Experiment No: 04 Test on pressure relief valve

 

Expt No :04 Test on pressure relief valve

Aim: Test on pressure relief valve (Plot its characteristics curve)

Apparatus:  Automation studio Software 5.7/ Fluidsim

Theory:

Pressure-relief valves limit the maximum pressure in a hydraulic circuit by providing an alternate path for fluid flow when the pressure reaches a preset level. All fixed-volume pump circuits require a relief valve to protect the system from excess pressure. Fixed-volume pumps must move fluid when they turn. When a pump unloads through an open-center circuit or actuators are in motion, fluid movement is not a problem. A relief valve is essential when the actuators stall with the directional valve still in shifted position. A relief valve is similar to a fuse in an electrical system. In a hydraulic circuit, a relief valve opens and bypasses fluid when pressure exceeds its setting. The valve then closes again when pressure falls. This means that a relief valve can bypass fluid anytime, or all the time, without intervention by maintenance. There are two different designs of relief valves in use: direct-acting and pilot-operated. Both types have advantages and work better in certain applications.

 

Fig: Pressure relief valve

 

 

 

Fig : Characteristics of a relief valve

 

Diagram: 

Fig : Test on Relief Valve  

 

Procedure: 

1.      First  build the simple circuits in software as shown in fig .

2.      Set PRV cracking pressure to 90 bar ,Load on cylinder 10 KN.

3.      Simulate the experiment, & capture the values of Pressure & flow form software .

4.      Plot the graph Pressure Vs Flow through PRV

Observation Table:

Sr No	Flow (LPM)	Pressure (Bar)		Sr No	Flow (LPM)	Pressure (Bar)
1
2
3

 

Graph:

 

 

Conclusion:  

1.       The pressure at which the valve begins to open is called cracking pressure.

2.        It should be noted that the poppet must open sufficiently to allow full pump flow. The pressure that exists at full pump flow can be substantially greater (90.22 bar ) than cracking pressure  (90 bar). The pressure at full pump flow is the pressure level that is specified when referring to the pressure setting of the valve. It is the maximum pressure level permitted by the relief valve.