Search results
Results From The WOW.Com Content Network
Surge control products have been used in many industries to protect the maximum working pressure of hydraulic system for decades. Typical applications for surge relief equipment is in pipelines at pump stations, receiving manifolds at storage facilities, back pressure control, marine loading/off loading, site specific applications where pressure surges are generated by the automation system ...
A relief valve DN25 on cooling water pipe from heat exchanger Schematic diagram of a conventional spring-loaded pressure relief valve. A relief valve or pressure relief valve (PRV) is a type of safety valve used to control or limit the pressure in a system; excessive pressure might otherwise build up and create a process upset, instrument or equipment failure, explosion, or fire.
There are two types of hydraulic fuses. The first one acts like a pressure relief valve, venting in case of a pressure surge. The second is more or less like a check valve. The only difference is a check valve is in place to prevent upstream fluid from coming back and venting out.
When a valve with a volumetric flow rate Q is closed, an excess pressure ΔP is created upstream of the valve, whose value is given by the Joukowsky equation: =. In this expression: [30] ΔP is the overpressurization in Pa; Q is the volumetric flow in m 3 /s; Z is the hydraulic impedance, expressed in kg/m 4 /s.
Sequence valves control the sequence of hydraulic circuits; to ensure that one hydraulic cylinder is fully extended before another starts its stroke, for example. Hydraulic circuits can perform a sequence of operations automatically, such as trip-and-reclose three times, then lockout, of an oil-interrupting recloser .
Over pressurization is prevented by a pressure relief valve which opens at 1,700 psi (11.7 MPa). A pre-charged accumulator dampens and absorbs pressure surges. Two motor-driven shutoff valves will stop hydraulic flow to the engine-driven pumps in case of an emergency.
When the pilot valve reaches set pressure it opens and releases the pressure from the dome. The piston is then free to open and the main valve exhausts the system fluid. The control pilot opens either to the main valve exhaust pipe or to atmosphere. Snap acting At set pressure the valve snaps to full lift.
In most steam engine designs there is a short time at the end of the return stroke of the piston when all the valves are shut and it is compressing any remaining steam. Water can be introduced from the boiler or in a cold engine, steam will condense to water on the cool walls of the cylinders and can potentially hydrolock an engine.