Spare Parts

Sl.No. Description Qty.
1 Socket Head Cap Screw 1
2 Bonded Seal 1
3 O' Ring 2
4 Choke 2
5 O' Ring 1
6 Spring 1
7 Bush 1
8 Ring 1
9 O' Ring 1


Part No. Description / Material Qty Size (PPR10) Size (PPR20) Size (PPR30)
* 10   O' Ring (Nitrile) 2 17 x 2.5 30 x 2.65 34.5 x 3.55
* 11   O' Ring (Nitrile) 4 7 x 1.5 7 x 1.8 9.25 x 1.8
* 12   O' Ring (Nitrile) 1 12.5 x 1.8 12.5 x 1.8 15.55 x 2.62
* 13   Bonded seal 1/2 G 1/4 G 1/4 G 1/4

Note : * Recommended seal kit. 
            While ordering the individual spares/seal kit, give complete details of the model code as on the label

Maintenance Manual


Operation and Maintenance Instructions :

Polyhydron make Pilot Operated Pressure Relief Valves are reliable hence require very little attention from user. However it is necessary that following points must be kept in mind while storage, assembly, commissioning and maintenance.

Storage :

It is necessary that during storage the valve must be well lubricated and properly covered. This will prevent ingress of dirt/dust in the working mechanism of the unit and during commissioning it will be easy to install the same.

Operation :

The Pilot Operated Pressure Relief valve performs the same function as the direct operated design in that it serves to protect the system components from the over pressure and it limits the maximum output force. This model , however, offers advantage in both versatility and performance which make it more desirable than direct operated valves.

A Pilot Operated Relief valve operates in two stages. The pilot stage in the upper valve body contains the pressure limiting valve, a poppet held against a seat by an adjustable spring. The port connections are made to the lower portion of the body, and diversion of the full-flow volume is accomplished by the balanced piston in the lower body.

When the pressure reaches the setting of adjustable spring, the poppet is forced off it’s seat limiting pressure in the upper chamber. The restricted flow through the orifice into the upper chamber results in an increase in the pressure in the lower chamber. This unbalances the hydraulic forces and tends to raise the piston off it’s seat .When the difference in the pressure between upper and lower chambers is sufficient to overcome the force of light spring, the large poppet unseats permitting the flow directly to the tank.

Commissioning :

During commissioning Pilot Operated Pressure Relief valves do not require major attention, however it is necessary to keep the following points in mind.

The port ‘P’ should be connected pressure side, port ‘T’ to tank and port ‘X’ to pilot side.

Cap screws and the corresponding tightening torque should be as per the data sheets.

Maintenance :

The Pressure Control Modules do not need any major attention, but it is necessary to keep the following points in mind.

The oil must be of prime quality and clean as per ISO 16/13 and must be changed periodically. Contaminated oil may clog the orifices provided and thus impairing it’s proper working.

O’rings must be checked periodically.

The working temperature should be in the range of –20 to +70 degree Celsius.


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Subject to revision.

Regd. office & Works :
78-80, Machhe Industrial Estate, Machhe, Belgaum - 590 014. Karnataka, INDIA. 
Phone :
+91-0831-2411001.  Fax : +91-0831-2411002 ,  
E-mail : ,  Website :


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Polyhydron Pvt. Ltd, Belgaum, India.

Updated on February 04, 2015 03:05 pm .