Advantages of a blow down tap/valve?

[Joe]

Hi, just wondered would it be worth fitting a bow down valve to a loco like a mamod who doesn't have one (i dont think) ?

cheers
Joe

[williamfj]

One has been fitted to my Millie on the bottom of her water gauge and I'd say it's been very useful as I can get reliable readings from the gauge, blow down excess water if I was a bit too enthusiastic when filling her up and draining the boiler at the end of the day is very simple. On the other hand it rarely seals properly.

[Joe]

One has been fitted to my Millie on the bottom of her water gauge and I'd say it's been very useful as I can get reliable readings from the gauge, blow down excess water if I was a bit too enthusiastic when filling her up and draining the boiler at the end of the day is very simple. On the other hand it rarely seals properly.

ok cheers

[Lner fan Sam]

Would the mamod that you are fitting the valve too have a upgrade copper boiler fitted or the orginal brass boiler?

[Joe]

Would the mamod that you are fitting the valve too have a upgrade copper boiler fitted or the orginal brass boiler?

i don't have one yet but i was wondering as my mate has one and hes thinking of adding a blow down valve, not sure what boiler it has though.

[Lner fan Sam]

A blow down valve would be a useful addition but it would be a bit of a pain fitting it to what ever boiler is fitted to the loco. My mamod is fitted with a copper boiler and the only real place a valve could be fitted is on top of the water gauge which wouldn't really help drain water from the boiler.

[Joe]

A blow down valve would be a useful addition but it would be a bit of a pain fitting it to what ever boiler is fitted to the loco. My mamod is fitted with a copper boiler and the only real place a valve could be fitted is on top of the water gauge which wouldn't really help drain water from the boiler.

Ok thanks

[Chris Cairns]

Blow down valves are used in full size boilers to remove accumulation of contaminants, or to provide a method of rapidly lowering the boiler water level.

Not sure they would be of benefit on the small volume Mamod boilers, although I agree that a sight glass drain valve on the high pressure replacement boilers would be a welcome bonus given the general inaccuracy of the sight glass fittings used (they suffer badly from air bubbles and can get blocked with steam oil being sucked out of the lubricator when the boiler cools down causing a vacuum).

To drain my boilers where the water will not come out by gravity when inverted I use a syringe with a long piece of silicon tubing, and leave one of the boiler fittings (safety valve, filler plug, etc.) off and let it dry out naturally.

Chris Cairns

[Joe]

ok thanks

[MDLR]

The Accucraft boiler inside "Rincewind" had one - I altered it (and the lubricator blowdown valve from the clumsy original fitting} to a cylinder drain cock.

Advantages: you fill the boiler all the way up, light up and open the blowdown valve - water (and then steam) coming out tells you when the boiler water's at the correct level. At the end of the run, blowing the lubricator down blows all the condensate and crud out - you can them open the top and fill the lubricator with oil whilst it's hot - MUCH easier than doing it on a cold loco on a cold day!

[Andrew]

I've only had a loco witrh a blow-down valve for a short time and haven't yet got my head round any practical applications - but I have noticed you can take really cool photos!



Cheers,

Andrew.

[TonyW]

Advantages: you fill the boiler all the way up, light up and open the blowdown valve - water (and then steam) coming out tells you when the boiler water's at the correct level.

That's a water level valve, not a blowdown valve, and the same arrangement that I have on some of my locos. A blowdown valve is mounted at the bottom of the boiler.

... blows all the condensate and crud out ...

Crud? Other than water and emulsified oil (which is what lubricates the loco and will separate back to oil and water in time) what crud is in your lubricator?

[Joe]

ok cheers, so what would one below a lubricator do then? would it just get rid of waste oil after use?

[TonyW]

ok cheers, so what would one below a lubricator do then? would it just get rid of waste oil after use?

The oil floats on top of the water, so it would drain the unwanted water from the lubricator and can be shut as soon as the water stops. The oil is pristine and unused as "used" oil has already gone through the cylinders, up the chimney and is probably either on your track or all over your loco. If you drain the lubricator completely you are (a) making an unnecessary mess, and (b) throwing money away.

