Rerouting a Current Piping System

[James89]

Hey Everyone,

This is my first post here. I am currently working on an issue we have had with our Chemical Injection line for our boiler feedwater system. We currently have a poorly designed piping layout which has constant clogging issues and a pump that may not be properly rated for the system. At the moment we are pumping caustic (~2%) at about 2.4 gph into a makeup water pipe for our flash tank.

I am looking to move the injection site to one of two areas: further down the pipe or onto a spillback line for our boilers. My manager had suggested a third location right after the exit from the flash tank. This leads into a large PD pump with flow of 150 gpm rated at 50 psig.

I guess my question is, would that third option even be feasible? If so, should I treat the Injection system as though it were dropping into a header?

Some other info that might be useful:

Metering Pump Specs:
Flow: 2.4 gph
Rating: 1100 psi
Design: Simplex, Integral Motor
Power: 1/4 HP

PD Pump Specs:
Flow: 150 gpm
Rating: 50 psig
Power: 15 HP
Suction Piping Length: 2 ft from flash tank to pump.

Thanks for any help!

 

[bimr]

You state that you are pumping into the suction of a large PD pump. You would expect that the pressure that you will be pumping into will be relatively low pressure. I don't see any issue with this situation.

Most of the time, these small chemical injection systems use a back pressure injection valve to allow one to pump into a pressurized pipe.

http://www.neptune1.com/pumps/backvalv.htm

Note that you should oversize your chemical injection piping. It is typical to size these at 3 times the average flow because of the pulsing action of the PD pumps.

Also, be sure you have some type of pressure relief.