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When ‘right first time’ is the only option Derek Ashburn Application Engineer Pump Services
Hindsight is a wonderful thing. If only we had the ability to foresee issues before we encounter them. Having a better understanding of a challenge from the beginning would be a bonus, but we all know, that’s often not an option we are afforded with. Many large-scale projects leave very little room for error. Not only is the customer looking for a speedy resolution as downtime can cause serious issues, but your reputation is also at risk. As an engineering services provider, people are placing their trust in you to deliver. So, ‘right first time’ is the only option. ERIKS were recently involved in a project with a water company that was experiencing issues with one of its river abstraction pumps. A series of condition checks were carried out resulting in ERIKS Specialist Engineering Services being enlisted to support the fullscale overhaul programme of both the pump and motor. The water company had a history of working alongside other service providers, with one of the sister pumps having been out for repair for over a year. This and relatively short MTBF was worryingly short for these types of units. As is often the case there was very little in the way of repair history, original drawings, or parts lists to support the repair process, so much of the procedure and assessment was going to rely on experience and sound engineering best practice. As you can appreciate, this was a significant challenge – but one ERIKS did not hesitate to accept. Issue 42
The challenges were building up The pump in question dated back to the early ‘70s, and as we know, ageing assets come with their own risks, particularly, those that operate in arduous conditions. Exposure to silt and foreign objects in the water stream was a constant issue, with poor suction conditions also causing cavitation damage along with erosion problems. With the initial inspection and scoping of the task complete, a quality plan was drawn up; it was now time for removal which was a huge operation in its own right. Removing the pump-set involved partial dismantling of the unit into sub-sections. In these cases, you are relying on key skills within your team, fundamentally - experience, meticulous engineering know-how, and safe systems of work. Understanding all the health and safety risks with electrical and mechanical disconnection was essential. Up front, detailed risks assessments and methods statements were required, so that the team knew exactly what to expect, how to execute the work, and how to mobilise for operation. On top, it was pivotal to understand and adhere to relevant legislation, internal health
and safety rule, and those of the customers, including testing and proving for dead/ LOTO regulations and PTW (Permit to Work) compliance. Working in an unfamiliar environment poses its own risks, and itself an ever-changing landscape, therefore must also be constantly assessed and re-appraised via POWRA (Power of Work Risk Assessments.
Say what you see With removal and transportation completed, our Chesterfield Engineers were all set to inspect and produce the condition report. The findings of the initial examination discovered that the OEM had used different impellers to achieve the duty requirement while boosting suction performance, even so there was evidence suggesting that the pump had been running with very low NPSHa, resulting in serious cavitation damage on the first stage impeller and bowl vanes. The second impeller was also showing excessive amounts of residual weld on one of the vanes, this had been left over from a previous repair. More seriously however, the upper drive shaft had snapped through fatigue due to an incorrect machined taper angle from a previous repair within the coupling
Recommend. Overhaul. Repair Due to the age and history of this type of equipment, it is likely that these units will have been repaired several times during their lifecycle, often without any records or history surrounding the work that has been carried
