Q - Is it necessary to glue a case gasket to the casing? If it is, should it be glued to the case upper, or lower half? (See Replacing Case Gasket)
A - If the liquid is non-hazardous, and temperature and pressure are low, it is not necessary to glue the gasket to the casing. Unglued gasket is easier to replace every time the casing is opened for inspection. Glued gasket is hard to remove and there can be a build-up of residue on the surface if one does not do a good job of removing the old gasket material thoroughly.
But there are instances where a gasket may be glued:
when the liquid is toxic, flammable, or hazardous
when the operating pressure is high (where a nozzle flange rating of 300 lbs, or higher, is required)
when the liquid temperature is high (250 degrees Fahrenheit, or higher)
when the finished gasket has narrow sections that can wash out easily, such as the narrow sections around the volute, the stuffing box, the wear ring land, and adjacent to bolt holes where the potential for leakage, or by- passing, exists.
When a gasket is glued to the casing, pump vendors typically recommend gluing the gasket to the lower half for ease of installation. But maintenance and service people prefer that it is glued to the upper half because it is easier to pull out the upper casing and move it away to a safe place so that gasket debris do not fall into the lower casing when the gasket is removed.
When removing old gasket make sure that the gasket which might be asbestos- laden, or contaminated with hazardous liquid, is handled and disposed of safely.
Q - If the gasket on an axial-split case pump should be glued to the case parting flange, would it not make sense to glue it on both sides to ensure a leak-proof fit?
A - When the upper and lower halves of the casing are put together, the upper half might move to find its equilibrium during the bolting process. The gasket might shear apart if it were glued on both sides. To avoid damaging it, the common practice is to apply adhesive on one side and a light lubricant on the other side.