Injector blowing steam back into the tender

[Glenn Brooks]

Had an interesting problem last night. One of my newly rebuilt 3/8” Penberthy injectors failed to pick up water and started blowing steam back into the tender. I didn’t think it was possible to backfeed steam in this manner. My shut off valve at the forward end of the boiler was open, and the check valve is new, previously working.

The specific conditions were:

1) boiler pressure around 80 PSI
2) tender was low on water, maybe 2-3” water left in the bottom. but the tender intake was submerged below the water line.
3) injector mounted mid boiler, so has to pick up water about 18”
4) injector was hot and I was trying to get it to pick up.

I thought Penberthy’s couldn’t backfeed steam in this manner. Why would this happen?


Thanks,
Glenn

[AnthonyDuarte]

Mostly likely reason is a clogged delivery cone, or the overflow check is not opening fully.

Anthony

[Fred_V]

If the boiler check is stuck open would that cause the blowback? I usually see that as steam out the overflow.

[Bill Shields]

Listen to Anthony...but my money would be on something downstream (like a check not opening) or a clogged line between the injector and the interior of the boiler.

Question: did you CHANGE anything about the injector position / piping when you rebuilt it?

[Fred_V]

A stuck overflow valve would do that.

[Fender]

+1 on the stuck overflow. Many locomotive injectors had a manual valve that closed the overflow, so the injector could be used to blow steam back into the tender, to keep the water lines from freezing in the winter. The handle on the left side of this photo controlled this valve. So if the overflow check valve is stuck closed, you'd get the same result