What are the best practices for inspecting and replacing seals?

1 Seal types and functions

Seals can be classified into two main categories: static and dynamic. Static seals are used to seal fixed joints or gaps, such as between flanges, pipes, or housings. Dynamic seals are used to seal moving or rotating parts, such as shafts, pistons, or valves. Static seals are usually simpler and cheaper than dynamic seals, but they may require more frequent replacement due to thermal expansion, corrosion, or vibration. Dynamic seals are more complex and expensive than static seals, but they can withstand higher pressures, speeds, and temperatures. Some common types of dynamic seals are O-rings, lip seals, mechanical seals, and hydraulic seals.

2 Seal problems and causes

Seals can fail or malfunction for a variety of reasons, such as improper installation, incorrect sizing, inadequate lubrication, excessive wear, chemical attack, or environmental factors. If you notice any signs of seal problems, such as leakage, noise, vibration, overheating, or loss of pressure, inspect your seals right away to determine the cause and extent of the damage. Common causes of seal problems include misalignment, hardening, swelling, cracking and abrasion. Misalignment occurs when the seal is not aligned with the mating surface or the shaft, causing uneven stress and friction on the seal. Hardening occurs when the seal material becomes brittle or stiff due to exposure to high temperatures, oxidation, or aging. Swelling occurs when the seal material absorbs fluid or moisture and expands and distorts. Cracking occurs when the seal material develops cracks or splits due to mechanical stress, thermal shock, or chemical attack. Lastly, abrasion occurs when the seal material wears away due to contact with rough or contaminated surfaces.

3 Seal materials and designs

Seals come in various materials and designs, depending on their application and operating conditions. Common seal materials are rubber, plastic, metal, and composite, each with its own advantages and disadvantages regarding heat, pressure, chemicals, and abrasion resistance. When selecting seal materials, you must consider factors like compatibility with the fluid or gas being sealed, hardness or durometer, temperature range, pressure capacity, and speed. Seal designs also vary depending on the type and function of the seal. Examples include O-rings – a simple and versatile seal consisting of a circular ring of rubber or plastic that fits into a groove; lip seals – a flexible seal with a metal case and a rubber or plastic lip; mechanical seals – complex and sophisticated seals consisting of two or more components; and hydraulic seals – specialized seals used for sealing fluid or gas in a hydraulic system.

4 Seal installation and replacement

Seal installation and replacement are critical tasks that require proper tools, techniques, and precautions. Improper installation or replacement can cause seal damage, leakage, or failure, so it is important to follow some best practices. Cleanliness is essential; you should clean the seal, the mating surface, and the surrounding area to remove dirt, dust, or debris. You should also inspect the seal and related components for any defects, wear, or damage. Additionally, lubrication is a must to reduce friction and facilitate insertion. Aligning the seal and the mating surface is also important for a proper fit and contact. Lastly, you should protect the seal and the mating surface during installation or replacement to avoid any scratches that could affect sealing integrity.

5 Seal preventive maintenance

Seal preventive maintenance is the process of performing regular checks and actions to prevent or minimize seal problems and failures. By following best practices for seal preventive maintenance, you can extend the seal life, improve the equipment performance, and reduce the maintenance costs. This includes monitoring the seal condition and performance regularly with visual inspection, leak detection, vibration analysis, or temperature measurement; adjusting the seal settings or parameters; cleaning the seal and related components with appropriate methods and agents; and replacing the seal and related components according to manufacturer's recommendations or experience.

6 Here’s what else to consider

This is a space to share examples, stories, or insights that don’t fit into any of the previous sections. What else would you like to add?