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Injectors

Paule

Joined: 1-01-70

Topics: 1

Replies: 1

Posted: Sat 10th Nov 2012, 6:34pm
Injectors

Hi
Just built a Sweet William running at 120 PSI but I'm having trouble getting the injector to pick up above 80 PSI. I was wondering what ideas or what types of injectors other members use and if anyone has any experience of this? I'm running a N0.6 4 pint injector.
lforward to any ideas
 

Replies To This Post

donaldcottle

Joined: 1-01-70

Topics: 1

Replies: 31

Posted: Sat 10th Nov 2012, 10:39pm

Hi Paule, I would have thought that 120psi is a bit high for a 'Sweet William'! I had one many years ago, & that one operated at around 100 p.s.i.at the most. I find that the performance of quite a number of injectors, starts to fall off when steam pressure gets to around 100 p.s.i. I had until this week a large passenger loco. in 7.1/4" Gauge, & I would not have contemplated above 100 p.s.i. It wasn't necessary for one thing, & it always made all the steam I required.
(Especially with 'Ffos-y-fran' Welsh Dry Steam Coal which I call rocket fuel, but that's another matter).
 

Mick

Joined: 1-01-89

Topics: 7

Replies: 114

Posted: Sun 11th Nov 2012, 8:43am

Hi Paule, I run my 7¼" loco ELLA at 120 lbs. The right hand injector was fitted in 1991 when she was built and has never been off for cleaning or other attention since then and works perfectly right up to maximum pressure. It came from Blackgates and is a 4 pints per minute. The left hand injector is new as I gave away the orginal to a fellow in need. It was from Reeves and is a 60 oz (just over 3 pints per minute) rated at 125lbs max, 65 lbs minimum pressure and that works fine too. It is rated to cut out at 38 lbs but I have had it go lower when filling the boiler at the end of a running session. Reeves model number is 77, perhaps you could try one of them? Or as Don suggests, run at a lower pressure as replacing injectors is a costly business! And I totaly agree with Don's comments about FyF coal too.
Hi Paule, I run my 7¼" loco ELLA at 120 lbs. The right hand injector was fitted in 1991 when she was built and has never been off for cleaning or other attention since then and works perfectly right up to maximum pressure. It came from Blackgates and is a 4 pints per minute. The left hand injector is new as I gave away the orginal to a fellow in need. It was from Reeves and is a 60 oz (just over 3 pints per minute) rated at 125lbs max, 65 lbs minimum pressure and that works fine too. It is rated to cut out at 38 lbs but I have had it go lower when filling the boiler at the end of a running session. Reeves model number is 77, perhaps you could try one of them? Or as Don suggests, run at a lower pressure as replacing injectors is a costly business! And I totaly agree with Don's comments about FyF coal too.
 

ianholder

Joined: 1-01-78

Topics: 0

Replies: 4

Posted: Sun 11th Nov 2012, 12:55pm

Irrespective of the pick-up ranges of injectors I just don't think that you need to be running at that high pressure. I ran my 4" scale Hunslet at 80psi and it would pull loaded four coach trains all afternoon on the Frimley railway without any problems. The other big advantage was that when doing a repeat hydraulic test you only had to go to 120psi which was a lot easier with all the fittings in place.
 

Paule

Joined: 1-01-70

Topics: 1

Replies: 1

Posted: Sun 11th Nov 2012, 7:06pm

Thanks for your replies, The reason I'm running at 120 PSI is because the boiler and safety valve (Nabic) is the design used on the Stafford class locomotive by Station road steam. The valve is factory set and calibrated to 120 PSI. When running the pressure is adequate at 100 PSI but I would like the injector to pick up at 120 PSI for the steam test.
Thanks again
Paul.
 

Xz

Joined: 1-01-92

Topics: 17

Replies: 244

Posted: Sun 11th Nov 2012, 10:38pm

I remember a chap who built a 5" Royal Scot and had it set for 120psi, but not for long, he found it difficult to control at low speed with high loads and therefore soon dropped it back to 100 which was more than adequate. Re-setting your valve for 100, or even 90 (sufficient for a S/William) shouldn't be too difficult should you decide to do it. Your boiler inspector will not be concerned, other than to make a note on the certs.
 

