Steam at the end of the Tunnel...

It's been a long time since Joyce's original superheater (SH) blew a hole in June 2022. Getting a new one up and running has not been easy but I'm now only a few odd jobs away from being ready to do a test firing.

Despite all the difficulties, I did eventually receive the SH but it arrived as a poorly assembled kit of parts.

I'm very grateful to my friends at the North Yorkshire Moors Railway (NYMR) for helping me with transport logistics.

On initial examination, it was obvious that the coils were not secured properly; they had shifted and were no longer properly supported.

These photos illustrate the point.

Centre of photo shows coil clamps (Upper is displaced)

Coil spacers poking out on one side correctly...

 

...But not on the other side

RH bottom clamp out of line and not supporting inner coil

I did of course make this known to RBS but was assured that it was fine when it left them and denied all responsibility.

Let's consider this:

1. It's a superheater required to operate in a very harsh environment whilst being continually shaken, rattled and rolled by the surrounding steam loco. If it cannot survive a ride in a van, it is not fit to be in a steam locomotive.

2. On collection from RBS, I was told by the NYMR driver that it had been unceremoniously dumped outside RBS leaving the driver no option but to borrow a fork lift truck from a neighbouring company to put it into his van. 

These photos were taken at NYMR on my collection visit.

My first view of the completed unit

Same location - the clamps were already displaced
Note the SH spreader plates tied on, not fitted

Welded locking bar

So why had this happened?

I removed the two welded locking bars and loosened the two supporting struts and did my best to pull things back into shape. However, I had limited facilities and could not make any impression on it.

I did however try taking off the top plate and substituting ½” spacers under the large nuts. The idea being that with the top plate out of the way, I would have better access to pull things into shape. But to no avail.

It was at this point that I realised why the coils had shifted. When I tried to tighten one of the clamping brackets with the ½” spacer present, I found that I could not tighten the clamp down on the coils because the nut had reached the end of the threads on the supporting strut.

As such, with the top plate in place, it would not be possible to clamp the coils securely.

In the next photo, the fixing rods are shown protruding through the brackets but there is insufficient thread to tighten the brackets and secure the coils.

Limited thread on the struts

My conclusion at this point was that, although the coils were actually pretty good, the unit as a whole was not fit for purpose - certainly not the ready-to-drop-straight-in item I had ordered.

So what next? 

When I had originally begun looking for someone to make the new SH, I started with JR Goold Steam Ltd whom I had worked with during Joyce's restoration. They were unable to do the tube bending, however, given completed coils, the job was now well within JR Goold's capabilities. They had also done the same work first time round during Joyce's restoration.

(Check out https://www.gooldsteam.com/sentinel_superheaters).

I was certainly not prepared to continue with RBS for obvious reasons. (https://sentinel7109.blogspot.com/2024/04/renewing-joyces-superheater-1.html).

Initially I discussed the problems with JRGS referring to a Sentinel boiler drawing similar to Joyce's and photos of the problem shown above.

These were my requirements:

1. Flatten the top plate so that the funnel bases will seal properly. There is a dip in the middle of the cross-piece at present.

2. Make the necessary spacers to hang the SH coils properly from the top plate.

3. Reassemble the tubing and top plate and tighten the coils in place.

I also provided some dimensions as to where the tube flanges would need to be should any adjustment be necessary.

A few weeks later all was complete and I asked Peter Hawkins, Joyce's boiler inspector since 2009, to examine it before accepting from JRGS. All was well and a preliminary certificate was issued covering the work and giving me the go-ahead to reassemble all into Joyce ready for a test steaming to check for anything untoward. A formal inspection run would follow as in previous annual inspections. (The test run is to make sure that all is well - Boiler inspectors still have to be paid even if they don't issue a certificate).

The final unit from JRGS

Clamps holding the coils correctly

New spacers supporting coils on one side...

...and on the other

Clamps in line and supporting the coils

The unit followed by the funnels was craned-in with help from local company R J King Ltd. Their driver, Paul, had craned in the entire boiler back in October 2011 and so it was almost a repeat performance for him.