[Joe]

ok cheers, so what would one below a lubricator do then? would it just get rid of waste oil after use?

The oil floats on top of the water, so it would drain the unwanted water from the lubricator and can be shut as soon as the water stops. The oil is pristine and unused as "used" oil has already gone through the cylinders, up the chimney and is probably either on your track or all over your loco. If you drain the lubricator completely you are (a) making an unnecessary mess, and (b) throwing money away.

Ok thanks , so a worth while investment

[Chris Cairns]

A blowdown valve is mounted at the bottom of the boiler

More accurately these are called bottom blowdown valves which we are used to in live steam locomotives (particularly the larger scale ones).

However there are also surface/continuous blow down valves which are placed in a continuous use boiler to remove impurities from the top of the boiler water.

It is interesting that Accucraft use a water check valve on their no sight glass boilers whereas Roundhouse do not. I've been watching fellow enthusiasts this year at various Garden Railways & Exhibitions and it is amazing how much water gets dumped on layouts (particularly those at the exhibitions). Having done some experiments I've adopted a similar technique to that used by Roundhouse by removing a known quantity of water from a full boiler. In the case of my Ragleth I settled on 53 mls which stops any water being blown out the water check valve (just steam) and I'm now going to try raising steam with the check valve closed to see if that will reduce the rather long time it takes to raise working steam pressure (I kept being asked at our Industrial Railway Group 45mm layout sessions this year - Are you ready yet?).

My first experience of a displacement lubricator was on a Cheddar Models marine engine. These are not fitted with drains and you were provided with a blunted needle & syringe to suck the water out - it is still in regular use. As Tony has posted above I've watched others blowing out the remaining steam oil from their lubricators which needs to be collected in kitchen towel paper to stop making a mess of the layout.

The Accucraft manuals I've read only call for opening their drain valve about 1/2 a turn to release the water, and similarly Roundhouse manuals call for opening their drain valve 2 to 3 turns but not to remove it.

Each to their own I guess!

Chris Cairns

[TonyW]

It is interesting that Accucraft use a water check valve on their no sight glass boilers whereas Roundhouse do not.

Roundhouse used to, although in a very basic form. The picture shows Fowler (left) and Jack (right) boilers from the early 1990s that had a water level plug fitted as a standard item. The idea was that you filled the boiler and then opened the plug to drain off the excess water. The plug was bored out and with a cross-hole to make this easier. Loco owners, should they wish to do so, could take this one step further and replace the plug with the necessary plumbing to have an easier to use valve.

As Tony has posted above I've watched others blowing out the remaining steam oil from their lubricators...

For reasons which continue to be a mystery to me.

[MDLR]

Tony wrote:

Advantages: you fill the boiler all the way up, light up and open the blowdown valve - water (and then steam) coming out tells you when the boiler water's at the correct level.

That's a water level valve, not a blowdown valve, and the same arrangement that I have on some of my locos. A blowdown valve is mounted at the bottom of the boiler.

I wouldn't see a point in that, unless you were running on water with a lot of nasty dissolved stuff in (which we're all advised not to)

... blows all the condensate and crud out ...

Crud? Other than water and emulsified oil (which is what lubricates the loco and will separate back to oil and water in time) what crud is in your lubricator?

By crud I meant the remains of the oil.....................

[TonyW]

By crud I meant the remains of the oil.....................

I'm genuinely sorry if I am coming across as labouring the point here, but why do you do that? I have seen many loco owners do this but not one has been able to tell me why they do it other than "it's what I was told to do by a mate", or similar.

[MDLR]

If you open the drain tap and take the top off the lubricator, the condensate will usually dribble out, but it can take time and there's no guarantee that it will all be gone (particularly if you leave it until the loco is cold - the oil thickens up and isn't always too happy to flow) whereas if you blast the lubricator clear with the last of the steam in the boiler, you can guarantee that EVERYTHING - condensate and remaining steam oil - will be gone. It's then very easy to take the top off the lubricator (even if it IS a bit hot) and refill it with fresh oil, which will flow delightfully into the lubricator. The loss of the small amount of residual oil doesn't amount to much in monetary terms.