Weight required to relief pressure 1

[sree555]

We have a blast furnace working with a top pressure of 0.6Kg/cm2. Whenever we find the top pressure increasing more than 0.6 Kg/cm2 the bleeder valves are not opening on its own.
We have two bleeder valves with 0.4mt dia duct two numbers.
The counter weight on each bleeder is 1500 Kgs.
Please let me know how to calculate the weight required so that the bleeder opens to relief high top pressure.

 

[JoeTank]

The answer will depend on the size of the outlet opening and the physical configuration of the relief equipment such as lever arm length, pivot localtions, etc.

Joe Tank

 

[reena1957]

Dear Sree, It appears that the force on the bleeders is about 750Kgs . As the counterwights are 1500kgs, the ratio of the lever arms should be 2:1 with the longer arm on the bleeder side and the shorter one on counterweight side. Check and adjust accordingly the position of the counterweights. Also check the weights are not loose and drifting. Further check the fulcrum as well as the levers are not getting restricred by some other restrainint.
Best wishes and let us know your findings. Also the weights may be checked to make sure that the counterweight is 1500kgs only and not more.

 

[sree555]

Dear Joe Tank,
The outlet dia of the valve is 430mm.
The pivot distance from the centre of the duct is 475mm.
The distance from the centre of the duct to the counter weights is 1125mm.
The distance from the centre of the pivot to the counter weight is 1600mm.
The lever is intersecting the centre of the duct at an angle of 45 deg.

Dear Reena 1957,

Contrary to your expectation the longer arm is on the bleeder side and the shorter arm is on th pivot side.

 

[reena1957]

Dear Sree, Can You show us dimensions in a sketch? Your description is slightly confusing. I also said Longer arm should be on the bleeder side. Read it carefully.
Best Wishes

 

[instrument1717]

reena1957 is Correct ,

The weight (force ) required for 0.6kg/cm2G with inlet Dia of 0.4mt shall be calculated as follows.

Weight(force) =
Set pressure (in Kg/cm2G) * inlet area of the valve (in Cm2)

In your case it is

0.6 kg/cm2G * 1256 cm2 = 753.6 kgf.

The Lever system should excert 753.6 kg on the valve for the releive at 0.6kg/cm2G.

Per Kg change in force at valve the setpressure will vary
by 0.000796 kg/cm2G.

( Note : This is a gauge pressure system , Means the system is to relieve at 0.6kg/cm2 above the atmospheric pressure [atm.pressure is variable ! ] ).


Respectfully,