Author Topic: Water/Steam/Pressure question  (Read 422 times)

Offline RussellT

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Water/Steam/Pressure question
« on: May 09, 2017, 11:16:57 AM »
Hi All

I'm sure there'll be someone on here who can answer this.

I have taken a radiator off the wall, and taken it for powder coating as it's a pain to paint.  To stop it dribbling rusty water into the car I put a couple of old radiator valves on the ends.  I didn't mention it at the powder coater's and remembered on the way home and thought - "They're bound to vent it for safety's sake." :doh: :doh: :doh:

Unfortunately the radiator appears to have swollen during powder coating, the spot weld dimples are deeper and it won't fit on the radiator brackets.  The powder coaters say they are sure they vented it.  The powder coating on the valves and bleed screws disagrees. :bang: :bang: :bang:

My question is what pressure could it have reached during the powder coating process?  The numbers that I think are needed are: :smart: :smart: :smart:

Radiator internal volume = 12.8 litres
Powder coating oven temperature = 200 degC
Quantity of water left in radiator = 100 mls approx

My thinking is - if there is enough water it'll boil until it reaches the pressure at which the boiling point is 200 degC - but is that affected by the low volume of water compared to the volume of the radiator.  I think that there will be an effect from the expansion of the initial quantity of air - but that's effectively cancelled out by the effect of it's pressure on the boiling point. :scratch: :scratch: :scratch:

I'd be grateful for any advice.

Russell

Offline shipto

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Re: Water/Steam/Pressure question
« Reply #1 on: May 09, 2017, 11:38:44 AM »
If they didn't vent they got really lucky

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Offline awemawson

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Re: Water/Steam/Pressure question
« Reply #2 on: May 09, 2017, 11:46:40 AM »
Yikes they were lucky that that didn't  :zap:

I once bought the contents of a Launderette - all the machinery boiler etc - and there was a nice copper hot tank that I wanted to re-use. When I came to install it I wondered why it rocked on it's base - they are usually domed concave so sit nicely on a timber pad.
well as you are probably guessing by now the concave had become a convex dome  :bugeye:

Examination of the pressure release valve showed that it had been wired shut  :bang:

(This was from Coldharbour Lane in Brixton - a rather rough area then (and probably still!) )
Andrew Mawson
East Sussex

Offline RussellT

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Re: Water/Steam/Pressure question
« Reply #3 on: May 09, 2017, 12:16:44 PM »
I agree with you both.

Unfortunately the boss of the powder coating company doesn't.  Earlier he said I'll check our CCTV and if it doesn't show them venting it I'll buy you a new radiator.  Now he says they couldn't see as it was behind something else in the oven and the CCTV is missing a few seconds.

Myson (the manufacturers) test their radiators to 7.5 bar.  I think this will have got to about 15.5 bar.  Unfortunately I have no data on the pressure needed to distort a radiator.

I'd still be grateful if anyone can confirm or deny my pressure calcs.

Russell

Offline chipenter

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Re: Water/Steam/Pressure question
« Reply #4 on: May 09, 2017, 03:16:16 PM »
Depends on the water volume it could go over 1000psi http://www.che.ksu.edu/docs/imported/SteamTable.pdf , they were very lucky , the only thing I have seen to blow a rad is ice .
Jeff