The critical aspect of sealing of flanges

While nonmetallic flanges such as glass and reinforced plastic are used for some services, most flanges are metal. Metallic flange surfaces can range from a rough casting to the smoothness produced by lapping. A critical and fundamental aspect of sealing is the level of friction between the flange and gasket surfaces. The roughness of the flange faces can have a dramatic effect on gasket creep relaxation, blow out resistance and bolted joint tightness. Depending on the type of gasket used in the connection, different flange surface finishes should be utilized to optimize gasket performance. The ANSI accredited ASME Standard B 16.5 requires that the flange face have a specified roughness to ensure the compatibility of the surface with the gasket and a high quality seal. This Sealing Sense is intended to be consistent with this standard.

Metallic Gaskets

As a general rule, metal gaskets and those with less conformable metallic contact surfaces require a very smooth surface finish. Given the creep resistance and structural stability of most metal gaskets, the two mating surfaces can create a very tight, reliable seal. Alignment, parallelism and flange finish must be within specified limits to achieve an optimal result. Metal gaskets such as solid metal and corrugated designs offer very little forgiveness to flange finish or bolting and assembly deficiencies. A typical flange surface finish recommendation for these types of metal-contact gaskets is 64-μin Arithmetic Average Roughness Height (AARH)/Root Mean Square (RMS) or smoother. duplex steel fittings manufactures

Nonmetallic Gaskets

Soft gaskets-such as compressed fiber sheet and rubber that are more compressible-can be more forgiving to misalignment and out-of-parallelism of the flange. However, these materials are more susceptible to creeps relaxation and movement while under a load. The flange surface finish can play a critical role in the gasket's service life and long term reliability. A smooth surface finish will not create the necessary friction between these mating surfaces, making a nonmetallic gasket more susceptible to creep under load. This creep can translate to a loss in bolted joint tightness and potential leakage, duplex steel flange suppliers. A rougher surface finish is generally recommended for soft, non-metal reinforced materials to create the necessary friction for stability and tightness between the mating surfaces. A typical surface finish recommendation for these materials is 125- to 250-μin or rougher.

Semi-Metallic Gaskets

These gaskets are made by combining soft nonmetallic materials as fillers, facings or insertions with a metallic core or cover, stainless steel forged flanges wholesale. These combinations include spiral wound, corrugated and jacketed designs. The combination of the tougher, more creep resistant metal with a more conformable facing or filler-such as PTFE and flexible graphite provides serious advantages, particularly in more severe services. For those with facing and spiral wound gaskets, a wider range of surface finishes can be tolerated such as 125- to 250-μin. For metal jacketed gaskets with soft filler, 64- to 125-μin is generally preferred.