The Importance of Sealant Selection

When performing an online leak repair, choosing the correct sealant can be the difference between a successful and unsuccessful repair.

Manufacturers have formulated many sealants over the years in a variety of consistencies. They range from liquids and pastes to putty-like compounds. Most of these products consist of fibers, fillers, resins, and solvents. During the mixing process, air pockets are typically trapped inside the compounds due to the dense, thick materials being mixed. This causes some compression to occur during injection.

Sealants are generally classified as

• Curing or
• Compressible (non-curing).

Curing sealants

Curing sealants go through chemical and physical transformations when subjected to temperature and pressure from leaking components. This causes them to change to tough, durable, flexible, gasket-like solids.

After injecting an enclosure, technicians allot a time period for curing. Once the material is cured, they pump additional sealants into the enclosures to allow for shrinkage, pocketing, and honeycombing the curing process causes. Be aware that the gases created during the curing process can be flammable. Evaluate each application to determine whether you need to take precautions to avoid a flash or fire.

Compressible sealants

Compressible sealants suppress leaks during the injection process. Compression occurs when technicians fill the total void with sealant. The pump applies the sealant and a pressure gauge monitors compression. The engineering department determines maximum injection pressure to ensure technician and equipment safety.

Sealants have been tried and tested over the years, and there’s a lot of data showing sealant compatibility with the wide variety of processes used in the industry.

When choosing a sealant for a particular application, it is of utmost importance that the operating data you provide is accurate. This ensures that the sealant we choose is suitable for the process and temperature technicians will expose it to.

When evaluating a leak for sealant repair selection, technicians typically use four criteria to determine the best sealant for the job.

1. Chemical compatibility — The client provides the line process on a data sheet. We then compare this information to a chemical compatibility chart to determine which sealants are compatible with the process.
2. Operating temperature — The client provides the operating temperature on a data sheet. This allows us to choose a sealant rated for the temperature.
3. Curing sealant or compressible sealant — We evaluate the nature of the leak (e.g. leak size, aggressive or not, gasket leak vs. thin wall, and so on) and line contents to make a judgement on which route will provide the best success in suppressing the leak.
4. Experience — Having worked with a large variety of sealants in many different applications allows us to draw on experience from past leak suppressions to make judgement calls on sealant selection.

As you can see, all sealants are not created equal and each behaves very differently. Choosing the correct sealant can make or break leak repair success. Having accurate process information is critical in making the right sealant selection.