The pressure relief valve is a kind of self-powered regulating valve. It throttles using a valve member, reducing the inlet pressure to the desired outlet pressure. When the inlet pressure and the amount of flow change, it relies on elastic components and the power of transmitting the medium to keep the outlet pressure largely unchanged.

What are the types of sanitary pressure relief valves?

The commonly used sanitary pressure relief valve is usually level one throttle whose valve flap is cone-shaped. The pressure relief valve of level one throttle has a better effect under the low-pressure drop. Under high-pressure drop, cavitation is prone to occur, which will lead to premature damage of throttling members. In light of this, two or more pressure relief valves are often used in parallel, which increases the operating cost of the system and the instability. In order to solve the problem of pressure-relieving under the high-pressure drop, a kind of two-stage throttle balanced sleeve type pressure relief valve was designed.

According to structural forms, the pressure relief valve can be divided into direct-acting film type, direct-acting bellows type, pilot film type, pilot bellows type, and pilot piston type. Regardless of the structural form, they all automatically balance the pressure of the medium using the elastic component to regulate the opening of the valve flap to throttle and reduce pressure.

What is Balanced Sleeve Type Pressure Relief Valve?

The valve flap is the core component of the pressure relief valve. Whether its design is reasonable or not directly affects the operating performance of the pressure relief valve.

The valve flap of the pressure relief valve uses two-stage balanced sleeve type throttle. In the middle of the valve flap, six throttle holes of the same area are drilled and are evenly distributed circumferentially. These are level two throttle holes. The medium enters the cylindrical space of the valve flap from the inlet of the pressure relief valve, through the six throttle holes in the middle of the valve flap. Because the upper and lower area of the cylindrical space is the same, the liquid pressure sustained by the upper and lower sleeves is offset to reach a balance. Thus, the area of throttling is not affected by the change in the pressure of the inlet. Then, the medium enters the outlet of the pressure relief valve through the upper and lower throttle holes.

The total area of the upper and lower twelve two-stage throttle holes is the same as the total area of the six first-stage throttle holes in the center. Two-stage throttling pressure is close, that is, the total throttling pressure of the pressure relief valve is basically evenly distributed, which controls the speed of the liquid flow. In addition, the respective six throttle holes at the upper, middle, and lower parts are circumferentially positioned, eliminating the lateral force.

A two-stage throttle balanced sleeve type pressure relief valve has many advantages:

1. Two-stage throttling can be achieved, which solves the problem of pressure reducing under the high-pressure drop, alleviates the hydraulic shock, avoids cavitation, and lowers the noise. It can also be used to reduce pressure under a low-pressure drop.

2. Through simple structural design, the valve flap is horizontally balanced while being vertically balanced, which reduces the cost of design and manufacturing.

3. The lateral thrust of the valve flap is balanced, the piloting is smooth, the service life of the sealing surface of the valve seat improves, the structural optimization is reasonable.

4. The valve flap can be quickly disassembled in whole, which is easy for repair and maintenance.

5. The elastic component only corresponds with the outlet pressure of the two-stage throttling, which can improve the stability of the outlet pressure.

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The sanitary pressure relief valve is an essential component of pneumatic sanitary regulating valves. Its main use is to reduce the pressure of the gas source and to stabilize it to a fixed value so that the regulating valve can get a stable gas source force for regulating.

According to structural type, they can be divided into film type, spring film type, piston type, lever type, and bellow type.

According to the number of valve seats, they can be divided into single-seat types and double-seat types.

According to the position of the valve gate, they can be divided into positive-acting type and reaction type.

How does a pressure relief valve work?

When the pressure relief valve’s output pressure is high or the diameter is large, regulating the pressure using a regulator spring will make the stiffness of the spring too big. When flow changes, the output pressure has a big fluctuation, so the structural size of the sanitary valve will increase, too. In order to overcome these shortcomings, pilot-type pressure relief valves can be used.