Sky Hook?

And seated!

Watch this space.

Steam Heating (4)

Following on from Steam Heating (3), Sentinel 7109 had a brief steam test a few days before the start of the 2019 Santa specials. (I'll write about the reason for the brevity in due course).

To the casual observer, the carriage heating performed well although it also showed that the carriages themselves have a number of leaks and cold areas to be attended to. The leaks certainly add to the atmosphere but not always where you want it.

Carriage Warming up and running (Photo: Roger Burfitt)

To the not-so-casual observer, i.e. me, all was not quite as perfect as I'd hoped.

Spirax-Sarco PRV on the left

The Blue Spirax-Sarco Pressure Reducing Valve (PRV) can be adjusted to give the 20-40 psi output pressure range required but it is faced with a very variable load. (For carriage warming, steam is squirted down the steam heating pipe and it exits as steam or water through a series of drip valves after passing through various heat exchangers. There is thus a back pressure from the carriage pipework and hence a 'load' on the steam generator. On initial starting-up, the far end of the pipework is opened to atmosphere to allow the steam through rapidly with much reduced back pressure).

When initially started from cold, the steam is fed into a large cold space. It immediately condenses and this takes place progressively along the two carriages until all is warmed through and steam is exuding from the hose at the far end of the train.

The loading thus initially varies considerably and then will vary yet again depending on how many carriage heaters are switched on and off.

Whilst the PRV can be set initially so that it supplies the right pressure, the changing load then plays with the setting. The PRV also tends to oscillate with a repetitive 'kerr-dunk' noise which I doubt is particularly kind to it.

Setting the PRV to be either on the high side or low side of the pressure range seems to calm down the oscillation. It can also be calmed by limiting the inlet flow using the isolation valve.

I've put a reducing-flow orifice in the inlet steam feed to the PRV which has also helped a little. However, I suspect that if I did the same on the PRV outlet, I would have more success as it will smooth out the load from the carriages. The inlet orifice is easy to fit but the outlet one requires taking it all apart again under the buffer beam.

Adjusting the PRV outlet pressure is also a bind as the PRV is under the buffer beam and not easily accessible.

The PRV does its job well but depends on the loading being more constant than here. More tweaking is required to get this right and make it simple to operate but, according to the Santa Special passengers, it seems to be entirely satisfactory!

Beginning the climb, steam everywhere! (Photo: Roger Burfitt)

In Steam Heating (3), I anticipated that the carriages would be too cold, too hot or somewhere in between. Oddly, I was right so without too many reservations, I declare Joyce's new Steam Heating apparatus to be a success!😊

Steam Heating (3)

Following on from Steam Heating (2), I've fitted the carriage warming equipment to Sentinel 7109 ready for a steam test with a train in a few days time.

I began with the boiler connection and isolating valve.

Isolating valve plumbed into the boiler orifice

Having removed the boiler orifice plug and cleaned out the threads, I checked the 1/2" BSP thread type using a parallel tapping tool. The thread was clearly a parallel type and the BSPT tapered thread of the hex nipple was loose unless tightened firmly. This was as expected so I converted the thread to a tapered type using a tapered tapping tool. Now the BSPT tapered thread of the hex nipple fitted much more positively.

I completed the joint using Rocol steam seal. Total loco unavailable time: about half an hour!

I then fitted the standard buffer beam equipment using the purpose-designed flange.

Standard buffer beam equipment fitted to buffer beam (1)

Standard buffer beam equipment fitted to buffer beam (2)

The blue Spirax Sarco Pressure Reducing Valve (PRV) and Safety valve assembly came next followed by the flexible hose to link the isolating valve to the buffer beam equipment.

Blue PRV and safety valve attached to rear of flange (1)

Blue PRV and safety valve attached to rear of flange (2)

Also showing above is the narrow copper pipe to link the buffer beam outlet pressure to the gauge on the cab's rear panel near the roof on the fireman's side.

