plan 53 flange system question

[YoYo2000]

Got a question. I have seen pump vendors having a flanged (welded) plan 53 system and tubing running from the flange to and from the the seal. Is this common? Why would they do tubing rather than piping? If system is not to see the process media, why not NPT rather than flanged? I dont see the reasoning. Can anyone shed some light on this?

Thanks in advance.

 

[1gibson]

These are sensitive to friction losses, so you don't want hard pipe with elbows, you want tubing with smooth bends. The plan 53 is usually in pump vendor's scope, and the exact location relative to the pump is unknown, so the connecting has to be done in the field. Tubing is easier, bend it by hand.

Why would you prefer flanged hard pipe? Don't say cost because after all the cutting/threading/fitting labor, you're in the hole compared to stainless tubing.

People are also less likely to stand on tubing, compared to hard pipe.