Conventional pre-cut compression gaskets are potentially prone to shrinkage, relaxation, extrusion and breakage, all of which can promote leaks between the bearing frame and adapter, or between the stuffing box and pump casing, for example. According to Henkel, the optimum way forward is to completely eradicate the requirement for a cut gasket by switching it with a liquid gasketing adhesive. Such a product fills all the air space between the mating parts to create a perfect seal, while simultaneously eliminating flange face corrosion.
It says that among the increasingly popular solutions for this application is Loctite 518, a methacrylate-based gasketing product said to be ideal where low strength is of paramount importance. For many MRO workshops this product is delivering a 50% time saving thanks to fast cure times, reducing the time required before reaching the test bench. In addition, as a single-component adhesive, the product is easy to apply using either a gun or a brush, while low cost and easy removal are further advantages. The adhesive is suitable for use on all types of pumps, including centrifugal, submersible, diaphragm, disc and double-jacket.
A typical process would involve the use of Loctite SF 7063 general purpose parts cleaner, before applying Loctite 518 for flange sealing. To remove the cured product, simply spray the surface with Loctite cleaner.
Among those testifying to the benefits is a manufacturer of cast iron gearboxes and geared motors. While the company was already using liquid gasketing on an adapter assembly flange, the resulting poor seal was causing a 5% leakage rate, along with testing and production delays due to the adhesive’s slow cure rate. After trialling alternative brands, the manufacturer found that a Loctite gasket sealant met all of its performance criteria. The product effectively fills the gaps between the flange surfaces and cures quickly so that close-fitting parts can be instantly pressure tested to 276 kPa (40 psi). Leaks are now a thing of the past and disassembly is far easier.
Another common issue with pumps is shaft misalignment. When shafts on rotating equipment are misaligned, the potential for costly, unplanned machine downtime rises dramatically. Typical among the outcomes is premature bearing failure. A simple and cost-effective way to ensure and maintain critical shaft alignment is to fill the airspace with a suitable liquid adhesive. This strategy has the effect of resisting vibration, shock, thermal expansion and contraction by unifying the assemblies. Such an approach maintains the clamp load and keeps bolts from loosening, which in turn ensures ongoing shaft alignment. Ultimately, pump users can extend mean time between failures (MTBF) and enjoy full bearing life expectancy.
Growing numbers are said to be turning to Loctite 290 medium-strength thread locking adhesive for this critical task. A case in point is an industrial maintenance/engineering services facility that had issues with shaft alignment for an electric motor and centrifugal pump that supplies water to the boiler of a commercial building. Previously, the loosening of mounting bolts was leading to shaft misalignment and failures.
To overcome the issue, the maintenance specialist opted for a new process. The company began cleaning the nuts and bolts using Loctite SF 7603, before aligning the shaft with a laser and applying Loctite 290 to the threads prior to fastening at the proper torque. This solution is proving successful in maintaining alignment until the next scheduled maintenance (every three years).