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Moog Radial Piston Pump

Moog Radial Piston Pump

Moog Radial Piston Pump

We are using Moog RKP 80 cc pumps (radial piston pump) in our press machines. The maximum tonnage of this machine is 1150 Tons at 300 kg/cm2. The image showing the installation of the pump is attached.



The suction line of the pump is a 3” line (through and through). The 3” Suction Strainer of 0.15mm is fitted inside the tank in a horizontal manner. The internal drain line of the pump is a 1” hose and is connected to the bottom of the tank. The internal drain oil goes into the tank half way through it and exits via a U bend. This is to ensure that the case is always filled with oil. We also use an auxiliary filtration system which is built into the machine. The image shows the same too. The return line filter of the auxiliary pump is 0.025mm. This ensures the neatness of oil. This auxiliary pump also pushes the fluid through air cooled oil cooler before it enters the tank again. We use Hydraulic Oil Grade 68. The video of the machine can be seen at https://www.youtube.com/watch?v=rJ_6GqxJqhU&t=...

Now my question is:

In winters, the ambient temperature falls below 0 degree centigrade. This results in thickening of the oil. If a suction strainer is present in the suction line of the pump, then WILL IT cause cavitation and hence damage the pump? This is very essential for us to know. The reason why we are using a suction strainer in Moog pumps because it is mentioned in their catalog that we can use a minimum of 0.150 mm strainer. This helps in preventing the pump sucking up bad oil and in turn would save the very costly pump.

Also the working principle of this pump is a bit different from an axial piston pump. The extract of the datasheet is also attached herewith.


By reading the datasheet, what I understood is that the piston moves out of the cylinder block due to centrifugal force (unlike axial piston pumps where the retainer rings pulls the piston out of the cylinder block). So I think if the suction strainer is clogged, the pump will simply rotate with no flow. But this will not damage the pump as the case is already filled up with oil. But had it been an axial piston pump, it would have been immediately damaged.

Am I correct? Please suggest. Or shall I simply throw away the suction strainer..

RE: Moog Radial Piston Pump

The use of suction strainers has divided opinion for a long time.

Some people insist on them, others avoid them at all cost.

The moog radial piston pump has fixed pistons and it oscillates the sleeves to create the pumping action. It is more robust than an axial piston pump. Blocking the pump inlet with a blocked strainer will cause excessive depression of the oil and although it won't harm the pump if the pressure is too low, if the pressure drops below the oil vapour pressure, the resulting cavitation will kill your pump very quickly.

If you can keep the oil clean, then remove the strainer. If there is a chance that contaminants bigger than 0.150mm can get into the oil, then you will need to keep the strainer in place.

If you want to protect the pump, put a pressure sensor on the inlet. Use an absolute pressure sensor 0 to 600kPa. Set an alarm for 50kPa. Then if the pressure goes too low, you can trigger a warning. Mineral oil vapour pressure at 100 degrees C is very close to absolute zero. You will need a serious blockage to get the pressure that low and you will probably notice that the pump flow drops off before the oil boils in the pump inlet.

RE: Moog Radial Piston Pump

Is it possible to increase the area of the strainer so the pressure drop is lower or add an oil heater?

RE: Moog Radial Piston Pump

Change to viscosity grade 32 oil with a viscosity index of 150 or higher. I am in the no strainer school of thought.


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