MPA (Mineral Products Association) guidelines state that pressure relief valves (PRVs) should be tested to ensure they will operate at the correct pressure. Historically this has not been possible unless the PRV were to be removed from the silo, which has never been practical. The same has been true of the critical pressure sensor - without removing it from the silo it could not have been tested, so it was never deemed practicable to test its operation fully. Additionally, staff members would be exposed to additional risks through having to climb to the top of high silos regularly. This combination of problems has led to silo-top safety equipment maintenance largely being ignored.
The entire system is reviewed in just six seconds, and functionality must be confirmed before allowing filling. If any component is not functioning correctly, the system will alert the user, and the valve will not open – it’s that simple.
Testing is an essential part of a maintenance programme. Still, it has often been ignored by staff as it is time-consuming, or it has not been practical in the past to test properly. With a GLT-based Hycontrol silo protection system, a silo cannot be filled without a full test operation. Testing of the safety equipment is strongly recommended in the latest MPA guidelines to prevent over-pressurisation of silos during the delivery of powders.
During the GLT, the filter air supply is checked and will not pass as ‘OK to fill’ if the filter air is not switched on. The test used to confirm that the pressure sensor and pressure relief valve are both correctly operating utilises the same air supply as the filters. If there is no air supply, the tests cannot be performed. This is an important check - if the air compressor is off, it can lead to the development of over-pressurisation. This function is controlled automatically by the Hycontrol silo protection auto shut-off system.
The pressure sensor, level sensor and pressure relief valve all have to pass a function test before every delivery. As a result, operators know their equipment is correctly functioning before infilling begins. They also know that it will alarm as required at any pressure or level issues that arise during the fill.
The combination of tests described above will:
• Eliminate filter damage by protecting and monitoring the pressure within the silo
• Reduce product loss through overfills and wastage and avoid incurring clean up expenses
Most importantly, this system will reduce maintenance levels significantly and provide a safer working environment for site operators. Your over-pressurisation safety system must be tested regularly to ensure it is fully operational.