Darrell Howard reports on pump maintenance in power generation
The power generation sector, like many others, is under constant pressure to minimise downtime and maximise productivity. This means pump equipment is expected to run for longer periods with reduced maintenance intervals. When repairs are needed, they have to be completed within tight deadlines to comply with ever shorter maintenance windows. Here, we look at some of the key points that affect a successful repair project.
A great deal of the rotating equipment used in the power generation sector has been in place for many years. Pump equipment has been rigorously maintained and serviced to ensure reliable performance. As service and maintenance intervals increase, the attention to maintenance procedures has become more focused. Employing a properly structured and managed program enables large sites, equipped with vast numbers of assets, to achieve high productivity levels while maintaining the long-term reliability of the plant.
One of the most critical aspects of asset maintenance is understanding the requirements of each piece of equipment and the implications to the overall production process of taking the asset offline. In most cases, assets will have standby systems that can keep a process operational, even at a lower productivity rate. Ultimately, it is the experience and knowledge of the on-site maintenance engineers that provides the most useful information and by working closely with a repair provider, an efficient maintenance schedule can be developed.
The diversity of pump design and technology used within the power generation sector means that finding a repair partner can be a daunting task. At face value, the OEM would seem to be the obvious choice to complete any repairs, however, across an entire facility there could be a wide range of pump designs that in turn, would mean coordinating a maintenance programme with a large number of third-party organisations. This carries a high burden and stress of administration and site coordination. Therefore, selecting the most appropriate partner that delivers both OEM technology and the ability to support equipment of multiple manufacturers is key in achieving the maintenance goals of the business.
Assessing the skills and capabilities of a maintenance provider is crucial for determining the overall level of service that can be delivered. Providing preventative maintenance services is important, but when a component fails, the priority must be with delivering a fast turnaround and getting the equipment back into service. Today, with the number of complex pump designs in service, there is a real demand for a single-source solution that has the ability to repair, re-engineer or remanufacture damaged components using in-house resources.
The alternative; using providers that sub-contract repairs to compensate for a lack of in-house facilities can increase the complexity of the project, degrade the communication process and ultimately lead to less dependable repairs.
Furthermore, those with experienced design capabilities can also integrate improvements into the design of components, enabling clients to benefit from the latest manufacturing technologies and improve both efficiency and reliability.
It’s worth noting that or some power providers and first-tier contractors the requisite combination of skills and facilities needs to be available to a combination of fuel sources from natural gas and fossil fuels to nuclear and renewables anywhere in the world, since power generation is often a global business.
Developing a plan
When partnering with a maintenance provider, it is important to develop a program of planned actions as well as making contingency plans for unexpected failures. By implementing a carefully organised plan it is possible to increase reliability and maximise productivity by utilising a range of techniques and facilities.
At the most basic level, condition monitoring is a vital tool that can use vibration, pressure and temperature monitoring equipment, plus manual thermal imaging cameras to provide vital information and indicate the early signs of an impending failure. Both of these predictive maintenance methods can be used without having to stop the equipment and they can provide regular data for a preventative maintenance programme.
This forms the basis of a planned maintenance scheme that should be supported with additional information such as pump performance data ,which can also reveal the early indications of a performance issue. Collectively, this information enables the on-site maintenance team to schedule repairs during planned shutdown periods, minimising the impact on productivity.
However, despite this, component failures will still occur and it is the ability of the repair partner to react quickly and deliver a solution that will determine the long-term viability of any maintenance agreement. Sulzer, for example, recognises this crucial aspect of the partnership and has developed an internal communication structure that allows a local service centre to deliver the full range of technical services to its clients, while drawing on the company’s global engineering and logistics resources.
This can be better illustrated by way of an example repair that was recently delivered by one of Sulzer's service centres. The challenge came from a major energy provider that required a 21-day turnaround on two high-speed boiler feed pumps.
The equipment owner presented a very detailed repair specification that was to be followed precisely. Some of the challenges with this particular style of pump included developing clear and precise inspection templates, instructing and reviewing with the shop personnel where and how to inspect the critical fits and recording the required information to meet the customer's inspection criteria on the initial inspection.
One of the first requirements was a special cleaning procedure that the service centre managing the repair was not equipped to do. However, by using the other Sulzer facilities located nearby to accommodate the demand, the cleaning procedure was quickly completed without incurring any delays. Once complete, the pumps were returned to the original Sulzer site to begin disassembly.
Inspection of the individual components determined that some of the impellers were damaged and were deemed irreparable. The hub side plates on at least half of the series impellers were cracked through and required replacement. This level of damage had not been planned for and replacement components are not typically stored by either the customer or the manufacturer.
Having advised the customer of the unexpected discovery, enquiries were made with the OEM about the best lead time for new impellers, which came back as 20 weeks. Sulzer was able to offer a full set of new components, available in just five weeks, an offer that the client gladly accepted. The damaged impellers were sent to one of the company’s manufacturing centres, which has full reverse engineering and design capability for both hydraulic and mechanical components.
A 3D design of the original impeller was created using coordinate measuring machines (CMMs) which allow on-site data acquisition quickly. These machines gather three-dimensional data and allow the obtained dimensions to be repeatable to within 0.001in. The 3D model was completed within one week and the data immediately transferred to the engineering and manufacturing departments where the new designs could start to take shape. However, with such extensive and unexpected damage, meeting the original programme deadline of three weeks was going to be impossible to achieve. Following discussions with the client, Sulzer proposed to rebuild one of the pumps using the best components from both pumps. This required moving diaphragms and diffusers between the pumps and correcting all the fits and clearances in order to achieve the required design specifications.
The first pump was completed and returned to the customer one day early, while the second pump was completed and shipped back to the customer on schedule to meet the operational requirements of the plant.
In today's world of large scale pump maintenance it is essential for repair specialists to have a wide range of skills and adaptability in order to deliver a comprehensive service. Equipment is becoming more complex and the facilities required to maintain them, more expensive. Although technology has evolved since much of the equipment in the power generation sector was manufactured, it is possible, with the right engineering expertise, to improve reliability and efficiency by remanufacturing certain components as part of the regular maintenance program. In the long term, this helps to improve productivity and reduce the likelihood of unexpected breakdowns.
Darrell Howard is repair engineering manager at Sulzer.