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 fully test its operation. Coupled with this, the risks staff members would be exposed to by having to regularly climb to the top of high silos are both self-evident and onerous. This has led to silo-top safety equipment maintenance being largely ignored.
Hycontrol’s silo protection systems are the first to eliminate working-at-height risks with the introduction of complete ground-level test (GLT) capability, enabling all essential safety components (including the pressure relief valve and pressure sensor) to be checked before each and every fill. The entire system is checked in just six seconds and functionality must be confirmed before allowing the fill. 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 but has often been ignored by staff as it is time consuming, or it has not been practical in the past. 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.
As part of the GLT, the air supply to the filters is checked before every delivery 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 operating correctly utilises the same air supply as the filters and cannot be performed if there is no supply. This is important because if the air compressors have not been turned on this 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 each and every delivery. This means that operators know their equipment is functioning correctly before infilling begins, and 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; avoid incurring clean-up expenses.
Most importantly, this system will reduce maintenance levels significantly and provide a safer working environment for site operators.
To ensure your over-pressurisation safety system is fully operational it must be regularly tested!