Features / Benefits

• Capacities up to 1000 m³/h
• Range of self priming arrangements
• Pressures up to 300 bar 
• Medium viscosities up to 8,000 cP (mPas)
• Extreme abrasiveness
• High corrosiveness
• Elevated temperature
• Up to 8mm particle size
• Up to 75% solids content

The principal difference between a piston and a piston diaphragm pump is the genuine diaphragm that protects the piston and liner from the sliding contact with the abrasive slurry. The diaphragm is a pre-moulded design that eliminates elongation of the elastomer. Its long fatigue life allows for routine annual maintenance to be carried out. The diaphragm position is controlled in either direction of the stroke by adding or removing propelling fluid that fills the cavity between the piston and diaphragm. A guide rod connects to an insert and enables the position control. A number of duty related elements cause the diaphragm not to flex uniformly.

After quantifying the disturbing elements and empiric validation of the equations, we reliably select from the range of eight diaphragm sizes. The only wear parts in the pump are the suction and discharge poppet valves. Various slurries require a different valve design and a unique combination of metal and elastomer components. These may be altered in operation as a result of a life cycle cost analysis.

A dampener with nitrogen precharged bladder reduces the pressure variation at the discharge flange for flow and acceleration induced pressure disturbances. The dampener volume is contingent upon the pump variables, the service and the residual pressure variation specified. A suction dampener or air vessel may serve to increase the Net Positive Suction Head (NPSH) available or for charge pump convenience. Weir Minerals Netherlands builds a complete range of GEHO® double acting (ZPM) and single-acting (TZPM) piston diaphragm pumps.

We select either type based on objective technical and commercial considerations. The modular design enables combinations of various sizes of power end, piston, diaphragm, valve, etc. The proprietary selection guidelines (for example rod load, stroke rate, diaphragm load and valve velocity) evolve from technological development backed up by an unmatched performance track record. Corrosive slurry carrier fluids may dictate the use of duplex, super duplex and Titanium material for the wetted pump components. Linings can be used as a precaution against microbiologically induced corrosion and high slurry abrasiveness.
The emphasis on the design and production of the high pressure water end components and bolted joints, in particular the diaphragm housing with diaphragm clamping rim, is on the avoidance of fatigue and stress corrosion due to the oscillating pressure. Weir Minerals Netherlands has researched and validated a design code and selectively applies hydraulic stud tensioning, cold rolling and ‘auto-frettage’.

GEHO® has built and has in operation the largest power end in the world for driving piston diaphragm pumps. Reliability requires the use of a forged steel crankshaft, in our selection direct driven, purpose built preloaded connecting rod bearings, hydraulic piston rod connections and a nodular cast iron frame, eliminating welds. These pumps afford full pressure operation at five strokes per minute for pipeline unblocking. A supervisory control panel with plc performs all logic, sequencing and alarm raising functions. The Gehographics® display allows the operator complete interaction with the pump and facilitates communication protocols.