In developing its new breed of high performance, heavy duty PAC H pumps, Atlas Copco has focused on improving pump and seal design to increase MTTR and reduce the time and cost associated with pump maintenance.
High head pumps are the workhorses of many industrial fluid control systems. Their role can often be mission-critical, particularly in settings such as water transfer in the oil & gas sector, municipal water treatment and supply, and dewatering applications in construction and mining, where the control and removal of surface water is a primary safety concern.
In such applications, it is vital that the pump operates reliably for extended periods of time. Maintenance outages need to be kept to a minimum: both in terms of the mean time to repair (MTTR) and the length of time required to complete any necessary repairs or servicing. Any unexpected outages due to the failure of a seal, or premature corrosion of the impeller, for example can have serious consequences, impacting on productivity, operational efficiency, operational safety and therefore on profitability.
Problems with pumps However, maintaining high head pumps can be challenging. The uses to which these pumps are put mean that they are often located in cramped and/or remote environments and spend much of their time submerged. As a result, there are few opportunities for visual inspections which would spot early signs of sub-optimal performance, such as excessive vibration or unusual wear and tear.
On top of these adverse operating conditions, the design of the pump itself must be considered. To perform effectively, a pump needs to be built for maximum flow and minimal leakage. However, the robust outer casing can mean that hydraulic elements are difficult to access, reducing maintenance efficiency.
Of course, some breaches in the outer casing are integral to pump design: for example, where the impeller shaft enters the pump housing. Here, a mechanical seal is introduced to preserve the integrity of the pump by preventing fluid leaks and keeping contaminants out.
The downside is that mechanical seals have maintenance requirements of their own. A mechanical seal can easily leak or become damaged if the pump is allowed to run dry. Incorrect installation, or failing to clean the areas surrounding the seal, can also lead to premature failure.
As part of its development strategy toward its new breed of high performance, heavy duty PAC H pumps, Atlas Copco focused on improving pump and seal design to increase MTTR and reduce the time and cost associated with pump maintenance.
Design improvements The issue of ready access to the pump hydraulics has been addressed with development of an innovative hinge kit. This comprises a ‘swing door’ that allows quick and easy access to the pump’s internal workings. Ease of maintenance is further enhanced with the use of a single bolt to remove the impeller. Bolted wear rings make for precise and simple replacement compared to pressed alternatives, and link belts are used to enable changeovers without having to dismantle the entire wet end of the unit.
The semi-cartridge seal design on the PAC H pump comes as standard, allowing seal access and replacement from the front. Atlas Copco’s SEAL design allows changeout without dismantling the pump and makes the lip seal and impeller easily accessible via reducing downtime and simplifying maintenance. An integral seal oil bath prevents damage if the pump runs dry, while a visual inspection port makes leakage inspection simple.
To prolong pump operational life and protect the seal, Atlas Copco has developed a closed impeller that is equipped with deflector vanes. This provides two benefits: it improves thrust balance on the shaft and impeller to minimize wear and keeps the mechanical seal clean. Essentially, the vanes create a vortex that prevents the accumulation of detritus. This helps the mechanical seal last three times longer. Moreover, it eliminates the need to use flush water to keep the pump clean: offering significant energy and cost savings over the pump’s operational lifetime.
To further support minimal downtime through more efficient maintenance, PAC H pumps take advantage of digital technology. They are equipped with QR codes that mean essential information about parts and spares is just a scan away. Users can also take advantage of the fleet link secured and remote monitoring feature that means they are always in control of pumping operations.
Conclusion Atlas Copco has addressed traditional issues of inaccessible hydraulics and the need to disassemble pumps to perform simple tasks like replacement of consumables. In combination, these features can improve MTTR by up to 30%. However, improvements to pump design can only achieve so much in the drive to improve efficiency and optimize uptime. Availability of spares and adequate training are also essential and these support services are provided through Atlas Copco’s global network of customer centers.