Курсовая работа по дисциплине: Инжиниринг кип
Full Open Position – Normal Operation
жүктеу/скачать 2,11 Mb.
|
Курсовая работа финальная версия
- Бұл бет үшін навигация:
- Unlocking Assured by Position Indicator
- Figure 1.2 Emergency Shutdown Valve
| Full Open Position – Normal Operation
The ESDV provides minimal pressure differential when the valve is in full open position. The full-bore ball valve virtually acts as a pipe, decreasing process fluid turbulence. Full Closed Position – Emergency Situation Setpoint pressure has been exceeded and the ESDV has fully closed, providing bubble-tight shutoff with its double-seated design. Unlocking Assured by Position Indicator Once the pressure has been equalized to a safe level the device can be opened by either: - Manual reset - Reaching low set point - Restoring power The ESDV comes equipped with an easy-to-read position indicator on the actuator, helping to confirm that the valve has been secured in the full open position. Figure 1.2 Emergency Shutdown Valve Source: https://cdn.instrumentationtools.com/wp-content/uploads/2018/05/Shut-down-valve.jpg An ESDV must act fast to minimize the effect of a hazardous operating condition. The quarter-turn ball valve design provides an inherently fast operation. Additionally, with its equal percentage flow characteristic (high gain), it not only can close fast but it can significantly decrease the amount of process fluid passing through. Emergency isolation devices should be arranged so that they can be fully function tested without affecting the process operation. This requires that a full-flow bypass may be necessary at each isolation valve if flow cannot be easily interrupted. These bypass installations should be locked closed when not in service for function testing the ESDV. There are 2 types of testing methods available. Proof test: A manual test that allows the operator to determine whether the valve is in the “as good as new” condition by testing for all possible failure modes and requires a plant shutdown. Diagnostic Test: An automated on-line test that will detect a percentage of the possible failure modes of the shutdown valve. An example of this for a shutdown valve would be a partial stroke test. Where motor-operated valves (MOVs) or air-operated valves (AOVs) are selected as ESDVs, they should, as a minimum, have backup activation power sources, and the utility service lines should be highly reliable and protected. It should be noted that full motor-operated and air-operated ESDVs are not the same as fail-safe spring return valves, even if frequent functional testing is undertaken. The reliability of an internal spring return actuator is considered better than a self-contained MOV or AOV with its own local power source and protection of cabling. This is because additional components of an MOV or AOV contribute to additional failure points and will also have a higher level or vulnerability from external events than an internal spring mechanism. Emergency Shutdown Valve is actuated valve which is closed when triggered by signal from ESD level signal during emergency condition occurs. Emergency Shutdown Valves are commonly located in incoming line and outgoing line of the plant or platform. жүктеу/скачать 2,11 Mb. Достарыңызбен бөлісу:
|