I never like the words “no go” !
There is always an answer.
However, our current product range for Chemical dry pumps with flameproof electrics has the modern “intelligent on board control” CXS range in 160 and 250 sizes only. The next screw pump in the range is the CDX1000 at 1000 m3/h.
Alternatives are the vertically mounted claw type EDP series, available in 80, 160, 250 and 400 sizes, the latter of which is similar in performance to the CPH they have. But not easy to configure, as there are two stages of boosters upstream and plenty of plumbing…
In some ways, a “proper” overhaul of the CPH400 might be an alternative. We don’t know just what has been tried up to now, but if it is just replacing seals and bearings then it is possible the rotor/stator clearances are now excessive, both radially and axially, as well as wear in the piston rings between the stages, all allowing more gas leakage and worse performance. A major rebuild with new claws and slices where needed, would restore the performance to new condition. It would not be cheap for a repair, but probably similar cost to investing in a new pump.
Some of the main differences we have to consider when rebuilding a CPH pump are the detail design mods from the “donor” GV400, including those pasted below :
2 Differences between Chemical CPH Pump and GV Pump
The CPH pump is mounted horizontally like the GV pumps.
There are two sizes the CPH250 and CPH400, with CPH400 having a 50 and a 60Hz variant.
The pump can only be directly cooled at this time. Water cooling runs in the reverse direction to the GV pumps.
There is no clutch in the motor coupling.
The pump will be fitted with a flameproof motor.
A LV bearing purge is required and a PT100 to monitor the cooling water temperature.
The Inlet and Outlet flanges are ANSI style.
The pump has ATEX approval to T4.
The PRV is the same as used on the DP pumps. (PTFE bushes and Chemraz O ring)
Internal Lip Seals are the same as GV pumps (PTFE lip seals).
The customer supplied water should be clean and free from debris.
C. This is done to prevent salt deposits inside the pump cooling jacket.The TCV controls the pump temperatures. This is fixed at 50
Shaft seal purge flow is Nitrogen (typically 22 litres/m) and the pressure should be set to 0.3bar above the CPH exhaust pressure.
This purge is considered essential for reliable pump operation.
C. This does not provide a warning.C above the pump case temperature. E.g. on direct cooled pumps this is 65A PT100 is fitted and should be set to trip 15
The only realistic alternative is to offer our EDP400 pumps to fit alongside the existing systems. Approx dimensions are shown below