WOLFRAM SYSTEM MODELER

CompoundReliefValve

Pilot-operated relief valve

Diagram

Wolfram Language

In[1]:=
SystemModel["Hydraulic.Valves.PressureControl.CompoundReliefValve"]
Out[1]:=

Information

This is a model of a compound relief valve with lumped volumes. This valve is also known as a pilot-operated relief valve. It attempts to limit the pressure difference between ports a and b. This valve can be used to maintain a safe pressure level in the part of the system connected to port a. The path between port a and b can be opened by connecting the ventilation port to a low pressure.

Implementation

The model is an assembly consisting of a pressure relief valve, a pressure compensating valve, and a restriction. When pressure on port a builds up, a small flow goes into the chamber through the small chamber orifice. When the chamber pressure reaches the cracking pressure (pMin) of the pilot valve, it starts to open. When the pilot valve opens, it keeps the chamber pressure around the pilot valve's cracking pressure.

As the pressure difference between port a and the chamber reaches the cracking pressure of the piston (pMin), it starts to open. When the pressure difference reaches the piston's pMax, it is completely open.

The pMin and pMax parameters of the piston are much smaller than that of the pilot valve. The flow through the chamber orifice and the pilot valve is much smaller than the flow through the piston.

When the chamber is ventilated via the vent port, it causes the piston to open since the high pressure on port a is now unchallenged by the chamber pressure.

Reference

Industrial Hydraulics Manual, 5th ed., Maumee, OH: Eaton Hydraulics Training Services, 2008 p. 281.

Parameters (15)

medium

Value: Oil()

Type: Medium

Description: Medium in the component

V

Value: 0.0001

Type: Volume (m³)

Description: Volume of control valve

Gleak

Value: 9.999999999999999e-21

Type: PressureDependentLeakage (m³/(s·Pa))

Description: Leakage between ports

pMaxPiston

Value: pMaxPilot / 50

Type: Pressure (Pa)

Description: Pressure when piston is fully open

pMinPiston

Value: 0.95 * pMaxPiston

Type: Pressure (Pa)

Description: Pressure when piston starts to open

t1Piston

Value: 0.01

Type: Time (s)

Description: Time constant for first-order system of the piston

AMaxPiston

Value: 0.001

Type: Area (m²)

Description: Maximum opening area of the piston

CdPiston

Value: 0.62

Type: Real

Description: Coefficient of discharge for the opening of the piston

pMaxPilot

Value: 21000000.0

Type: Pressure (Pa)

Description: Pressure when pilot valve is fully open

pMinPilot

Value: 20000000.0

Type: Pressure (Pa)

Description: Pressure when pilot valve starts to open

t1Pilot

Value: 0.01

Type: Time (s)

Description: Time constant for first-order system of the pilot valve

AMaxPilot

Value: AMaxPiston / 10000.0

Type: Area (m²)

Description: Maximum opening area of the pilot valve

CdPilot

Value: 0.62

Type: Real

Description: Coefficient of discharge for the opening of the pilot valve

AOrifice

Value: AMaxPiston / 10000.0

Type: Area (m²)

Description: Opening area of the chamber orifice

CdOrifice

Value: 0.62

Type: Real

Description: Coefficient of discharge for the opening of the chamber orifice

Connectors (3)

port_b

Type: Port_b

port_a

Type: Port_a

port_vent

Type: Port_a

Components (7)

medium

Type: Medium

Description: Medium in the component

pilotValve

Type: PressureReliefValve

piston

Type: PressureCompensatingValveNormallyClosed

volume_a

Type: Volume

volume_b

Type: Volume

chamberOrifice

Type: RestrictionTurbulent

chamber

Type: Volume

Used in Examples (1)

AccumulatorAndCylinderCircuit

Hydraulic.Examples.Accumulators

Example circuit with an accumulator and cylinder