A revolution in maintenance

With budget cuts hitting the wastewater industry, downtime caused by blockages to pumps is the last thing that plants can afford. Which is why, says Simon Lambert, the new MIP pump is the most important design development in decades.

THE PROGRESSING cavity (PC) pump is widely known for its ability to easily and efficiently transfer a number of difficult media, such as liquids with solids and entrained gases.

Wastewater treatment is one sector in particular that uses a high number of PC pumps due to the difficult pumping applications it faces, from the transfer of products ranging from raw sewage through to thickened sludges and sludge cake.

However, current problems facing the industry, such as diminishing in-house expertise, reduced maintenance budgets and unsuitable items finding their way into the sewers, are making difficult processes even more of a challenge.

Mono conducted a survey in the wastewater industry to find out what common problems it was facing. The overriding response was that ragging has become a serious problem and is increasing in severity to the point where it can cause serious disruptions to the efficiency of the treatment process. While PC pumps can cope with low levels of rag much better than most other types of pump, higher concentrations will undoubtedly cause blockages.

The survey revealed that the options available to engineers when de-ragging a pump were limited, time consuming and in some cases unsafe.

Downtime
Clearly the industry needed a pump solution that would minimise plant downtime and maintenance, and provide a safer and easier option for today's plant engineer. In response, leading pump manufacturers have developed new pump technology, that has been specifically designed to provide a quick and easy way to disassemble, de-rag and maintain a PC pump in-situ, eliminating the costly maintenance and downtime that servicing can often cause.

On average, this new type of maintain in place (MIP) pump can reduce the maintenance time needed to replace a rotor, stator, coupling rod and joint by up to 95%. The average time to strip down and replace the drive train elements is usually one day on typical sludge pumps; with this new MIP pump it takes just 30 minutes.

Blockages can occur in the suction or inlet chamber of a PC pump. Here, a rotating shaft can become entangled with pieces of rag.

While intervals between maintenance on a PC pump are typically long, its design means that access to the suction chamber during maintenance requires dismantling of the pump and pipework connections, to get at the chamber.

When the suction chamber is blocked, especially with fibrous material wrapped around the rotating shaft, the material has to be removed. Blockage of the inlet can rapidly cause damage to the rotor, stator and drive train, so it is imperative that it is caught in time.

If detected in time, the maintenance engineer frequently tries to free up the suction chamber by removing the rag elements with as little of the pump dismantled as possible. This can be a temptation to adopt dangerous practices, such as inserting a sharp blade through the inlet flange and hacking away at the wound-on and compacted rag, then trying to retrieve the pieces.

The alternative has been to dismantle the pump, which even by a highly experienced maintenance engineer, is a process which can take up to a day and the actual cleaning out portion is only a fraction of the time taken to complete a maintenance procedure.

Burden
By completely rethinking the design of the suction chamber and drive train element of a PC pump, it is possible to eliminate the difficulty, time and cost of de-ragging and maintenance.

The MIP's chamber has a two-piece design, which can be dismantled and assembled in place without requiring years of expertise. It can be opened up and rebuilt with a spanner and an Allen-key in a fraction of the time previously required; trials have indicated that it can save up to 95% of the time normally required to provide full maintenance for a PC pump.

The coupling rod can be accessed in less than a minute, the suction chamber and rotating parts de-ragged and the chamber reassembled; the whole operation taking less than two and a half minutes depending on the blockage.

The development of the MIP pump design revolutionises the maintenance requirements of any PC pump and will reduce the burden of maintenance on not just wastewater treatment works but all facilities that use PC pumps. As such, this new pump innovation is the biggest leap forward in PC pump design for 30 years.

Simon Lambert is general manager, Europe for NOV Mono. T: 0161 339 9000

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