Introduction
The rear hatch is the access cover that seals the rear of a silo trailer tank. On Spitzer SF and SK series silo trailers, a reliable airtight closure is essential for maintaining the working pressure in the pneumatic aeration system and for keeping the transported PE/PP granulate or bulk material free from contamination. A leaking rear hatch means pressure loss, prolonged discharge and the risk of load contamination. The closing mechanism — a handle assembly with a clamping bolt — is operated by the driver manually at every discharge cycle.
The rear hatch closing system we supply comes from the tipping silo configuration used in the Spitzer-Feldbinder design. A tipping silo is a hydraulically raised tank — a design that corresponds to the Spitzer SK series, in which the tank tilts upward during discharge. PHS Magnum holds complete rear hatch closing systems in stock at our facility in Chorula near Opole, meaning a worn or damaged mechanism can be replaced in full or component by component, without waiting for delivery from abroad.
Specifications and materials
The rear hatch closing system is a complete, universal assembly of three cooperating components. Each has defined specifications and a material chosen for its role.
| Component | Material | Specification |
|---|---|---|
| Handle | Galvanised steel | M20 thread |
| Eye-cross bolt for handle | Galvanised steel | M20x110, 18 mm eye |
| Spring for eye bolt | Stainless steel | — |
The choice of materials reflects the function of each component. The handle and eye-cross bolt are made from galvanised steel, combining mechanical strength with corrosion resistance — these are the force-transmitting elements. The spring for the eye bolt is made from stainless steel; it operates under cyclic loading with every closing cycle, so enhanced corrosion resistance and fatigue resistance are critical to the longevity of the complete mechanism.
Dimensions and variants
The rear hatch closing system is based on an M20 thread, consistent with the hatch hardware used on the same class of trailers. The full specifications of the kit are set out below.
| Component | Thread / size | Eye | Material |
|---|---|---|---|
| Handle | M20 | — | Galvanised steel |
| Eye-cross bolt | M20x110 | 18 mm | Galvanised steel |
| Spring | — | — | Stainless steel |
The handle and eye-cross bolt share an M20 thread, and the bolt eye is 18 mm — the same as the butterfly bolts used on fill hatches, which simplifies maintaining a consistent hardware inventory across a mixed fleet. The system is universal: it is described as a solution for the Spitzer-Feldbinder tipping silo and is not limited to a single trailer variant. Components are available as a complete set or individually, depending on which part requires replacement.
Compatibility with Spitzer silo trailers (SF/SK)
The rear hatch closing system originates from the Spitzer-Feldbinder configuration for the tipping silo. Since a tipping silo is a hydraulically raised tank, this design applies to the Spitzer SK series, in which the tank is lifted during discharge. On Spitzer SF/SK trailers, the rear hatch is secured by a handle mechanism with an M20x110 eye-cross bolt and spring — precisely the assembly we hold in stock.
PHS Magnum services both Spitzer silo trailers and related Feldbinder designs; the universal nature of this closing system means the same set of components covers both brands. When ordering, please indicate whether you require the complete system or an individual component (handle, eye-cross bolt or spring), and provide the make and type of trailer so we can confirm the fit for your specific hatch.
Common failure points
In service practice, the rear hatch closing mechanism wears at the points subject to load at every tank discharge cycle. Typical symptoms that indicate a component or complete kit replacement is needed include:
- Weakened or broken spring — the handle fails to return to the working position and no longer maintains clamping force; despite being made from stainless steel, the spring is subject to fatigue wear.
- Worn M20 thread on the eye-cross bolt — the bolt cannot hold the required clamping pressure, and the rear hatch no longer closes securely.
- Corroded or damaged 18 mm eye — makes operation difficult and creates a risk of fracture under clamping load.
- Damaged or loose handle — the driver is unable to close the rear hatch correctly.
The remedy is to replace the worn component with its original equivalent from the kit, or to renew the complete closing system. When replacing, it is worth simultaneously inspecting the rear hatch seal — the closing mechanism and the sealing work together to maintain hatch integrity.
Availability and delivery
The complete rear hatch closing system — handle (galvanised steel, M20), eye-cross bolt (galvanised steel, M20x110, 18 mm eye) and spring (stainless steel) — is held in stock at our facility in Chorula near Opole. Components are available as a complete set or individually. We ship by courier throughout Poland and to DACH countries (Germany, Austria, Switzerland).
To identify the right kit, please provide the make and type of silo trailer and indicate whether you need the complete system or a single component. For details and a tailored quote, request a quote.
Related categories
- Fill hatch bolts — complete butterfly bolts for the upper fill hatches of Spitzer, Feldbinder and Kässbohrer silo trailers.
- Rear hatch seals — seals that work in conjunction with the closing system to maintain rear hatch integrity.
- Fill hatch seals — seals for the upper fill hatches of Spitzer, Feldbinder and Kässbohrer silo trailers.
- Spitzer SF and SK parts — overview of wear and structural parts for the SF and SK series.
- All spare parts — full catalogue of silo trailer parts held in stock at PHS Magnum.
- Silo trailer service — PHS Magnum — overhauls, repairs and specialist silo trailer servicing.
- pasternak.me — expert portal covering trailer service, transloading and bulk material transport.
See also: This category in the full PHS Magnum network catalogue (all brands) →
Author: Aleksy Pasternak — Managing Partner, PHS Magnum, 20 years in the industry, ISO 9001:2015 internal auditor (DEKRA).
