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Cartridge seal arrangement improves vacuum pump performance

 

Moving from a maintenance regime involving the replacement of gland packings on vacuum pumps every nine weeks to one where the pumps have run for 18 months without any maintenance is a remarkable achievement. For Solvent Resource Management Limited (SRM), one of the largest companies in Europe handling the disposal of organic waste materials, this turnaround has been achieved at its Knottingley solvent recovery plant thanks to the fluid engineering skills of AxFlow.

SRM has been using Nash SC series ring type vacuum pumps for many years on a processing system that uses scraped film evaporators for solvent recovery. On the recovery sector the plant has the capacity to produce in excess of two million litres per month. Using vacuum pumps in the recovery sector enables the scraped film evaporators to boil the liquid at lower temperatures. The pumps are also used to pull the crude liquid from barrels into the processing system tanks. However, the packed gland sealing arrangement which came with the pumps required replacement almost every nine weeks, resulting in costly plant shutdown. Getting the pumps out for maintenance purposes was not an easy job to do due to their position and installation.

Having accepted that mechanical seals would be preferable to packed glands, a change to this sealing arrangement was impossible because of the way in which the pumps were originally installed. Inevitably the situation could not be allowed to carry on and the installation was eventually removed and replaced with an altered configuration in late 2007 recommended by Tom Cooper at AxFlow’s Huddersfield base. The new configuration enabled the customer to fit mechanical seals.

AxFlow’s recommendation was to supply its GLK liquid ring cartridge mechanical seals with carbon/silicon faces and Kalrez O rings to withstand the aggressive nature of the solvents being pumped. This sealing arrangement was recommended because the cartridge unit it is mounted on a sleeve and pre-set to the working length of the mechanical seal, thereby making installation and subsequent maintenance simple. AxFlow also made sure that the seals were supplied with a clean water flush arrangement, using service water diverted from the main flow to the pumps. From order intake to complete installation of the seals in the pumps at the Huddersfield plant and return to duty, the contract was completed in just seven weeks.

“We have been providing mechanical seals and undertaking the maintenance of mechanical seals for a number of years,” says Tom Cooper. “As a result of our long working relationship with SRM, both in the supply of mechanical seals and pump maintenance we had a good understanding of their processes and requirements. This enabled us to provide a solution that met their needs in terms of pump operation and one that would reduce plant downtime.”

In terms of payback, the savings made on maintenance and downtime has enabled SRM to recoup their investment in the cartridge seals in a space of just six months. Having recouped these costs, the company is now benefitting from not having to shut the plant down every few weeks and spend valuable man hours on taking the pumps out, refitting the gland packing and reinstalling the pumps and associated pipework.

AxFlow Ltd

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