What do \"accident on\" and \"accident off\" mean?
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There is also something about what it means to open a lead seal and to close a lead seal.
It is related to the process: for example, in the case of a failure in the control valve for the cooling water used in exothermic reactions, such as a power outage, the valve remains in the fully open position; the feed of the reaction medium is completely shut off, while emergency or accident discharge systems are kept in the fully open state.
This post was last edited by ylb913 on 2015-10-27 at 13:53. An accident shut valve is one that closes automatically when the instrument air or instrument power is lost, while an accident open valve is one that opens automatically when the instrument air or instrument power is lost. ——This is for the safety of the installation; it prevents the equipment from overheating, overpressuring, or having its liquid level or interface pressure become too low in the event of a sudden shutdown of the instrument air supply. For lead-sealed switches, the sealing should be applied after they are opened (such as the manual valves before and after a safety valve), or after the valves are closed (such as the bypass valves of safety valves, as well as the bypass valves of certain metering devices for inflow and outflow).
There should be two types of valves: those that open in case of pressure buildup and those that close in such situations (or valves that close in the event of power loss and those that open). These valves are installed according to the requirements of the process; in abnormal situations or when there is a loss of power or pressure, they automatically open and close to ensure the safety of the system. It can also be considered a form of intrinsically safe design
Accident open/close refers to the open/closed state of the control valve at the time of an accident, in order to meet various process and safety requirements. Sealing the valve on/off involves applying a lead seal after the manual valve has been opened or closed, in order to prevent accidental operations.
The installation can be understood literally: \"Accident open\" means that the valve is in the fully open position during an accident, while \"Accident close\" means the opposite – the valve is in the closed position during an accident.
Emergency open and emergency close generally refer to valves equipped with pneumatic or electric actuators on process pipelines and fire safety pipelines; in the event of failures such as a loss of air supply or power, these valves need to be maintained in a specific open or closed state in accordance with process requirements or safety regulations. Valves such as those used to open and close the cooling and pressure-reducing media, as well as fire suppression spray valves, which are required by process specifications, are generally designed to operate in an emergency mode ； Valves with hazardous properties in terms of operation, when opened and closed, are generally required to be of the fail-safe type.
Taking pneumatic valves as an example, in the case of faulty opening (FO), the valve opens when air supply is lost; this is also known as air-operated shut-off； Fault Close (FC): the valve closes in the event of a loss of air pressure; it is also known as air-open type ； Fault protection is achieved through spring return as the driving force. Opening and closing the lead seal is related to safety valves.
Accident open and accident close refer to whether a pneumatic valve remains in a closed or open state when the air supply pressure is lost. An accident opening refers to the valve opening when the gas supply pressure is lost ； The rule for accidents is the opposite.
An accident open valve is a wind-shut type control valve, while an accident close valve is a wind-open type control valve. This is for safety reasons.
Where was the term \"opening a seal\" and \"closing a seal\" first heard to be used?