Function of the pump inlet pipe drain valve
Thread Content
I would like to ask fellow sailors: When installing the piping for the inlet of the centrifugal pump in our company, we always install a drain valve downstream of the inlet isolation valve, with a DN20 size, as shown in the figure below. What is the function of this drain valve? Is it possible to omit the installation of this drain valve? In that case, the flanges with necks paired with the valves could be welded directly to the elbows, thereby saving one welding joint. I would appreciate your guidance on this matter. Thank you.
Not clear, for draining? Connected to a pressure gauge?
I don’t think it’s necessary. Downcomers are generally located on horizontal pipes.
Why does this inlet pipe need to be connected upwards?
This drain valve should be located in the horizontal pipe section; it’s not possible to direct drainage from above, so purging is the only option
It’s probably not meant for drainage purposes.
Even in the absence of such a valve, the necked flanges associated with the large valves cannot be welded directly to the elbows; a section of straight pipe is required, so this welding joint cannot be avoided.
It plays a crucial role when introducing oil after the maintenance of mechanical pumps. Slowly open the outlet valve or the preheating valve, so that the oil circuit can be drained through the pump body; this helps to remove any remaining water or air, thereby preventing the pump from running dry. This is especially important for hot oil pumps. I welcome any feedback or comments.
May I ask why? Are there any standard regulations? “The \"SH 3012-2000 General Rules for the Design of Pipeline Layouts in the Petrochemical Industry\" stipulates that butt-welded flanges should not be connected directly to elbows without a straight pipe section. I have not seen any rule stating that necked flanges cannot be connected directly to elbows.
I agree with you; it should have such a function. Thank you! Are you in charge of machine pump maintenance?