December 2015

Focus on the Cost of Sealing

Gaskets exist to seal joints or interfaces. They’re either keeping something in or keeping something from getting in, and if they do their job no one notices them. That’s probably why some gasket buyers find themselves under pressure to go with the cheapest. Only later do they find that a very expensive mistake.

Gasket failure is expensive

The consequences of a leaking joint range from the trivial to the fatal. At one end of the spectrum, if a pipe flange gasket lets a trace of toxic chemical into the environment the results can be unthinkable, and will probably incur the wrath of the EPA. Fines and clean-up costs could sink the most successful company. Or consider other less serious but still expensive examples. Water penetrating an electrical enclosure gasket could damage equipment inside, causing lengthy unplanned downtime. Failed boiler seals might shut down a heating system, sending employees home. Even when the impact is minor, a lot of time might be spent cleaning up, and a lot of product wasted.

Gasket replacement is expensive

There’s the time and materials to do the job and perhaps other expenses involved in accessing the gasket location, but these pale next to the cost of lost production. A single leaking pipe can bring an entire plant to a halt while a new gasket is installed. Planned replacement is always preferable to reacting to a leak, but either way takes equipment out of service for a period of time.

Lifetime reliability

The price of the gasket is a very small part of the cost of a sealing problem. Logically then, anything that extends the life of the gasket is worth doing.

There are many options for sealing a joint or interface. Gasket materials come with long lists of specifications. Interpreting these and selecting the optimal combination takes in-depth product knowledge and understanding. Gasket experts might find what they need in a catalog, but for most buyers the best option is to ask their supplier. They’ll be happy to explain the characteristics of each gasket material

Open or Closed-Cell Gasket Material

When it comes to gasket material hardness the general advice is that softer is better, providing it seals the joint. Elastomeric gaskets used for sealing enclosures are a good example. When the enclosure door is closed there’s often a large and uneven gap remaining, (especially in the case of light-duty plastic enclosures.) A soft gasket compresses easily where the gap is smaller while filling the larger gaps, providing a seal all the way around the opening.

Interconnected cells

Many softer gasket materials, such as silicone, urethane and neoprene, are available with a cellular structure that makes them very soft. These cells are easily seen in cross-section. What gasket material buyers may not appreciate though is that these cells may be open or closed. This matters because it gives the gasket material different performance characteristics.

In a closed cell material, each cell is completely sealed off from its neighbors. That makes it feel harder because when compressed the air inside has no place to go. In an open material the cells are interconnected, so under compression the air moves through and out of the material, making it feel softer.

Different characteristics

Closed cell materials take on a compression set more readily than do open materials. This is because, under load the air inside permeates slowly through the cell walls. When the load is removed, although the material tries to spring-back it can’t draw air in, leaving the gasket material permanently deformed. In contrast, an open cell material “breathes,” drawing air back in to each cell as the material rebounds.

The weakness of open cell gasket materials is a lack of water-resistance. Just as in a sponge, the interconnected cells let water move through the structure. Although a load may close up the openings and provide some resistance, open cell gasket materials are not recommended for situations where water exposure is possible.

Consider the application

An open cell structure makes for a softer gasket, and one less likely to take a compression set. However, a closed cell material provides better water resistance. Select your gasket material based on the application.