Pumped return banging

greatopportunity

Hi, I'm working on a steam system that has no gravity return, condensate is returning by pump only. The problem is that as soon as the pump kicks on to bring the condensate back, the return line starts banging a lot.

The way the return line ties into the boiler is as follows: the pipe goes down all the way to the floor, then after the 90 there's about a 3" nipple, then a tee bringing it up to about water level hight, then a 90 and a about 18" long nipple ( definitely wrong with a gravity return) into a tee into the equlizer.

Thanks all

JUGHNE

Is the return line you refer to the one between the pump and the boiler?

Can you do some pictures?

greatopportunity

Yes.
I'll post some pictures but not sure how much you'll be able to see.

greatopportunity

JUGHNE

So this is a remote "transfer pump"?

The water enters above the water line?

greatopportunity

It enters into that tee at about the water line.

greatopportunity

greatopportunity

Any insight?

JUGHNE

My guess is that the cond water is hitting the steam in the equalizer and causing the water hammer.

I would first try throttling down the cond water flow at the pump discharge.

Those things have a pretty high flow rate and could be shooting the water up the equalizer into the steam.

I even put a bypass piping on the pump to return some discharge into the tank to cut down on the flow. And also throttle the flow to the boiler.

If that does not work then perhaps lower the tee on the equalizer drop.

greatopportunity

Thanks for responding.
I don't believe its in the equlizer or riser since the banging is clearly in the return line.

JUGHNE

Do you hear the banging as soon as the pump turns on or after it shuts off?

Any pictures of the pump showing all the piping floor to ceiling?

JUGHNE

You could look at the book "The Lost Art of Steam...Revisited".

On page 303 your problem might be described.

Although you do not have a receiver boiler feeder pump at the boiler, you are pumping into a gravity return at the boiler.

greatopportunity

Wow! I've looked at that chapter before but didn't connect it to my problem, now I can't see why..

I'll follow that and let you know.

Thanks a lot.

greatopportunity

It's been over a year now and everything is still working nice and quiet.

Thanks all.

EdTheHeaterMan

I think this may be the problem. The reason for the close nipple is to reduce the noise that a long strait run of pipe will cause here.

The Loop connects into the equalizer through a close nipple and here's why. Steam rises up through the equalizer, just as it does through the boiler sections. When the relatively cool return water meets that steam at the close nipple, the rising steam bubbles quickly condense. Naturally, the return water rushes in to fill the void left by the collapsing bubbles, and this creates a slight water hammer inside the tee connecting the return to the equalizer. If you use a long nipple instead of a close nipple, the returning water will have more room to move, so it creates more water hammer through its inertia. Long nipples acts like gun barrels in this case, and you should always avoid them. Stick with a close nipple, or use a "Y"

That info can be found here: https://www.massengineers.com/Documents/Hartford%20Loop.htm

EBEBRATT-Ed

The nipple coming out of the hartford loop is too long. Disconnect the pump line and pump it into the bottom of the boiler and make sure the pump discharge has a check valve . You pumping water up into the header causing banging. You may be able to fix it by slowing the pump flow by throttling the valve in the pump discharge try that first