Questions about blowdown valves

Hi Andrew,
I think that we all find what works for us, and with advice, hopefully don't do things to mess up our locos.
None of my live steamers have a blowdown valve at the bottom of the boiler to empty it.
I have a couple with a valve on the bottom end of the water gauge that can sort of do that, but not completely.
I am fortunate in living in an area with very soft water, so for some fifty years have never bothered to empty boilers after running, and no issues to date.
If I needed to transport a loco by air (only once so far), I would remove the safety valves and fillers and do my best to get all the water out of the boiler by shaking it upside down, and then let it sit for a few days to dry out.
After running, I just let the loco cool down naturally without getting rid of pressure, although always careful to open throttles and blowers to prevent them getting stuck when cooling, or a cooling boiler sucking water from a tender if equipped with axle pumps or hand pumps.
Now you can wait and see what other conflicting thoughts you receive.
As long as you are enjoying steaming up, and there's really not too much that can happen to mess things up.
All the best,
David Leech, Canada

A lot of these issues relate to cooling your loco after a run. In general, you want the throttle closed so it doesn't suck oil into the boiler as it cools. With the throttle closed, it is good to have something equalising the pressure - a Goodall valve at minimum, or as David suggests, if you have a water pump it will have a check valve that will allow air or water in to the boiler as it cools.

astack said:

relieving any pressure after a run by blowing the whistle

Click to expand...

While that will help, unless you keep the whistle valve open there will still be some 'cool-down' that may attempt to suck in something undesirable.

astack said:

not entirely sure doing that is rinsing deposits out of the boiler, which is another function of a blowdown valve.

Click to expand...

I've not heard anyone with our size locomotive mention that as a function, (until now.) While it may be true on a full-size loco, it doesn't really apply if you are using distilled water, as we all are. Right?

astack said:

a third reason for a blowdown valve is to remove water from the boiler for long-term storage.

Click to expand...

Never heard that either. But yes, it can help.

My Accucraft EBT #12 had one, and I fitted a globe valve (MBV Schug had Accucraft make them,) so I could easily open it when I parked the loco to cool down. The escaping steam produced some lovely affects! But I emptied the boiler at the end of the season by turning it upside down after removing the filler valve on the manifold.
So for me, it was way to let the boiler suck in air. However, the loco had a check valve and a tender waterpump, so it wasn't really necessary.

I personaly beleive in emptying the boiler for the following reason : All the boiler fittings beneath the water level should be made of bronze so as to not dezinctify. (IE the electrolisis process where ions are atracted by other ions: Notably the zinc in brass going towards the stailess steel ball in a clack valve.) I have purchassed two used engines from friends (One from JVR who never emptied his boilers and used tap water) in both cases when I stripped them down for renovation the clack valve broke like glass in my hands when attempting to unscrew them from the bush. Thank god at the time Aster still had a spare parts service... I have read in an OS advertisement that the large scale boys demanded from OS to make all the under water level fittings from bronze for this reason. We should also! Outside of that all that the gentlement advised above is true, let the engines cool down naturaly do not empty when you have just shut off.I installed tracks for that purpose in my steaming bay folowing Chris Ludlows example. and of course open the regulators and blowers so they dont lock up. (due to reduction of expansion) Of course the manufacturer isn't going to tell you to empty your boilers...
Now to get to the point there is one good reason to have blow down fitted : It is when the engine is really big. I have an accucraft T1 which is very big, and since I broke my back a few years ago I regret that it is not fitted with one. When I empty it I have to hold it upside down and it takes ages - while I pile up ages myself... Another useful feature is to have a blow down on your water level so as to have a more accurate reading of the level in your boiler.
Another friend does like me empty his boilers and we both have never had problems since. Also you should pump up the hand pum to empty it of residue water, likewise move the engine around if it is fitted with an axle pump to empty it also. Since I do that I never have stuck clacks...
Happy steaming, Simon