Industrial seals are used to prevent leakage, hold pressure, and deflect contamination at interfaces between components. These components are used at static and dynamic interfaces.
Dynamic interfaces are typically linear (such as the seal between pistons and cylinders) or rotary (such as the seal between bearing housings and axles). Adhesives and gaskets are typically used as static seals. Examples of static interfaces include the entry point of bolts and screws, and the interface between an engine block and cylinder head.
Adhesives, or sealants, include a range of substances that are capable of holding materials or two items together. A gasket is a flexible spacer that sits between two mating components. It’s made of a material that’s more malleable than these components, allowing it to fill any ridges or gaps due to surface imperfections. The mating surfaces are often nominally planar and a gasket is cut from sheet material to fill the gaps between them.
Typically, a gasket is shaped as a ring or sheet and is available in several materials, such as rubber, polymers, metal, fiberglass, paper, felt, and others.
A gasket works by forming an air-tight seal between stationary components that can resist fluctuations in pressure and temperature. Such components are typically bolted together, exerting considerable pressure on the gasket. As a result, it’s extremely important that gaskets are correctly specified and installed for their intended application and operating conditions. Incorrect gasket applications can damage an otherwise perfect assembly.
Along with pressure and temperature considerations, certain applications might have corrosive substances, unwanted gas, liquid emissions, or hygiene requirements (such as with medical device equipment). In other cases, electrical or electromagnetic forces might be a concern.
The primary purpose of most gaskets is as a seal, preventing ingress or escape of fluids. However, gaskets can do more than that. They can dampen and reduce sounds or vibrations. These gaskets are commonly used in appliances, HVAC systems, industrial machinery, and other equipment. These flexible components can also function as a safety pressure release. For example, it may be a vital function of a pipe gasket that if pressure builds, the gasket will fail before the pipe bursts.
When choosing a gasket, an often-overlooked consideration is whether it’s reusable. Several gaskets allow parts to be disassembled and then put back together, with the original gasket forming a seal once again. Some gaskets, however, can only be tightened to form a seal once and then must be replaced if the components are taken apart.
A few different types of gasket include:
- Gaskets cut from sheet material –to seal engine and gearbox housings (such as the head gasket in an engine)
- Gaskets cut from neoprene rubber – to create a weatherproof seal, typically used in electrical enclosures
- Pipe gaskets – that resemble a large washer and sit between pipe flanges
- O-rings – a torus-shaped loop of elastomer that can be seated in a groove and compressed to form a seal.
Gaskets ideally serve as a type of seal against pressure or vibration. However, other product choices are available depending on the application. Adhesives can reduce the time and cost of certain assemblies. Sometimes they’re used to permanently bond a gasket. But that also means they’re more difficult to disassemble than mechanical fasteners — and not reusable.
Additionally, a spacer (meaning a length of tube or even a washer) or a shim (a narrow wedge used for packing or leveling) might be the ideal choice to fill small assembly gaps between parts. Know your options and research the pros and cons of every component before making a choice.