Emergency shutdown valves

In recent years much more attention has been given to pipeline isolation, after instances in which the contents of export pipelines fed platform fires, adding significantly to damage and loss of life. Many export and in field pipelines are now fitted with emergency shutdown valves (ESDV) close to the production platform, to isolate the pipeline in the event of an emergency. 

The gas riser failed below its Emergency Shutdown Valve, so the resulting leak could not be readily isolated. The leak ignited very quickly and fire engulfed MHN (the process platform) and MHF (the accommodation platform), while NA and the jack-up Noble Charlie Tester were severely damaged. 

Activation stations for emergency shutdown valves (ESDV) should be located at least 15 meters from the hazard the valve is intended to isolate. 

Allow 3 minute liquid surge time from LLL to low low liquid level (LLLL), and 3 minute su e time from ULL to high high liquid level (HHLL). It is assumed that at HLL or LLL, liquid level alarm will be sounded to alert the operator, and at HHLL or LL1.L, the feed flow or liquid outlet flow will be stopped by an emergency shutdown valve. HHLL and LLLL is user s option to have them or not. 

Per application flow control valve, pressure control valve, temperature control valve, level control valve, on- ofT control valve, manual control valve, emergency shutdown valve. 

Rupture pin technology is patented in t9K7-I990. Commercial production is started from 1990. Basically there are two types of products. One is rupture pin relief valve, which is like rupture disk, that its pin will buckle at set pressure to open the valve to relieve fluid. The other is buckling pin relief valve, which is like an emergency shutdown Valve, that its pin will buckle at Set pressure to close the valve to Slop fluid flow. This chapter will discuss the ruptiue pin valve oitly. 

The next step is to apply a number of loss control credit factors such as process control (emergency power, cooling, explosion control, emergency shutdown, computer control, inert gas, operating procedures, reactive chemical reviews), material isolation (remote control valves, blowdown, drainage, interlocks) and fire protection (leak detection, buried tanks, fire water supply, sprinkler systems, water curtains, foam, cable protection). The credit factors are combined and appHed to the fire and explosion index value to result in a net index. 

Emergency shutdown systems/valves not readily accessible. 

Most refinery process units and equipment are manifolded into a collection unit, called the blowdown system. Blowdown systems provide for the safe handling and disposal of liquids and gases that are either automatically vented from the process units through pressure relief valves, or that are manually drawn from units. Recirculated process streams and cooling water streams are often manually purged to prevent the continued buildup of contaminants in the stream. Part or all of the contents of equipment can also be purged to the blowdown system prior to shutdown before normal or emergency shutdowns. 

Safety valve releases are routed to blowdown drums when the presence of liquid, toxic properties or other factors would make discharge to the atmosphere hazardous. Product and intermediate process streams may need to be diverted to alternative disposal if they are off-specification (e.g., during startup) or in the event of emergency shutdown of downstream equipment. 

AS—Air Supply BD—Blowdown BF—Blind Flange CBD—Continuous Blowdown CD—Closed Drain CH-O—Chain Operated CSO—Car Seal Open CSC—Car Seal Closed DC—Drain Connection EBD—Emerg. Blowdown Valve ESD—Emerg. Shutdown FC—Fail Closed FO—Fail Open HC—Hose Connection IBD—Intermittent Blowdown LO—Lock Open ML—Manual Loading NC—Normally Closed NO—Normally Open OD—Open Drain... 

Valve 29 in line 14 is a quick opening bypass valve which is normally closed. However, in case of an emergency shutdown, this valve can be instantly opened to shut off the supply of alcohol to the reaction zone and return the alcohol stream via line 31 to alcohol supply tank 11. Such a quick opening by-pass valve normally is not employed in the nitrating acid line, since in case of an emergency shutdown, nitrating acid is employed to sweep out the tubular reactor... 

