Why are two safety valves required to be in use simultaneously in medium-pressure boilers?
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As the title suggests: One of the medium-pressure boilers in our facility is equipped with two safety valves, both of which are in use at the same time. It seems that one should be in use while the other serves as a backup. I ask experts to give an explanation!
Double insurance! It seems that all important pressure vessels are equipped with 2 safety valves
Requirements for safety valves installed on boilers: 1. Boilers with a rated evaporation capacity of more than 0.5 t/h must be equipped with at least two safety valves; boilers with a rated evaporation capacity of 0.5 t/h or less must be equipped with at least one safety valve. Safety valves must be installed at the outlet of the split-type economizer and at the outlet of the steam superheater. 2. The safety valve should be installed vertically at the highest point of the boiler drum or header. No steam extraction outlet pipes or valves shall be installed between the safety valve and the boiler drum or header. 3. Lever-type safety valves must be equipped with devices to prevent the weight from moving on its own and guides to stop the lever from going out of position; spring-type safety valves must have lifting handles and mechanisms to prevent the adjustment screws from being turned arbitrarily. 4. For boilers with a rated steam pressure of 3.82 MPa or less, the throat diameter of the safety valve shall not be less than 25 mm; for boilers with a rated steam pressure greater than 3.82 MPa, the throat diameter of the safety valve shall not be less than 20 mm. 5. The cross-sectional area of the connection pipe between the safety valve and the boiler shall be no smaller than the inlet cross-sectional area of the safety valve. If several safety valves are installed together on a short pipe directly connected to the boiler drum, the cross-sectional area of the passage of this short pipe shall be not less than 1.25 times the total venting area of all the safety valves. 6. Safety valves should generally be equipped with exhaust pipes, which should lead to a safe location and have sufficient cross-sectional area to ensure smooth exhaust. At the bottom of the safety valve exhaust pipe, a drain pipe leading to a safe location should be installed; no valves are allowed to be installed on either the exhaust pipe or the drain pipe.
Thank you! There are also too many requirements and specifications regarding equipment. :handshake
One is a control safety valve, and the other is an actuation safety valve; their pressure levels are different, and it’s not a backup valve
Safety valves are not like water pumps or fans that need to operate continuously without stopping; so why is it necessary to have one in operation and another as a backup?
Hello! How should a control safety valve be understood?
The operating pressure of the control safety valve is lower than that of the main safety valve. When the pressure during operation exceeds the specified value, the control safety valve opens first to release steam; if the steam pressure returns to normal, the main safety valve does not need to activate. If the pressure continues to rise after the control safety valve has opened, the main safety valve will also open to release steam and thus control the pressure. You really need to learn more, buddy – asking questions like this means you’re on your way to being left behind by the times: lol
:(Luckily, I was lucky as a child and managed to get a job!) It feels like all my colleagues these days are really old; they really can’t keep up!
Safety valves all have a set pressure; once it is set, they are put into use and there is no such thing as a backup version.
The two pressure values are different; one is low pressure and the other is high pressure. During startup, the low pressure side activates first, followed by the high pressure side