Electric heating 3 meters tariffs no one supports it

[SimonH2]

Why didn't you ask one of the companies to supply a tank, and then fill it as required (which is what normally happens)?

They didn't want to do that either And it's not like I didn't use a fair bit of gas - an old joke about driving behind a V8 is "pass anything but a petrol station" I think it was mostly a case of "it's not something I understand" on the part of the people I was talking to - another common "objection" being a belief that what I wanted to do was illegal since they didn't know how to deal with the correct VAT & Road Fuel Duty.

If it's not their tank, for the maintenance of which they were responsible, then could there be safety-related regulatory issues.

True, but if the tank is "in test" then it's not their "problem".

In addition to the visual inspections which occur every time there is a delivery (and occasional re-painting, as necessary), the major inspections for my Calor tank are already 'scheduled' for the next 26 years. The 'ultrasonic inspections' usually take a whole day - I don't know what the 30-year "thorough tank inspection" would amount to since, once my previous one hit its 30th birthday, they simply replaced it. ...

I'd expect the full inspection to involve emptying & purging the tank, strip off the fittings (valves etc), a full internal inspection, and a pressure test - so they'd just swap out the tank and ship yours back to a depot for inspection & test. In the automotive world, the tanks have a 10 year life - but after that it's cheaper to just scrap them than inspect, test, and re-certify them. From your test schedule, it looks like they are extending the full inspection periods by using ultrasonic examination - which will be to look for corrosion inside the tank (typically where a small amount of water will collect in the bottom).[/QUOTE]

 

[JohnW2]

I'd expect the full inspection to involve emptying & purging the tank, strip off the fittings (valves etc), a full internal inspection, and a pressure test - so they'd just swap out the tank and ship yours back to a depot for inspection & test.

Indeed. I rather doubt that those 30-year "thorough inspections" ever take place on-site.

In the automotive world, the tanks have a 10 year life - but after that it's cheaper to just scrap them than inspect, test, and re-certify them.

Seemingly different with LPG tanks. I had some interesting chats with the folk who did my tank change. They said that they never scrap tanks unless they develop significant faults - they simply inspect, test and 'refurbish' (re-paint!), install new fittings and then put them back into service. The guy was actually able to look up the history of the 'new' tank I got, and found that it was just starting it's third 30-year period of service (i.e. it was just over 60 years since it had first been installed).

.. From your test schedule, it looks like they are extending the full inspection periods by using ultrasonic examination - which will be to look for corrosion inside the tank (typically where a small amount of water will collect in the bottom).

Indeed.

There was obviously a lack of ideal internal communication within the company, since they filled my tank with best part of 2000 litres just a few days before they changed it! The tank-emptying process was quite interesting to watch - they used propane gas to 'push' the liquid propane out of my tank into their tanker.

Kind Regards, John

 

[SimonH2]

Seemingly different with LPG tanks. I had some interesting chats with the folk who did my tank change. They said that they never scrap tanks unless they develop significant faults - they simply inspect, test and 'refurbish' (re-paint!), install new fittings and then put them back into service. The guy was actually able to look up the history of the 'new' tank I got, and found that it was just starting it's third 30-year period of service (i.e. it was just over 60 years since it had first been installed).

That does not surprise me. Unless damaged or corroded, there is nothing to go wrong on them - so a steel bottle made 60 years ago should be good to go with up to date valvegear. Obviously there's a difference in economics between automative tanks which generally cost less than £100 - and larger bulk tanks that cost order of magnitude more. There's also a difference in that your bulk tank is static, while automotive tanks (especially if mounted under the vehicle) are subject to all sort of hazards - not least of which is a good dousing with salt each winter. IME externally mounted tanks are "well scabby" by the time they reach 10 years.

There was obviously a lack of ideal internal communication within the company, since they filled my tank with best part of 2000 litres just a few days before they changed it! The tank-emptying process was quite interesting to watch - they used propane gas to 'push' the liquid propane out of my tank into their tanker.

The hardest part will be accessing a liquid draw-off port if a suitable valve and plugged port wasn't installed when the tank was installed. As long as they have that, then only a small pressure difference will move the gas. If thy didn't then you need to chill the tank till you can take a fitting out - I've done that when replacing a valve set on an automotive tank, it's "interesting" to look inside and see the liquid bubbling away inside.
I imagine they used a pump to transfer vapour from above the load in the tanker to the tank to be emptied. Contrary to what you might think, this does not (significantly) raise the pressure in your tank - all that happens is that the vapour they pump across condenses to maintain the saturated vapour pressure. But, condensing the vapour raises the temperature, and the corresponding evaporation of liquid to vapour in the tanker will lower the temperature in the tanker. The pressure is linked to the temperature - so as the tank temperature raises, and the tanker temperature lowers, then a pressure difference will appear which will drive liquid across.
In the past I've recovered refrigerant by simply putting my recovery vessel into some iced water. In the same way, lowering the temperature caused the refrigerant to condense and lower the pressure - drawing in vapour from the system I was "acquiring" the refrigerant from. It was amazing just how quickly the ice melted !

 

[JohnW2]

The hardest part will be accessing a liquid draw-off port if a suitable valve and plugged port wasn't installed when the tank was installed. As long as they have that, then only a small pressure difference will move the gas. If thy didn't ...

I would imagine that the valvegear will always include that facility, since a tank will virtually never be taken out of service (to be replaced. or just removed) when totally empty - so some degree of 'emptying' will probably virtually always be required. I presume that there must be a pipe which dips down to the bottom of the tank, since their connection (for 'liquid draw off') was to part of the gear at the top of the tank.

I imagine they used a pump to transfer vapour from above the load in the tanker to the tank to be emptied. ....

That is, indeed, what they did. I'd never really had any reason to think about it previously, but I had probably previously imagined/presumed that the liquid gas would be 'pumped out' (just as {I presume} it is 'pumped in').

Kind Regards, John