Materials of Construction - Gaskets (Weak Acid)
February 23, 2003

Introduction

Chemline GA Series Low Torque Gaskets or equivalent gaskets are recommended for all plastic and FRP piping systems to prevent initial flange leakage due to bolt over tightening. They are especially recommended for all solid plastic flanged body valves. The unique double convex ring design provides optimum sealing with a fraction of the bolt torque required for flat face gaskets.

Elastomers such as EPDM and Viton are generally used.   The material selection will depend on the fluid conditions particular its composition as related to minor contaminants such as chlorides, fluorides, etc.   Alternatively EPDM gaskets with a 0.4 mm overlay of PTFE or PVDF can be used for greater chemical resistance.  As well, the overlay gaskets have increased elasticity and lower bolt torques required to seal than pure PTFE or PVDF gaskets.

The following are recommended gaskets for use in weak sulphuric acid service.

Acid Concentration : 0 to 10% H₂SO₄ 
Temperature: 90°C (194°F) maximum

The ability of a gasket to effect a seal depends not only on the quality of the materials, but also on the thickness of the material, the design of the flanges, the amount of pressure exerted on the gasket by the bolts, and how the gasket is assembled into the flanges and tightened.  Consult the manufacturer for specifics regarding your application.

Samples

Bolt Torques

Recommended Bolt Torques ft-lb (150 psi working pressure)