Gaskets perform a vital function in numerous applications. Placed between two surfaces to fill the gap, gaskets help to prevent leaks by providing a robust sealing solution.
Spiral wound gaskets are the most common and well-known type of gasket, as they are suitable for a variety of applications across a number of different industries.
However, in applications where harsh chemicals are present, selecting the right gasket material becomes vital.
In this post, we look at what materials are best for sealing aggressive chemicals and the benefits each provides.
Spiral Wound Gaskets
A spiral wound gasket is typically made up of three component parts:
Outer ring – made of stainless steel, the outer ring helps with positioning and over-compression.
Inner ring – supports the gasket and prevents windings from warping when compressed.
Winding – alternating strips of filler material and metal are wound to provide the spring-like element of the gasket.
The filler material is vital in the construction of the spiral wound gasket, as the filler material you choose will also form the inner ring of the gasket, so these must be suitable for the chemical compound they will be sealing against.
Sealing Aggressive Chemical
Certain applications within specific sectors will use and contain harsh and aggressive chemicals. Chemicals that, when they come into contact with certain spiral wound gasket materials, can burn through them, eroding the ill-suited gasket and leading to potential leaks.
This presents several significant sealing challenges, as chemicals can degrade the sealing element, as mentioned, causing leaks; it can adversely affect the flange face and ultimately affect and compromise a joint’s integrity.
Of course, this can be extremely hazardous due to the nature of the chemical potentially being exposed, so it is essential that the spiral wound gasket manufacturing process is not only carried out correctly, but the gasket is manufactured using the appropriate material suitable to the substance it is exposed to, i.e., specific chemical bases must be matched against the seal material type it is intended for.
Aggressive chemicals can include:
- Strong acids – citric acid, sulphuric acid, hydrofluoric acid
- Strong alkalis – sodium hydroxide, potassium hydroxide
- Halogens – chlorine
- Aromatic hydrocarbons
- Bleaching agents.
Gasket for Sealing Aggressive Chemical
Some of the best solutions for aggressive chemicals include:
Nitrile rubber – mainly found in the automotive industry and machinery environments due to its excellent resistance to fuels and oils. (Note: other types of rubber seals are available; however, most of these will collapse and age quickly when they come into contact with such fuels and oils).
EPDM – for concentrated acids and alkalis, opt for EPDM gaskets. Providing good resistance to ozone, steam, and strong acids and alkalis; however, this material is not suitable for solvents or aromatic hydrocarbons.
FKM (fluoroelastomer) – also known as Viton- is resistant to a range of acids, alkalis, oils, and dichotic hydrocarbons. However, it is unsuitable if you require a seal for amines, esters, ketones, or steam.
PTFE – an all-around great sealing solution. PTFE is a gasket material that performs well when there are flange surface irregularities, and this material selection also offers good chemical resistance to a range of corrosive compounds and has high compressibility. However, it’s important to know that this type of spiral wound gasket can be prone to creep and relaxation, so this should be built into the manufacturing process.
Note: When using gaskets in aggressive chemical applications, it’s vital to use new gaskets at all times and not reuse them after use, as performance on reused gaskets cannot be guaranteed.
Chemical leaks are not only problematic but extremely hazardous and must be contained as quickly and effectively as possible.
At SSP, we supply a range of gaskets for sealing, all of incredibly high quality and providing you with excellent performance levels.
Applications where you will require specific gaskets and seals to contain harsh chemicals include:
- Pumps
- Mixers
- Instrumentation
- Filling systems
- Valves
- Pipework
- And more.
Points to consider:
- The material you opt for must have the right level of chemical resistance
- Gasket material should be resistant to premature aging
- The material should not cause an adverse reaction with the chemical that is being sealed
- Spiral wound gasket material must be able to withstand cleaning and sterilisation processes if this is required
- Gaskets, ultimately, must be able to perform at the necessary temperature fluctuations, pressure ranges, and chemical concentrations that the application requires.
Spiral Wound Gaskets
There are various types of spiral wound gaskets, and it’s important to recognise that what one type works for one application might not be the most suitable type to work for another.
Instead, when working with chemical applications, you must match the gasket material to the chemical compound to ensure the best sealing outcome.
In addition to sealing aggressive chemicals, gaskets also play a crucial role in various other applications, such as vibration damping.
Specialist Sealing Products (SSP) are well-versed in providing the right gaskets to meet specific application requirements.
On hand to answer your questions, contact us today to see how we can help you.