Mick

Joined: 1-01-89

Topics: 7

Replies: 114

Posted: Mon 12th Nov 2012, 8:38am

Sorry to keep this going, but I use Kunkle valves on ELLA which are virtually identical to Nabics. You can't interfere with them, they are sealed and I imagine breaking the seal will invalidate your boiler's steam test. In any event to interfere with a commercially produced valve used in industry cannot be a good idea. The Stafford is a superb loco, by this Wednesday there will be three of these locos running at Abbeydale (Sheffield SMEE). Higher pressure gives better performance and shouldn't make low speed operation difficult, it isn't with the six locos running at Abbeydale which run at 120 or even 140 lbs!.
 

ilvaporista

Joined: 1-01-70

Topics: 0

Replies: 4

Posted: Mon 12th Nov 2012, 12:32pm

The injectors made by Double B designs work well at the higher pressures.  Most of the locos on the Naples track use these and they never fail to pick up, these were supplied tested for use up to 140psi.  One is also used at 160psi with no issues

Here's me getting ready for the day
The injectors made by Double B designs work well at the higher pressures. Most of the locos on the Naples track use these and they never fail to pick up, these were supplied tested for use up to 140psi. One is also used at 160psi with no issues

Here's me getting ready for the day
 

bruce morgans

Joined: 21-01-05

Topics: 6

Replies: 18

Posted: Mon 12th Nov 2012, 2:02pm

Hi Firstly I agree with those who say it is unnecessary to opperate above 80/90psi as you have all the power you need at this pressure. With regards to your specific question I am wondering whether you have an adequate water supply. As the pressure rises so does its temperature and when the steam leaves the steam cone the water must be able to condense it. If this is not happening the injector will not operate.
 

bobbramson

Joined: 23-09-00

Topics: 1

Replies: 3

Posted: Sat 8th Dec 2012, 8:24am

In my article to be published in the NEWS "All you need to know about miniature ejectors and injectors" I will explain the design principles that will enable an injector to deliver at higher pressures. I have supplied several injectors working up to 175 psi (see example in picture)and there is really no difficulty in making an instrument of that sort provided you follow the guidance outlined in my article. The limitation of the performance of an injector should not be a bar to adopting higher pressures in miniature steam locos. However, as has been discussed elsewhere in this topic, unless an engine has adequate adhesive weight, there is really no advantage (in fact a positive disadvantage)in using higher pressures. Member 2945
In my article to be published in the NEWS "All you need to know about miniature ejectors and injectors" I will explain the design principles that will enable an injector to deliver at higher pressures. I have supplied several injectors working up to 175 psi (see example in picture)and there is really no difficulty in making an instrument of that sort provided you follow the guidance outlined in my article. The limitation of the performance of an injector should not be a bar to adopting higher pressures in miniature steam locos. However, as has been discussed elsewhere in this topic, unless an engine has adequate adhesive weight, there is really no advantage (in fact a positive disadvantage)in using higher pressures. Member 2945
 

gavinfdavies

Joined: 1-01-70

Topics: 0

Replies: 4

Posted: Thu 24th Jan 2013, 8:35am

I'm looking forward to reading that article on injectors bob. I've not heard yet how these things work, and I can't seem to work it out on first principles.
 

roystonthomas

Joined: 1-01-85

Topics: 5

Replies: 16

Posted: Tue 29th Jan 2013, 6:19pm

I'm also looking forward to Bob Bramson's article appearing in The News. Meanwhile, if you need to know more about injectors now, can I recommend DAG Brown's book "Miniature Injectors Inside and Out" published by TEE Publishing. Its available from several suppliers and probably from fleabay and Amazonia too!
 

stuartcompton

Joined: 1-01-70

Topics: 4

Replies: 10

Posted: Mon 18th Feb 2013, 9:55pm

Couldn't agree more about recommending Derek Brown's book 'Miniature Injectors - Inside and Out'. Looking into the subject for my Sweet William build and wouldn't be without his book. An invaluable work on the subject in my opinion.
 
 
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