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Case study: Pump efficiency takes flight at Heathrow

With more than 100 wastewater pumping stations, Heathrow Airport was able to make significant energy and cost savings by putting the focus on efficiency

Three years ago the Civil Aviation Authority (CAA) advised Heathrow Airport that it needed to reduce the passenger levy. The Water Services Division looked at how they could incorporate more energy efficient measures into the airport’s pumping system to reduce costs, and three years later reflects on the results.

“At Heathrow Airport, we are committed to effectively and carefully managing the disposal of water to reduce the risk of environmental impact” says Ian Jolly, System Specialist within the Water Services Section at Heathrow Airport. “With a workforce of over 76,000 and around 200,000 passengers passing through our terminals every day, it’s fair to say that waste management is a considered a vital issue.”

“The main problem we face is the energy required to pump wastewater from the airport, which is naturally built on extremely flat land. Added to this is the fact that we receive no flushing water from rain, so the airport exterior alone requires over 100 wastewater pumping stations, discharging 80 litres of water to the sewage treatment works every second, to combat this.”

These range from small packaged pumping stations to large multi-pump installations with a combined holding capacity of 2,500m3.

“In 2013 the Civil Aviation Authority advised that we would need to reduce our passenger levy from £22 to £19, meaning Heathrow Airport needed to cut costs by more than £600M over a five-year period. As a result, cost reduction was reviewed by all departments and for the Water Services Section, our main aim was to reduce energy consumption through energy efficiency and better procurement of pumping equipment.”

The Water Services Section commissioned Xylem Water Solutions UK after investigating the terminal’s operational requirements and the most effective means of achieving this. Xylem undertook a trial on the cargo area near terminal four, which itself has ten wastewater pumping stations and a further four storm water stations.

“After reviewing Ian’s requirements for the cargo area, we recommended the use of our Flygt Experior range,” said Guy Fitzpatrick, Strategic Relationship General Manager at Xylem Water Solutions UK.

“The Flygt Experior range consists of an intelligent pump controller, high efficiency motor and adaptive ‘N’ impeller hydraulics. All these factors work interactively with each other to deliver the lowest cost of ownership for waste water pumping stations, making the range the ideal solution for Heathrow.”

Guy and his engineering colleagues from Xylem installed two of its Flygt Experior Adaptive ‘N’ submersible sewage pumps and two SmartRun Intelligent Pump Controllers in the cargo area’s sewage wet well in less than six hours.

Guy continues: “The use of adaptive N hydraulics in the Flygt range makes it especially suited to Heathrow’s needs. The airport is dealing with vast amounts of water and so smaller applications can lack sufficient torque in the motors, for the impeller to turn and pull the solids through. The hydraulic technology in the Flygt range removes the necessity of a larger, and by default higher energy-consuming motor. The Adaptive N-impeller is designed to move axially upwards when needed, allowing the most bulky of rags and toughest of debris to pass through smoothly. After the debris has been passed, the hydraulic pressure returns the impeller down to its original position. The axial movement of this hydraulic reduces stress on the shaft, seals and bearings. It also utilises a unique N designed impeller, all of which results in sustained improved efficiency over the pump’s lifespan. 

“Should a solid object get caught on the leading edge of one of the vanes, it will simply slide along the N designed impeller towards the perimeter of the inlet, if a bulky rag appears it will simply lift and allow it to pass through – ultimately resulting in fewer blockages, more consistent performance, and fewer maintenance call outs.”

The two SmartRun Intelligent Pump Controllers that accompanied the Flygt adaptive ‘N’ pumps are pre-programmed to provide sump and pipe cleaning functions which are automatically triggered. The SmartRuns have also enabled Heathrow’s Water Services Section to monitor the specific energy use of the pumps during their normal pumping cycle. The controllers reduce a pump’s speed on every pump cycle until the minimum specific energy is found, a continuous cycle which effectively adjusts the pump speed to ensure only the minimum specific energy available for that site is being used throughout the year. 

Three years on from the installation, Heathrow has witnessed some impressive results. “The pumps have performed around 8,000 hours to date, and are still running at their optimum efficiency of 30 - 33Hz,” says Jolly. “This frequency equates to the energy consumption being cut by around 50 per cent over a five-year period at just one pumping station.”

“Additionally, the SmartRun Intelligent Pump Controllers have reduced maintenance call out incidents and virtually eliminated pump blockages. This is where the real value of the system comes into play: technician time is freed up for other tasks, as maintenance time is reduced to an annual four hours, as opposed to the previous 21 hours. In fact, the previous regime cost around £2,300 per annum, whereas the revised schedule is under £300, a saving of over £2,000. Previously, in the same twenty-month time frame, the wet well would have been fully cleaned three times due to ragging, fat and debris build up.”

“These are fantastic results and the system is still performing as effectively now as it did in the first few months of installation.”

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