In Brief
Silo trailer discharge failure is most commonly caused by worn aeration pads (60% of cases), aeration lines blocked by set cement (20%), or a compressor fault (15%). Before calling for service: check the pressure gauge — if the compressor reaches 3+ bar but no material moves, the problem is in the aeration system, not the compressor.
A discharge problem is one of the most costly operational failures — the driver is standing at the customer’s site, time is running, and the material won’t come out. The following is a systematic guide from the simplest cause to the most complex.
Step-by-Step Diagnosis
Check these first
Before any technical diagnosis — a few operational questions:
- Could the material have set hard? Cement and lime set solid inside the tank within hours of moisture contact.
- Is the discharge hose connected to the right nozzle? On multi-chamber trailers, connecting to the wrong chamber is a common mistake.
- Is the pressure gauge reaching working pressure (typically 1.8–2.5 bar)?
No working pressure — compressor
If the pressure gauge doesn’t reach nominal pressure:
- Drive belt — broken or slipped. Visible after removing the guard. Replacement: 30 minutes, inexpensive part.
- Clogged inlet filter — reduces output by 20–40%. Clean or replace.
- Worn piston rings — symptom: oil traces in the air line downstream. Requires compressor disassembly.
Pressure OK but no discharge — aeration system
If the gauge shows correct pressure but discharge is impossible or very slow:
- Blocked aeration pads — cement or lime has glazed the membranes. Rare on new trailers; common on older units with a history of moisture.
- Blocked aeration line — cement has set hard in the pipework supplying air to the chamber.
- Material bridged in the tank — cannot be shifted pneumatically. Requires mechanical breaking from above through the manhole.
Slower-than-normal discharge
- Worn aeration pads — lose permeability gradually. Symptom: a 60-tonne load takes 3 hours to discharge instead of 90 minutes.
- Air-line leak — pressure escaping instead of reaching the chamber. Audible hissing from under the bodywork.
- Pressure regulator out of adjustment — too little pressure to the chamber.
Material left at the chamber floor
- Mechanically damaged pad — membrane perforated or torn, airflow uneven.
- Incorrect chamber pressure — too low for the material. Plastic granules require lower pressure than cement.
Repair
For a breakdown at a customer’s site — call: +48 602 716 551. For simple causes (belt, filter, pressure adjustment) we can often assist by phone or send a mechanic.
For faults requiring a workshop (pad replacement, compressor overhaul, line welding) — come to the service workshop in Chorula or we can arrange vehicle transport.
Mobile silo trailer service A4 — response time 45–110 minutes from Chorula.
Spare parts for most faults held in stock.
Related: Silo trailer service overview · Pneumatic system repair · Silo trailer faults guide · Mobile service A4