Introduction — the air-assist unit in a silo trailer discharge assembly
PHS Magnum supplies parts for silo trailers of various makes — since 1990 we have served mixed fleets in which Spitzer, Feldbinder, Kässbohrer and other European manufacturers’ trailers work side by side. In this category you will find air-assist units for ball valves — the component that decides whether bulk material flows out of the tank evenly and completely.
The air-assist unit is a flow- and discharge-support component. It works together with the product ball valve: it introduces an additional impulse in the outlet zone, so that material with poorer flowability does not hang behind the ball and discharges smoothly. The valve itself opens and closes the channel, but it is the valve + air-assist pair that forms a complete, functioning discharge assembly. For this reason the air-assist unit is always matched to a specific valve — of the same type and size.
For a fleet manager, one simple rule matters most: the air-assist follows the valve, not the trailer make. What counts is the type of valve gear (Prokosch or ZR) and its diameter (DN80 or DN100), not the logo on the vehicle. That is why one well-organised stock of air-assist units can serve an entire multi-brand fleet.
Technical specification
For each of our ball valves we offer air-assist units in DN80 or DN100, for the Prokosch or ZR type.
| Component | Material / value |
|---|---|
| Body | cast iron |
| Seal | Desmopan |
| Ring | steel |
| External seal | NBR |
| Size | DN80 or DN100 |
| Type | Prokosch or ZR |
The material selection reflects the component’s function. The cast-iron body provides mechanical strength in the outlet zone, where the air-assist unit works under pressure and in contact with the medium. The internal Desmopan seal withstands contact with the flowing bulk material, the steel ring stabilises the construction, and the external NBR seal secures the interface between the air-assist unit and the rest of the valve gear.
We also stock complete, ready-to-fit sets consisting of a factory-assembled ball valve and the matching air-assist unit (Prokosch or ZR). This is the solution for fleets where a fast, error-free replacement of the entire assembly matters — factory assembly guarantees a perfect match between both components and shortens installation on the vehicle.
In service, the air-assist unit works in a demanding spot — the outlet zone, where discharge pressure meets abrasive contact with bulk material. The internal Desmopan seal and the external NBR seal wear out most often; the symptoms are reduced air-assist effectiveness (material discharges more slowly or unevenly) or a leak at the interface with the valve gear. Because the air-assist unit and the product ball valve form a single assembly, it pays to look at them together when replacing: a worn air-assist unit next to an overhauled valve is often replaced together with a full ball seal kit, and when in doubt, the safest choice remains a ready-made valve + air-assist set with factory matching. We do not quote invented service-life mileages — the interval depends on the medium, the discharge pressure and the intensity of fleet operation.
Compatibility with silo trailer makes
Because the air-assist unit is selected by ball valve type and size, the same DN80/DN100 range serves silo trailers from various manufacturers fitted with Prokosch or ZR valve gear:
- Spitzer — SF (non-tipping) and SK (tipping) series. The product assembly in both families uses Prokosch/ZR ball valves in DN80 and DN100.
- Feldbinder — EUT (horizontal non-tipping tank) and KIP (tipping pressure silo) series. In multi-chamber versions each outlet has its own valve + air-assist assembly.
- Kässbohrer — K.SSK and K.SSL series. Selection is analogous: by outlet valve type and diameter.
- Other European manufacturers — silo trailers fitted with compatible Prokosch or ZR ball valve gear; we select the air-assist unit based on the valve type and size, regardless of the vehicle make.
A note on terminology: Prokosch and ZR are types of valve gear (valves and air-assist units), not trailer makes. When ordering, state the type and size of the outlet valve — these determine the right air-assist unit.
Warehouse in Chorula
We keep DN80 and DN100 air-assist units for the Prokosch and ZR types, as well as ready-made valve + air-assist sets, in stock at the PHS Magnum warehouse in Chorula near Opole. Located 4 km from the A4 motorway junction, it is a convenient supply point both for domestic fleets and for hauliers running routes across the EU — parts reach the vehicle en route, without a detour.
Instead of stocking a full catalogue, we hold what actually moves in the multi-brand fleets we serve. As a result, typical air-assist configurations and valve + air-assist sets are available quickly, while non-standard items are sourced via direct delivery. Every delivery comes with the appropriate material documentation, and we consult component selection as part of PHS Magnum service.
Specialist portals
We run dedicated parts portals for selected makes, with a catalogue and language versions for the DACH market:
- Spitzer — air-assist units for ball valves on SF/SK silo trailers: spitzer.pl/czesci-zamienne/podmuch-zaworu-kulowego/
- Feldbinder — air-assist units for the EUT/KIP outlet assembly: feldbinder.pl/czesci-zamienne/podmuch-zaworu-kulowego/
For mixed fleets, the full overview of parts categories remains here, on the magnumchorula.pl/en/czesci-zamienne/ hub.
Related categories
- Prokosch product ball valves — aluminium product ball valves, Prokosch type (Typ 420) and ZR, DN80/DN100
- Segment ball valves — segment ball valves for air, ZR type (Typ 500)
- Ball seal kits — ball seal kits (PTFE + NBR) for silo trailer ball valves
- Full catalogue: /en/czesci-zamienne/
Author: Aleksy Pasternak — Managing Partner at PHS Magnum, 20 years in the industry, ISO 9001:2015 internal auditor (DEKRA).
