Rainman WM Series User manual

WM and WMR Series
High Pressure Pump Service
Rainman Technology Pty Ltd
#17 / 10-18 Orchard Road
Brookvale, NSW 2100
Australia
www.rainmandesal.com
[email protected]
[phone]
Version 1.1

Table of Contents
Pump Description 1
Routine Pump Maintenance 2
Oil Change 2
Preventing Cavitation 2
Replacing the Valves 3
Overview 3
Procedure 4
Replacing the Packings 6
Overview 6
Procedure 7
Setting Relief Valve 12
Troubleshooting 14
Maintenance Log 15

High Pressure Pump Servicing Instructions – Page 1
Pump Description
The high pressure pump is the heart of your Rainman watermaker. It creates the high pressure required for
the reverse osmosis membranes to extract the fresh water from seawater. We use the best quality piston
pump from General Pump, an American subsidiary of Interpump Group in Italy. Although it is a very simple
and highly reliable pump, basic maintenance is required to maximise its performance and life span. Many
customers may never need to read beyond the Routine Pump Maintenance section of this manual. However,
the rest of this manual is included to assist those that may need to perform greater levels of maintenance on
more heavily used systems.
Depending on which Rainman watermaker model you own, there will be one of two different high pressure
pumps in your system. If you have the older Mk1 electric (either AC or 12VDC) manufactured through
January 2019, or any petrol (gasoline) model, your system will have a General Pump WM Series pump. If you
own an electric (AC or 12VDC) Mk2 system, manufactured after February 2019, your system will have a
General Pump WMR Series pump.
The internals of both pumps are almost identical with only minor changes that are mostly in the manifold
(stainless steel section of the pump). The photos and exploded diagrams in this document are for the WMR,
but are almost the same for the WM pumps. All procedures described in this document apply equally to the
WM and WMR pumps.
General Pump WM Series (left) and WMR Series (right) high pressure pumps

High Pressure Pump Servicing Instructions – Page 2
Exploded view of WMR series pump showing pistons and manifold
Routine Pump Maintenance
Very little routine maintenance is required on your General Pump high pressure pump. Required
maintenance is in your operations manual, but is also included here for completeness of this document.
Oil Change
When replacing the oil in the pump, use SAE-30 weight oil. General Pump generally recommends an oil
change after the first 50 hours, then after each 300 hours of use thereafter. These pumps are designed for
significantly higher operating pressure and flow rates, so the oil break down is slower than normal operation
for this design. As such, it is not critical to maintain high discipline on this oil change schedule.
The method to change oil in your pump is outlined in the watermaker operations manual.
Preventing Cavitation
The most important maintenance required to maximise the life of your pump is to prevent pump cavitation.
Symptoms of cavitation include extra noise, high pressure hose vibration, and significant pressure
fluctuation. Causes are anything that restricts flow to the pump. The watermaker operations manual covers
more detail, but the two most frequent causes are not changing the prefilter or lift pump impeller frequently
enough.
Extended cavitation will prematurely wear the packings.

High Pressure Pump Servicing Instructions – Page 3
Replacing the Valves
Overview
Each of the three cylinders in the pump has two spring loaded one way valves. One valve allows water to be
pushed into the cylinder by the lift pump as the piston retracts. The second valve opens as the piston forces
the water under high pressure through the manifold. O-rings are used to seal around the valves.
Only one valve kit (RM01) is necessary to replace all the valves in the pump. The kit includes new O-rings and
valve assemblies.
Exploded view of WMR series manifold, showing valve configuration

High Pressure Pump Servicing Instructions – Page 4
Procedure
1. Using a 22mm spanner or socket, remove the valve cap. Examine threads and O-ring. Replace O-ring
(item 1) if there is any evidence of cuts, abrasions, distortion or wear.
2. Remove valve assembly (item 2) from valve cavity.
3. Remove valve seat O-ring (item 3) from valve cavity.
4. Inspect manifold for wear or damage.
5. Install new O-ring (item 3) in valve seat cavity.

High Pressure Pump Servicing Instructions – Page 5
6. Insert valve assembly (item 2) into valve cap as
shown.
7. Coat the threads of the valve cap with anti-seize
grease (such as Renolit ST-80) and reinstall valve cap.
Torque to 40 Nm (30 Ft-Lbs).

High Pressure Pump Servicing Instructions – Page 6
Replacing the Packings
Overview
The purpose of the packings is to allow the pump to push water through at high pressure while also
preventing it from leaking out of the pump along the pistons. The hard high pressure seals contain the
pressure within the manifold of the pump, but some moisture slides out with the piston on each stroke. The
softer low pressure seals then prevent the water from leaking out of the pump. Normal symptoms of worn
packings is water dripping from the weep holes underneath the pump.
General Pump WMR packing kit

High Pressure Pump Servicing Instructions – Page 7
In the photo to the right are the following seals from top to
bottom:
• Low pressure seal (item 2 in diagram).This is the one
with stainless steel spring visible inside .
• Stainless ring case (item 4 in diagram) with O-ring
(item 3). Ensure O-ring is on the case, and is sitting in
the correct groove as per photo to the right (the one
without holes). If O-rings in the kit came separated
from steel casing put them on before proceeding
• Glyd high pressure seal, (item 5 in diagram).
• Square high pressure seal, (item 6 in diagram).
Procedure
1. Remove head bolts using a 5mm Allen key and slide manifold away from the crankcase. Remove it as
straight as possible so as not to stress the plungers or rods inside the power end of the pump. It is
normal for some packing assemblies to remain on the plungers. It may be necessary to rotate the
crankshaft and/or use pry bars to separate manifold from crankcase.
2. Remove the low pressure seals (item 2) using your
fingers. Take careful note of which way seals were
facing in order to correctly insert the new seal later.

High Pressure Pump Servicing Instructions – Page 8
3. Remove the stainless steel case (item 3 / 4) where low pressure seals (item 2) were installed. Tightness
of stainless casings varies from pump to pump. It may be possible to remove the rings by inserting a
finger and pulling outwards. If more force is necessary, use a 17-18mm diameter object (such as a
blind bearing puller or screwdriver handle) and gently pull them out with a slight rocking motion. Since
they are being replaced, damage to the old packings is inconsequential. Important: take care not to
score or mark the manifold's machined surfaces.
4. Remove high pressure seals (item 5 / 6) using your
finger by gently pulling them upwards. If more force
is necessary, try using plastic or timber tools in order
to avoid damaging machined surfaces of cavity. Take
careful note of the seal’s orientation in order to
correctly insert the new seals later.
5. Thoroughly clean and inspect cavity for unusual wear
or cracks.
6. Press the glyd high pressure seal (item 5) into square
high pressure seal (item 6).