Emergency shutdown valves equipment

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. 

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... 

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. 

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). 

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... 

SIF description Detection of low low level by LT-4011 initiates an emergency shutdown and valve SDY-4012 closes to prevent high pressure gas flow to downstream equipment. ... 

Equipment Shutdown A system of equipment stoppage and emergency isolation valves that are used to isolate individual equipment within a process unit and prevent the release of potentially toxic material in the event of a fire, rupture, or loss of containment. 

Safety instrumented systems (SISs) should be completely separate from the normal control system. AU elements in the safety loop (measurement devices, logic systems, and actuators) must be highly reliable. This alarm system protects the facility against major catastrophes and will often take corrective actions to safely shutdown and isolate a piece of equipment or a facility, using emergency shutdown (ESD) systems that activate emergency block valves and emergency isolation valves. 

ANSI/ISA-84.00.01-2004 contains several references to the need to provide a manual shutdown backup for the logic solver. The main reference is clause 11.2.8, which states, Manual means (for example, emergency stop push button), independent of the logic solver, shall be provided to actuate the SIS final elements unless otherwise directed by the safety requirement specifications. This clause outlines a specific way a manual shutdown may be implemented, but allows the user to specify other ways to provide a manual shutdown. Manual shutdown can be initiated by the operator using the BPCS, remote or local pushbuttons and switches, or directly with process equipment, e.g., manual closure of valves. Manual shutdown capability should be provided for any SIS where maintenance bypasses are used to support online equipment repair, maintenance, and proof test. 

Total Plant Shutdown A total plant BSD effectively shuts down the total plant or facihty under emergency conditions. Isolation valves are closed to stop the flow of combustible, flammable, or potentially toxic fluids and to stop heat input to process heaters or reboilers, and rotating equipment. Activation of a total plant BSD should not stop or impede the operation of fire protection or suppression systems, deluge systems, sump pumps, or critical utilities such as instrument or process air. 

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