The LNER Encyclopedia

Good Morning,

I'm in the process of refurbishing a model of a K3/2. It's taking a bit of work and there are a few bits missing. I can source the missing Wakefield lubricator, but there's a valve missing and I'd like to know what it's called so I can try and source a replacement.

Under the cab on the K3, on each side, there's a pipe that runs vertically down (from the footplate?) and turns towards the rear of the loco, through a valve of some description which is attached to a stay on the loco cab steps. It's not the sander pipes that I'm thinking of. I think that valve is called an ejector, but I'm no expert.

Is there an expert out there that could help me please?

Regards,

Vernon

Hi, I'm no expert either although I do have a grasp of how locomotives work and what the various components on a locomotive do. From what you're describing I would think that the items to which you refer are the live steam and exhaust steam injectors, which are devices for feeding water into the boiler. My understanding is that the exhaust injector is the more efficient of the two, as it uses exhaust steam rather than newly generated steam to feed water into the boiler. I hope this is of some use to you, but I'm sure if I have given you incorrect information the more knowledgeable on this forum, of whom there are many, will give you a fuller, more correct answer.

Dave

Ay up!

Injectors mix steam and water and the increased velocity of the feedwater is used to overcome the boiler pressure keeping the clack valve closed and so inject feed water into the boiler. On LNER engines, these clack valves are usually on the firebox backhead in the cab. Stanier and GWR locos have them in a "top feed" arrangement atop the boiler. Bullied and the BR standards had them on the boiler "shoulder."

Most locomotives have two injectors. However, only the larger engines have an exhaust steam injector. This is because they are far more complex than live steam injectors, having automatic changeover from live steam to exhaust steam operation. They can be a maintenance nightmare, which is why many locos in the late '60s had the exhaust steam feed blanked off.

It isn't true to say that the exhaust injector is more efficient per se. It is only insamuch as it uses exhaust steam as it's source of energy. However, when the engine's regulator is closed, then it uses live steam.

Much as I dislike Wiki, this article (http://en.wikipedia.org/wiki/Injector) gives a decent explanation.

Hope this clears it up.

I understand that the outlet pressure from an injector must be higher than boiler pressure but does anyone have any figures. If you have a 200psi boiler, what pressure would one expect to see as it enters the boiler?

NG

OK thanks to you for giving me some help. I guess I'll be looking for exhaust and live steam injecyotrs then.

Regards,

Vernon

If my memory serves, exhaust steam injectors were only fitted to locos with more than two cyliders due to the number of exhaust beats and even then, they would not work on exhaust steam until the valve gear was well notched up and a fair speed.
The B1 for instance had two live steam injectors. A few of the D49's had a seperate valve lever at the boiler face where you could transfer, manually, from live to exhaust only fitted to some of the Shire class and not the Hunts with rotary cam gear.
Speaking of LNER loco's.

neilgow wrote:I understand that the outlet pressure from an injector must be higher than boiler pressure but does anyone have any figures. If you have a 200psi boiler, what pressure would one expect to see as it enters the boiler?

Injectors work because of the Bernoulli's principle. That is because a stream of steam and water enters the boiler at high speed it lowers the local boiler pressure. This allows steam at boiler pressure to force water into the boiler.

As a matter of interest, can you work out which injector is on which side?

Regards,

Vernon

neilgow wrote:I understand that the outlet pressure from an injector must be higher than boiler pressure but does anyone have any figures. If you have a 200psi boiler, what pressure would one expect to see as it enters the boiler?

NG

The answer is that the velocity of the water delivery exceeds the pressure. Basically, the middle of the injector is open to the atmosphere and it is the increased velocity of the steam as it "jumps the gap" between the two cones that sucks in the water and overcomes the boiler pressure.

The injector works through energy conversion. Pressure is potential energy. By passing pressurised steam through a convergent nozzle the steam is given velocity and the energy is converted to kinetic. As the high velocity steam exits the steam cone it meets cold water and imparts the kinetic energy to the incoming water and as it condenses the high velocity mixture is passed through a set of convergent nozzles known as the combining cone, further increasing the velocity. The stream of hot water enters the delivery cone which is a divergent nozzle and as the water passes through the increasing area the stream slows and the kinetic energy is converted to potential and thus the pressure increases, and so long as the resultant pressure is greater than the boiler pressure the water will lift the delivery or check valve and will enter the boiler. The invention of the injector is attributed to Giffard, a french engineer, in 1835, and by 1850 the use of mechanical feed pumps on railway locomotives had more of less died out. Many improvements were made to injectors over the years, mostly to ensure reliable starting and automatic restarting but the basic principal remained. The exhaust injector is a complex instrument, but it was worth the extra cost and maintenance because of the significant improvement in the overall efficiency of the locomotive when in use due to the reuse of the exhaust steam. There is an argument that injectors approach 100% efficiency since all the energy inputted finds it's way into the boiler except for that lost by radiation form the external surfaces of the injector and delivery pipework.

