In Brief
TDT inspection cycle: every 2 years (external); full pressure test every 6 years. Silo trailers lose their TDT immediately if: the safety valve fails the pressure test, weld cracks are found in the tank wall, manometers are expired, or hatch seals leak beyond tolerance. Polish TDT certificates are valid across the EU (PED 2014/68/EU). PHS Magnum prepares trailers for TDT inspection and coordinates the TDT inspector visit, typically in 2–5 working days.
In Poland, every silo trailer operating as a pressure vessel must hold a valid TDT (Technical Inspection Office) certificate. Without it, the trailer is legally barred from carrying pressurised loads. Here is a clear breakdown of when certification expires and what can trigger immediate suspension.
Standard Inspection Intervals
TDT inspections for silo trailers fall into two categories:
| Inspection type | Frequency |
|---|---|
| Periodic technical inspection | Every 2 years |
| Detailed (full) inspection | Every 6 years |
The periodic inspection covers external condition, aeration system function, pressure safety devices and documentation review. The detailed inspection additionally includes internal examination of the tank, weld testing and thickness measurements.
What Triggers Immediate Loss of Certification
Certification can be suspended outside the regular cycle when:
- Accident or impact damage — any incident that could have affected tank integrity requires re-inspection before the trailer returns to service.
- Unauthorised repairs — welding or structural repair carried out without TDT-qualified personnel and documentation invalidates the certificate.
- Modification of the pressure system — changing the compressor rating, adding or removing aeration zones, or replacing the pressure relief valve with a non-approved unit.
- Expired documentation — if the TDT certificate lapses even by one day, the trailer must not operate under pressure until recertified.
Common Compliance Failures
Many operators are caught out by:
- Overlooking the calendar: the TDT plate shows the inspection date, not the expiry date. Inspection intervals run from the date of the last inspection, not from 1 January.
- Incomplete records: missing repair logs, unsigned aeration service sheets or absent compressor service history can cause an inspector to withhold certification.
- Used trailer purchases: a second-hand trailer’s certification history must be fully verified. Previous owners may have carried out repairs that are not in the documentation.
How PHS Magnum Helps
Our TDT department handles the complete process: pre-inspection service, submission of documents to the TDT inspector, and presence during the inspection itself. We also maintain a library of technical documentation for Spitzer, Feldbinder and Kassbohrer trailers, which simplifies the paperwork significantly.
For trailers that fail their inspection, we perform the required repairs and arrange a follow-up inspection, minimising the time the trailer is off the road.
Related: TDT inspections · Failed TDT – what to do · Silo trailer service
