Compressor Explosions

[jugs]

Ever wonder why some people bang on about having stuff presure tested, uptodate certificates & all that tripe, when you know it's all a wast of time & money.

- well here are some clues

Slight damage to wall > Here <

&

An untested 100 psi air recever

Also tyres

>3 examples < of misuse

What happens >when a tyre explodes<

Have a nice day.

 

[Lewis Medlock]

Split rim wheels are naughty, I was shown some photos of a (Swedish I think) tyre fitter who was leaning over a wheel inflating it after fitting a new tyre. The split rim wasn't seated properly and shot through the roof taking his head with it.

We used to change the tyres on our humungous 6x6 Foden recovery trucks without removing the wheel. The wheels wouldn't fit in the 'elf and safety cage so we parked close to a wall and blew them up with the tyre valve removed so if anything was going wrong we could just pull the airline off from a safe distance and the tyre would dump air without anyone getting too close. If the rim went bang there'd be a dent in the wall

 

[tigler]

Would be interesting for someone with maths knowledge to calculate the potential energy in say a 200 Ltr air reciever at 150 PSI ? It's obviously like a small bomb !!

 

[pondy]

that looks nasty, i have a fiac 200l compressor, thats about 15 years old, i dont use it a great deal but would be a little put off using it now, i no the recevers get rust in them, but when i drain mine from 130psi full somtimes the drain gets blocked with flakes of rust

 

[Sam(GTD)]

Would be interesting for someone with maths knowledge to calculate the potential energy in say a 200 Ltr air reciever at 150 PSI ? It's obviously like a small bomb !!

It's quite a complicated equation if you wanted to know the exact energy (you'd have to input temperature and know how to adjust away from using ideal gas constant.
Then there is adiabatic effects....

A simple calculation would give the energy density of 150psi air being 0.0049MJ/L (or 4900J/L)

So you are talking 980,000J (0.98MJ) i think? for the 200l@150psi.

And to quote "The megajoule (MJ) is equal to one million joules, or approximately the kinetic energy of a one-ton vehicle moving at 160 km/h (100 mph"

(i'm just trying to think if 200 litres of compressed air at perfect efficiency could accelerate a car to 100mph?? i guess it could)

I may have made a mistake as i havn't done physics for several years now, anyway even if you had the energy of a one ton vehicle moving at 30mph in your workshop then you are going to have issues.

Another way to think about it:
Psi .....Pounds per square inch, think how many square inches on the inside of your 200 litre tank, that's a lot of pounds pushing the metal out from the middle should it blow....

 

[tigler]

Yes, I was thinking of calculating the surface area of the receiver x the PSI for a ballpark idea of the force involved. It's going to be pretty massive, which is scary when I think of the pressure in a welding gas cylinder !!! Then even more scary when the 200 odd PSI in one the big, late designs of steam Loco boilers, which was superheated steam !!!!!!!
Anyway, going back to the safety issue, it's quite easy to test your own receiver if you have a high pressure water pump. Just remove all the air connections, stop all the ports up, attach the water pump with an indicator gauge, fill the receiver with water and pump up to 1.5 x working pressure or the test pressure marked. Rectify any leaks then leave at test pressure for 30 mins or so, check for any signs of leaking or distortion in the walls, job done. Any distortion or leaks in the walls or any seams condemns the receiver.

 

[michael1703]

Ive been thinking of boxing my compressor in, this might sway me!

its a 1970 something, 550 litre and there are two access plates on the receiver and i always worry about a plate blowing out

 

[Sam(GTD)]

How destructive a pressure vessel explosion is becomes very variable.

You could have a 200 litre tank 'burst' next to you and other than being deafened and blasted with a pressure wave come off scratch free, expanding high pressure air itself is not that dangerous it's if the tank fragments, launches intself in a particular direction or provides energy to nearby debris it will be catastrophic.

Ive been thinking of boxing my compressor in, this might sway me!

Could make it worse depending on construction, make a framed cage with heavy gauage mesh making about 80% of the surface area.

That'll allow the pressure wave to dissipate without turning the box into a bomb.

----

Oh and above someone mentioned steam boilers........steam is far, far worse at the same pressure because it will expand to a higher volume more quickly. (and burn the hell out of you!)

 

[jugs]

How destructive a pressure vessel explosion is becomes very variable.

You could have a 200 litre tank 'burst' next to you and other than being deafened and blasted with a pressure wave come off scratch free, expanding high pressure air itself is not that dangerous it's if the tank fragments, launches intself in a particular direction or provides energy to nearby debris it will be catastrophic.



Could make it worse depending on construction, make a framed cage with heavy gauage mesh making about 80% of the surface area.

That'll allow the pressure wave to dissipate without turning the box into a bomb.

----

Oh and above someone mentioned steam boilers........steam is far, far worse at the same pressure because it will expand to a higher volume more quickly. (and burn the hell out of you!)[/QUOTE]

Gunpowder detonated, expansion = x 400
Superheated water into steam @ atmospheric pressure (boiler explosion) = x 1600

 

[brightspark]

if your not happy about using an old pressure vessel turn it upside down and tap along the bottom edge with a chipping hammer or simlar .as they mainly only rust at the bottom . if it dents easily the metal is thin if its still in good condition tapping with the hammer wont damage or dent the cylinder and all should be well .most of the older tanks are a lot thicker than the new ones. if u realy feel the need fill with water and do a hydraulic test on it

 

[Sam(GTD)]

if your not happy about using an old pressure vessel turn it upside down and tap along the bottom edge with a chipping hammer or simlar .as they mainly only rust at the bottom . if it dents easily the metal is thin if its still in good condition tapping with the hammer wont damage or dent the cylinder and all should be well .most of the older tanks are a lot thicker than the new ones. if u realy feel the need fill with water and do a hydraulic test on it

And only when it's empty!

