Water gauge problems

I have been rebuilding a 5 inch gauge Tich and fitted a new boiler. The loco has been steamed successfully numerous times, since January of this year (2013). The problem is that the water gauge always reads low, when there is, in fact, an adequate water level. The gauge glass itself has been increased proportionally in size for this 5 inch version to 3/16 inch O/D.

Recently, after a steaming, the water gauge showed level with the bottom nut of the gauge. I tilted the loco towards the rear, and on levelling again, the water level rose to just below the top nut and stayed there.

One thought was the top fitting of the gauge: this is a outside the wrappper, (as it is on Rob Roy). The hole from the boiler to this top fitting on LBSC's original drawing for the 3.5 inch version, is 5/32 dia. I have made the 5 inch version 7/32 dia. Is this hole big enough?

Any answers would be very welcome.

Dave.

Seen this a few times on boilers ive made - put it down to waterways being too narrow.

Thanks for the info. you are the only one who has replied! Do you think that a1/4 inch water gauge might help?

Your 7/32" dia gauge seems adequate, but do you have a blow down cock on your water gauge, if so blowing down the gauge should restore the true water level, and can be done every so often while running the engine.

On blowing down, the water will disappear then bob back to the boiler water level, when the blow down is closed.

I had erratic readings this year on my newly commissioned Simplex, it was down to a buildup of muck which had accumulated in the bottom fitting, so blocking the water feed into the bottom of the glass. After clearing this out and further steamings this has not recurred.

hi david,

just to add a few words to michael's very good advice,

you cannot under any circumstances have a water gauge which is unreliable or shows a false reading.

you need to take the whole thing off, and investigate same.

there is no point having a glass larger in diameter than the passageways on the bottom fitting. the top fitting can have slightly smaller passageways but not the bottom fitting.

the boiler bush for the bottom fitting must not or should not protrude much beyond the inside of the backhead on the water side. neither must the bottom fitting extend beyond the bottom boiler bush inside the water space. there isnt a lot you can do about the bottom boiler bush apart from carefully use a dremel engraver and dental burr to reduce the length of the bush if it protrudes too far into the water space. if the bottom fitting is too long then that is easily remedied.

it isnt unusual for swarf and crap to partly block the bottom fitting on a new boiler if it hasnt been thoroughly cleaned before use. obstructions in all the passageways need to be checked for as this can easily lead to false readings.

always fit a white background with diagonal lines on it behind the water gauge as this shows the difference between air/steam bubbles and water. there's a pic of one of my locos with same made out a bit of painted card with the diagonals marked in biro. it's lasted 23 years so far!

cheers,

julian

Many thanks to all you forum posters, particularly with reference to the bottom fitting. I was concentrating more on the top one. I will now investigate, as you all suggest, and hopefully, post success!.

Dave.

I have stripped the water gauge today, (having just completed a decorating marathon for 'er indoors), and did not find any grunge in the passage ways in either fitting. I tried a piece of tapping size rod in the bottom fitting, and found it went along the side of the water space in the boiler rather than strike the inner firebox, so no constriction there. Also I found no extra amount of bush beyond the the inner face of the backhead plate.

What I also noticed was that the 'feed bore' of both parts of the water fitting was at 5/32 dia. This is 1/32 bigger than the bore of the 3/16 O/D glass. I have been looking at as many drawings of gauge glass fittings as I could find, and in all cases the glass bore and the 'feed bores' were the same. Could it be that the glass itself is the obstruction? And reducing the 'feed bores ' to 1/8 dia would be the solution. Or does this matter?

I am getting desperate! Please help.

Dave

hi dave,

simple answer no it wont matter. re-assemble and i think you will find all will be ok, strange as that may seem.

it is quite possible that something you havent noticed on taking apart was a problem. at least you know now all is ok and if further problems occur let us know.

cheers,

julian

I followed Julian's advice and reassembled the water gauge earlier this week. I tested it today (Saturday) on my short (80ft) track in the garden. Before steaming, I filled the boiler to half a glass. Annoyingly, at the beginning of the run, due to my glasses steaming up, I wasn't able to watch the gauge! When I managed to be able to see again, the level had fallen to the bottom nut, and stayed there as last time. I tried blowing down as Stick suggested, but it didn't help.

I continued running with the pump bypass valve closed all the time, and at least the level did not fall out of sight. I tried tilting the loco back during steaming, and the level did not change. As lunch was ready, I stopped the test after about 1/2 an hour, and let the loco cool down.

When the loco had cooled down , I tried tilting it back again, and the result was exactly the same as last time: the level rose to half a glass, and stayed there. To say I was disappointed is an understatement!

Has anyone any further ideas as to what I can try, please?

hi dave,

can you post a pic of the backhead and gauge?

sorry to hear of the further problems. my suspicion is that when in steam the boiler level is showing accurately. why would you let the boiler 'cool down' instead of blowing the water out of the boiler using the blowdown valve at 15 psi? you should never leave water in a new boiler or any other time when cool.

cheers,

julian

michael's advice as always is excellent.

perhaps fill the boiler with boiling water from lots of kettles with sodium hydroxide added? (drain cleaner from wilko's £2.50 a bottle). it is recommended by johnson matthey for removing flux deposits.

cheers,

julian

I am not familiar with the Tich layout but I did once experience similar problems and eventually found they were due to an interaction between the blower and the top water gauge fitting. The latter had been fitted to a turret outlet and one could observe the water level changing when the blower was turned on and off. I imagine this might occur if the top water gauge fitting was closely adjacent to the source of blower steam, although the dynamics of the situation are difficult to understand. As a builder of small G3 locos I often fit the water gauge to an elbow on top of the boiler as this gives room for a longer glass. I have never had any problems with this arrangement.