Steam Heating Pressure Gauge

The weight of the PRV assembly is supported by a clamp between the PRV and safety valve linked to the footplate above by M10 studding.

Having fitted the buffer beam equipment and attached the hose, I hitched up the hose end using the standard support links. It then became obvious that the assembly was somewhat lower than expected. On examining a MK1 carriage for comparison, the assembly is 6 to 8 inches lower.

Hitched with shortened support linkage

To avoid the end dragging on the ground or catching the rails, by wiring the two end parts of the support links together, I've pulled it up to a safe height above the rails as shown above. A more permanent version will be devised in due course.

Prior to steaming, the first test was to to check that the lower height would not prevent a connection being made to a carriage. As shown below, it is all OK.

May be low but fits perfectly.

Now all we need to do is a steam test. I anticipate that the carriages will be too cold, too hot or somewhere in between. If these are the pass criteria, then all should be fine!

Steam Heating (2)

After some pretty hectic weeks, I have most of the sub assemblies ready to fit. Rapid progress has been made possible by Amanda and Rob at South West Engineering Supplies at Bumpers Farm industrial estate near my home in Chippenham. Without them, I'd have been struggling to obtain all the bits and pieces in a short time and they have given me ready access to trial and error items. So a big thank you to them.

Following on from 'Steam Heating (1)', this is how it's developed.

What equipment is needed?

1. High pressure pipework and an isolating valve able to withstand the Sentinel boiler temperature & pressure (212DegC & 275psi).

High Pressure Pipe Fittings and Valve

In the photo above, the steel 'T' fitting's leg links to a 3000psi stainless steel union and thence to a taper threaded hex nipple which will screw into the boiler orifice. This union allows the angle of the 'T' to be set after securely fixing the nipple into the boiler orifice. The plug at the top of the 'T' fitting is to provide another steam outlet for future use.

The second union below the 'T' fitting allows the valve to be orientated appropriately. The valve is a three-part ball valve made by Valtac. I've written about these before. The hex nipple below the valve will connect to flexible braided hose to take the steam down to the buffer beam. Although the nipple in the photo is a steel type, I will be using a parallel threaded hydraulic fitting machined to take a copper washer sealed mating connector.

2. Pipework to carry the boiler pressure steam to the buffer beam apparatus.

Purists might criticise me for using modern flexible stainless steel braided hose instead of copper pipe with braized end fittings. I can order and receive the flexible hose with welded end fittings and a pressure test certificate within a week and be confident in the result. Using copper pipe, I cannot do this. (In fact, the hose arrived in four days!).

I've covered this before in detail here.

3. A pressure reducing valve to take the boiler pressure down to the carriage requirements (about 40psi).

Blue Pressure Reducing Valve (centre) (and one assistant)

Blue Pressure Reducing Valve (and other assistant)

The blue Spirax Sarco PRV is a 1/2" BRV2S with a Green Spring to allow a range of 20-60psi.

Arguably, to reduce the length of high pressure hose, I could have put the pressure reducing valve below the ball valve instead of behind the buffer beam. However the PRV needs to be mounted upright and would have taken up too much space in the cab.

4. A safety valve to prevent exceeding the carriage maximum pressure.

Gunmetal Safety Valve

The safety valve is a 1/2" ART 642 type made by Albion.

Safety Valve Detail including 3 bar setting.

5. A pressure gauge to allow the carriage pressure setting.

3" Steam Pressure gauge

The safety valve has been delivered certified to 45psi (3 bar) so 100psi full-scale is fine. I purchased it new from "thegaugeman61" on Ebay".

6. Heavy duty bracketry to fix the pipework and standard buffer beam equipment to the buffer beam itself.

Flange made to fit the standard buffer beam equipment to the buffer beam

The flange's central hole is tapped to 1.25" BSPT (tapered) to take a 1.25" section of pipe. The pipe section is then held by a Stauff clamp with an additional supporting bar screwed to the bottom edge of the buffer beam. A third bolt fixes the flange through the buffer beam. It is pretty strong and intended to survive heavy handling.

