To recap from the previous article, FIP (Formed-In-Place) gaskets are applied as a bead or a screen print of a liquid material, just before the two mating flanges are assembled. As the flange surfaces come together, the sealant is smeared between them and forced into surface imperfections, providing total contact and forming into a durable seal.
Unlike conventional gaskets, cured FIPGs adhere to every part of the joint and therefore don’t require extreme compresive loading to form a seal. With FIPG you can also forget about gasket relaxation and need for re-torquing. The metal to metal contact that FIPGs secure enables more accurate maintaining of tolerances while any scratches or damages to either of the surfaces can be sealed by the liquid material. Most of the FIP sealants have really good resistance to solvents and other industrial chemicals and unlike solid gaskets can be applied to vertical surfaces without any need for additional adhesive to hold them in place till assembly.
In terms of curing chemistry, there are two most frequently used types of FIP sealants:
- Anaerobic (curing between metal surfaces in the absence of oxygen)
- Room Temperature Vulcanising (RTV) elastomers
Anaerobic sealants are best suited for sealing of very rigid flanges such as gearbox housings, bedplates to crankcases, water pumps to engine blocks, and cam covers to cylinder heads.
They ensure minimum movement between parts, optimum stiffness between the two surfaces and transmit forces from one part to the other.
RTV elastomers cure to rubbery solids by reacting with the moisture in the environment. They are best suited for flexible flanges, like gearbox covers, timing chain covers, stamped sheet steel parts, thin walled metal castings and oil pans. Normally, they do not support the function of the component so micromovements can be tolerated.
Some of the additional benefits that RTV Elastomers offer are: high gap filling, sealing of T-joints, creating seals on non-machined flanges as well as between metal and plastic or two plastic components.
For more details, please request your copy of the Gasketing design guide.