How do I shut down an electric emergency shutdown valve when there is a power outage due to a fire?
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How can an electric emergency shut-off valve be closed in the event of a power outage due to a fire? Nowadays, many oil depots and chemical storage tanks are equipped with electric emergency shut-off valves, such as electric gate valves used as emergency shut-off devices. So what happens if a fire breaks out in an oil depot or a chemical facility? If the wire burns out, what is used to shut it off? (In the event of a fire, it’s not possible to shut it off on site.) In the event of a fire, the wiring is also the first to get damaged and cause a power outage.
When the electric valve loses power, it remains in the state it was in before the power was cut, by default. The accident conditions generally refer to power outage or interlock status, rather than cable burnout. If such situations are to be taken into account, then FC pneumatic valves should be used, along with fire shields.
How to shut off the electric emergency shut-off valve in order to cut off power immediately in case of a fire? The emergency shut-off valve (the electric gate valve is of the normally open type)
If it was turned on before the power went out, there is no way to turn it off. To solve this problem, there are two methods: one is to use power supplied by a UPS ； Second is the use of pneumatic valves. The use of electric emergency shut-off valves poses inherent risks: electric valves operate slowly and do not have a fault status indicator. To use an electric cut-off valve, it is generally necessary that the material in the tank is not very hazardous, and that the power supply is stable.
There is usually a backup power supply (UPS), or else pneumatic valves should be used.
If the power circuit of an electric valve is damaged, the motor cannot operate and can only remain in its previous state.
This is related to whether the electric gate valve selected is fail-safe closed or fail-safe open.
Please refer to: Fire protection requirements for electrical equipment and cables in emergency shutdown systems; SINOPEC Construction (2011) No. 518 – Design specifications for emergency shutdown valves of liquefied hydrocarbon spheres, 4.7.11. Electric actuators and their accessories shall have fire protection measures; preferably, fire protection covers should be installed, and such covers must comply with UL1709 standards (safety requirements for rapid heating and combustion tests of protective materials made of structural steel). SH/T 3038-2017 Code for Electrical Design of Petrochemical Plants 8.1.5 For the following locations or circuits that need to remain powered during a certain period under the influence of an external fire, exposed cables shall be provided with fire-resistant protection or cables with fire-resistant properties shall be used: (Designation: Fire-resistant cable – NH; Flame-retardant cable – ZR) a) Important circuits such as those for fire suppression, alarm systems, emergency lighting, DC power supplies for circuit breaker operation, backup power supplies for emergency shutdown of generator sets, UPS systems, and UPS distribution circuits ； c) Circuits in flammable areas such as oil tank farms, as well as other important public building facilities, require fire resistance. GB 50016-2014 Code for Fire Protection Design of Buildings 10.1.10 Fire protection power distribution circuits shall meet the requirements for continuous power supply during a fire, and their installation shall comply with the following provisions: 1 When installed exposed (including within ceilings), they shall be protected by metal conduits or enclosed metal trays; such metal conduits or enclosed metal trays shall have fire protection measures in place (explanation: application of fire-resistant coating) ； When flame-retardant or fire-resistant cables are used and installed in cable trays or trenches, they may not require protection through metal conduits or enclosed metal enclosures ； When mineral-insulated non-flammable cables are used, they can be installed openly ； (Strong bar)