Water Gauge blockage

My 7¼" gauge Elidir has a commercially made copper boiler and, because I live in a hard water area, I use finely filtered rain water exclusively. The loco only gets steamed about once a year and is blown down after each steaming. I always leave it with about ¾ glass of water in the boiler. I didn't have any problem with the water gauge blowdowns when last steamed..

I drained the boiler down and left it empty for about two weeks while I made and fitted a double clack valve. I've just refilled the boiler to find that both the water gauges were blocked in the lower fittings. One was blocked so hard that it needed significant poking with steel rod to move the blockage.

I wondered if anyone had any idea what this blockage could have been and what steps I could take to prevent recurrence.

Hi Denis, is the rain water tank clean and does it get well flushed? We are on tank water exclusively and find the levels of phosphorus and dissolved solids are still pretty elevated even for topping up the aquarium. Probably a long shot but worth considering. What type of rain water tank? Concrete, plaster? Andrew

I suppose that where it is being harvested from will also add some contaminates

Thanks for the replies,

The water is taken from a plastic water butt which is never cleaned out. However, all water goes into the saddle tank through a very fine brass mesh sold for the purpose by one of our ME suppliers. It does trap a number of particles which are discarded. I think this eliminates any solid contamination being introduced which to my way of thinking leaves two possibilities - 1. Build debris. This is a relatively new professionally built boiler (builder advertises in ME every issue) and I find it hard to believe the boiler was not adequately flushed out after construction. 2. Dissolved solids in the rainwater. I know nothing about this area of water chemistry and wondered if, even though it's a copper boiler, water treatment is recommended. Certainly I need to think about blowing down the water gauges more often when the loco is in steam.

Dennis

I would have a good look at the contents of that water-butt! Last month I replaced one and although the water at the tap looked OK the inside of the old butt was unpleasant. Much more like drowned snail soup than Evian.

Rainwater is acidic due to Carbon Dioxide and pollution. Just how acidic your rainwater is depends on where you live and how polluted your air happens to be when it rains.

My water-butt is fed from a tiled garage roof. There is plenty of opportunity for minerals and other nastiness such as bird poo to be dissolved by the acidic water as it drains into the butt. Once inside the mixture can go to work on the snails. Given enough time the result will be hard water because snail shells are made of Calcium Carbonate. And there will be lots of microscopic rotting vegetable matter and bacteria in the water as well.

Rainwater is a good idea for boilers but you have to be careful to keep it clean during collection and storage. I doubt that a filter on an ordinary water-butt is good enough, especially if the water has had time to develop an eco-system!

I'm not quite at the steaming stage yet but really considered acquiring a distillation unit. As I already have a requirement for ultrapure water for my research business and the aquarium also receives pure water, makes sense to produce some extra for my copper boiler. Question is, I guess, how much water would be consumed by a 5" gauge boiler in a day. As an interest, I often test our tank water supply for phosphates and 2ppm is about the average. Total Dissolved Solids are also elevated but also begs the question of how to remove all flux residue etc from the boiler. Its had many an acid bath so I assume all is good. Also checked inside with a remote camera (to check integrity of silver brazing) and it looks clean.

I've just used a soil testing kit to check the PH of the rainwater I'm using and it seems to be basically neutral. I suspect that the result is not very accurate but I think it means that the water is not dramatically far away from neutral.

Hi Dennis,
You could try boiling a sample of the water away in a clean container to see if there is any residue. If you have a dehumidifier you could use the water from that as that would only contain some dust from the air and some dissolved carbon dioxide.

Les.

hi dennis,

i suspect your beautiful loco has as you suspect a combination of neutral ph or slighty acidic ph rainwater boiler feed plus undissolved flux from the commercially made boiler that is causing the problem.

the only way i know of dealing with flux deposits (that may be hardened) to remove them is boiling or nearly boiling water and a strong solution of caustic soda (obtainable from Boots or Wilkos very cheaply in powdered form). then frequent washing outs subsequently before attempting to steam the boiler again. in fact there is an indentation in the family domestic bath due to one boiler where this procecedure was carried out!

cheers,

julian

Edited By julian atkins on 08/05/2015 20:48:08

Hi Dennis,

Your strainer is probably not removing all of the dissolved solids and the blockage could be a calcium build-up. (very hard deposit, like the build-up in a coffee maker or a steam iron which has to be flushed with a cleaner to dissolve the calcium).

A gauge glass blow-down test should be performed at every start-up (and change of operator) to ensure that the passages are clear. Water sample tests and boiler blow-downs should be performed regularly to remove rubbish at the bottom of the boiler.

Paul.

Water treatment in full sized boilers addresses two problems.

The first is oxidation ( rust). This is prevented by using tannins in cases where steam will not contact food material and sodium sulfite as oxygen scavengers which react with any oxygen in the water to prevent it attacking the boiler.

The second is to supply sodium phosphates, which will prevent the calcium deposits which result if water with calcium carbonates is boiled . The water leaves the boiler as steam but the calcium carbonate remains and accumulates to the point where it is no longer soluble in the water and deposits as "kettle scale". The addition of sodium phosphates replaces the calcium ions with sodium. This does not form a hard scale and get blown out at every blow down.

You can not filter out dissolved calcium no matter how fine a filter you use. It can only be removed by chemical means

Probably worth a mention but to blow down correctly, the water side and steam side need to be isolated inn turn when opening the drain.

My 5" gauge boiler has one gauge glass drain cock. If the water outlet is blocking steadily, the pressure will flow through the path of least resistance. So, it's possible that the water outlet can be almost completely blocked and blowdown will just clear the steam outlet.