API Plan 13 1

[RS82]

I have a vertical in-line pump with a plan 13 piping. The piping has a high point vent on it..is the plan 13 line not a vent in it self? The piping comes off horizontally from the seal (highest point) and goes down towards the drain line where it Tee's off..

Some say the high point vent is necessary if the piping coming off the seal is slightly higher than the seal before it goes down to suction..is this true??

 

[JJPellin]

In a strict sense, it might not be completely necessary. But there will be gas at the high point around the seal when you start the pump. Until the pump build sufficient pressure to displace this gas and flood the area around the seal, the seal faces will run dry. This might only be for a second or two. But, it would be preferable to vent the seal and the associated piping completely full before starting the pump. Unless your product is very hazardous I would recommend that you leave the vent in place and use it.

Johnny Pellin

 

[RS82]

Thanks Johnny! As of right now, the line comes off the seal horizontally to a Tee which has a bull plug on one side and the line running down to the suction. If there is gas build up at the seal face and we are waiting for enough pressure to build to push the gas through the line, even if we remove the bull plug and vent the pipe the gas should not leave the seal chamber as there is not enough pressure to push it through the line. once the pressure is suffice, then it will push the gas through the line as it is back to suction..then why do we need to vent it prior? Gas should remain in the seal chamber for a couple of seconds or so no matter what..am i seeing this right? Apologies if this is a stupid question

 

[JJPellin]

You did not list your process conditions. Most of the pumps that I work with have positive (higher than atmospheric) suction pressure. The pump is flooded from the suction. The positive suction pressure is sufficient to vent the high point to atmosphere and flood the pump. If your suction pressure is negative, then this will not work with your pump. But, centrifugal pumps with negative suction pressure are unusual.

The Plan 13 piping cannot vent the pump when it is not running because both ends of the line are at suction pressure and there is no differential pressure to drive any flow. It is only after the pump is started, that the seal chamber pressure increases and provides the pressure differential to vent the chamber.

As I said, venting is desirable but not mandatory. We have dozens of pumps of this configuration with this piping arrangement. Some of them are set up for venting and some of them are not. I prefer to vent when it can be done safely.


Johnny Pellin