The mechanism of pilot-type pressure relief valves is basically the same as that of the direct-acting type. The regulating gas that the pilot-type pressure relief valve uses is supplied by a small direct-acting pressure relief valve. If the small direct-acting pressure relief valve is installed inside the valve, then it’s known as the internal pilot-type pressure relief valve. If the small direct-acting pressure relief valve is installed outside the valve, then it’s known as the external pilot-type pressure relief valve.

How do you adjust a pressure relief valve?

With a slotted screwdriver, turn the screw in the center of the knob clockwise, until flow can be heard escaping from the internal valve. Slowly turn the screw counterclockwise until the flow from the relief valve stops. Turn the screw an additional 1/8 to 1/4 turn counter-clockwise. Replace the silver cap in the knob.

Conclusion

Thank you for reading our article and we hope it can help you better understand the mechanism of pressure relief valves. If you want to learn more about pressure relief valves, we would like to advise you to visit Adamant Valve homepage for more information.

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1. Control failure, so that the host doesn’t run
Failure of pilot relief valve will cause the host to stop running. Possible reasons include: the valve core spring of pilot valve is broken; damping hole is blocked; poor sealing of valve opening of pilot valve; the main valve core is stuck. The corresponding solutions are: replacement or adding a flattened pad at the broken place for emergency use; cleaning and dredging; grinding or cutting off the oil pipeline for emergency use; grinding and cleaning.

2. Instable limit pressure
Instable limit pressure of pilot relief valve is demonstrated as lower or higher hydraulic system pressure, weakness of hydraulic actuator or burst of oil tube, pump and valve body.

The causes of this failure include: improper pressure regulation; bending or softening of pilot valve core spring; overly dirty oil or unsmooth flow of the oil. The corresponding solutions are: readjustment; recalibrating, pad-adding or replacement; replacement and cleaning.

Limit pressure instability of pilot relief valve is a gradual failure. It mostly occurs in construction machinery with more motorcycle hour reserve. Limit pressure failure of pilot relief valve is a sudden failure. It mostly occurs in construction machinery with less motorcycle hour reserve. After troubleshooting, we should readjust the pressure of pilot relief valve according to the pressure defined by the system.

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There are many kinds of sanitary pressure relief valves, they can be divided into two general categories: direct-action type and indirect-action type. The direct-action type uses the energy of the medium itself to control the required pressure. The Indirect-action type uses external power, such as air pressure, hydraulic pressure, or electric power to control the required pressure. Compare these two types, and it’s easy to conclude that the former has a relatively simple structure while the latter has higher precision.

According to the structure of pressure relief valves, they can be divided into:

Piston-type pressure relief valve:

It uses the piston to balance pressure and drive the movement of the valve flap.

Membrane-type pressure relief valve:

It uses a membrane as a sensing element to drive the movement of the valve flap.
Air bag-type pressure relief valve: It uses the pressure produced by the medium entering the air bag to balance pressure.

The above classification method is based on the structure of the valve.

According to the types of valve seats, they can be divided into single-seat valves and double-seat valves.

On the one hand, a double-seat valve can make the force on upper and lower seats mostly balanced and offset, reducing the resultant effect on the valve stem.

On the other hand, a larger channel area can be achieved, and the overall size of the valve can be reduced. However, the valve seat technology of the pressure relief valve is not good, and machining and grinding of it are difficult. The Assembly size chain should be well controlled in order to ensure assembly accuracy, making the valve normal and stable when working.

Conclusion

Different types of hydraulic pressure valves include relief, reducing, sequence, counterbalance, safety, and unloading. All of them are typically closed valves, except for reducing valves, which are usually open. For most of these valves, a restriction is necessary to produce the required pressure control.

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There are many types of sanitary pressure relief valves. Piston type and spring film type are the main two types. Piston type pressure relief valve is a type of valve that uses a piston for pressure relief. Spring film-type pressure relief valve relies on spring and film for pressure balance.

The use of a pressure relief valve:

A pressure relief valve is a kind of automatic valve that reduces the medium pressure to a certain value. Generally, the pressure after the valve is less than 50% of the pressure before the valve.