The flange 3-point mounting to the rear buffer beam

The Complete Assembly

I've pre-assembled the 'flat-pack' version of the equipment to show it all together before it disappears out of sight in and under Joyce's metalwork.

Complete 'flat-pack' and assistants

The boiler fitting is at the top. It passes steam via a 'T' fitting to a ball valve and thence to the braided flexible hose. The hose links to the blue PRV which passes lower pressure steam to the safety valve and pressure gauge pipe. Finally the pipe connects to the back of the flange and to the standard buffer beam equipment.

Now all I have to do is fit the kit and test it. Initial fitting will be quite quick for test purposes. I'll clamp the pipework properly when I'm happy it performs satisfactorily. The assistants will not be allowed on site at Midsomer Norton as they haven't passed their Personal Trackside Safety exam (honest!).

Steam Heating (1)

Carriage Warming Steam Hose link

I've been asked by the Somerset & Dorset Joint Railway Co. Ltd. to fit steam heating, aka carriage warming equipment, to the cab end of Sentinel 7109 'Joyce'. I'm slightly bothered by the idea as the gear involved will take up even more of the already limited cab space. However, I will give it my best shot, hopefully in time for the cooler weather coming on.

There are some critical feasibility questions:

• How much steam is required?
• Does the boiler have the capacity?
• Where can I tap-off the steam supply?
• What size of pipework is needed?
• What equipment is needed?
• How to minimise the out-of-service time during installation?
• How to ensure the installation is safe?
• How do I test it?

How much steam is required?

In 2014, the Heritage Railway Association (HRA) produced a Steam Heating Apparatus guidance note which I am using as the authoritative document. It states the following:

"Most steam heated coaching stock contains thermostatically controlled heaters which limit the steam consumption once the heater has reached working temperature. Because of this and the reduced length of trains now running, a pressure of 40psi is sufficient to maintain a flow to the end of a rake of vehicles. Allow about 80-100lbs of steam per hour per carriage to heat a train."

As a worst case, I'll assume Joyce will need to provide 100lbs of steam per hour per carriage.

At Midsomer Norton, Joyce is generally limited to two carriages although she could encounter more if operated elsewhere. I am thus basing calculations on three carriages and deem the requirement to be 300lbs/hour.

Does the Boiler have the Capacity?

Joyce's boiler has the capacity to produce 4600lbs/hour. Thus only about 6.5% of the boiler output would be used when supplying the 300lbs/hour to the carriages. I doubt if Joyce would notice this and if it did hold her back, the heating could always be turned off while climbing the 1 in 50 hill from the station, usually for about 5-7 minutes.

Where can I tap-off the steam supply?

Joyce's entire boiler output has to be able to be passed through the safety valves. The manifold which supports the safety valves is fed through a 3/4" diameter orifice. This means that 4600lbs/hour can pass through a 3/4" orifice.

There are two 1/2" diameter plugged orifices near the top of Joyce's boiler, one on the left and the other on the right hand side. A 1/2" orifice has 4/9ths of the area of a 3/4" orifice. Thus it is easy to say that 300lbs/hour will have no difficulty with a 1/2" orifice.

I plan to use the left side orifice as it will allow the fireman to control the heating. I will also use a plugged 'T' pipe fitting to make it simpler to add a steam wand later.

There are some other options I dismissed:

1. The super-heater input manifold at the front of the boiler. This would require removing the coal bunker to get access and would put an isolating valve out of the reach of the footplate crew.

2. The regulator assembly. This would have supplied super-heated steam complete with cylinder oil - I'm not sure how hot the passengers really want to be in cold weather!

3. The right hand 1/2" orifice. This would add to the already heavily populated driver's side of the cab and it's really the fireman that should be in control.

4. The safety valve manifold/fittings. Same as in 3 above but could well make for a lengthy down-time during installation and require the disturbance of well proven installed items.

