A recent Hycontrol service call-out has highlighted the vital role that a fully-testable Silo Protection System plays in spotting maintenance issues before they become major problems. The call-out came from a concrete block plant in Lancashire. The site was already using Hycontrol’s SPS on the cement silo, and had also replaced the dust filter unit a few months previously as part of their regular service routine. However, whilst the safety equipment was passing the pre-delivery tests, during filling the pressure alarm was triggering regularly according to the system logged data.
Naturally, the site safety manager was concerned by this, presuming the filter was OK as it had recently been changed. Hycontrol were asked to investigate the issue. The system was found to be in good working order, with the pressure sensor operating within the correct range and the PRV opening and closing correctly during the test cycle. This indicated to the diagnostic engineers that the safety system was not at fault, pointing instead to an issue with pressure exiting the silo system.
Upon investigating the condition of the filter, the engineers discovered that the diagnostic information from the Silo Protection System was correct. One of the solenoid valves controlling air-flow to the reverse jet cleaning nozzles over the filter cartridges had failed. Three of the units’ seven cartridges were not receiving any air-flow during the filter self-cleaning process and were now totally blocked with product (see photographs below). This meant a 43% reduction in air-flow out of the unit. As a result, trapped air was building up inside the silo, triggering the SPS over-pressurisation shut-down in order to prevent disaster!
From the images above and below, it is easy to identify how the central row of filter cartridges had become severely blocked compared to the neighbouring cartridges which were still receiving the cleaning air-jets (see image below). By the systems’ log of over-pressurisation events, service engineers were able to quickly pinpoint the issue with the filter vent unit and rectify it before it became a major problem for the site.
This example highlights that, even on a site with a regular maintenance schedule that replaced the filter cartridges only weeks before, a potentially disastrous situation can quickly emerge. A regularly tested safety system is essential when a problem as seemingly simple as blocked filters can rapidly deteriorate into a potentially dangerous over-pressurisation situation.
For further case studies, photos and silo advice, please visit www.siloprotection.com