Pressure testing method:

The strength test of the pressure relief valve is usually for assembly after the test of a single piece, or for test after assembly. The duration of a strength test: 1 minute for DN<50mm; more than 2 minutes for DN65~150mm; more than 3 minutes for DN>150mm. After the bellows and the components are welded, apply 1.5 times the maximum pressure and use the air to perform a strength test.

When performing the sealing performance test, it should be based on the actual working medium. When tested with air or water, the test is to be carried out at 1.1 times the nominal pressure. When tested with steam, the test is to be carried out under the maximum working pressure allowed in the operating temperature. The difference between inlet pressure and outlet pressure shouldn’t be less than 0.2MPa.

The testing method:

After the inlet pressure is set, gradually adjust the regulating screw of the valve so that the outlet pressure can sensitively and continuously change within the range of maximum and minimum value without stagnation or jamming.

How are pressure relief valves tested?

Pressure relief valves are tested depending on their operating conditions, and the valves are instrumented to verify correct operation at their set point pressure.

Conclusion

The most commonly mandated form of pressure relief valve testing, bench testing is unique in that it requires you completely shut down your facility’s system and remove all pressure relief valves. The valves are then transported to a lab where they are tested and repaired as necessary.

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The high-pressure chamber of the oxygen pressure relief valve is connected to the steel cylinder. The low-pressure chamber is for gas emission and also has access to the system. The indication of the high-pressure gauge is the pressure of the stored gas in the steel cylinder. The outlet pressure of the low-pressure gauge can be controlled by the regulating screw.

How does a pressure relief valve work?

When using sanitary pressure relief valve, open the master switch of the steel cylinder first, and then turn clockwise the pressure regulating screw of the low-pressure gauge to compress the mainspring and drive the film, spring pads, and mandrel to open the shutter. This way, the high-pressure gas at the inlet, after throttling and decompression, goes from the high-pressure chamber into the low-pressure chamber and then through the outlet to the work system. Turn the regulating screw to change the height of the shutter, so that the amount of high-pressure gas can be regulated and the required pressure value can be achieved.

What is a Pressure relief valve?

Pressure relief valves are all equipped with safety valves, which are the devices used to protect and ensure the safe use of pressure relief valves. Also, they are signal devices when the pressure relief valve encounters failure. If the shutter pad or the entire shutter is damaged, causing the outlet pressure to rise on its own and exceed a certain allowed value, the safety valve will automatically open and exhaust.

Conclusion

Pressure relief valves (safety relief valves) are designed to open at a preset pressure and discharge fluid until the pressure drops to acceptable levels. When the force of the steam pressure acting on the valve exceeded the force of the weight acting through the lever arm the valve opened.

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The pressure of a pilot-operated sanitary relief valve is provided on the upstream side (the system being protected) at the dome often by a small pilot tube. The downstream side is the pipe or open-air where the PORV directs its exhaust. The outlet pipe is usually larger than the inlet. 2 in × 3 in (51 mm × 76 mm), 3 in × 4 in (76 mm × 102 mm), 4 in × 6 in (100 mm × 150 mm), 6 in × 8 in (150 mm × 200 mm), and 8 in × 10 in (200 mm × 250 mm) are some common sizes.

What are the pressure and safety relief valves?

The upstream pressure tries to push the piston but it is opposed by this same pressure because the pressure is directed towards the dome above the piston. The zone of the piston on which the force of the fluid acts is greater in the dome than in the upstream direction; the result is a greater force on the dome side than on the upstream side. This produces a net sealing force.

The pressure from the pilot tube to the dome is routed through the actual control pilot valve. There are many designs but the control driver is basically a conventional PRV with the special job of controlling the pressure at the main valve dome. The pressure at which the pilot is released is the functional operating pressure of the PORV. When the pilot-operated sanitary relief valve reaches the set pressure, it opens and releases the dome pressure. The piston is then free to open and the main valve discharges the fluid from the system. The control pilot opens either on the exhaust pipe of the main valve or on the atmosphere.

What is the functioning mode of pilot-operated sanitary relief valves?