Dick

Dave.

You have had some good advice from the forum posters just one more thing comes to my mind, could your gauge glass be a bit long in the top fitting and causing a partial flow problem by restricting the passage slightly.

If your boiler water has any gunge floating about you will know as the gauge glass will show a mucky tide mark.

Many thanks to all you Forum posters. You all have been most generous with your time, and it is much appreciated. There is much there to look into.

Julian, I have made two attempts to send a photo of the backhead without success. Every time I upload the photos, this is carried out, but at the end of the upload, the page crashes, with the usual apology for the inconvenience, and that seems to lose the upload, because the album has the title, but no pics. I will ask someone who is more computer literate than I to help, and then have another go.

I will check/clean/etc and then get back to you when I have had another steam up. The problem will be finding a dry day!

Thanks again, and best wishes for Christmas if my next steam up is delayed.......

Dave.

hi dave,

there is a simple method of proving the water gauge reading from your pic (which is very useful). if the regulator gland isnt tight (if so slacken it off) see when the water gauge reading gets to the regulator level. a slow drip of water should disappear and turn to steam (perhaps easily seen on a cold day than a hot summer's day!). similar to the GWR try cock arrangement..

my initial thought from your pic confirmed my view that the water gauge reading is perfectly ok as the bottom fitting is quite high. check via the inside of the firebox with a rule allowing for the thickness of the inner firebox wrapper - the water gauge reading should be 1/4" dia above same when the water level is at the firebox crown ( the water gauge usually showing a reading 1/4" above the actual water level when in steam).

i do like the manifold/turret and steam valves - you have done a very tidy job which looks very good!

cheers,

julian

Part 1

After the last run, the boiler was drained into a container for inspection. I found the water looked clean. On filtering, I Found there were only a few small bits of grit, and some fibres, but no oil. These ’foreign bodies’ may have been from the container used for the draining down. Thanks, Michael.

Next I completed all the points mentioned in the previous posts from you kind people. Viz:

1. Length of gauge glass. Stripped the top section, and found there was no extra length restricting the passage ways, either top or bottom. Thanks, Stick.

2. Boiler cleaning: I bought some Sodium Hydroxide from Wilko to clean the boiler. I made up a solution from the powder, using boiling water, and filled the boiler with it. I left this in for about 3 hours. On draining, I looked at the solution, and found it looked cloudy but otherwise clean. I am not sure if this is the appearance of the original mixed solution, because I did the mixing in a translucent container. The boiler was then rinsed through with clean water, a couple of times. Thanks, Julian, for the idea, and particularly for a supplier of sodium hydroxide. ( Wilko are selling it at £1.50 now, too.)

Taking advantage of good weather earlier this week, (Tuesday, 15.12.13) I had a steam up.

On reaching working pressure, the water gauge reading dropped to ¼ of a glass, and stayed there for the rest of the test, which, though better, was ominous, as one would expect SOME variation.

Sorry, this should have preceded Part1!

You may have seen my photo of the backhead, which was posted with this latest ‘saga‘. The photo worked, but the ‘saga’ didn’t. I think that there is too much verbiage. Stupidly, I hadn’t saved it, so I have typed up this new account, in Word first, saved it, and will hope to copy it into another post. It will have to be in smaller chunks.

Part 2

Steaming was good, until the end of the test, when just as I decided to finish, the boiler pressure dropped to nothing. Lacking steam pressure, I could not properly blow down the boiler. (I should say that the reason I have been leaving the boiler to cool, is to be able to see the true level of water in the gauge. Since LBSC said leave any residual water in the boiler until the next steaming, this is what I have always done. I must change this.)

I then let the boiler cool down. When cooled to room temperature, I found that the water gauge level now reached the top nut. Since with cooling, the water contracts, it is likely that the level, when hot, had completely filled the boiler, which probably explains the drop in pressure. This is probably just as dangerous as too low a water level. And this is what water gauges are supposed to show!!

It occurred to me afterwards, with much too high a water level, as detailed above, that during the run I had, as usual kept the axle-pump by-pass closed, but had done some experiments with ‘notching up, thus saving steam (and water). Also, I had used the hand pump to try to raise the level back to ½ a glass. (It didn’t affect the water gauge reading, but these two actions explains, perhaps, the rise in water level).

So what to do? I wonder if the cleaning needs repeating, but how many times? If so, this is surprising since the boiler has been steamed many times this year - January to December.

However, I was totally ignorant of any need to remove remaining flux deposits in a new boiler.( I also have a new boiler waiting for the 3 ½” gauge LNER A3 Pacific I’ve been building, so the ’education’ on this is very timely. All thanks to you, Julian.)