PUMPS AND PUMPING SYSTEMS
LRC’s decision has enabled Scottish Water, which now has responsibility for the PS, to reap the benefits over 10 years and this pumping station is deemed one of the best on their network.
Chris Turton of Scottish Water’s operations team said, “The pumps continue to be reliable and successful. I would say that Hidrostal pumps were most definitely the right solution for the site, having coped with all flows and everything that has been thrown at them, never choking or tripping.
“The pump selection has been the most robust feature of the whole station. I’m not aware of any of the pumps having had a major repair; with only impeller changes and adjustments in line with normal operational maintenance.”
Since 1993 spares usage is recorded as four complete hydraulic ends and one complete pump as a dry standby, purchased due to age of assets, which to date has never been required. This is an incredible outcome for a sewage pumping station located in a coastal area.
Welsh Water’s Tynywaun water treatment works stayed in operation
The usage time is estimated at 50% or 4,380 hours / annum. Some 80% of this time is spent at DWF in low speed from which we have estimated the passed forward flows per year are approximately 5.3Mm3 of raw sewage.
Outcome
The site has been proven in service since 1993 and has required very few call outs. Maintenance is planned around any trend in flow reduction compared to increased power consumption per m3 pumped.
Measured data is then compared against known benchmarked figures of performance from new. This simple and inexpensive method of monitoring makes use of the standard equipment already installed on site to indicate when excessive wear has taken place. Prestonpans has a record of next-to-no call outs over 20 years. This means: Low energy from pumps running free of partial or full blockage
Low maintenance and spares usage Best whole life cost for a sewage pumping
station in the region
Chris Turton, Scottish Water’s operations manager commented, “Prestonpans is one of the most reliable sewage pumping stations we have in Scottish Water. Callouts and maintenance here are the exception rather than the rule.
“This station delivers Scottish Water low cost of ownership in both maintenance, with very few call outs, and also low energy from the pumps operating blockage free.” Prestonpans illustrates the possibility that new technology can actually consume more power, probably block more frequently and require frequent upgrades to expensive electronics with built-in obsolescence once user-dependency has been established. Hidrostal has been promoting the benefits of ‘true life cost’ for the past two decades, delivering durable and stable systems the world over, now proven by time.
The full version of this paper was presented at the Pump Centre Conference in May.
Drives arrive in the midnight hour
The failure of drives on two pumps at a Welsh Water treatment works required an urgent response, says James Chalmers, Northern European water industry manager, ABB
O
vernight work by ABB drives supplier APDS allowed Dŵr Cymru Welsh Water (DCWW) to continue to serve its customers after two variable-speed drives (VSDs) failed at its Tynywaun water treatment works. The treatment works, near Treorchy in South Wales, has a capacity of 10Ml/day to serve the upper Rhondda Valley.
The works uses two variable-speed drives for the interstage pumps, in a duty/standby operation. The duty drive suffered a failure and when the pumping load was switched to the standby drive, this also failed.
The drives had been in operation for 15 years since the water treatment works was built and were reaching the end of their lives. When the second failure occurred, at around 7.00pm, Marek Cegielski, DCWW’s mechanical, electrical
wwtonline.co.uk
and instrumentation supervisor for the region, was faced with a major problem. With no pumping capacity, by 7.00am the next day the area would run out of water as stored capacity would be exhausted and water would have to be brought in by tanker.
Cegielski said, “Initially, I called our incumbent drives supplier, but they told me they could only get a drive to me following a four-week lead time. I called our capital investment team who recommended calling APDS, as they had done previous installations for us and we were already considering ABB as a drives supplier under a new framework contract.”
APDS, based in Bristol, is an ABB Authorized Value Provider. On receiving the call from Welsh Water at 8.00pm, sales and marketing manager
Alan Jones responded by getting the drives to the site as soon as possible.
“I loaded two ABB ACS800 75 kW drives and reached the site at around midnight,” says Jones. “By 5.00am, we had the drives up and running and pumping water, before the first tanker was due to arrive.”
Cegielski takes up the story, “Alan pulled out all the stops to get us back in action. At first I did not have much hope that we could be back on- line by the morning, but Alan and APDS sorted it all out in the middle of the night and we have had no problems with the ABB drives since they were installed.
“We have since used ABB drives on several other installations and the company is now a preferred supplier for variable-speed drives.”
August 2013 Water & Wastewater Treatment 21
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