What should I do if an electric dark stem gate valve will not close?
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Hello everyone, the gas outlet valve of the latest blower in our drum recycling workshop will not close properly. Could anyone help me figure out what the cause is and how to fix it? The valve is a DN 1200 electric gate valve with a hidden stem, used for carrying gas. A few days ago, when trying to operate the valve manually, it got stuck; even after removing the electric actuator, two people were unable to move it using a lever. Now the valve cannot be opened or closed, and it is almost in its fully open position. We tried stopping the fan and using steam for internal heating; the temperature of the valve body reached around 90 degrees, but it still wouldn’t rotate. This issue has occurred with all 3 outlet valves when it’s cold; the other two valves work fine after being manually operated, but this one cannot be moved at all. Even after installing an electric actuator, it still won’t move when switched on and off. Is this because the tar temperature is too low, causing it to solidify and jam the gate, or is there a problem with the screw inside the valve?
It’s not easy to determine the cause in this case; it’s possible that the gate has come to its limit and has become dislodged from the tracks, or else the gate may be tilted to one side or the other. You can try hitting both sides of the valve body with a hammer to try and get the gate back into place
The main reason is that I really don’t want to use blind plates for isolation – it’s too troublesome and carries risks. Previously, this valve also had problems where it wouldn’t open, but it could be opened again after several days of steam cleaning. This time, the main suspicion is that tar condensation has caused a blockage, but half a month of cleaning so far has been ineffective
For a DN1200 valve, does knocking on both sides work?
You might give it a try. Steam cleaning worked before, and if it doesn’t work now it’s probably not due to tar condensation getting stuck. When we encountered this issue in after-sales service, we would try hitting it with a hammer. Anyway, you’re already looking for solutions; if nothing else works, you can kick it a few times;P;P
Don’t hit cast-iron valves too hard; if the valve body cracks, don’t come to me
For media containing solidified tar, it is advisable to 1. use valves with visible stem drives to prevent the internal moving parts from solidifying. ； 2. If a dark rod drive is selected, it is required to order the valve with a steam purge port. This preliminary analysis indicates that the transmission part is stuck by solidified tar. Consider how to resolve this from this perspective.
It is correct to consider the risk of clogging due to coal tar; I have clients who use hot gas, and they previously used gate valves. We recommend using butterfly valves designed specifically for gas, as this provides a more appropriate design. Gate valves are prone to clogging, although the situation is somewhat better with cold gas.
Just clean the valve sealing surface thoroughly, and that’s it.
Currently, the valves are almost all open and connected to the system; it’s not possible to clean them unless a blind flange is used to isolate the system. There are also a lack of steam purge holes; currently, a small screw on the top of the valve body has been removed to allow a steam pipe to be inserted for purging. Additionally, could prolonged steam purging dry out the tar, thereby increasing the risk of the gate getting stuck?