Note: references to 1/2" or 3/4" are to nominal inside pipe diameters and the BSP thread size.

What size of pipework is needed?

Using a 1/2" boiler orifice indicates that 1/2" pipework will be adequate and it is good news as 1/2" pipework won't fill too much of the limited cab space.

I was surprised at this but the figures tell the story. However, as we are only allowing for 3 carriages, not 14 or so as might have been the case in the days of British Railways steam, I am convinced 1/2" pipework will be fine.

What equipment is needed?

I'll cover this in a subsequent article as it will be quite extensive.

How to minimise the out-of-service time during installation?

The only part of the installation work that will actually make Joyce unusable is when making the steam connection to the boiler. The rest of the apparatus can be fitted to Joyce before making the boiler connection without disturbing the ability to operate.

How to ensure the installation is safe?

The critical part of the apparatus is the link from the boiler orifice to an isolation valve fitted as close as possible to the boiler.

Either a male parallel threaded fitting sealed with a Copper washer will be used to connect to the parallel female thread of the boiler orifice or, preferably, both tapered male and female threads as they lock more effectively. Tapered male threads with parallel female threads are not suitable for this application as they have a limited contact area with the female thread and are not as strong.

Heavy duty forged steel or 3000psi Stainless steel fittings will be used where full boiler pressure is involved. Malleable iron fittings will be used at carriage pressure.

'Red-band' grade steel pipe or braided/annularly corrugated flexible hose or a combination of both will be used.

The isolation valve will be of the same type used for the vacuum ejector isolator, whistle/pressure gauge isolator and blown-down valve. These are high grade carbon fibre reinforced PTFE-sealed stainless steel ball valves as previously described here.

How do I Test it?

I'm not planning any special equipment to test the new apparatus. Instead, it will be a matter connecting Joyce to a three carriage train and trying out various functions.

1. With the hose link valve closed so that steam cannot leave the loco, initially turn on the isolator valve; the out-going pressure should not exceed 45psi. A safety valve should open to prevent it going higher than 45psi (3 bar).

The pressure reducing valve's pressure control should be varied to show that the outgoing pressure can be set as desired. (It may not be possible to do this without a flow of steam. If this is the case then it should be done carefully with the valve to the carriages open).

2. If not already done so, open the valve to the train and check the loco can supply the required pressure to the three carriages when all their heaters are set to maximum.

3. Check that the set pressure can be maintained with the boiler pressure between 100 and 275psi. Experience with the vacuum brake ejector pressure reducing valve suggests that as the boiler pressure reduces, the outlet pressure may rise but not above the safety valve setting.

Testing Times (1)

Tuesday 23rd February 2016 was an important day - the day an inspector called. In this case Peter Hawkins the boiler inspector.

It had been a busy few weeks leading up to this but essential to be ready for action on the S&D 50th anniversary of the line closure on March 6th 1966.

There were various tests: A general inspection of paperwork covering materials used, certificates of conformity and calibration; a hydraulic test to 1.5x working pressure (412.5 psi) to check boiler fittings were attached properly; a maxed-out steam accumulation test to abuse the boiler and check the safety valves could cope; a test of the ability to keep the boiler filled with water under maximum output conditions.

Giving the clouds a shock!

If you are wondering what Sentinel 7109 sounds like when being steam tested, try this video clip: (Higher def. on YouTube)

We also tried a less formal haulage test on the 1 in 53 gradient as in the following video clip (Higher def. on YouTube):

There are interesting times ahead!

(And it passed the tests too!).

Certified Gauges

Perhaps not a particularly gripping subject but important all the same. Sentinel 7109 has two steam pressure gauges and a vacuum brake system vacuum gauge; all of these are 'previously owned' and far from new.

All three gauges were initially taken to Brunel Metrology Services Ltd in Paulton, near to Midsomer Norton. The vacuum gauge passed first time but the two pressure gauges failed - not what was wanted but not surprising for vintage items.

