Steam condensate return pump

bassman

I maintain a steam boiler at our local Catholic school. My charity work. I have been having problems with leaking pumps for the last 3-years on the Hoffman condensate return tank. I am also going down there and the pump is always running but not pumping. I have replaced the check valve and installed a bleeder valve which as soon as I open it the pump takes off and starts pumping return water back to boiler. The return is connected to Hartford loop at boiler. I am getting sick of changing leaking pumps. I ended up buying a spare so I always had one to replace the leakier why I have the other repaired. Any suggestion why the pump is air locking and burning up the seals

RJ_4

pump

You may be getting steam back to the cond. pump.   Time to check your traps and replace or rebuild as necessary,  when were they last checked ?

MTC

Make sure

that the vent pipe on the condensate is not plugged. This often occurs, and you get a pressurized, potentially steam filled, tank. Not good, and potentially could cause problems with your pump, as well as a multitude of other problems in the system.



If it is plugged and you remove the plug and see steam coming out the vent pipe, then you know your traps need attention.

Pumpguy

Is there

a vacuum on the receiver tank this pump discharges from?  And, does this pump discharge to a vented boiler feed tank? 



If yes, see if the pump discharges OK with no vacuum on the receiver tank. 



This is a common problem if the answer to both of the above questions is yes. 



If yes, a temporary solution is to be sure the new check valve for the condensate pump is air tight.  It will eventually wear and leak air again and the problem will come back. 



A permanent solution is to provide a water seal across the opening of the condensate pump's discharge pipe where it dumps into the vented boiler feed tank. 



This can be accomplished in any of 3 ways. 

1)  Repipe the discharge pipe so it fills the boiler feed tank FROM THE BOTTOM.



2) Install a reverse stand pipe inside the boiler feed tank that dips down below the lowest water level, providing the water seal.



3) Repipe the discharge pipe from the condensate pump so it taps into the boiler feed tank's drain tapping, and then up into the normal boiler feed tank's inlet connection.



Any of these changes will provide the necessary water seal, and now the only fluid that will back flow through the condensate pump is water, not air. 



Hope this helps.  Let us know.

Pumpguy

More thoughts

Thought about your problem some more. 



First of all, is the float switch sticking in the on position?  This should be checked first. 



Where have you installed the bleeder valve? 



I would remove the bleeder valve and install a bleed line, piped back to the condensate receiver above the pump's suction flange.  This can be 1/4' OD copper tube and should be a permanent solution. 



Is the pump a vertical type?



Most vertical condensate pumps have a copper tube bleed line piped from the seal cavity just under the motor to the condensate pump's receiver, above the pump's suction flange. 



The purpose of this line is to bleed air from the seal cavity, and also to allow a flow of water past the seal to cool and lubricate it. 



1/4" is a barely marginal size for this service.  I have seen 5/16" copper tube and even 3/8" pipe used for these bleed lines.  Obviously, the larger the bleed pipe, the more air it can vent back to the receiver. 



Some vertical condensate pumps have this vent in the form of drilled passages back to the pump suction.  If yours is like this, I would check that this passage is clear, and not obstructed with debris, gasket sealing compounds, or incorrect assembly. 



Almost always I have found that this air bound problem is found on a vertical pump, not horizontal.  My theory is that the case would always be at least half full, and this is enough for the pump to pick up its prime and start pumping. 



So, if you can turn your pump on its inlet flange so its horizontal, that should help. 



I hope this information is useful to you.  If not, post more details and I'm sure we can come up with a solution.

schrod

schrod is bassman

I want to thank all of you for your responses. I didn't know I would get that much good feedback. I had to create another account. I couldn't remember password and the system kept telling me it was sending a email to change it . I never received a email even in my junk mail so I just set up another account. First of all I haven't really had the time to work on this last couple of days. I know the steam traps in building have been neglected for some time and I may change them all out this summer if Church comes up with money. I will check the vent pipe to see if it is plugged 2" black pipe vented outside building and was installed about 7 years ago. The pump discharges back to the bottom of Hartford loop. I just dont see how pump  [ it is a vertical pump]could be getting air locked or want every is happening because the tank is always showing about 1/2 full or more in sight glass. I like the idea of bleed line at pump and will check it out. Thanks for all the ideas

MTC

I just did an entire building of steam traps

in one day, including all the F&T traps. Its a 7 unit building, 35ish radiators, 5 F&Ts. If it wasn't for a couple broken bolts that had to be drilled out, the wrong size socket at first (barely, but enough to slip on a couple), etc, I'd have done the whole building in half a day.



Why am I telling you this... if you don't have an impact gun, go to Harbor Freight or something and buy one for $40. It will make changing traps a breeze. And get exactly the right size socket for it, preferably in a hex, not 12 point pattern. I did fine with a 12 point that fit tightly, but why take chances?



We had changed one of the traps shortly before with a breaker bar and pipe wrench to stabilize the trap while working on a leaking push nipple in a radiator. It probably took 10 times as long, 100 times the effort, and put 50 times the stress on the fittings. There's just no comparison



Good luck with your pump, I'm not really your guy for that, but there's a pumpguy on here :-P