Progress Report 51: Hunslet steam locomotive out of service for a while

Pete’s Hobby Railway Hunslet steam locomotive out of service for a while and this Progress Report explains why — first with a short version, followed by a far longer and more detailed explanation…

The short version

A trial steaming of PHR’s operating steam locomotive, Hunslet 1187/1915 “Torpedo”, on Thursday, 21st February, following the fitting of a repaired steam turret, disclosed a second hairline crack developing, with steam blowing through at 80 lbs psi. The fire was immediately dropped.

Following discussions with our Boiler Inspector and other experts, and because of the age of the cast iron turret, the decision has been made to construct a replacement turret. A plan has already been prepared for the approval of the Boiler Inspector. Obviously, until completed, the Hunslet will be out of service.

The full story

The Hunslet was last steamed on Wednesday, 10th October 2018 (last year), preparatory to being prepared for its annual boiler inspection.

Four days later, as part of preliminary works for the construction of the new locomotive and storage shed (see previous Report), a temporary inspection pit was constructed under the main line, using a hired-in bob-cat. This was completed in double-quick time -– in fact, it took longer to install the form-ply sides to the pit.

Wednesday 24th October saw the Boiler Inspector on site to give the Hunslet a going over as well as the Fowler (covered in a Progress Report 48). This was the first occasion that he was able to gain access under the locomotive and within the firebox itself. The Boiler Inspector was more than happy with the condition of the Hunslet’s boiler, advising that it continued to be good for its full operating pressure of 160 lbs psi. This pressure is higher than is required for service on PHR, but I did agree to a resetting of the safety valves to 130/135 lbs psi.

During the examination, the Boiler Inspector did draw our attention to a developing crack between the inner firebox and the foundation ring. At this stage the crack had not extended into the area which would affect the pressure vessel itself but could be anticipated to do so with subsequent steamings. Arrangements were accordingly made for a qualified pressure welder from Ainsworth Engineering at Goulburn to travel to PHR to undertake the appropriate remedial works. This will take place shortly. My appreciation is extended to the Company for making this possible.

Earlier in the year, during the 2018 Rhythm n Rail Festival steamings, then on 30th June at the official opening of the waiting shed on Loftus station, a faintest wisp of steam had been observed by Matt (PHR’s fitter) emanating from one side of the steam turret on top of the firebox. This was kept under observation and initially did not develop further. When it appeared to become more noticeable, it was decided to remove the turret, locate the actual source of the wisp and ascertain what could be done. As part of any works to be undertaken, various studs which hold the safety valves etc. would need to be replaced owing to their deteriorating condition.

Wagga Iron Foundry was contacted and were prepared to undertake not only the removal of the studs, but also to attempt to cut out and weld to crack from which the steam had been wisping.

On return of the repaired turret, there was an extended delay while we attempted to chase up replacement gasket materials which provide the necessary seals between the steam fittings. Here again, I extend my appreciation to Ainsworth Engineering at Goulburn who was able to supply a number of surplus off-cuts sufficient to meet our requirements.

Matt and Rhys returned the turret to its position on top of the firebox, refitted the safety valves, pressure gauge and other fittings using new high tensile threaded and fire bars, ready for a test steaming. This was necessary to confirm that all fittings were steam-tight, as well as recalibrating the safety valves to the higher pressure bolts, also the various washout plugs and reinstalled the ashpan.

And so it was, on Thursday, 21st February, “Torpedo” was lit up for the first time in some four months and steam pressure slowly raised. Matt had taken the opportunity to prepare the safety valves for resetting, which basically involve setting each so that would blow off at base boiler pressure, then slackening the retention nuts until the desired pressure was reached — 130 lbs psi in the case of the first safety valve. However, Matt could not get the safety valve to seat properly. Accordingly, it would be necessary to remove the valve and dismantle same to find the source of the problem.

At 80 lbs pressure, a new steam wisp was found emanating from the turret, in a different location to the earlier leak. Disheartened, the fire was dropped and when the turret was cold Rhys was given the job of dismantling first the steam fittings (pressure gauge first, followed by safety valves) and then the turret.

While the turret could be returned to Wagga Foundry for repair, and as covered at the start of this Report, the consensus of the experts was that it would be more economical to construct a new turret which would meet current technical standards. Matt has already prepared technical drawings for the new turret which are now being sent away for the appropriate approvals.

In the interim, Matt has dismantled the first of the two safety valves for reconditioning and removed the old turret.

It looks like several months before the Hunslet will again be ready for steaming, hopefully in time to make a grand entry into the new shed and servicing area.

That’s all for this Report.

Feedback, favourable or constructively critical, is always welcome.

Cheers,

Pete
SM Loftus