Any locomotive could be fitted, but generally locomotives that ran under steady state conditions made the best use of them, so express passenger and fast goods engines were the usual candidates. The change over from live steam to exhaust steam was made when the steam chest pressure i.e. the steam at the cylinders, reached 50 psi, thus ensuring sufficient exhaust pressure (10 to 15 psi) was available. Closing the regulator would cause the injector to revert to live steam with some waste of water until the injector picked up again, so it was not wise to use the exhaust injector when shunting or traveling at low speeds. There could be a point when running at high speed that there was insufficient exhaust pressure for the injector and it would stop feeding because there was still enough steam chest pressure to prevent it changing back to live steam.

The exhaust injector was usually put on the fireman's side of the engine. This encouraged it's use and made it easier for the fireman to operate the water regulator which gave some control over the rate of feed. Usually the tender water valve could be left open as exhaust injectors were fitted with an automatic water valve operated by the live steam feed.

An interesting story is that of the Franco Crosti 9Fs, where the contract for the boilers included a clause that guaranteed an increased efficiency over the standard boiler with a substantial cost penalty if they failed to do so. Crosti had not reckoned with the efficiency saving of the exhaust injectors fitted to the standard 9Fs and made no money on the contract.

Eddie

Ay up!

Thanks for the explanation for the principle behind the injector.

Certainly engines on other railways used exhaust injectors on 2-cyl locos. Black 5s, Stanier 2-6-0s, Crabs and 8Fs all had exhaust injectors and also many 4F and 2P locos on the LMS. The last 2 reveal the fitment by means of a small pipe beside the smokebox. Most GWR 4-6-0s had exhaust injectors as well.

To pick them out, the exhaust injector is a much larger diameter than the live steam injector. Most (not all - see comments regarding 2Ps and 4Fs) have a large diameter steam pipe going into the front of it. On Stanier engines, the exhaust injector is found beneath the fireman's side of the cab.

K3 injectors, it's some 60 years since I last worked K3s but if an exhaust steam injector was fitted it would always be on the drivers side. The steam valve on that side was a pull out handle.I do remember we always had a short firing shovel for a K3.
Boiler pressure say 180 psi and injector pressure supplied also 180 psi. How did the clack lift ??
The hot water being supplied to the boiler would "expand" giving the extra energy needed to lift the clack.
JB 51B.

Hi Jim,

I've just been looking at some K3 pictures and drawings. The original GNR H4s and the earlier LNER K3s were right had drive and the exhaust injector was on the left side. The later engines, built mostly by contractors were left hand drive and the exhaust injector was on the right (I have GAs and pipe and rod drawings for Armstrong Whitworth and Robert Stephenson locos). I do have a photo of a footplate of a K3 with left hand drive and an exhaust injector on the left. I think it is one of the earlier engines as it has piano stool seats, the later ones had bucket seats, so I wonder if engines that were rebuilt from right hand drive to left hand kept their exhaust injectors on the left. Both the drawings and the photographs show handwheels on both injectors. The pull out steam valve handle strikes me as being odd. I always thought this was fitted to the B1s and perhaps other Thompson locos that had the long across the back plate regulator handle, to lessen the chances of the fireman getting his wrist chopped if the driver shut the regulator when the fireman was operating the valve, and the only one I know of in preservation is on 61306. Of course there is nothing to say that other locos didn't pick up odd bits and pieces when they went through the works, or even on shed.

Where were you in 1953? According to Yeadon there were no K3s on Teesside then. Thornaby had one or two in '60, 61 and 62, 61818,61844 and 61986. I have a picture of 61985 at Thornaby as well, but it was either at Tweedmouth or Dairycoates at that time. Presumably locos worked in from all over and you might have worked my favourite 61962 which was at Heaton and Tweedmouth at various times in the 50's.

Eddie

K3 61962 at Tweedmouth. St Margarets, Tweedmouth and Heaton had a fleet of K3s which with the V2s monopolised the Newcastle Edinburgh goods work in the 40s, 50s and early 60s.

Hi 52D,

Super photo. Shows that 61962 was fitted with a hopper ashpan (you can see the bracket at the bottom of the frames for the operating handle just behind the driving wheel) a fact that Yeadons doesn't record.

Eddie