Overview
Ball valves are among the most heavily loaded components in the discharge system of Feldbinder silo trailers. In the horizontal, non-tipping EUT line, the ball valve controls material flow from the bottom outlets during fully pneumatic discharge, where the ball operates under working pressure and is continuously swept by a stream of granulate or bulk cement. In the hydraulically tilting KIP silo, the same valve type is used during discharge assisted by hydraulic tank lift — and here too, the sealing condition of the ball seats, rather than the ball itself, determines whether the valve holds.
The service life of a ball valve is not determined by the metal body or the ball, but by the seals. The kit consists of the PTFE seat rings on which the ball rotates and the NBR O-rings that seal the valve body. After hundreds of discharge cycles, the PTFE rings wear through contact with bulk material, and the NBR O-rings gradually lose their elasticity. The result is always the same: the valve either begins to leak or becomes stiff to operate. In PHS Magnum’s silo trailer service experience, this is one of the most frequent causes of leakage in Feldbinder discharge pipework — and one of the most cost-effective to remedy, because replacing the seal kit rather than the entire valve restores full function at a fraction of the cost.
It is worth distinguishing between valve replacement and valve rebuild. A complete ball valve assembly comprises the body, the ball, and the seal kit. Of these three elements, the seals wear first, while the body and ball in Feldbinder silo trailers typically withstand multiple rebuild cycles. Routine ball valve servicing therefore most commonly involves disassembly, cleaning of the seat, inspection of the ball surface, and fitting a new set of PTFE rings and NBR O-rings. Carried out in good time, this prevents a leaking valve from halting a discharge operation on the customer’s premises.
We hold seal kit stock in Chorula near Opole, covering the bore sizes standard to Feldbinder ball valves.
Specification and Materials
A ball valve seal kit comprises a fixed set of components:
| Component | Qty per kit | Material | Function |
|---|---|---|---|
| PTFE seat ring | 2 | PTFE (polytetrafluoroethylene) | Ball seats; sealing at the working surface |
| O-ring | 2 | NBR | Valve body sealing |
The PTFE seat rings form the seats in which the ball rotates; they are responsible for sealing and low rotational resistance. The NBR O-rings seal the body joints. The entire kit is replaced as a unit to restore original valve integrity.
Sizes and Types
Seal kits are available in bore sizes corresponding to the standard Feldbinder ball valves:
- DN80
- DN100
These are the sizes found in the discharge pipework of Feldbinder silo trailers. The correct kit is determined solely by the valve bore. DN80 applies to valves on the narrower sections of the material path; DN100 covers the main discharge ports. When ordering, simply state the valve bore — there is no need to send in the complete valve, as the kit configuration (2× PTFE ring + 2× NBR O-ring) is fixed for a given size.
Compatibility with Feldbinder Silo Trailers (EUT/KIP)
- EUT — ball valves in the horizontal non-tipping silo trailer regulate material flow during pneumatic discharge. The DN80/DN100 seal kit is selected to match the valve bore fitted to the trailer.
- KIP — in the tilting silo, the same ball valves are used during hydraulically assisted discharge; the integrity of the PTFE seat is critical here, as material flows under pressure while the tank is raised.
Since the seal kit is fitted inside the ball valve, compatibility depends on bore size (DN80/DN100), not on the Feldbinder trailer type.
Common Failure Modes in Feldbinder Silo Trailers
From our silo trailer service experience:
- Valve leaking in the closed position — worn PTFE seat rings no longer form a tight seat; material seeps through even with the ball fully closed.
- Stiff or seized ball rotation — contamination of the seat with bulk material, or swelling/deformation of the PTFE rings.
- Leakage at the valve body — NBR O-rings have lost elasticity; presents as dust leakage or seepage at body joints.
- Accelerated seat wear with abrasive materials — when carrying sharp-grained bulk material, PTFE rings wear faster; in such applications, seal kit replacement becomes part of the routine service interval.
Where valve specifications permit, Feldbinder silo trailer ball valves can be fitted with more chemically or thermally resistant elastomers (e.g. Viton-grade for elevated temperatures or aggressive media) — compatibility is confirmed case by case. The standard specification for the kit described here remains PTFE + NBR.
A common operating error is attempting to re-seal a leaking valve by overtightening rather than replacing the seats. With worn PTFE rings, increasing clamping force does not restore sealing — it merely raises rotational resistance and accelerates wear. The correct response to a leaking ball valve is disassembly and fitting of a new seal kit. This is a brief operation, and in Feldbinder silo trailers it avoids the considerably higher cost of a complete ball valve replacement.
Availability and Delivery
We hold ball valve seal kit stock at Chorula near Opole (4 km from the A4 motorway, approximately 180 km from the German border). DN80 and DN100 kits are normally available off the shelf.
Delivery by courier within Poland and across the EU; kits can be combined with other ball valve component orders. For availability and pricing — ask for a quote. Ball valve rebuilds including seal kit replacement are also carried out within PHS Magnum silo trailer service, including during TDT inspections.
Related Categories
- PTFE Ball Valves — ball valves with PTFE seats for discharge pipework.
- Segmented Ball Valves — segmented ball valves for Feldbinder silo trailers.
- Ball Valve Blow-Through — purge element for ball valves in the discharge system.
- Prokosch Bulk Ball Valves — Prokosch-system bulk ball valves.
- See also: spare parts catalogue, PHS Magnum silo trailer service, pasternak.me.
See also: This category in the full PHS Magnum parts catalogue (all makes) →
Author: Aleksy Pasternak — Managing Partner PHS Magnum, 20 years in the industry, ISO 9001:2015 internal auditor (DEKRA).
