Nitrile Static Friction Grip?
Nitrile Static Friction Grip?
(OP)
I'm trying to use HNBR (Nitrile 70 Shore A) as a kind of stationary gland packing - at the same time holding and sealing a 304 SS tube (Bright 320 grit polish finish). I've made a test rig - see pictures below. But when I apply the load of 6000N, the tube slips. There doesn't seem to be a minimum load at which it doesn't slip (It was still slipping at 2000N when I stopped testing). I know static coefficients of friction are quite variable, but calculations tell me that it should easily hold the tube at 5-10 Nm of bolt torque.
So first of all - why is the tube slipping?
Secondly, is there a material I could use in place of nitrile that would ensure a slip-less hold and seal? (needs to be oil resistant and non-hygroscopic) - Polyurethane?
At this stage I'm not so interested in changing the design unless there are fantastical improvements to be made.


Thanks in advance
So first of all - why is the tube slipping?
Secondly, is there a material I could use in place of nitrile that would ensure a slip-less hold and seal? (needs to be oil resistant and non-hygroscopic) - Polyurethane?
At this stage I'm not so interested in changing the design unless there are fantastical improvements to be made.


Thanks in advance





RE: Nitrile Static Friction Grip?
RE: Nitrile Static Friction Grip?
I don't want to add a taper as I think this would jam the rubber spacers and inhibit further adjustment.
The rubber is tight on the tube with 0.05-0.1mm clearance on diameter in the housing.
I was thinking that at the force indicated, the pressure exerted by the rubber would be roughly the same in all directions.
RE: Nitrile Static Friction Grip?
How did you arrive at the 47 kN clamp force?
I had to rebuild a frozen snow plow cylinder once and it was not easy getting it apart (the packings had swelled) which leads me to believe you can achieve your goal.
Have a good day!
RE: Nitrile Static Friction Grip?
Thanks.