HYDRAULIC PRESSURE CONTROL VALVE

PRESENTED BY :- Vikram Golchha (A -65) Shubham Sankhala (A -42)

keshav Patil (A -31)

GUIDE :- S.P. Mankani Sir

ContentsIntroductionClassification of Pressure control valvePressure relief valveDirect acting relief valvePilot operated relief valveSequence control valve ConclusionReference

INTRODUCTIONPressure development via restriction. control and check of the developing pressure thus pressure relief valve is used. manipulation of pressure and flow of oil in different circuits.

Terms related to Pressure Valves

a. Cracking Pressure :-

The pressure at which the valve just begins to bypass the pressurized fluid to reservoir is called Cracking-Pressure.

At this pressure the force developed by fluid at ball or poppet (which ever is used) just over-come the compressive force of spring retaining ball or poppet on valve seat.

b. Full-Flow Pressure :-

As fluid start by-passing through the valve, the poppet gets lifted from it seat. This lifting of poppet cause compression of spring. As spring get compressed its force on poppet increases. Hence to further compress spring and allow more passage to fluid for free flows require more pressure.

Hence for full-flow of fluid through relief valve is at much high pressure than cracking pressure.

The pressure at which full-flow of pump by-passes to reservoir is called “Full-Flow Pressure”.

Types of Pressure Control ValvesThere are six types of pressure-control valves are:

1. Pressure Relief valves

2. Unloading valves

3. Sequence valves

4. Pressure-reducing valves

5. Counter-balance valves

6. Safety value

Pressure Relief Valve (PRV)

A closed valve is to limit the pressure in to prescribed maximum by diverting some or all output of pump to tank.The pressure can rise in a hydraulic system if:

1. The flow rate from the pump is larger than the flow rate through the actuator

2. The volume of a closed system is reduced.

3. The hydraulic resistance of the system rises.

4. The pressure relief value are normally closed.

construction

It consists of a valve body, poppet, spring and adjusting screw Poppet held on valve seat by spring compression, which is adjusted by screw.

WORKING

Pilot Operated Relief Valve: - In case of direct acting relief valve the pressurized fluid Is stop by spring loaded poppet against by-passing to the reservoir

While in case of pilot operated relief valve a balanced piston or spool block the passage of pressurized fluid against bypassing to reservoir.

Excess pressure cause unbalances of the piston, because of which it slides to one side allowing pressurized fluid to by-pass to the reservoir.

WORKING OF PILOT OPERATED PRESSURE RELIEF VALUE

Advantages

a) Smaller package on larger pipe sizeb) More option for controlc) Seals more tightly as system

pressure approaches but doesn’t reach the set pressure.

d) Control pilot can be mounted remotely

e) It can be used in engines

DISADVANTAGE

a) More complex ,resulting in various fail –open failure modes

b) more expensive at smaller sizec) Small parts in pilot values are

sensitive to contaminants particles

SEQUENCE VALVEThe function of sequence valve is to provide flow to a second consumer in the case when the pressure level at a particular consumer has reached a threshold valve.

As the name implies it is used for sequencing the operation one after another.

Such application is mostly for in “Tooling and Automation” where several operation are sequenced in pre determined manner.

A check valve is connected in parallel with sequence valve so that both cylinder will retract simultaneously ( no sequencing is desired in retracting).

Applications

Counter balance valve

Control the vertical cylinder to not allow it to fall freely.

Also known as back pressure valves.

APPLICATIONSMainly Used in FORKLIFTS when heavy

loads are to be brought downAlso used in loaders and JCB’S for easy

load pickup and lowering of loads .Hydrolic machines

Pressure Reducing ValveOpen pressure control valvesUsed to maintain reduced pressure in the

required portion. done by increasing the area where the

oil could release the pressure.

APPLICATIONSAir CompressorsUsed in inlet of flow of load in pressure

reactors.Aircrafts and AerospoaceCooking water pressure reduction. Oxifuel welding and cutting.Propane/lpg gas – industrial.

transportation and storing.Mining industries

Safety values All the pressure relief values are kind of

safety values.

Safety values are values that acts as a fail safe in a thermal hydraulic plant.

Safety value came to existence as the early steam boilers ware prone to explosion.

Questions…….??