Should Feeder Pump discharge be throttled down... Picture of wire drawn erosion.

JUGHNE

Have hospital with 2 80HP Kewanee steam boilers. Only one on line at a time.
Operator has mentioned they wear out the brass check valves at the pump quite often. 1 1/2" check, poppet in vertical line type, steam rated. He said there are groves cut into the brass/bronze from use.

These vertical poppets are just above the pedestal pumps, there is also a swing check where it goes into the HL. (maybe 12' of piping involved)
These pumps will run just a few seconds for their cycle. I suggested throttling the discharge down to reduce the velocity thru the checks reducing wear. Also I wonder if that inrush would surge the water level up to shut off the feeder switch prematurely thereby not getting a full level of fill each time and increasing the recycling of feeder.
There is a older gate valve above the check and a good ball valve below it. I suggest throttling the ball valve below.

Pump is controlled by MM 150 SHD. System runs at 5 PSI.

Operator is leery of changing anything....... just because........ it has always been that way.

SWEI

Sounds like the pumps are quite a bit oversized. Perhaps you could shave the impellers?

JUGHNE

Installed new in mid 1970's, sized for more load than might be today with 65 amb. Shaving impellers would be drastic for the operator.......throttling the output shouldn't hurt anything IMO or not?....simple and reversible.

Mark Eatherton

It will eat the ball valve too. If the ball valve isn't critical, then go for it, but if it is needed for isolation, proceed with caution. What you're seeing is called fine wire drawing. It is hydraulic erosion corrosion, the physical eating of material due to velocity. It is enhanced when oxygen is present.

If there is a union present, you might be better off putting a round restrictive orifice inside the union to give it something to work against. That too will eventually fail, but is replaceable without a lot of work. Use the hardest metal you can find that is non ferrous, stainless steel?

ME

JUGHNE

Ball valves a fraction of the cost of steam rated check valve though.

Harvey Ramer

Is controlling the pump speed an option?

JUGHNE

Probably not feasible....another thing for someone to adjust or monitor. Just choking down the discharge seems the simplest way. If not enough flow the burner would shut down. Water level would have to drop another inch or so before the float feeder would kick in with fresh water.
Looking at some piping diagrams for feeder pumps most show a throttling valve installed after the check valve. So I'm guessing it may be a common practice.

SWEI

Globe valve?

Jamie Hall

SWEI said:

Globe valve?

Yup. If one wants reliable flow control, a globe valve is the way to do it. Depending on the size, it can be manual or -- more in larger sizes -- there is a variety of trims which can be added to maintain a constant flow, constant pressure drop, constant upstream or downstream pressures... etc.

JUGHNE

Thanks to all. From Dan's book it seems that both condensate pumps and feed pumps would have the same piping between pump and boiler. There is really no problem other than the wear on the check valves. I will try to convince the operator to cut down on the ball valve. (even though it is before the check with the gate after). Hope to get pictures of the worn check.

JUGHNE

These are the check valves that failed. Both are "Strataflo" made in Fort Wayne, IN...USA.

The one with the serious wire draw scoring is on the left and is marked "F 6 #300 1 1/2" 200 LB." Was just replaced. (don't have the poppet here). Looks like it was passing metal files or hacksaw blades........I wonder if the poppet was sticking and barely opening??

The one on the right, with it's poppet, is from the other pump and is marked "2014 E No. 400 1 1 /2" 400 LB". It had failed within the last year. (only had 2 deep scores)

JUGHNE

Thought I would bump this up before it fell completely off the edge. Quite the severe wear on the check valve....any comment?