Waterproof Gasketing | Design Considerations for Water Sealing

The number one media everyone is trying to seal is water. When we hear liquid sealing, our first question is typically, “Well how much water, at what pressures, and how often?”. There are a number of “waterproof” standards. Typically NEDC considers the gasket immersed in water as a waterproof gasket. 

water immersion bubbles

Consideration when Picking a Material for Water Sealing/Waterproof Gasket:

Pressure to seal the gasket, and get it to seat properly. We look at water sealing gaskets in two categories. A lot of pressure to seal the gasket, or a little pressure to seal the gasket. A gasket material works because the pressure from outside forces whether by mechanical means, or other means seals media from intruding into the application.

A lot of Pressure on the Gasket:

When you have the luxury of a lot of pressure when it comes to gasketing materials, you should pick a gasket that adjusts into the hardness, or durometer of the material. For example, applications that have a lot of pressure such as flange gaskets can tolerate high durometer materials such as 70 or 80 Shore A durometer. In comparison applications such as small # 10 screws may only tolerate a gasket at 30, or 40 Shore A. 

A little Pressure on the Gasket:

When little pressure is provided on the gasket, the important thing to realize is that that:

Sealing significant intrusions of media, aka. Under high pressure itself may become a challenge. At this point usually cellular foam, or cellular sponge is what you are going to want to use. Other considerations can be very soft solid rubber materials such as 10A, or 20A shore durometer materials. Usually those are available with silicone rubber polymers.

Environmental Concerns of Materials

1. Will the gasket be exposed to other fluids besides water? Is it required to seal out other fluids that could be hazardous to typical materials? Examples could include fuel immersion requirements that could be a big concern. For example, fluorosilicone, or Viton may be a gasket of choice in these cases.
2. What temperature ranges will the gasket be exposed to? Is the gasket being exposed to temperature ranges that can be hot, and cold depending on the requirement? This concern also relates to compression set that can occur with poor resistance to temperature. 
3. Other peripheral concerns such as fungus resistance, ozone, or weathering requirements. Gasketing materials like silicone rubber, or EPDM are good selections for these type requirements. Silicone compounds for consideration: IST26, or CHR90XX (CHR 9030, 9040, 9050)

Dimensional Note:

When compressing gaskets for water/liquid sealing, it’s important to note that thin cross sections especially near bolt, or screw holes can become a big concern and an area for leakage/leaks. With high pressures, we suggest keeping the holes and bolts having as much space around them as you can provide in the design. Some customers also call a gasket with a thin cross section near the holes as a “small wall”. 

Water valve meter high pressure broken burst gaskets on bolted flanges spraying onto grass roadside verge outdoors.

Specifications for Waterproof Gaskets:

As we mentioned in our post on IP Ratings, there are two numbers in your typical IP rating for liquid sealing, which usually looks like something like this: IP67, = IP 6= dust tight, and IP X7=robust temporary immersion. We posted the chart below for ease of use. This post is mainly discussing IP68, or in other words totally waterproof gaskets that are fully immersed under pressure.

Liquid Matter Ingression Prevention Table

More Information on Water Sealing Gaskets

NEDC does die-cutting, waterjet cutting, or laser cutting for custom gasketing materials. For more information on water sealing gaskets, please contact sales@Nedc.com.