Design And Construction Of Pressure Safety Valve Calibration Rig

CHAPTER ONE

INTRODUCTION

1.1                                                         BACKGROUND OF THE STUDY

A safety valve is a valve that acts as a fail-safe. An example of safety valve is a pressure relief valve (PRV), which automatically releases a substance from a boiler, pressure vessel, or other system, when the pressure or temperature exceeds preset limits. Pilot-operated relief valves are a specialized type of pressure safety valve. A leak tight, lower cost, single emergency use option would be a rupture disk.

Safety valves were first developed for use on steam boilers during the Industrial Revolution. Early boilers operating without them were prone to explosion unless carefully operated.

The function of a pressure relief valve is to protect pressure vessels, piping systems, and other equipment from pressures exceeding their design pressure by more than a fixed predetermined amount. The permissible amount of overpressure is covered by various codes and is a function of the type of equipment and the conditions causing the overpressure.

A pressure Relief Valve is a safety device designed to protect a pressurized vessel or system during an overpressure event. An overpressure event refers to any condition which would cause pressure in a vessel or system to increase beyond the specified design pressure or maximum allowable working pressure (MAWP).

The primary purpose of a pressure Relief Valve is protection of life and property by venting fluid from an overpressurized vessel.

Many electronic, pneumatic and hydraulic systems exist today to control fluid system variables, such as pressure, temperature and flow. Each of these systems requires a power source of some type, such as electricity or compressed air in order to operate. A pressure Relief Valve must be capable of operating at all times, especially during a period of power failure when system controls are nonfunctional. The sole source of power for the pressure Relief Valve, therefore, is the process fluid.

1.2                                             PROBLEM STATEMENT

Over-pressure in industries can lead to accident and at the same time causes loss of life. One of the most critical automatic safety devices in a pressure system is the pressure safety valve. The primary purpose of a pressure safety valve is the protection of life, property and environment during an over-pressure event in a pressurized vessel or equipment. An over-pressure event refers to any condition which would cause pressure in a vessel or system to increase beyond the specified design pressure or maximum allowable working pressure. A pressure safety valve is designed to open and relieve excess pressure from vessels or equipment and to re-close and prevent the further release of fluid after normal conditions have been restored.

1.3                                              AIM OF THE PROJECT

The primary aim of this work is to build a safety valve that is used for protection of life, property and environment. A safety valve is designed to open and relieve excess pressure from vessels or equipment and to reclose and prevent the further release of fluid after normal conditions have been restored.

1.4                                                          OBJECTIVES OF THE PROJECT

Objectives of this work are:

1. To prevent damage to equipment
2. To avoid injury to personnel

• To eliminate any risks of compromising the welfare of the community at large and the Proper sizing, selection, manufacture, assembly, test, installation, and maintenance of a pressure relief valve are critical to obtaining maximum protection.

1.5                                                        APPLICATION OF THE PROJECT

This device can be used In the petroleum refining, petrochemical, chemical manufacturing, natural gas processing, power generation, food, drinks, cosmetics and pharmaceuticals industries.

1.6                                                          LIMITATION OF THE PROJECT

Pressure relief valve does not control or regulate the pressure in the vessel or system that the valve protects, and it does not take the place of a control or regulating valve.

1.7                                                                DEFINITOIN OF TERMS

1. Relief valve (RV): an automatic system that is actuated by the static pressure in a liquid-filled vessel. It specifically opens proportionally with increasing pressure
2. Safety valve (SV): an automatic system that relieves the static pressure on a gas. It usually opens completely, accompanied by a popping sound

• Safety relief valve (SRV): an automatic system that relieves by static pressure on both gas and liquid.

1. Pilot-operated safety relief valve (POSRV): an automatic system that relieves on remote command from a pilot, to which the static pressure (from equipment to protect) is connected
2. Low pressure safety valve (LPSV): an automatic system that relieves static pressure on a gas. Used when the difference between the vessel pressure and the ambient atmospheric pressure is small.
3. Vacuum pressure safety valve (VPSV): an automatic system that relieves static pressure on a gas. Used when the pressure difference between the vessel pressure and the ambient pressure is small, negative and near to atmospheric pressure.

• Low and vacuum pressure safety valve (LVPSV): an automatic system that relieves static pressure on a gas. Used when the pressure difference is small, negative or positive and near to atmospheric pressure.