A mechanism, not a single bolt
The rear hatch closes off the rear section of a silo trailer’s tank. Unlike the top filling hatch, which is clamped with a simple wing bolt, the rear hatch on tipping silos is operated by a complete locking mechanism. The reason is structural: on a trailer with a hydraulically raised tank, the rear manhole must stay tight not only in the transport position but also when the silo is tilted during discharge. A single tightened bolt cannot guarantee that — an assembly is needed that maintains clamping force regardless of position and vibration.
The system we offer comes from the tipping silo solution in the Spitzer-Feldbinder configuration and is described as universal — the same set serves the related designs of both brands. PHS Magnum keeps complete locking systems in stock in Chorula near Opole, so a worn mechanism can be rebuilt in full or only the weakened component replaced, without waiting for a delivery from abroad.
System specification
The system consists of three components working together. Each has a specific material matched to its function.
| Component | Material | Parameter |
|---|---|---|
| Handle | Galvanised steel | M20 thread |
| Cross eye bolt for the handle | Galvanised steel | M20x110, 18 mm eye |
| Spring for the eye bolt | Stainless steel | — |
The handle and the cross eye bolt transmit the clamping force, so galvanised steel — combining strength with resistance to road corrosion — is sufficient for them. The spring works cyclically under flexing and is the component that most often suffers fatigue — hence the stainless steel execution, which improves its durability and corrosion resistance. It is worth noting that the M20 thread and the 18 mm eye are shared with the wing bolts of the filling hatches, which makes it easier to keep a consistent hardware range within one fleet.
Brand compatibility
The system is described as universal for the Spitzer-Feldbinder tipping silo, which translates into specific designs from both brands.
- Spitzer (SF/SK) — the tipping silo is the hydraulically raised, tippable tank corresponding to the SK series; the rear hatch is closed by the handle mechanism with the M20x110 cross eye bolt and the spring.
- Feldbinder (EUT/KIP) — the system applies directly to the raised-silo design, i.e. the KIP line (Kippsilo), where the tank tilts during discharge; for the rear hatch of a given trailer we confirm the match based on dimensions.
The universal nature of the set means the same kit serves both brands. When ordering, it helps to state whether you need the whole system or an individual component, and to give the trailer’s brand and type so we can confirm the fit to the specific hatch.
When to replace — signals from operation
The rear hatch locking mechanism wears at the points that work through every tank-emptying cycle. Whether we are servicing Spitzer’s SK series or Feldbinder’s KIP line, similar symptoms indicate replacement of a component or the whole set:
- Weakened or broken spring — the handle does not return to the working position and does not maintain clamping force; despite the stainless steel, the component wears through fatigue and is the one replaced most often.
- Worn M20 thread on the cross eye bolt — the bolt no longer holds the clamping force and the rear hatch stops closing tightly.
- Corroded or damaged 18 mm eye — makes operation difficult and risks breaking when clamping.
- Damaged or loose handle — the operator cannot close the rear manhole properly.
Because the three components act as a single assembly, replacing one weakened item is often enough to restore the reliability of the whole closure. During service it is worth checking the condition of the rear hatch gasket at the same time — the locking mechanism and the seal work together to keep the manhole tight and should be assessed jointly.
Chorula warehouse
We keep complete locking systems — the handle (M20), the cross eye bolt (M20x110, 18 mm eye) and the stainless steel spring — in stock at the warehouse in Chorula near Opole (4 km from the A4 motorway, approx. 180 km from the German border). The components are available as a set or individually; the most frequently replaced single item is the spring. Warehouse processes are run under an ISO 9001:2015 quality management system, and the location by the motorway and close to the DACH border shortens delivery times both domestically and to customers in Germany, Austria and Switzerland.
Matching is geared towards multi-brand fleets — a locking set can go out in a single shipment together with rear hatch gaskets and other hardware. For a set — ask for a quote. Warehouse contact: +48 604 800 869, magazyn@magnumchorula.pl.
Specialist portals
We describe the locking system in the context of a specific brand on our dedicated portals: Spitzer and Feldbinder — there we cover the mechanism in the context of the SK series and the KIP line.
Related categories
- Rear hatch gaskets — the sealing element working together with the locking system to keep the rear manhole tight.
- Filling hatch wing bolts — complete M20 wing bolts for the top filling hatches.
- Filling hatch cover gaskets — gaskets for the top filling manholes of many brands.
- Feldbinder parts — parts for the EUT and KIP lines.
Author: Aleksy Pasternak — Managing Partner at PHS Magnum, 20 years in the industry, internal auditor ISO 9001:2015 (DEKRA).