I've done the above test on my old vessel, although this was after when me and the guy i bought it off did a test run after it being in a garage un-used for several years whilst it was in the back of my volvo.....
Naughty of me trusting him saying it was near perfect inside. (as far as i know it's pretty good, never seen any orange water either)

It'd be interesting to see inside the tank with an endoscope...... hopefully wouldn't spot any puff pastry in there.

To be honest the walls are so thick i reckon it'd have to be in the sea for a decade before it was in danger of rusting thin enough.

 

[Drains]

approximately the kinetic energy of a one-ton vehicle moving at 160 km/h (100 mph"

(i'm just trying to think if 200 litres of compressed air at perfect efficiency could accelerate a car to 100mph?? i guess it could)

I may have made a mistake

Dunno about your calcs, which might be good! But the energy required to accelerate a vehicle to 100mph is a shed load more than the kinetic energy of a vehicle maintaining 100 mph.
We have a hydraulic drive BMW at work which can do 0 to 30 off an accumulator (engine off), but the nitrogen in that is compressed to about 400 bar.

 

[Sam(GTD)]

Dunno about your calcs, which might be good! But the energy required to accelerate a vehicle to 100mph is a shed load more than the kinetic energy of a vehicle maintaining 100 mph.
We have a hydraulic drive BMW at work which can do 0 to 30 off an accumulator (engine off), but the nitrogen in that is compressed to about 400 bar.

Yeah, you'd need perfect energy transfer to accerlerate it to 100mph on it's final kinetic energy.
(it'd have to be in vacuum with a perfectly efficient drive system and friction free!)

Compressed air would probably be the worst way to do this! (adiabatic losses)

I wouldn't say it was a shed load more tho (from the output energy of the wheel compared to kinetic) prob less than 100% i'm not that good on vehicle dynamics.

That BMW sounds interesting, how does the accumulator drive the hydraulic pump.....is it a turbo-pump or an open system?

You should see the turbo pump/accumulator set up they power the 'stealth' ride at thorpe park.
Accelerates the coaster with about 20 people to 80mph in 1.8 seconds
I think i'm excited for different reasons at theme parks to most people.

 

[Drains]

Yeah, you'd need perfect energy transfer to accerlerate it to 100mph on it's final kinetic energy.
(it'd have to be in vacuum with a perfectly efficient drive system and friction free!)


That BMW sounds interesting, how does the accumulator drive the hydraulic pump.....is it a turbo-pump or an open system?

Yes, you're right. Took me ages to work that out.

The BMW - look here
There's some other stuff there too you might find interesting.

 

[Sam(GTD)]

Yes, you're right. Took me ages to work that out.

The BMW - look here
There's some other stuff there too you might find interesting.

Very useful, thank you.

The net result of the rapid sequenced valve actuation is that, at the end of each stroke, each cylinder can be reconfigured to either pump, motor or idle. By controlling the sequence of cylinder enablings, the machine can pump fluid to a hydraulic service or accept it back (while the returning fluid actually helps to drive the crankshaft of the machine) at infinitely variable flow-rates.

The system is complicated but that's very clever, essentially a mechanical/hydraulic version of regenerative braking.

 

[tigler]

The only practical demonstration I've ever seen to display the power of compressed gas is that show where celebs (yuck) compete in various ways with cars. One of the rounds was trying to hit a target with a car propelled from a compressed nitrogen cannon, didn't reach anywhere near 100 MPH but it did travel quite a few metres !

 

[series2]

You should see the turbo pump/accumulator set up they power the 'stealth' ride at thorpe park.
Accelerates the coaster with about 20 people to 80mph in 1.8 seconds
I think i'm excited for different reasons at theme parks to most people.

I pestered one of the engineering team when it first opened!

It uses nitrogen compressors to pressurise the accumulators to around 350Bar, this is then used to force about 14,000 litres of hydraulic oil through the 24 hydraulic motors that turn the winch drum. The recharge time is around 60 seconds. The power consumption (continuous) is 945 KVA.

The test bed version was "Rita" at Alton Towers, that one only has 18 motors.

The whole caboodle is housed in a reinforced concrete bunker, that is designed to contain it should it go pop. No-one is allowed in the bunker while it is running.

 

[John_S.]

When we had the truck garage we had a new Broomwade twin cylinder compound compressor about 45 CFM.

This was insured with Vulcan Insurance, same as the garage cranes, both made in the UK by Armstrong, one 1 tone and one 2 tont one.

In 19 years they never performed a test on the compressor, never had a mudhole door off and never tested a crane under load.

At one time the 1 ton crane wasn't used because the ram leaked oil out under load and we used the big crane but these people signed it off every year as working.

One day on the 2 ton crane with the arm in the centre hole, 30 cwt, and a Leyland 680 hanging on it whilst we were swapping bits over, the legs which were 4" x 2" thick walled box slowly twisted over and this thing gracefully dropped the engine on the floor, no damage to anyone or the engine fortunately. Could understand it on uneven floor barring it all ways but it was stationary when it happened.

We cut the legs off and replaced them with 4" x 4" thicker walled box, painted it all up nicely and they never even knew.

 

[graffian]

the legs which were 4" x 2" thick walled box slowly twisted over and this thing gracefully dropped the engine on the floor, no damage to anyone or the engine fortunately.

So you think I should check my crane?
Made it around 1983 and it's lived out side nearly all it's life;-)

 

[stucktoweld]

Gunpowder detonated, expansion = x 400
Superheated water into steam @ atmospheric pressure (boiler explosion) = x 1600

You mean matbe like an exploding water heater
http://mythbustersresults.com/myth-evolution