Hydraulic Drive & Controls 3(2+1)

LESSON 27. Hydraulic Valve installation, Valve failures and remedies, valve assembly, Troubleshooting

Valve installation

Hydraulic valve is a device in a hydraulic system or equipment which gives better control of the fluid flowing through the lines and pumps. There are various types of  hydraulic valves like flow control, pressure control and directional control valves. A flow-control valve meters the  flow in one direction only, and hence the inlet and outlet ports are required to be connected correctly. The  drain connection of  valve should be connected to tank to avoid pressure surges if any. The location of a flow-control valve with respect to workload should be proper. The basic types of flow-control valve installations are

• Meter-in circuit - In this type of circuit flow control valve is installed in pressure line.

• Meter-out circuit – In a meter-out circuit, a flow-control valve is installed on the return side of a cylinder to control cylinder actuation by metering its discharge.

• Bleed off circuit – In general bleed-off circuit is not installed directly in a feed line.

Valve failures, remedies and troubleshooting

Hydraulic valves are manufactured with  precision and are required to be as accurate as possible to control pressure of fluid , direction, and flow in the hydraulic system.  Valve failures are normally due to contamination  in the hydraulic fluid . Small amounts of dust, dirt, rust, or sludge may cause improper functioning of valve parts and may lead in leakages in the valve.

Possible causes their remedies in the valve

Source of trouble	Causes	Remedies
Excessive noise	a)      Valve chatter due to dust or dirt b)      Flow noises during operation c)      Wrong design	Clean the valve     Check for noise Redesign
Inadequate power	a)      Operating pressure set too low b)      Internal leakages c)      damaged valve seat	Reset pressure   Remove leakages Correct the valve seat
Excessive temperature	a)      constant flow is low b)      pressure setting too high	Make more constant flow Make proper pressure setting
Jerky motor or cylinder movement	a)      Valve chatter due to dust or dirt b)      Non suitable remote control valve	Clean the valve   Have suitable valve

 

valve assembly

The following points are to be considered while assembling of the valves-

• Wash the parts of valve  in kerosene

•  Blow the air to dry them and then dip in hydraulic oil with rust inhibitor to prevent rusting.

• Make sure that valve mating surfaces are free of burrs and paint.

• Replace all the seals and gaskets when repairing a valve assembly.

• Soak the new seals and gaskets in clean hydraulic oil before assembling.

•  Make sure to assemble a valve sections in their correct order.

• Check for distortion if any while mounting valves.

•  Make sure that spool of valve is working properly