Selection of Safety Valve in Chemical Engineering Design

1 safety valve and its selection method

    Safety valve is a safety valve with automatic, involving personal safety. It does not rely on any external force but the use of the media itself to discharge a certain amount of fluid to prevent the system pressure exceeds a predetermined safe value. When the pressure drops to the specified value, the valve closed in time to protect the equipmen t or pipeline safe operation.

    Safety valve design considerations in the most unfavorable factors. The safety valve (or other safety measures) shall be provided if the following conditions may cause an explosion of equipmen t or piping beyond the design pressure due to fire, operation failure or water supply failure, power failure, etc.:

Positive displacement pump and compressor outlet piping;

At both ends may be closed, resulting in the pressurized liquefied hydrocarbon pipe on the pipeline;

Combustible gas and flammable liquid may be heated to expand the design pressure of the pipeline;

Design pressure is less than the source of pressure at the pressure vessel and pipeline;

A steam outlet pipe of a condensing gas turbine;

All pressure vessels require pressure relief devices.

1.1 safety valve classification

Safety valve by different methods are as follows:

1) According to its overall structure and loading mechanism can be divided into different types of lever hammer (usually used for lower pressure, usually installed on the device), playing yellow and control type;

2) According to the valve flap opening height and valve flow diameter ratio can be divided into micro-open, semi-open and full open style safety valve;

3) by gas emissions can be divided into fully enclosed, semi-closed and open;

4) according to whether the back pressure balance mechanism is divided into back pressure balance type and conventional type;

5) According to the principle of action is divided into direct action and indirect action (including the pilot-type and power assisted devices).

1.2 safety valve selection instructions

Safety valve in the form and type more, for different occasions, should use the following form of safety valve

1)Vent gas or steam, the choice of full open type safety valve 2) When the discharge of liquid, the general selection of micro open style safety valve; 3) the discharge of water vapor or air, the choice of a safety valve with a wrenc h; 4) The design of a set of safety valve; 5) the general flammable, explosive or toxic media should be used to close the valve, the pressure should be greater than 3MPa, the temperature of more than 235 degree Celsius with gas safety valve, you should use a safety valve with a heat sink to prevent leakage of media directly erode the spring; 7) high back pressure of the occasion, should use the back-pressure balance or the use of high-pressure, high pressure, high pressure, high pressure, high pressure, high pressure, Pilot - operated safety valve.