Should I Use Gasket Sealant?

Gasket Sealant…. the whys and wherefores. We have answered this question many times at RAM and as often happens, there is no straight answer. There are many different applications and requirements and 1000’s of gasket sealants available.

Most of our gaskets do not require sealant. If a solid gasket is being newly fitted to new products/flanges sealant is not necessary. We most commonly supply some of our gaskets with adhesive backing – to allow for perfect placement and no slippage when fitting, the adhesive backing is stable and only adheres where you want it, it won’t extrude or leak into places it shouldn’t.

Be aware that the main issue with gasket sealant is that it is often not necessary as an addition to a solid gasket and can make replacement of solid gaskets/old sealant much harder Another example is using sealant on delicate flanges such as aluminium, it can be a nightmare to remove leaving an even more pitted and dented surface.

Gasket Sealant can be Helpful in Some Cases.

We would recommend gasket sealants alongside our solid gaskets only when necessary, if a flange is very uneven and it could help to fill any gaps and when leakage of the sealant would not be an issue. There are many types of gasket sealant available, just the same as gasket materials, each for different applications. A general rule, if you are using gasket sealant, you don’t need a lot! A tiny amount skimmed over a surface to fill any slight indents is all that is required for most applications.

Automotive applications commonly use gasket sealant alongside solid gaskets, as they are repairing older parts. Gasket sealant can be used to make cheaper gasket materials more robust, increasing adhesion and chemical/water resistance.

RTV sealants are Room Temperature Vulcanising and needs to be at room temperature to cure. There are non-setting compounds, anaerobic sealants which does not set hard and maintains a consistent seal.

There are liquid gaskets used to create a seal. These have many benefits and are used solely as a liquid, not alongside a solid gasket. RAM does not supply liquid gasket materials.

Seals are generally moulded or machined product, often flat and round such as an O-ring. Gaskets are cut into different shapes so that they fit the design and bolt spacing of a component.

Gaskets are used to seal two components or flanges that have a flat surface. Seals are used to describe parts that are used between engine parts, pumps and shafts that rotate. Gaskets are used as static seals.

When a seal is used between engine parts, pumps and shafts that rotate, it is described as a dynamic seal. Seals are required to keep leaks from occurring within a moulded or machined product.

When a gasket breaks down or a machine is serviced the gaskets need replacing. A seal within a bearing needs complete replacement of both the seal and bearing if there is a seal breakdown.

The Science of Sealing

A gasket is just one part of an assembly. The quality of a gasket seal is a function of the quality of the assembly. Gasket failure is often attributable to defects in flanges or mating surfaces. The quality of a seal depends upon the quality of not only the gasket, but also of the surfaces of the joint to be sealed.

Creating a seal with a gasket is a mechanical process.

A seal is created when the material of the gasket is compressed between the two surfaces of a joint, or faces of a flange, thus preventing the leak or ingress of fluids or gases through the joint.

To seal, the pressure of the flanges on the gasket must exceed the pressure exerted by the contents of the vessel. Once the gasket has been seated properly, there must be sufficient forces continuously operating on the gasket to maintain intimate contact between the gasket and the seating surface, to prevent leakage or blow outs.

As the flange bolts are tightened the gasket typically changes in a way that causes it to compensate for any imperfections on the faces of the joint by flowing into, around, and over the imperfection.

In sealing a flange with a gasket the following are important to prevent the joint leaking:

• Are the flanges, or mating surfaces, flat and free from imperfections?
• Is the gasket made from a material with the required chemical resistance?
• Does the gasket have sufficient resistance to operating temperature for the application?
• Is the gasket strong enough to resist the internal pressure of the pipe?

The correct selection of the gasket is important because the material must:

• Withstand the pressures exerted against it.
• Withstand any corrosive medium that may attack its structural integrity.
• Withstand the entire temperature range of the process it is a part of.