Torque required to tighten the cap for leak proof

In summary, the individual is asking for help in finding the torque required to tighten a cap with a polypropylene material and an EPDM rubber seal. They are seeking to know the amount of seal compression needed for the cap to be leak proof and able to handle water pressure of 600N in a plastic container. They are considering using a lead screw torque calculation but are confused by discrepancies in the results. They are using equations for thread engagement force and compressive torque to calculate the required torque.
  • #1
Acchu
5
0
Hello Anyone,
Could you help me in finding the torque req. for a cap to leak proof?
My cap (polyproplene) which dia. was 32mm and its detail specs are,
thread major dia.- 28.5mm, min. dia. - 26mm, pitch - 3mm, thread angle-45deg
which has a EPDM rubber seal placed inside (outer dia 26.5mm & inner dia-18.5mm with thick 1.5mm)

I want to know.. what should be the torque required to tighten the cap, so that It will be leak proof? or in other way what is the % of seal compression req. for leak proof? to handle the water pressure of ~600N in a plastic container.
 
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  • #2
Acchu said:
Hello Anyone,
Could you help me in finding the torque req. for a cap to leak proof?
My cap (polyproplene) which dia. was 32mm and its detail specs are,
thread major dia.- 28.5mm, min. dia. - 26mm, pitch - 3mm, thread angle-45deg
which has a EPDM rubber seal placed inside (outer dia 26.5mm & inner dia-18.5mm with thick 1.5mm)

I want to know.. what should be the torque required to tighten the cap, so that It will be leak proof? or in other way what is the % of seal compression req. for leak proof? to handle the water pressure of ~600N in a plastic container.

What approach should I consider? Shall I go with lead screw torque calc.? or any other
 
  • #3
You should calculate how much you want to compress the interior rubber seal, this should give you an estimate of force, and from there you can estimate the torque needed to achieve the desired compression force on the seal.
 
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  • #4
Mech_Engineer said:
You should calculate how much you want to compress the interior rubber seal, this should give you an estimate of force, and from there you can estimate the torque needed to achieve the desired compression force on the seal.
Thanks for your suggestion. As per the water pressure, I suppose to compress the seal by 40% based on this if I directly estimate the torque I'll get ~20Nm. If I use torque formula of lead screw concept, I'll get ~65Nm. So got confused. Guide me which way I need to go
 
  • #5
The discrepancy in torque may have to do with friction, are you taking friction into account when calculating the required screw torque?
 
  • #6
Mech_Engineer said:
The discrepancy in torque may have to do with friction, are you taking friction into account when calculating the required screw torque?
Yeah. I consider frictional force of thread engagement too while doing torque and got the result of ~20Nm. Hope in lead screw torque Calc. approach also friction parameter will be considered right?
 
  • #7
Acchu said:
Yeah. I consider frictional force of thread engagement too while doing torque and got the result of ~20Nm. Hope in lead screw torque Calc. approach also friction parameter will be considered right?

What equations are you using for each calculation?
 
  • #8
Mech_Engineer said:
What equations are you using for each calculation?
For thread engagement force :
Frictional force, Ff = m g (sin α + μ cos α)

For comp. of seal :
E = Stress / Strain
Stress = E*Strain
Force/Area = E*Strain
Force = E*Strain*Area

Resultant force = Frictional force + Comp. force

And the Compressive torque, Tc = K x Force x d (where k=Coeff. Friction of seal & d=PCD of seal)
Here I got 20Nm

2nd approach of lead screw torque formula:
Torque = F*Dm/2*(L+u*PI*DM)/(PI*Dm-u*L)
I got 60Nm.
 

FAQ: Torque required to tighten the cap for leak proof

What is torque and why is it important for tightening a cap for leak proof?

Torque is a measure of the twisting or rotating force required to cause an object to rotate around an axis. It is important for tightening a cap for leak proof because it ensures that the cap is securely fastened and prevents any leakage.

How do I determine the amount of torque required to tighten a cap for leak proof?

The amount of torque required depends on the size and material of the cap, as well as the type of seal or gasket being used. It is best to consult the manufacturer's guidelines or conduct a torque test to determine the appropriate amount of torque for your specific cap.

Can using too much torque damage the cap or container?

Yes, using too much torque can damage the cap or container. Over-tightening can cause the cap to crack or the threads on the container to strip, leading to potential leaks. It is important to use the correct amount of torque to avoid any damage.

Can the torque required to tighten a cap for leak proof change over time?

Yes, the torque required may change over time. This can be due to factors such as temperature changes, wear and tear on the cap or container, and the type of seal or gasket used. It is important to regularly check the torque and adjust if needed to maintain a leak proof seal.

Are there any tools or techniques to ensure consistent torque when tightening caps for leak proof?

Yes, there are tools such as torque wrenches and torque testers that can help ensure consistent torque when tightening caps for leak proof. It is also important to follow a consistent tightening pattern and to train employees on the proper technique to achieve consistent results.

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