Hi all,
Recently we received vendor drawing for Non-Metallic expansion Joints. In drawing apart from Axial ,Lateral & Angular stiffness vendor has provided value of FRICTION RATE with unit N/bar.
I am in doubt how to use the provided value.
Does it mean that friction rate X pressure & Value we get should be added into into Final Nozzle Loads of equipment.
e.g Friction rate= 250 N/bar & pressure=10 Bar.
Therefore
Force=250*10=2500N
Whether I am interpreting it right?

Thanks,
Anand
Force is always with you......................

Anand!!

Stiffness for these expansion joint depends on pressure. This can be considered by inserting a value for Cr (i.e. Angular Friction rate). This value can not be converted in to spring rate. I hope you are referring to angular expansion joint. Because this terms only come in angular expansion joint (correct me if I am wrong).
Resistance of angular expansion joint can be calculated by using below equation.
q=Cr*Po + (Ca + (Cp*Po))*dP
Cr, Ca, Cp = regulating powers of the expansion joint
Po = Operating pressure
dP = rotation of the bellow

Your interpretation of calculating the pressure thrust is not accepted, since the value of pressure thrust will not be based on Cr value. It will be based on the F = A * P0.

Regards,
R.K.

RK…..

I fully agree with you that Stiffness for the expansion joint depends on pressure. But the EJ we are using is TIED LATERAL NON-METALIC EXPANSION JOINT with Spherical Washer & Lock Nut( Both inside as well as Outside).So assuming that value provided is for Cr (Angular Friction rate) & what about Ca,Cp? Should I consider it as ZERO, as no other value is provided or should be consider it as same.

So accordingly Resistance of angular expansion joint can be calculated by using below equation.
q=Cr*Po + (Ca + (Cp*Po))*dP
Cr, Ca, Cp = regulating powers of the expansion joint
Po = Operating pressure
dP = rotation of the bellow

After getting value of q. How can I deal with this Value? I mean where should I add this Value.
Can you please provide Reference for the same.

Thanks,
Anand
Force is always with you......................

Waiting for Expert advice......

I believe if you want to include some sort of friction resistance to bending in CAESAR II, you will have to use a pair of bilinear rotational restraints (perpendicular to the pipe axis) with a Node/CNode definition across the joint. K1 would be "rigid", K2 would be the angular stiffness of the joint and FY would be the friction load.

Anand!!

I think it is better to ask your expansion joint vendor about the values of stiffness. As instructed by Dave, you can use this method also, but I never tried this. The expansion joint vendor "HYDRA" will give you the regulating powers, but if needed they can supply you with the stiffness values as well.

Regards,
R.K.