Getting pumped up about maintenance
September 1st 2008

Industrial pumps represent a significant capital cost, so it is important, to ensure they run efficiently and reliably. Colin Chapman of Henkel, maker of Loctite products, provides some helpful advice regarding assembly and repair

Pump breakdowns can be costly.

However, use of the right adhesives during assembly – and the instigation of a regular programme of efficient and proactive maintenance involving those same products – can radically cut the chances of disruption.

Let's start by looking at bearing frames and housings within pumps. The air space between threads on drain plugs, oiler nipples and other fittings could permit lubricants to seep out. Yet, this can be easily prevented through the application of an anaerobic adhesive to the threads.

Anaerobic products are liquids that cure on metal surfaces in the absence of air.

Indeed, the straightforward action of tightening mated threaded components will start that curing process. But not only is the space filled to prevent leakage, but also an impenetrable seal is created that keeps out moisture and corrosion. Yet even with such a positive seal, the joints can be disassembled for maintenance purposes using normal hand tools.

Further benefits Anaerobic engineering adhesives can also be used to avoid leaks and seizures between bearing housings and oil seals that incorporate press fits. Again, there is the potential for leak paths to appear within inherent air spaces. However, an anaerobic adhesive that is applied to the outside diameter of the oil seal, means the problem is preventable.

In addition, damage can occur when bearings spin on their shafts or within housings. By using an anaerobic compound on the outside diameter of the outboard bearing or the inside diameter of the inboard bearing the chance of damage is reduced – and often, eliminated.

The fast way to fastener security This adhesive technology also stops threaded fasteners, such as screws, bolts, and nuts from becoming loose though shock and vibration. That means, for example, using an adhesive on pump mounting assemblies during both assembly and maintenance can prevent bolts working loose and creating misalignment. This practice also permits preservation of the correct clamping load.

Couplings also benefit from the use of adhesives. For instance, should a setscrew loosen, the coupling could slide along the shaft and then disengage – causing wear in the keyway. This problem can be prevented through the use of an adhesive.

Goodbye gaskets A flange sealant can be effectively employed on a pump assembly in any position currently occupied by a traditional gasket – and with numerous benefits. For starters, an adhesive removes the requirement for an inventory of various sized gaskets. It also means that failures due to shrinkage, compression set, relaxation and breaks are a thing of the past. Furthermore, the clamp load is constant and, because the sealant migrates into surface imperfections, there is a complete seal.

Seize the chance Of course, exposed metal parts could be attacked by rust – leading to problems.

However, by applying an Anti-Seize product during assembly, moisture will be prevented from entering a joint but – just as important – the components will be easier to undo for maintenance. Of course, the same product can be applied when the pump is reassembled after servicing. Typical applications that could benefit include lock nuts, dowel pins on bearing frames, shaft impellers, power end and clamp bolts and gland nuts.

Proactive maintenance There are even more areas where adhesive-based products can be used for pump maintenance.

Minor worn areas of ring seats, casings, cutwaters, vane tips or impellers can be easily rebuilt with ferro-silicon or ceramic fibre-filled repair epoxies or wearing compounds. After abrading and cleaning the surfaces, these products are mixed and applied according to instructions.

This is followed by a coat of a brushable ceramic white. Once gel time is reached, a layer of ceramic grey is brushed on.

Similarly, worn shafts can be restored using an epoxy with high compression strength.

Worn keyways can be restored using a quick metal retaining compound. After application of a suitable activator, the compound is applied directly into the keyway. The new key is then pressed in and the assembly restored without having to take apart the pump.

Help available Pumps are frequently employed in harsh environments that mean wear, erosion and corrosion are almost inevitable.

However, the use of adhesive and related products in both assembly and maintenance tasks means many of the traditional problems are avoided. Even where other methods have been used for assembly, application of the right adhesive during maintenance often means parts that would otherwise be scrapped can be returned to service.

Henkel offers a brochure detailing the procedures that can be used for effective pump maintenance.

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