Friction - Due to a ratchet clamp 1

[Ryza00]

Hello,

On site one of our bursting disks is situated in a vent on top of the roof. The vent is covered by a canvas weather enclosure to prevent any water from gathering on the vent side of the bursting disc.

The weather enclosure is held down by a ratchet strap slung around the canvas and tightened around the circumference of the vent pipe, no holding down points etc. A question was raised recently: If the bursting disc were to rupture what pressure would the weather enclosure "blow off the vent". The bursting disc set pressure is only 0.1bar so there was a thought that potentially the weather enclosure could hold in the pressure, which I think is unlikely but would like to be able to demonstrate this without blowing the bursting disc!

Is it a "simple" case of finding the co-efficient of friction between the canvass and stainless steel pipework and using the applied force by the ratchet to calculate the force required to "blow it off" and then translate this into the pressure required from the vent pipework?

Or I'm I thinking too simplistic?

 

[zeusfaber]

That calculation would be a good start. You might want to think a bit about how the friction changes with the weather (not just as the canvas/stainless interface gets wet, but also as the web in the ratchet strap absorbs water or changes temperature).

How strong is the canvas itself?

How closely can you control the initial tension in the ratchet strap?

Could you find a gash 1m length of vent pipe and demonstrate what happens by fitting a cover to the bottom and then slowly filling the pipe with water? If the pipe gets more than about a third full before dumping on your toes, there's probably a case to answer.

A.

 

[SnTMan]

I agree that calc would be good to start, but establishing reliable and representative data (coef of friction, tension in the strap, etc) could be difficult.

Some kind of test might be easier and more useful. How about testing if the canvas material will even hold (presumably) gas pressure?

Regards,

Mike

The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[chicopee]

Can a flanged long radius turn elbow (90d or 45d) with rain cap be an acceptable solution?