3/8" Penberthy Injector

[dunoon]

 Hi,

  I'm in charge of a 1" scale H-8 Allagany live steam loco for the C&O Railway Historcial Scoiety.  We are having a problem with the injector, it won't pick up water.  I've taken it apart and checked it out and there is nothing amiss, it has a good flow of water and steam.  I've tried all kinds of combinations of opening the steam and water but nothing but, steam and water coming out the vent.  Does anybody have anyother suggestions to try.  Thanks

Rich Davis

[cabbage]

Check that the cold water feeder from the tender is actually suppling COLD water to the injector. Hot or warm water is not as effective. regards ralph

[Semper Vaporo]

ANY air leaks will kill the injector.  Double check all connections and any flexible piping (rubber or bending joints).

[Mik]

 First two suggestions were great - third suggestion. Make sure your steam supply valve isn't leaking and the injector isn't too close to the boiler. An initial amount of steam MUST be able to condense in the body for it to work.... It bears repeating; Too hot injectors will not work! That's why upending your water jug on a balky injector is sometimes all it takes to get it going.

[JamesP]

All good suggestions... make sure there is a good supply of cold water, no restrictions in the water line, absolutely no air leaks and make sure the injector isn't overheated by leaking steam from the supply valve.  Also, make sure that the check valve on the feedwater line into the boiler is in order.  It should not leak, so as to overheat the injector, but it should open up freely in the proper direction.  Make sure that the feedwater line all the way into the boiler is clear, this includes the plumbing into the boiler shell.  These pipes can get clogged with lime or scale, so check them carefully.  Also, make sure that the overflow check valve in the injector is seating properly, but opens freely.  On a 3/8" Penberthy, you should be able to check it with your lungs by placing your mouth on the overflow - you should be able to inhale, but not exhale.  Another item that happens with Penberthy's in particular - you may know this already, but it's worth mentioning - is that the steam jet under the steam inlet tends to get lost when the injector is disassembled.  Make sure it is there or the injector will never work!  I've run across two different Penberthy's like this - the injector is all assembled and plumbed, but absolutely would not pick up.  It will make you do a double take when you unscrew the nut & fitting on the steam supply side and there isn't anything underneath it!  These are easily lost, since nothing physically holds it in once the steam inlet fitting is removed.

Let us know what you find - best of luck!

 - James

PS - A couple of simple things that we all have done.  There is usually a shutoff valve in the feedwater line between the boiler and check valve - make sure it's open.  Also, open the water valve a couple of turns first, then open the steam valve wide open.  Water should flow out of the overflow.  Carefully start closing the water valve until the injector "picks up"; no water (or at least very little) should come out of the overflow.  If steam comes out the overflow, open up the water valve.  Rule of thumb, always open the steam valve completely and adjust the water valve to make it pick up.

[dunoon]

Thanks guys for the suggestions, I'll give them a try and let you'se know what I find out.

Rich Davis

[JamesP]

You know the old saying, a picture is worth a thousand words... I thought I would post some pictures to show what the steam jet looks like.

Picture 1 is just the venerable 3/8" Penberthy, in this case the "Special" configuration.  The steam inlet is on the top whether it is a "Special" or "Stock":

 

 The next picture shows what you should see when you loosen the nut on the top of the injector and remove the steam inlet fitting:

 

Finally, this is what the steam jet looks like when removed from the injector.  This is the part that can be easily lost, since sometimes it will fall out when the nut and fitting are removed:

When you take the steam inlet fitting loose, make sure the small jet is in place.  It is a critical part and the injector won't function without it.  Check all the other things that were mentioned too, since any one of these issues can or will cause the injector to malfunction.

Good Luck!

 - James