Emergency shutdown valves design

Release control equipment and systems such as emergency shutdown, nonreturn valves and blowdown, which are designed to limit the quantity of hazardous material involved in an incident... 

Excess flow valves shut when the flow rate exceeds design flow rates. They are frequently used on hoses. However, they are not generally used emergency shutdown or on storage vessels, loading points, or multi product systems, since they are not sufficiently reliable. 

Normal Operation. The designer of a chemical plant must provide an adequate interface between the process and the operating employees. This is usually accompHshed by providing instmments to sense pressures, temperatures, flows, etc, and automatic or remote-operated valves to control the process and utility streams. Alarms and interlock systems provide warnings of process upsets and automatic shutdown for excessive deviations from the desired ranges of control, respectively. Periodic intermption of operations is necessary to ensure that instmments are properly caUbrated and that emergency devices would operate if needed (see Flow measurement Temperaturemeasurement). 

With an available diesel emergency generator supplying power to critical pumps, the control room operators initiated shutdown procedures for the two reactor areas. An uninterruptible power supply (UPS) kept power to the DCS screens and instruments however, the DCS system was designed close all catalyst preparation and reactor feed valves on loss of power. Outside operators were sent to manually block in reactor feeds. 

The System 80+ Standard Design utilizes the Shutdown Cooling System (SCS), the Reactor Coolant Gas Vent System (RCGV), the Safety Depressurization System (SDS), the Atmospheric Dump Valves (ADV), and the Emergency Feedwater Systems (EFW) as the preferred means to bring the reactor plant from hot standby to a cold shutdown condition within a reasonable period of time. These safety-related systems are normally operated from the control room and are described in CESSAR-DC, Sections 5.4.7, 10.1, and... 

At 4.00 a.m. on 28 March 1979, the main feedwater pumps tripped this in itself was not an unexpected or particularly unusual event, and resulted in an automatic shutdown of the turbine it also caused the emergency feedwater pumps to start up, as they were designed to do. Unknown to the plant operators, however, the block valves on both of the emergency feedwater lines had inadvertently been left closed, so that no water was able to reach the steam generators. 

Arrangements have been provided to allow the operation of the channel emergency cooling system to be tested whilst the reactor is running. Similarly, the liquid shutdown trip valves are designed for testing Individually whilst the reactor is in operation. 

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