Injector Will Not Work

[arch1947]

Hi Everyone, I have steamed Virginia twice now and each time the injector failed to work. The injector is a Blackgates No.2 (11 oz/min) plumbed as shown in the attached photo. I will post 2 other photos 'cos I don't know how to put more than one in a single post. The injector is connected with 5/32" od copper tubing and the flexible connection is larger in bore than the copper.
The proceedure I use is water on, steam on. The water dribbles out and then when I turn the steam on all I get is a lot of steam issuing from the overflow.
Water flow from the tender connection without anything connected seems OK but I have no real idea of what OK is. I think all the connections are airtight but there could be a bit of a restriction in the barbed fitting on the loco. Tender water level is above the injector.
Any ideas?
Can the steam supply volume be too high?

I will conduct a test in a day or two by connecting a small header tank as directly as possible to the injector to see if that has any effect but, in the meantime, and suggestions are most welcome.
Cheers,
Arch

Attachments:

[arch1947]

Hi Again, This is the plumbing from injector to loco connectors.

Attachments:

[arch1947]

This is the tender end showing the quick connect fitting which, in turn, is connected via 5/32" OD copper to the water control valve. At the base of the valve is a banjo fitting to which the copper tube attaches.

Attachments:

[cotswold]

If it has worked before then...

1. Make absolutely sure that there is no air leakage into the water supply pipes or fittings

2. Check for blockages by removing the injector and then dismantle (taking notes so that you can put it together again). Wash all the bits in weak pickle (I use citric acid).

Hope this helps.

[JDEng]

Is the clack on the boiler stuck shut?

J.

[arch1947]

Hi cotswold and J, From my experience it hasn't worked from the start. Also I don't think the boiler clack is stuck shut, if anything it weeps a bit when cold.
Cheers,
Arch

[chris vine]

Hi Arch,

Sometimes I find that a tricky injector can be made to start by careful operation of the steam valve:

open water valve fully,
open steam valve slowly and watch the overflow of water build up to a steady and fast stream.
then open steam valve fully.

Somehow this seems to set up a flow through the injector. I first saw this trick on Russian steam locomotives when travelling across the Ukraine some years ago. Only two of us on the trip were interested in riding on the footplate. The rest of the party stayed on the train.

Travelling at night was awesome! you hear a funny noise and realise you have just been over a bridge over a river etc. It becomes very apparent that everyone on the railway has to do their job just right or you will end up in a disaster. You did need a regular supply of tickets to the footplate, packets of Marlboro cigarettes!

Sorry to wander...
Chris.

[arch1947]

Hi Chris, The trip sounds fascinating, what a great experience. You comments about the technique for operating the injector kind of ring true and are along the lines of my train (no pun intended) of thought. I was thinking that perhaps a sudden burst of steam was preventing the water flow rather than inducing it. I'll try you suggestion.
Thanks,
Arch

[NickM]

Hi Arch

It sounds like you aren't getting enough water. Opening the water valve full should give you a steady flow, not a dribble. I can best describe it as a solid 'bar' of water coming out of the oveflow.
Closely examining your first photo, the water feed pipe seems a bit constricted just behind the wheel. This migh be an optical illusion but did you use a pipe bender to make your bends or just your fingers? If you dont use a proper bender the inside of the bend will flatten off, particuarly on tight bends so restricting the flow of water.

There is some very good information about injectors here: www.pollymodelengineering.co.uk/global/technical-notes/diagnosing-injector-problems.asp

Sorry to say this but in all probability there is nothing wrong with the injector, it is most likely the pipework that is causing the problem.

Good Luck!

NickM

[pault]

Hi All,
Having had new injectors that did not work and plumbing issues that prevented good injectors working I would try and get an injector that you know works (See it working on another loco) and try that on your loco. Alternatively you could try your injector on a loco which is known to have good plumbing i.e. its own injector works without a problem. This way you will at least have one known factor in the system, at the moment you have none. It addition to what Chris was saying about turning on the injector flicking the water off and then back on quickly can often get them started.
Cleaning the injector out is a good thing to do, it does not have to be blocked up it only needs a foreign body to disrupt the flow to stop them working. Pickling does not always fix this if the obstruction is a bit of coal, paint, PTFE tape etc etc A quick way that often works is to block the overflow with a rag on the pricker, turn on the steam, then open the water. Maintain this condition until you hear the water bubbling in the tender. Turn the steam off and remove the rag from the overflow. Let the water run through the injector for a short while to cool it then try starting it.
Hope this is of some help
Regards
Paul

[jma1009]

hi arch,

i agree with JDEng... the symptoms you describe sound like the clack valve not opening.

take off the injector or the pipe to the clack valve and with the backhead valves open (blower, injector steam etc) blow through the clack valve to see if it is sticking, and check that it reseals by creating a vacuum by your lungs too. the lift on an injector clackvalve should be more than the lift on axle pump clack valves.

