Gasket sealant is used to improve the seal between two mating surfaces and help prevent leaks caused by small surface imperfections, scratches or irregularities. It can be used with some pre-cut gaskets or, where the correct product is specified, as a formed-in-place gasket.
However, gasket sealant is not suitable for every application. Choosing the correct sealant for the gasket material, temperature, pressure, fluid and flange type is essential for a reliable seal.
When Should You Use Gasket Sealant?
Gasket sealant can be useful when:
- The mating surfaces have minor scratches or imperfections.
- The gasket manufacturer recommends the use of a sealant or gasket dressing.
- Additional resistance to leakage is required.
- A flange requires a liquid gasket rather than a conventional gasket.
- A formed-in-place gasket is specifically specified by the equipment manufacturer.
- The application involves vibration or thermal movement and the selected sealant is designed for it.
A sealant should not automatically be used with every gasket. Some gasket materials are designed to seal without additional sealant, and adding the wrong product can actually reduce sealing performance.
For example, anaerobic flange sealants are generally designed for close-fitting, rigid machined flanges, while silicone gasket makers are available for applications where greater flexibility or gap filling is required.
Gasket Sealant or Gasket Maker?
The terms are sometimes used interchangeably, but there is an important difference.
Gasket sealant or gasket dressing is normally applied to a conventional gasket to improve sealing.
Gasket maker is a liquid product designed to form a gasket between two mating surfaces, potentially replacing a pre-cut gasket where the manufacturer permits it.
Always check the sealant manufacturer's instructions and the equipment manufacturer's requirements before replacing a conventional gasket with a liquid gasket.
How to Apply Gasket Sealant
Correct preparation is just as important as choosing the right sealant.
1. Remove the Old Gasket
Remove the existing gasket and any old sealant completely. Use a suitable scraper that will not damage the flange surfaces.
Avoid leaving pieces of old gasket material, sealant or debris behind, as these can prevent the new gasket from seating correctly.
2. Clean the Surfaces
Both mating surfaces should be clean, dry and free from oil, grease, dirt and other contamination.
Use a suitable residue-free cleaning solvent compatible with the materials involved. Some sealants may also require an activator or primer, particularly with certain metals or at low temperatures. Always follow the manufacturer's instructions.
3. Check the Flanges
Inspect both surfaces for damage, corrosion, burrs, distortion or deep scratches.
A gasket sealant can compensate for minor surface imperfections, but it should not be relied upon to correct badly damaged or distorted flanges.
4. Apply the Sealant
If using sealant with a conventional gasket, apply the product according to the sealant manufacturer's instructions.
For many liquid gasket products, a continuous, even bead is applied around the sealing area. Where specified, the bead should also surround bolt holes so that there is a continuous sealed path.
Avoid applying excessive amounts. More sealant does not necessarily produce a better seal, and excess material can be squeezed into the equipment or pipework.
5. Fit the Gasket and Assemble
Position the gasket carefully and bring the mating surfaces together without unnecessarily sliding them sideways.
Tighten the bolts progressively and evenly, following the manufacturer's recommended torque and tightening sequence.
Some sealants require assembly while still wet, while others require a specific curing or flash-off time. Always follow the instructions for the particular product being used.
6. Allow the Sealant to Cure
Do not assume that a gasket sealant is immediately ready for service.
Silicone gasket makers, for example, may skin over relatively quickly but require substantially longer to fully cure. Other products, such as anaerobic flange sealants, cure differently and are designed to cure between closely fitting metal surfaces.
The required curing time will depend on the product, temperature, humidity, materials and joint design.
Which Gasket Sealant Should You Use?
The correct sealant depends on the application.
| Application | Possible sealant type |
|---|---|
| Rigid machined metal flanges | Anaerobic flange sealant |
| Flexible or stamped flanges | Suitable RTV/silicone gasket maker |
| High-temperature applications | High-temperature gasket sealant |
| Dressing a conventional gasket | Sealant specifically approved for the gasket material |
| Oil, fuel or chemical service | Sealant specifically compatible with the fluid |
Chemical compatibility is particularly important. A sealant that performs well with water may not be suitable for oil, fuel, solvents, steam or aggressive chemicals.
Common Gasket Sealant Mistakes
Some of the most common problems include:
- Using the wrong type of sealant.
- Applying too much sealant.
- Applying sealant to dirty or oily surfaces.
- Failing to remove old gasket material.
- Using sealant where the equipment manufacturer specifies a dry gasket.
- Replacing a conventional gasket with liquid sealant when the application does not permit it.
- Using the wrong sealant for the temperature or fluid being contained.
- Putting equipment into service before the sealant has cured.
The correct sealant should always be selected based on the gasket material, operating temperature, pressure, fluid and flange design.
Do You Always Need Gasket Sealant?
No. Many gaskets are designed to seal without sealant when correctly selected, installed and compressed.
Sealant should be considered an additional sealing solution rather than something that should automatically be applied to every gasket.
For critical applications, follow the equipment manufacturer's instructions and the gasket and sealant manufacturer's technical data.
Gasket Sealant for Bespoke Gaskets
The performance of a sealed joint depends on more than just the sealant. Correct gasket material, thickness, hardness, flange design and compression are all important.
At TYM Seals & Gaskets, we manufacture and supply a wide range of rubber, silicone, sponge and specialist gaskets for industrial applications. If you are unsure which gasket material or sealant is suitable for your application, we can help you select the appropriate solution.
Frequently Asked Questions
Can I use gasket sealant on any gasket?
No. Some gasket materials are designed to be used dry, while others can be used with a compatible gasket dressing. Always check the manufacturer's recommendations.
Can gasket sealant replace a gasket?
Sometimes. Certain liquid gasket makers are specifically designed to form a replacement gasket, but they should only be used where the application and manufacturer permit it.
How much gasket sealant should I use?
Use only the amount specified by the sealant manufacturer. Excess sealant does not necessarily improve the seal and can cause problems inside the assembly.
How long does gasket sealant take to cure?
It varies considerably between products. Some are designed for rapid assembly, while others require hours or longer to fully cure. Always follow the product's technical instructions.
What is the best gasket sealant?
There is no single best sealant. The correct product depends on the gasket material, temperature, pressure, chemical exposure, flange construction and application.