When the pilot-operated valve reaches set pressure, it opens and releases the pressure. It is then free to open, and the main valve exhausts the pressure at the bottom of the dome. It opens either to the main exhaust pipe or into the atmosphere. There are typically two functioning modes: snap-acting and modulating.

Conclusion

Thank you for reading our article and we hope it can help you better understand the functioning mode of pilot-operated sanitary relief valves. If you want to learn more about sanitary relief valves, we would like to advise you to visit Adamant Valve homepage for more information.

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1. When installing sanitary pressure relief valve, make sure that the connection specifications are consistent with those of the steel cylinder and the system.

The pressure relief valve and steel cylinder use the hemispherical connection. The two are completely connected by tightening the nut. Therefore, when in use, the surfaces of the two hemispheres should be kept smooth and clean to ensure a good airtight effect. Before installation, dust can be blown off with high-pressure gas. If necessary, materials like PTFE can be used as gaskets.

2. Oxygen pressure relief valve is strictly prohibited from contacting with grease, so as to avoid fire accidents.

3. When the valve is not in use, the remaining gas inside it should be completely discharged, and then loosen the regulating screw to avoid deformation of elastic components under constant pressure.

4. Pressure relief valve should avoid collision and vibration. It can’t be in contact with corrosive substances.

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1. The size of the pipe in the system: This is of utmost importance because the size of the pipe will determine the size and even the type of pressure relief valve to be used in the piping system.

2. Setting pressure: This is crucial in determining the type of pressure relief valve for an application because; the differential pressure affects the sealing ability.

3. Temperature: This affects the material of the bodies of the various components of the piping system. The component materials used in high and low temperatures are different.

Materials with varying expansion rates can allow fluids to leak. Plastics can shrink, leak, absorb water or other media and become very fragile at low temperatures. Elastomers have a high coefficient of thermal expansion and can crack and harden in cryogenic service.

4. Type of: The pressure relief valves are of two main types:

• The “safety” or “pop-off” valve

This valve opens fully when the set pressure is reached. It then diverts all or almost all the flow through the discharge port of the valve.

• The type that pressure is relieved gradually diverts flow from the discharge port.

This valve functions as both a pressure limiter and a flow control valve. Here, a spring pushes a piston on a seat that is down. The pressure gradually exceeds the set pressure, moving the piston away from the seat and the flow is gradually directed outward through the discharge port. When the system pressure continues to rise above the set pressure, the flow is diverted. The maximum discharge rate is reached when the piston is furthest away. These pressure relief valves are used for flow control as well as for pressure control.

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Why does pressure mixing occur in the process of using an adjustable pressure relief valve?

As the pipe network at the rear end of the pipeline in sanitary pressure relief valve ruptures, close the valve at P1 or overhaul it, pump A in the pump station stops running, causing the water pressure at the rear end of the pipeline in pressure relief valve to become very low or even an empty tube.

When the normal water supply is restored, when the valve at the front end of the pipeline is suddenly opened or pump A in the pump station is opened, the pressure at the front end of the pipeline rapidly increases, and there’s a large pressure difference between the front and rear end of the pipeline in a short period of time.

The pressure relief valve is too busy working, and the pressure at the upper chamber of the valve is very small. The pressure relief valve is forcibly opened under such big pressure, causing the pressure at the front and rear end of the pipeline to be equal, and the valve experiences short-lived failure, that is, pressure mixing.

Solutions:

1. Based on the mechanism of the pressure relief valve, install a safety valve behind the pressure relief valve. When the pressure of the pressure relief valve is above P2, open the safety valve to relieve pressure, ensuring normal water supply pressure.

2. Shorten the time of pressure mixing, making it close to zero.

3. According to the mechanism of the adjustable pressure relief valve, properly increase the diameter of the pilot valve and shorten the time for the upper and lower chambers to reach balance, making it even close to zero.

As practical experience shows, the second solution is the most practical and economical. It can be quickly opened through the drain valve, making the upper chamber pressure bigger than the lower chamber pressure to expedite the recovery of the valve. The time of pressure mixing is basically zero.

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