Accident Mitigation 28 Detection of leaks/ruptures 29 Emergency shutdown switch locations 30 Accessibility of isolation valves 31 Potential for fire/explosion in unit affecting other equipment 32 Critical controls, mitigation, communication, and fire protection sy stems functional and accessible after initial explosion or release 33 Back-up power supply/redundant feeds for critical electrical systems 34 Water supply for fire fighting 35 Routing of utilities... 

The top event is written at the top of the fault tree and is indicated as the top event (see Figure 11-14). Two events must occur for overpressuring failure of the alarm indicator and failure of the emergency shutdown system. These events must occur together so they must be connected by an AND function. The alarm indicator can fail by a failure of either pressure switch 1 or the alarm indicator light. These must be connected by OR functions. The emergency shutdown system can fail by a failure of either pressure switch 2 or the solenoid valve. These must also be connected by an OR function. The complete fault tree is shown in Figure 11-14. 

Provide hand-operated or automatic block valves, or equivalent valves, for emergency shutdowns. 

Each of these steps might be performed either by direct action of operations or emergency response personnel or by automatic systems. An example of the latter might be an array of toxic or flammable gas detectors that might trip an emergency shutdown system that closes remotely actuated block valves and vents off the process pressure to a flare if two adjacent sensors read above a predetermined vapor concentration. 

Tubing, conduit, and valve operators Exception For safety or emergency shutdown purposes, some pneumatically operated valves may intentionally use plastic tubing that is intended to fail in fire or high heat exposure in order to ensure that the valve moves to the desired position. 15 minutes... 

Isolation or emergency shutdown (ESD) valves should be installed to stop fuel flow and the process feed flow into the heater in the event of heater tube rupture. These valves can be automatically actuated by controls or safety interlocks or can be manually operated remotely. Remote actuation can be from a control room console or in the field field actuation stations should be located at least 50 ft (15 m) from the heater. It is also common to provide a manual block valve, located at least 50 ft (15 m) from the heater, on each of the fuel and process feed lines. These should be accessible to operators in the event of an incident involving the heater. 

Where a loading system s emergency shutdown system closes a valve on gravity or pipeline fed transfer systems, care should be taken to ensure the line is protected against pressure surges or hydraulic hammers which may cause gasket blowout or line failure (NFPA 30). 

Control can be exercised by the operator in the control roam on the well chokes and manifold divert valves (although this is normally handled by the HOC), start/atop of the oil shipping pumps, utility equipment, switching valves, gas plant feed valves, gas compressor start/stop and emergency shutdown of any production train or the entire GC. Since the closed loop process control is performed by local pneumatic instruments, all set point changes and controller troubleshooting must be accomplished locally. 

NONE No Flow 1. Flow stopped upstream. 2. Line blockage OT the isolation valve shut in error. 3. Line fracture. No absorption in column. Entire process stops as tail-gas Row As for I. Pressure buildup in pipe and secon cooler. As for I. Gases escape into the surroundings. a) Ensure liquid feeds to absorber and Stops.Other process units shut down. b) Install LOW FLOW ALARM onto the FIC. Covered by a) and b). dary c) Install kick-back on upstream pumps and ensure pressure relief system is adequate. Covered by a) and b). d) Ensure regular patrolling of feed transfer lines. e) Plant emergency shutdown procedures. 

The primary system is intended to isolate the major equipment in order to prevent reverse flow and exhaust oxides in a gaseous state. It consists of a special restraint type valve (check) and two motorised shutdown valves, arranged in series. The system includes a low pressure detector on the main pipe that trips the sulphuric acid pumps, isolates the process and stops the helium flow into the reactor and heaters (emergency system EAS-200). 

Class 1 safety instrumentation loops include alarms and trips on storage tanks containing flammable or toxic liquids, devices to control high temperature and high pressure on exothermic-reaction vessels, and control mechanisms for low-flow, high-temperature fluids on fired heaters. Other Class 1 instruments include alarms that warn of flame failure on fired heaters, and vapor detectors for emergency valve isolation and sprinkler-system activation. All of these alarms, shutdown valves, and other critical instruments are regularly proof-tested to a well-defined schedule. 

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