Preventing problems with dry and powdered materials at silos

What you must do

If you transfer powdered materials to storage silos using compressed air as a carrier medium, you must be careful that the silo does not become pressurised. If the silo becomes over-pressurised, it can rupture, or it can blow out the filter unit from that silo.

Any material that spills from a silo could cause pollution, particularly if it enters surface water drains or watercourses. Report pollution incidents as soon as they happen to the UK wide emergency hotline on 0800 80 70 60.

Excessive pressure can be caused by:

too much pressure in the air delivered from the tanker
using a filter in the silo that is too small for the flow of air through the silo or
using the wrong size of filter for the size of the silo.

Good practice

To reduce the risk of silo rupture:

avoid delivering materials to silos at a rate that will result in pressurisation, especially towards the end of the delivery when the amount of material entering the ducting is getting smaller and the air flow is increasing
calculate the correct filter size; it must match the rate that air flows through the silo
regularly clean filter systems to prevent blockages and prevent the accumulation of powder in the filter system
visually check for emissions during all deliveries
fit all new silos with an automatic system cut-off in the event of pressurisation or overfilling
regularly inspect plant and equipment, including transfer line connections, pressure relief valves and safety systems.

During all bulk deliveries, watch silo inlet connections and the silo arrestment plant to check for emissions.

Keep a record of the type of material being delivered, and the start and finish times of all deliveries to help trace the cause of any incidents.

Where your supplier uses a road vehicle to deliver material to silos, where possible this should be a tanker with an onboard (truck mounted) relief valve and filtration.

Fit alarms or volume indicators on bulk storage tanks and silos that contain dry materials to warn of overfilling.