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Dehydration Towers
The temperature of these joints changes radically and rapidly from 40°C to 300°C in five minutes. Since the flanges are made of different materials (carbon steel vs. stainless steel), they expand and contract at different rates as the temperature changes. As they expand and contract, the bolt stress and gasket compression also vary. The resultant leakage was extremely dangerous due to the high concentration of H2S in the sour gas flowing through the flanges. These flanges are located atop the large tower-tanks, posing safety hazards in the use of conventional large wrenches, sledgehammers and/or hydraulic tightening methods. Potentially flammable leaking gas could mean serious problems from sparks caused by hammering or hydraulic systems. The reduced torque and smaller wrench requirements were well suited for this elevated location. Two men, using hand held torque wrenches completed the tensioner installation on one tower in only 45 minutes. All leaks at these tower-top flanges were eliminated.
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Problems: Contaminated,
or sour, natural gas leaking from these tower-top flanges was among
the reasons for shutting down this new plant after only two days
operation. Up to three days were wasted in attempts to stop the
leaking.
Solution: Installation
of special sour gas Supernut® Tensioners results in improved
preload on each stud, and provides consistent tension around each
entire flange and better gasket compression. Accurate preload and
inherent elasticity of the tensioner have proven to compensate
for the thermal expansion/contraction.