Counter Rotational Displacement – Standard VCR vs. OmniSafe

How much rotation is transferred to the components connected by a “VCR type”* metal face seal fitting as it is tightened with a nickel gasket?

This data below shows that the relative rotation of the components ranges from 6.7 to 18.2 degrees. This rotation is based on the plating inside the female nut and the machined finishes of the contact surfaces of the glands and nuts.

Counter Rotational Displacement

Standard VCR
Test NumberAngular Displacement
Test 111.40 Degrees
Test 26.69 Degrees
Test 316.60 Degrees
Test 4 17.90 Degrees
Test 518.25 Degrees
Average14.17 Degrees
OmniSafe Anti Torque
Test NumberAngular Displacement
Test 10
Test 20
Test 30
Test 40
Test 50

In the Omnisafe fitting the nuts rotate against the torque eliminators. The torque eliminators are locked together preventing any differential torque transfer to the glands. The torque eliminators allow only compression to be transferred to the glands.

* “VCR” is a trademark of the Swagelok Corporation

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