Working on a silo requires awareness of all the potential dangers and adherence to the strictest regulations and procedures when working at height. This requires experienced teamwork to ensure the safety of the workforce with stringent safety training undertaken and adhered to all personnel.
At Silo Facilities Management, our team has up to 40 years of experience of working at height, in this industry. We combine time-served expertise with keeping up with the very latest innovations in safety equipment and procedures. It means we implement proven best practice safety technology to ensure with absolute surety that anyone ascending or descending silos can working efficiently, comfortably and safely in position.
Following rigorous risk assessments and method statements, we use our fall restraint system to allow skilled personnel to access to the silo top to carry out their duties. This also prevents a worker from reaching a point where they could fall through the existing barriers.
Our proven safety systems are designed to allow an individual to work anywhere that is required for inspection, cleaning, maintenance or repair on the silo top with added protection and peace of mind.
Our fixed post chain and wire systems are pivotal to silo safety providing a vertical lifeline system that allows maximum freedom of movement for workers to conduct their duties with flexibility, security and confidence. Our silo safety measures result in quicker and more efficient results for our team and more importantly for your business operations.
Each silo has a three-point anchor system fitted with a central line that goes across the silo diameter. These angle irons are securely bolted to the existing barrier up stands.
For absolute safety, any person working on the silo top will automatically clip onto the central line to prevent any possibility of a fall.
Our systems are efficient and can be made bespoke to any silo. They are generally fitted to any silo within a single day making it quicker and easier to access your silo exterior in safety.
Silo Safety Systems
We offer the design and installation of safety systems for silos. We offer onsite training for all systems and can provide all PPE to be able to use these safely at all times.
Silo protection systems are essential to avoiding the dangers of silo over-pressurisation.
During the pneumatic filling of silos, powders are fluidised at the base of the tanker and blown through the connecting hose into the silo. While modern tanker vessels, hoses and couplings are pressure rated, in most cases the receiving silo is not.
There are three possible reasons for over pressurisation when a silo is being pneumatically filled:
1. Balanced: The airflow into the silo is the same as that leaving.
2. Elevated pressure due to limited air flow through the filter: This may be due to inadequate maintenance of safety equipment, or by filter blinding due to over-filling. An increase in air pressure above 1psi inside a silo can cause severe damage. Risks include rupturing the silo or blowing the filter off the silo roof.
3. Elevated pressure due to excessive air entering the silo: This is the most dangerous scenario and even a new filter will not cope. This most commonly happens at the end of a delivery when the silo is nearly full and there is limited ullage within the vessel. Recent evidence suggests that this problem is far more common than previously thought.
Tell-tale signs
Common silo over-pressure indicators include: Powder in and around the pressure relief valve; Blocked air filters; Dust emission upon filling; damage to safety equipment and; in extreme cases, buckling of the silo. Investigations must be carried out for any of these symptoms, as they are a warning that there is a fault in the silo system. Over-pressurisation poses three main risks:
Silo failure: It may take only a small pressure increase to buckle and weaken the silo and cause it to rupture, or even blow the filter unit off the roof.
Dust pollution: Over-pressurisation often leads to the ejection of cement/ flower/sugar/lime/plastic etc, to the air. Such blow-outs are a common sight, indicative of pressure problems.
Working at height: All silos fed from a road tanker should have safety equipment at the top, making working at height a significant concern. If this equipment can only be tested in situ, this means that silos must be climbed before every delivery to perform a functionality test. Even with correct safety equipment, working at height is very dangerous. We are all trained at working at height and we provide this service to many clients nationwide.
What about overfilling?
There is a common misconception that silos are at the highest risk from overfilling. While this can be problematic, the risks of over-pressurisation are much higher. However, overfilling requires consideration because it contributes to filter blinding, increasing the likelihood of pressure becoming trapped in the vessel.
Preventing over-pressurisation
The complex nature of this application, coupled with the speed at which pressure levels can change, dictate that it is unsafe for a human to control the silo’s pressurisation. We can recommend various silo protection system (SPS) to protect any type of silo.
Recommendations and services we can supply and instal comprises of:
Pressure sensor: The most critical component, the pressure sensor should be mounted at the top of the silo. It is designed to actuate and give a signal to close the inlet valve immediately upon reaching the maximum safe internal pressure. The signal should also trigger an alarm to alert site staff. The sensor should be calibrated so that the pressure alarm is triggered before the pressure release valve (PRV) opens. With the fill valve closed, the driver should also stop the tanker discharge. When the pressure has reduced, the fill can resume in a controlled manner.
High-level sensor: This detects the maximum safe level and instructs the operator to cease filling. It protects the silo against overfilling and filter blinding, which will lead to over-pressurisation. We consider the position of the filling of the silo and the location of the fill pipe, to avoid damage from powder as it is propelled into the container.
We can install new Pressure relief valve (PRV): The PRV is the last line of defence for the silo if the SPS should fail. Under regular operation, it should never open. The PRV should be appropriately sized to handle large volumes of air. It should have the facility to be tested by opening and closing before the fill and to signal to the control panel when it opens. Most crucially, however, is that the valve is calibrated to open at a slightly higher trip point than the pressure switch. If both the PRV and pressure sensor are set to the same pressure, the PRV will constantly open and powder will accumulate on and around the valve. Eventually this will block the PRV and compromise the entire system. We check this as part of our silo survey.
We can install a Shut-off valve:
A comprehensive SPS should include a normally closed shut-off butterfly valve to control inflow from the tanker and to seal off the silo in the event of a pressure event. The inlet valve must be a normally closed unit. In the event of a loss of air pressure or another such issue with the system, it will prevent filling from taking place until the fault is rectified.
We can inspect the cleaning system and filters cartridges and if required install a new silo, Filter.
Filter unit: This must be correctly sized to be able to vent enough air during the filling process. For this reason, it is essential that the self-cleaning mechanism is in good working order and replacement of the filters carried out according to the manufacturer’s guidance. We recommend 6 monthly inspections of the filter cartridges to ensure no blockages and potential damage to the silo.
The most common mistake when putting together an SPS is to assemble systems using a checklist of off-the-shelf general-purpose sensors, which are then often inadequately maintained and cannot correctly be tested. Crucially, they are unlikely to be failsafe and may stop working without warning.
Maintaining the system
We can offer a comprehensive silo servicing routine. Usually, silo servicing comprises a visual inspection with a quick once-over and if dusting is found we will assess why. We will in inspect the filter unit, filter cartridges, silo hatch seal, PRV and explosion relief panel seal. A clear danger which must be addressed before larger more expensive issues arise.
Our silo servicing checks are carried out by our trained, competent engineers. We thoroughly inspect and test all the essential elements and maintain them appropriately. We provide records of the inspections and any action required addressed as soon as it is highlighted. Our actions will help to keep an SPS in optimal working order.
Conclusion
Treating silo safety as a ‘box-ticking exercise’ has put sites at risk. Without monitoring the conditions inside the silo, we can neither control the delivery process nor prevent the risk of over-pressurisation. Given the potential for injuries or even fatalities arising from over-pressurisation, protection using an SPS is vital in all cases.
When installed and maintained correctly, our SPS will be comprehensive, failsafe and tested to ensure that each of the safety components is fully functional. We give all our clients the confident that the risk of a pressure-related issue arising is always under control.
For a quotation on Silo Safety just email or call us on 01427 668061
Silo Safety Lincolnshire
Safety Ladder System for any size silo