systems that prioritise health and safety. Safety is not an optional extra or bonus, but the central hub around which everything else should turn. This philosophy informs all aspects of Hycontrol’s product and system design. Hycontrol systems are not just ‘add-ons’ for plants; they are specifically-designed safety systems to protect silos, to improve site safety and to reduce the level of risk to which your workforce is exposed. We are confident in saying that no other company manufacturing and supplying silo protection systems can match us in terms of expertise in silo pressure safety.

With over three decades of experience in the design and manufacture of level systems, overfill and overfill protection, pressure safety systems and many other solutions for industry, Hycontrol has earned the right to be called experts in the field.

11. Do you understand the consequences of getting it wrong?
Recorded statistics show clearly that silo over-pressure events happen daily all around the world. There are two reasons for this: firstly, ineffective silo protection and filter management, and secondly, poor delivery control from tanker drivers.

If you are lucky over-pressurisation will only display itself through regular pressure relief valve openings with product deposited on your silo roof and surrounding area (again, this should not be confused with overfilling). Leaking powder creates significant environmental issues and is a clear sign of ineffective silo protection.

However, in the worst case, over-pressurisation will result in the filter unit being blown from the silo-top or the vessel rupturing. Such incidents have resulted in severe injury and death at several sites around the world. Unless sites rigorously pursue silo pressure safety, this will continue to happen. The consequences of an ineffective silo protection system cannot be stated any more starkly than this.