Most gaskets are used to seal fluids or for environmental protection. Every so often though we are asked for a gasket for a less common application. One interesting example is the silicone or EPDM gaskets used around manways in brewery tanks.
Brewing depends on fermentation, a natural process involving lots of enzymes and chemistry. If the equipment is less than perfectly clean bacteria may contaminate what will become beer.
To avoid this, breweries clean and sterilize rigorously. Every mash tun and fermentation tank, plus the pipework in between, is treated with steam, caustic cleaning solutions, or both. Larger tanks often need someone to go inside to do the cleaning, which is why they’re usually constructed with a “manway”.
A “manway” is an entrance point big enough for a man to enter through. Usually circular or oval, if located at the bottom of the tank, they need to withstand the pressure and temperature of the liquid inside. Some are just cover plates bolted to a flange, but in brewery equipment, it’s far more common to have a hinged door that clamps shut.
Regardless of design, every manway needs a gasket to stop it leaking. Those used in breweries must tolerate cleaning chemicals and steam as well as process heat. To avoid the need for high clamping forces, they should be soft, and ideally will resist taking a compression set. They also have to be food-grade to avoid imparting any kind of taint or contamination.
Suitable Gasket Materials
For manways in brewery tanks food-grade silicone and EPDM gaskets are the most common choice. Both are elastomers, so while they are elastic and deform under even quite light loads, they do not compress. Silicone gaskets have the higher temperature limit, typically 400°F (204°C), and are resistant to fungal attack, but have poor tolerance to steam.
EPDM gaskets have a lower upper-temperature limit, (250°F – 121°C) but are resistant to steam, ozone, acids, and alkalis. For this reason, these are the type of gasket used in many brewery tank manways.