4079 Pendennis Castle

Did the GWS not also sell their support coach to David Buck? I seem to remmeber WCRC going to pick it up last year sometime.

 

From DRC Facebook page

During the summer operation here at Didcot, we have noticed some issues with possible boiler water carry over into the cylinders of Great Western Society owned steam locomotive 4079, Pendennis Castle. These issues were kept under strict observation, pending the end of the August operating season at Didcot after which work could then be carried out.

Having completed some initial investigative work into what the issues may be, a number of concerns have been highlighted. Due to the nature of the investigations and work needed, the society has sadly taken the decision to withdraw the engine from service on a temporary basis. This unfortunately means Pendennis will now not be available to operate at Didcot or go on hire to other preserved railways until these assessments are complete and remedial work undertaken.

We know that this will be a disappointment to those who were expecting to see the engine operate in the near future, but we do need to prioritise the maintenance of this important historic engine for use and enjoyment for many years to come.

 

Glad I got some rides behind it at the DRC last month.

 

That's a bit of a vague statement as to what the problem is. I wonder if it is a suspected leak from the boiler into the main steam pipe? Pure speculation, though.

 

I have also heard this mentioned 'on the grapevine'. No evidence if this is correct or not, but would require a fair bit of dismantling inside the boiler to reach the pipe for repair.

 

Sad news,

Hopefully not anything too drastic that can be repaired.

Got to feel for the team who restored her having a setback like that such a short time into her operational period.

Chris

 

It has been running for three years now so is hardly newly restored.. It could be a blessing in disguise if it gives them the chance to sort out all the other steam leaks that seem to envelop the loco whenever it moves. Compare it to how steam tight the Bluebell's new Atlantic is and I think you will see what I mean.

I hope that doesn't sound too critical

Peter

 

I think it’s a fair observation. She has been a tad leaky at the front end on the occasions I’ve seen her.

 

Doubtful, because the pressure differential between the inside and outside of the steam pipe is minimal to nothing - remember the regulator is in the smokebox. The steam pipe is a large section thin-walled copper pipe, well above the water line. Unless the installation has been botched, it's unlikely to be the cause.

Priming the cause? The GWS have never been hot on water treatment. Also perhaps the gauge frame needs rodding out.

 

Interesting and I’m not inclined to disagree as I really know little about GW boilers. I’m just intrigued about why a loco should be withdrawn to investigate water carryover and how that could happen if that’s not the case. Simple priming is a result of a water quality/crew problem and not a loco problem.

 

The GWS seem to be quite unlucky with the boilers on their locomotives, IIRC 6023 didn't manage a full ticket due to boiler issues plus 5322 was withdrawn early due to boiler issues?

 

Just looking at the drawing of the main steam pipe for a No 1 boiler (Hall Class) It has two joints in it. Now, a joint is a weak point.
Does a No 8 boiler (Castle Class) have a similar main steam pipe?
Looking at a further drawing, I have answered my own question.
Yes, the steam pipes for both boilers are of similar construction.
So, is there a problem with one or both joints?
That is the question, but I do not have the answer.

 

Because the regulator is in the smokebox, the pressure difference between the inside and outside is minimal. The steam pipe is also above the water line. However if there is a leak at the joint with the regulator box or at the opposite end, water might enter the steam pipe when stopping.

 

You haven't understood what I have said. There are two joints within the length of the pipe. It is not a continuous pipe between the pick-up high in the top front of the outer firebox and the smokebox tubeplate.

 

I have fully understood your statement. Any joints within the pipe are unlikely to be the cause of the problem because they are above the water line and there is no pressure differential. The front joint with the regulator box is most likely where the problem is, if there is one. The rear-most section of the steam pipe is not normally removed during overhaul.

 

The pressure difference may be minimal but there will be a difference otherwise there would be no steam flow and, if there is a pathway, water will find it.

 

I guess the pressure difference will depend on how much you open the regulator.

 

The slightly counter-intuitive point @Steve is making is that if you were able to arrange a series of pressure gauges to read the local pressure in the main steam pipe along its length, starting from the opening and at intervals all the way to the regulator valve itself, those gauges would indicate a gradual fall of pressure along the length of the pipe as soon as the regulator opened. That has to be true, because if it were not, there would be no force to cause steam to flow along the main steam pipe. Therefore if that steam pipe has a small hole anywhere along its length, then there will be a local pressure differential across the hole (higher pressure outside, lower pressure inside and that will tend to cause water to enter - particularly because even if the mouth of the steam pipe is high above the water level, parts of the pipe necessarily sit much closer to the water level.

Tom

 

I think 6023 did do it's entire ticket but lost a few years at the start due to lengthy commissioning - so may have seemed a bit short! It was being considered for a rapid overhaul on withdrawal so couldn't have been too bad, but 4079 was considered priority.

 

4144 is also near to the end of it's ticket too. That did have a boiler lift in mid-2016 for some "snagging work" but has more or less been reliable since.