you will only get a dribble of water through the overflow on an 11oz pm injector rather than a stream of water coz it is such a small injector.

also suck through the injector water delivery pipe from where it attaches to the injector with the water valve closed...you should be able to tell if any air is getting into the water line, which is fatal to the correct working of an injector. with the water valve open, blow through and you should be able to blow through back into the tender without feeling any restriction.

good luck,
cheers,
julian

[pault]

Hi All
Just had another thought the “quick release” fitting that you have used may not be suitable for use with a very low pressures/vacuum (injectors can suck quite hard). The collets which grip the pipe and the configuration of the seals in these fittings are often set up so that a positive pressure both seals and holds the pipe. With very low pressures or vacuum this does not happen and so they can leak like a sieve. Personally I just use silicon tube pushed onto plain copper tube for the water connections.

It may also be an idea to ditch the banjo fitting, the are quite restrictive when it comes to flow
Regards
Paul

[jma1009]

hi arch,

having looked at your pics carefully, in addition to all the above suggestions i would also try the injector with your overflow pipe removed, and remove the clamp arrangement round the top of the injector. the clamp isnt needed anyway and can be removed permanently.

it is not unusual on a new loco for bits of flux or swarf etc to get into the pipes to the injector (including via the steam valve) and so gum up the works. i presume you have a decent fine mesh filter fitted to the tender? the filter should be big enough to avoid any restriction to the water flow, and a small injector like yours will require quite fine mesh (i use silk screen stainless mesh). ideally the filter should be horizontal in the tender tank.... if vertical there can be a tendancy for air to be draw into the filter if the top of it isnt covered fully by water in the tank.

just a few more thoughts!

cheers,
julian

[arch1947]

Hi Everyone, Thanks for all the thoughts, looks like I have a bit of work ahead. We have a friend visiting from Melbourne this weekend so don't know when I will get a chance to steam the loco again but I will keep everyone posted.
Thanks,
Arch

[arch1947]

Hi Again, Been thinking about a couple of comments.
1.Water flow through the quick connect fittings seems OK, solid stream without much projection but the head is low.
2. If anything the boiler clack weeps a bit without boiler pressure as witnessed by a little water dropping from the injector overflow. Under pressure is eems OK.
3. I used a bender for the pipe work but final tweaking was almost certainly done with fingers but I don't think the pipe is crimped significantly but I'll check.
4. The orifices in the injector are an order of magnitude smaller than anything else in the water supply line so wouldn't this suggest that restrictions in the piping etc. would not be significant?
5. I can get steam to blow back into the tender by blocking the overflow.
6. I have pulled the cones out of the injector and will do so. There is no strainer in the tender at the moment. The design of the water control valve is such that a getting any sort of decent surface area would be difficult. Might need to redesign the valve.
Not sure where I am going with this but, again, any comments would be appreciated.
Cheers,
Arch

[jma1009]

hi arch,

i recommend you check that the clack valve will open and isnt stuck, even if it may leak a bit.

you MUST have a filter on the inlet for the water before it reaches the injector! if there isnt room in the tender (and i dont see why not!) then you can make up an 'in line' filter anywhere before the injector...usually a large piece of tube with a filter inside that can be unscrewed for cleaning.

i would strongly suggest that you do all the other checks that everyone has recommended too. it isnt necessary to steam a loco to check ALL the injector pipework!

the largest hole on a 12 oz injector is the steam cone throat at say 33 thou...that doesnt mean the pipework can be 33 thou bore! 5/32" thin wall OD tube is used for a very good reason!

cheers,
julian

[NickM]

Hi Arch

Regarding filters; I messed around trying to fit an inline fuel filter to the injector feed fitting from one of my side tanks but it didn't work when the top of the filter became exposed, it just started sucking air.

Ended up using a small square of 20 denier nylon (my missus didn't miss that pair of tights!) held over the inside threaded portion of the fitting with a suitable diameter O ring. Simple, cheap, easy to replace and works a treat. Result!

Regards

NickM

[jgb7573]

The filter on my Hunslet is also from a pair of tights. It's on the tank filler, rather than the outlet to the injector. Hence it does not affect the flow of water from the tank to the injector.

[Deleted]

Mar 20, 2012 18:07:57 GMT jma1009 said:

remove the clamp arrangement round the top of the injector. the clamp isnt needed

Have to disagree here. I hate to see injectors swinging around in space, supported only by the pipework. When you try to undo a crusted-up union, the whole lot moves and you can easily twist some of the pipes.

My loco has a supporting bracket under the overflow outlet on each injector. The bracket is sandwiched between the injector body and a flanged male-to-male fitting that screws into the overflow hole, and goes through the bracket.

Not easy to describe, I'll take a photo if anyone's interested.

[ejparrott]

The RMES 'Netta' suffers from poor water flow from the tender, the injector has never worked properly. Feed the injector directly from a tin with a pipe at the bottom and it works perfectly. Before taking any of the injector plumbing apart, try that, you may be surprised.