Safety valve device, the operating principle and types

When the operation of any system of high blood pressure can occur in the pipes due to malfunction, which could lead to the destruction of the equipment. To protect the units in the system, a safety valve that if the increase in the pipelines higher than the nominal pressure, resets the excess working medium and the system is restored nominal pressure.

The principle of operation of safety valves

The protective device is installed on the high pressure in the piping and vessels under pressure. Depending on the purpose of safety design elements may be different, but the circuit and working principle all identical.

During normal operation of the equipment under the action of the spring seat mechanism is closed and has no effect on the system. the valve setting pressure equal to the operating pressure in the system. When the pressure in the pipeline exceeds the force of the spring element, the closing hole, the seat will open and there will be the release of the medium conductivity. As a result, the pressure drop and closes the saddle again.

Working environment can be different, water, steam, gaseous fraction and a lubricating oil and hydraulic oil. Therefore, the discharge pressure can be produced in excess atmosphere, e.g., steam, air, water, or back to the return line for corrosive materials.

Safety valve starts slightly opened for pressure relief with the pressure 3% lower than the nominal. Reset the working environment at first small, but if this is not enough and the pressure increases, the saddle will allow access to a sink at rates of 110-115% of the worker.

Once the pressure drops, the saddle block the access, and the system will continue to work normally.

The use of safety devices

To ensure the safe operation of the safety fitting is an indispensable element of any system that is under pressure.

Depending on the purpose they can be installed in the following locations:

1. Hot water and heating. Safety valve for heating systems installed on the pipes after the feed pump. Since hot water is aggressive, the discharge should be directed to a safe place, usually in the sewer. With large number of aggregate expenditure can be up to 2 or more.
2. Sanitary fitting for water is installed in the cold water piping drinking water supply. Resetting takes place directly on the ground.

   

3. Hydraulics. The hydraulic oil is used as working fluid. The hydraulic system serves to drive working mechanisms: hydraulic motors, hydraulic cylinders. The safety fitting is installed on the tubes, or may be composed of a pump or control valve. Resetting the oil produced in the drain line.
4. gas pipelines. Increasing the pressure in the pipes may lead to emergency situations - is flame detachment from the burner, the accumulation of surplus gas and explosion in the room. Therefore, the armature is set immediately after the pressure regulator, a reset is performed in the atmosphere.
5. System air compressors. The protective device is installed in the compressor housing, discharge occurs in the atmosphere.

Types of protective mechanisms

In industry, there are various constructions of protective devices pipes, depending upon their place of installation and ongoing media. It can be spring, lever, membrane, and rocker other applicable safety valves.

Consider the details of the device and principle of operation.

Safety valve spring

The most widely used safety valve, particularly for heating systems. Its main advantages, ease of construction and the ability to easily adjust to the system operating pressure. There are the following kinds of protective mechanisms of the spring:

• direct action - the device is triggered by direct exposure to the working environment;
• indirect - discharge high pressure produced by external control, for example, an electric signal;
• rocker assemblies - fitting opening occurs immediately sharply at full speed, the fitting closes sharply after resetting the pressure, which can cause oscillations of the saddle and the mechanism of vibration.

Protective gear lever type

The mechanism of this fitting consists of a lever connected to the slide valve that closes the discharge opening. The lever is suspended from the load, and, depending on the weight of the load and the mounting points on the lever mechanism is regulated setting.

The load is fixed on the lever against accidental displacement, and change the setting. The disadvantage of this design is its bulkiness, however the use of such mechanisms is made in systems with large diameter tubes is greater than 50 mm.

Safety valve membrane

The main element of such a structure is a membrane. The principle of operation is that in the event of an emergency pressure in the pipes membrane breaks and a reset of the working environment. Membrane devices are easy to manufacture, tight and fast work.

Important! They have a significant disadvantage, after every operation the membrane should be changed to the new. Therefore, always with such a device and put a normal fitting.

Depending on the design, such a device may be a bursting disc and flapping membrane:

1. Mechanisms with a bursting disc is used in systems with liquid and gaseous working media. The form of the membrane is flat or domed, with a sudden change of pressure above the operating device is activated and the membrane is destroyed.
2. Mechanisms with flapping membrane most commonly used in a gaseous fluid systems. The membrane is made of a rubbery tissue and prevents the pipe from both the increase and decrease dangerous pressure. To do this, above and below the membrane positioned knives. When changing the pressure diaphragm is deflected, and when a sharp drop in the system, regard blades, the sheath incision occurs. Thus, depending on the magnitude of pressure occurs or is reset, or the completion of the additional capacity.

Installation and assembly

To ensure safe operation of gas and water pipes, when mounting the safety units is recommended that the following requirements:

1. On pipes suitable to a protective mechanism, and pressure relief piping can not be installed valves and filter.
2. fitting the spring axis is to be installed vertically. To the unit to be easily accessible for replacement and adjustment.
3. Lever arm-type protective mechanism during installation should be positioned horizontally.
4. Before fitting to monitor the pressure gauge must be installed.

   

5. Depending on the fluid outlet tube can be directed: in a steam atmosphere, and gaseous non-corrosive environments. For draining hot water to be sent to a special container or back to the system. If the pipes aggressive environment, the discharge must be discharged only in a closed container.
6. The length of pipe from the equipment to install a protective unit must be minimal. On this site is not allowed to connect branches to the selection of the working environment.
7. Safety valve for heating systems can be installed in several locations on the conduit, wherein consumption of the working fluid through the line must be 1.25 times greater than the total flow is set devices.

   

8. Before putting the system into operation be sure to check the correct setting of the safety valve as well as its ability to return to its original position and ensure a tight seal.

Exploitation

Durability of protective mechanisms depends on compliance with all the technical operating conditions. When the guard unit due to wear of the main parts of the following defects may occur:

1. Leaks in the saddle. The defect may result from contact with metal chips and the presence of scratches on the saddle. Defect is corrected by lapping the seat or its replacement with a similar fitting.
2. Underestimated due to the opening pressure of the valve spring device losing its elastic properties or misalignment adjustment. To eliminate failure need to replace the spring or very fitting, adjust the pressure, check in and put the seal.
3. If you need to replace the unit for repair, to replace him temporarily can not put the plug or valve. It is essential for the safety of the facility, to produce a pre-selection valve with exactly the same characteristics, and only install it instead of skim.
4. If a ripple occurs during operation, the rapid opening and closing of the shutter device, then such a defect can cause unwanted vibration pipelines, which may result in their deformation. The reason for the discrepancy could be sized sections main pipe and piping connected to the unit. In order to eliminate the defect is necessary during installation to install the pipe with same cross section.