Prokosch Bulk-Discharge Ball Valves

Introduction

At the discharge outlet of Feldbinder silo trailers — whether the horizontal, non-tipping EUT with bottom discharge spouts or the tilting pressure silo KIP (Kippsilo) — there is a shut-off valve controlling the flow of bulk material. This is the Prokosch Type 420 bulk-discharge ball valve: aluminium construction, DIN 28460 flange, designed for contact with powdered and granular materials under discharge pressure.

In Feldbinder silo trailers, discharge valves operate under different conditions from air valves: bulk material passes directly through them, so the ball and ball seal must withstand abrasion. This is why the Prokosch design uses a chrome cast-iron ball and a PTFE ball seal — a combination that resists wear whilst ensuring a reliable closed position. On the EUT, these valves terminate each discharge spout; multi-compartment versions have one valve per compartment. On the KIP, the discharge valve shuts off the tilting silo outlet, where the inclined tank assists emptying of low-flow-rate materials — making a positive seal and resistance to 10 bar operationally important for maintaining batch integrity.

PHS Magnum at Chorula near Opole holds stock of Prokosch Type 420 bulk-discharge ball valves in DN80 and DN100. The full parts catalogue is available at /en/spare-parts/; for service scope see magnumchorula.pl/en/service/.

Specifications and Materials

The Prokosch Type 420 bulk-discharge ball valve is an aluminium discharge fitting with a standardised flange connection.

We also offer the Type ZR — a sister design to the Prokosch Type 420 — with a stainless-steel ball, for more demanding bulk materials or hygiene-critical applications.

The choice between an aluminium and a cast-iron body depends on the mechanical load at the discharge point and weight requirements. Aluminium is lighter and more resistant to corrosion in environments where bulk material contains residual moisture; cast iron provides greater mechanical strength. The chrome cast-iron ball combines hardness with abrasion resistance — important because bulk material, not clean air, passes through a discharge valve. The PTFE ball seal gives low operating torque and a reliable shut-off, while the NBR body seal seals the DIN 28460 flanged connection. The Type ZR stainless-steel ball variant extends the application range where chrome cast iron is insufficient.

Sizes and Types

All bulk-discharge ball valves are available in both DN80 and DN100. This applies to the Prokosch Type 420 with chrome cast-iron ball as well as the sister Type ZR with stainless-steel ball.

DN80 and DN100 are the two most common discharge outlet diameters on silo trailers, covering the great majority of EUT and KIP configurations. The DIN 28460 flange ensures that a valve of a given diameter fits the discharge assembly dimensionally and can be replaced without modification. When ordering, please specify DN size, valve type (Prokosch or ZR), and — if you are replacing the air purge at the same time — details of the complete discharge node, so we can supply a matched valve-and-purge set.

Compatibility with Feldbinder Silo Trailers (EUT/KIP)

On the EUT (horizontal, non-tipping tank with pneumatic discharge through bottom spouts), the bulk-discharge ball valve terminates each discharge spout — it opens and shuts off material flow from each compartment. In multi-compartment versions the number of discharge valves matches the number of compartments, and the DIN 28460 flange ensures interchangeability across the assembly.

On the KIP (Kippsilo) — the tilting pressure silo where tank inclination assists the emptying of low-flowability materials — the discharge valve shuts off the silo outlet. Here, a positive seat closure and PTFE ball-seal abrasion resistance are particularly important: the outlet operates under pressure with an inclined, flowing load, and reliable shut-off directly affects batch purity. Selection (DN80 or DN100, DIN 28460 flange standard) is determined by the outlet configuration rather than the trailer type, so the same catalogue serves both EUT and KIP.

Common Issues on Feldbinder Silo Trailers

In service practice, the most frequently encountered problems with bulk-discharge ball valves on Feldbinder trailers are:

• Abrasive wear on the ball and seat — bulk material wears the chrome cast-iron ball surface and the PTFE seal; symptoms are leakage past the closed valve.
• NBR body seal failure — hardened or compressed body seal; a straightforward replacement item.
• High ball-operating torque — material deposits or dried residue preventing full rotation; valve typically returns to normal service after cleaning.
• Material compatibility selection — for demanding or hygiene-critical media, the Type ZR with stainless-steel ball is the appropriate choice; in food-grade Feldbinder nodes, chemically resistant seals (e.g. Viton where suited to the specific design) are used alongside the standard DIN 28460 flange.

Diagnosis starts with a leak-tightness check in the closed position and a ball-rotation test. A ball or seat worn beyond the regeneration threshold requires valve replacement; minor leakage issues can typically be resolved by seal replacement.

Availability and Delivery

• Stock at Chorula near Opole: Prokosch Type 420 bulk-discharge ball valves in DN80 and DN100 — standard positions available from stock.
• 24–48 h: most standard positions.
• Direct delivery lead time: Type ZR stainless-steel ball variants and non-standard configurations.
• Shipping: courier (PL), GLS/DHL (DACH and wider EU), EU VAT invoice.

Every delivery is accompanied by a material certificate. Valve and ball-material selection support is provided as part of PHS Magnum service.

Related Categories

• Ball Valve Air Purge
• Type ZR Segmented Ball Valves
• Ball Seals
• PTFE Ball Valves
• Full catalogue: /en/spare-parts/

See also: This category in the full PHS Magnum network catalogue (all makes) →

Author: Aleksy Pasternak — Managing Partner PHS Magnum, 20 years in the industry, internal ISO 9001:2015 auditor (DEKRA).