Air pressure and condensing steam

  WhiteTruckMan 01:04 29 Mar 2007

Here's something that I've done loads of times in the past. Delivered a bulk liquid load, then last thing got my tank washed out for a new load in the morning. When you wash a road tanker out its done in special wash bays. Manhole lids are opened and special rotating water nozzles are lowered in and a wash cycle is done, typically 15-20 minutes. Usually with scalding hot water and detergent, but it can vary depending on whats been in the tank. Everything drains out of the bottom valves and sometimes the driver can have quite a juggling act to clean his hoses out as well. Then afterwards you leave the lids propped open to vent the tank and cool it as well.

Now heres someone who closed his valves and manholes just after the wash. Inside the tank it is full of steam and VERY hot. Time passes. it cools down. the steam condenses. The rest is inevitable.

click here


  wiz-king 05:46 29 Mar 2007

As a little boy (Horror) I and my friends would get a old oil can with a little water in and put it on our camp fire, wait until it was boiling then take it off and screw the lid down. Then wait for it to crumple.
Not much fun now - all plastic cans!

  g0slp 07:10 29 Mar 2007

Good one, WTM. Bet his boss was impressed...

  Arthur Scrimshaw 13:19 29 Mar 2007

I thought it was security footage at first but the camera looks as if it being hand held, why would you video a truck unless you expected something to happen?

  namtas 14:06 29 Mar 2007

So do these vehicles not have anti vacum valves? and if not why does the tank not implode when you off load a full tank?

  WhiteTruckMan 14:16 29 Mar 2007

No they dont have anti-vacuum valves. They do have pressure relief valves to prevent bursting.

Tanks are offloaded by pumping out of the bottom valves, with the top either vented to atmosphere or with a pressure equalising system in the case of seriously dangerous materials.

One other common discharge method with non hazardous materials in drop tanks (a tank in a container framework liften on and off a skeleton frame trailer much like a container) is to pump compressed air into the top of the tank via a detatchable pipe from an engine driven compressor (not the brakeing system compressor).


  namtas 16:22 29 Mar 2007


  Fruit Bat /\0/\ 19:21 29 Mar 2007

Shows just what atmospheric pressure can do.

  interzone55 20:46 29 Mar 2007

It could be security footage, as it looks like the camera is pole mounted, so it could be blowing in the wind.

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