Brunel Metrology make use of the S M Gauge Company in Fishponds, Bristol, for more demanding calibration tasks. To save time, I took the two gauges to SMG myself.

In a few working days, a phone call came to say the gauges were now calibrated to within 1% so I collected them the same day.

Within 1%!

Calibration certificates have now been issued for all the gauges and one is shown here as an example.

It was a pleasure to work with both Brunel and S M Gauges and I would recommend either for gauge calibration services. Many thanks to them both for their helpfulness and rapid turnaround.

Chuffed (1)

Following on from my last article, Thursday 7th January 2016 also saw Sentinel 7109's boiler with 60 psi of air in it from a (somewhat fatigued!) compressor.

Boiler Pressure Gauge on cab front

The gauge gradually climbs off zero after a while.

60 psi (ish)!

Then... the regulator can be opened for the engines to turn, the cab's boiler feed pump operated, the blower blowing (it's hard to turn it off!), the whistle sounded, the steam brake operated and (blow me) 21" of vacuum on the train brake vacuum gauge.

Have a listen to this (visually not very interesting) video clip:

Does that sound good?

Streuth! I think it's going to work!

Boiler Fittings (8)

Thursday 7th January 2016 saw Sentinel 7109's original boiler water gauge glasses being fitted finally as in the photo below.

Right hand gauge glasses

I last wrote about these in April 2013 when I'd obtained replacement glass protectors and checked that they would fit. Now the valves are in for good (hopefully).

Gauge Glass Valve arrangement similar to 7109's

Having remembered to insert the new 3/4" stainless steel balls into the lower valves to reduce the amount of steam escaping should the glass tube break, I proceeded to attach the component parts to the boiler. The upright steel tube is very straight and is used to ensure that top and bottom valves are aligned accurately when the glass tube is tightened in place.

Steel tube passing down through the upper valve to the lower one

It was not that difficult to achieve the alignment which is probably down to the 
curved surface of the valve faces matching the curvature of the boiler. I'm glad that new valves with flat faces did not have to be used!

Upper valve

Not so obvious from these photos is that each valve face is sealed to the boiler using a combination of graphite gasket with suitable lashings of Rocol Steamseal.

Lower valve showing close fit around the steel tube

I was then able to put the glass tubes in place and tighten them up. The word 'tighten' here is quite subjective. Sentinel used hexagonal graphite packings for this situation as below.

Hexagonal glass tube packings (photo from Heritage Steam Supplies' website)

They fit around the glass tube and are compressed to seal the tube. However, they should not be overtightened to prevent the glass being destroyed and they should align with the hexagonal spaces within the screw clamping mechanism. One of the glasses did not seal well so I may not have got this right and will have to recheck.

But how did I know that the seal was not so good...? That will have to wait for my next article (and I promise it will be worth the wait!).

Implementing 'A Little Arithmetic'

In a recent Sentinel 7109 article, I did some 'arithmetic' to enable a new boiler blow-down valve to be fitted. The result was this elongated heavy duty hex nipple pipe fitting made by Justin Goold.

Elongated Hex Nipple

The photo below shows that it has provided the solution required and is a good, strong fit to support the substantial high-spec blow-down valve.

The Valve is firmly screwed into the wash-out plug-hole

Another view shows valve handle in its closed position. An extension handle like those used to turn-off your household water supply in the street will be useful here.

The handle is reached from the off-side
preferably with a long reach extension

Down-stream of the valve, the pipe fittings are galvanised malleable iron as there is no longer the boiler pressure to withstand.

Not a good place to be when the valve is opened!

Another hole in the boiler plugged!

Important Note: The boiler has four washout plug holes at 90 degree intervals. For washout purposes, only the three actual plugs should be used. Only under extreme circumstances should this valve and its hex fitting be removed. The result would be that it will not be able to be tight and in the correct orientation after refitting due to wear on the threads when it was tightened up previously. Thus, it has to be a fit once and leave well alone item.