Seepex: From Rags to Riches
A waste water treatment work in the United Kingdom has an incinerator plant burning dewatered sludge. The quality of the sludge is critical to the efficiency of the plant, if for any reason the sludge feed is interrupted then expensive gas oil has to be pumped into the incinerator to keep the incinerator bed at the optimum working temperature.
The starting situation
Periodically, under storm conditions, the system allows rag and other debris to passs the inlet screens and enter the main works. This debris causes problems for equipment downstream including pumps and mixers.
A competitor was asked to provide a solution and subsequently supplied four of their twin shafted, low speed, high torque munching grinders which were installed between the huge consolidated sludge holding tanks and the existing incinerator plant feed pumps.
It soon became apparent that the debris problem had not been resolved. The works still experienced frequent ragging and blocking issues with both grinders and progressive cavity pumps. The design of progressive cavity pump with long thin flexible shaft exposed within the suction casing is particularly prone to ragging – each blockage had to be manually cleared. Prior to contacting seepex the supplier of the equipment was given the opportunity to rectify the problem as blockages were occurring on a daily basis and compromising operation of the plant.
The solution
The alternative grinding solution put forward by seepex was greeted with some reservations by site personnel so strict trial criteria were put in place. For the trial to be deemed a success the equipment had to function for an eight week period with no more than a single blockage occurring. The other obstacle was that the consolidated sludge tanks from which the sludge was being drawn from were at a low level, meaning that the sludge was thicker and contained a higher percentage of debris than normal. It was agreed that the trial would be a severe test.
The benefit
The trial was an outstanding success with no blockages or down time whatsoever. The grinder cutter stack was removed and inspected at the end of the eight week period and showed an as new condition.
The customer have calculated pay back time for supply and installation of new seepex grinders based on maintenance costs alone to be less than six months. This calculation excludes the additional costs incurred by burning gas oil in the incinerator when the existing sludge pumps and grinding equipment were not available.