Selection of Gasket Material Guide

 II JAY SHRI KRISHNA II

Hello Friends, how r u?.... hope all of you are doing well…as you all familiar with my previous blog about Gasket in ‘Pipe Fittings Significance in Piping Field Part – 4’, here, we are discussed about 

Selection of Gasket Material Guide

As we know that Gaskets are used to provide seal against fluid transfer across static mating surfaces. It is crucial for ensuring effective sealing in various industrial applications.

For Piping System, the purpose of flange gaskets is to ensure the Gasket is compressed sufficiently to maintain sealing contact with the flange under maximum fluid pressure expected in the system.
Selection of Gasket Material Guide

Selection of Gasket Material Guide, good flange design, complete preparation of surfaces holdup with attentive can avoid preventing maintenance dangers in plants.

Gasket at work:

When assembled Gasket is squeezed & is subjected to comprehensive stress then bolts, Gasket and Flanges get expands. Under this situation comprehensive stress in Gasket may be relieved. The pressure tending to force the joint apart is known as hydrostatic end thrust.

The hydrostatic end thrust or bursting thrust is product of internal pressure & area of crack in the Gasket. It is equal to load applied to bolts to first prevent the parts blowing apart. Bolts must be loaded more than hydrostatic thrust to maintain comprehension in Gasket when system under internal pressure, for effective seal.

Hydraulic End Thrust

The Gasket is also subject to side load due to internal Fluid pressure tending to extrude it through the Flange Faces. To resist extrusion, it is necessary to make effective comprehensive stress to be greater than the maximum internal pressure likely to be encountered & remain so.

All Gaskets meet a no. of common conditions in design & operation. All Gaskets must conform & be softer than the faces or flanges so that they can flow in joint surface imperfections or irregularities when compressed.

The Selection of Gasket material is depending on factors such as

• Type of Fluid/Medium or Gas being sealed,

• Operating temp. and internal pressure

• Bolt Force

• Specific requirements of the system application.

Gaskets must be impermeable to seal fluids effectively, they must resist deterioration from chemicals & corrosives carried in the system, in other words Gasket must be compatible with fluids being handled in the equipment; Gasket must withstand heat/temp. & pressure of fluid.

The base materials of Gaskets are often treated with other materials to get better surface properties encouraging/discouraging adhesion to joint surfaces or providing chemical compatibility to fluids in the system.

Pressure Rating & Temperature Rating of Gasket:

The value of internal pressure a Gasket can withstand without extrusion, is related to compressive stress that the material can withstand plus its ability to resist creep & cold flow. The Gasket material should be sufficiently hard to be able to combat creep & still be soft enough to achieve sealing without excessive bolt & flanges loads.

Gasket material degrades with increase in temp. both the physical strength & deformation, the residual stress changes as well as bolt load. A satisfactory Gasket material yields less deformation with increase in temp. whereas poor Gasket materials suffer high deformation with increase in temp.

Common Types of Gasket

Gasket design should also take into consideration temp. effect. Thermal expansion of pipeline give rise to forces which tend to crush or compress the Gasket, unless compensated by suitable expansion device. Like other materials Gasket too loose strength & take set as result of stressing. This should be taken into consideration when designing Gasket.

Relaxation of Gasket:

The relaxation of Gasket varies with material thickness & Temperature. As a rule, thinner the Gasket minimum is the relaxation & thicker the Gasket higher the relaxation. Thus for high pressure & temp. thin gasket is to be selected, but this requires high degree of flange accuracy which is not possible. Hence as a compromise suitable just thick enough Gasket may have to be chosen to accommodate the flange conditions or improve or change flange design to accommodate thinner Gasket.

Gasket Selection & Joints:

Flange Joint geometry has an imp. Effect on the selection of Gasket. 

Two things common to all types of Flange Joints are:

1. Gasket contact face
2. Some means to compress the Gasket into these faces with enough force to seal off any leakage.

Gasket Materials & their compatibility:

Example of Gasket material used with type of service/fluid:

• Natural Rubber Gasket material use for Low chemical resistance service

• Neoprene Gasket Material use for Petrol, Mineral oils & hydrocarbons

• Nitrile Gasket material use for mineral oils, aromatic & aliphatic hydrocarbons & alcohols

• EPR Gasket material use for oxygen, steam & water

• Silicon Gasket material use for water & Ozone.

Conclusion for leak-free joint Gasket material which:

• Has resiliency to meet operating conditions

• Ability to easily conforms to flange or joint surfaces, such material has a low required seating stress.

• Requires low clamping force to hold seal.

• Has low modulus elasticity in recovery. Low modulus helps Gasket to expand when bolts stretch & flange distort.

• Gasket should be wide enough to seal all leakage paths when selecting fibrous material such as asbestos.

• It is compatible to the fluid at temp. to be sealed.

• It can withstand pressure & temp. of fluid being sealed.

Since Gasket seem simple, their importance is too often ignored. Leakey pipe flanges, leak from joints & all leak problems are shows their impact on plant efficiency and all kinds of cost to project, so to understanding or knowing their selection & use we can make good maintenance budgets & safety in industry.

Hope, you all are like and well understand whatever explained above about Selection of Gasket Material Guide.

Kindly, follow my all blogs and previous blog on 

Butt welded, Socket Welded & Flanged Fittings - Advantages and Disadvantages,

Pipe Fittings Significance in Piping Field Part – 4,

Art of Pipe Manufacturing

Valves Significance in Piping Field

Crucial Role of Pumps in Piping Field

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