Goodbye to cheap options
1 Aug 2008
Dave Sheppard has worked in the water industry for around 20 years, starting as a sandwich student with North West Water, now United Utilities, and since then for clients, consultants and contractors and now working for environmental and water consultant MWH. For the last 15 years he has specialised in the field of pumping station and system design:
Like many of my colleagues, I have been frustrated by the constant drive to provide plant of the lowest capital cost, usually with little more than lip service paid to considerations of whole life costs, plant efficiency and likely operability and reliability.
Because of environmental concerns the UK government is committed to a 20% reduction in carbon emissions by 2020. This issue is being increasingly focused upon by the world’s legislators - with tough emission targets meaning carbon output must decrease, despite increases in global energy consumption
Whatever your views on climate change, the only fact that matters from a pumping station designer’s perspective is that there is a perceived carbon crisis and that we urgently need to address our power usage to reduce emissions.
The current focus on these issues means that there is an increasing awareness of environmental concerns, and geopolitical drivers are increasingly influencing engineers, particularly those involved with power-intensive plant.
The climate change debate offers engineers a tremendous opportunity to bring to fruition the kind of efficient pumping systems that they have been advocating for years.
Around 80% of electrical power used by the UK water industry is used in pumping, so we who design, operate and maintain pumping stations are clearly at the leading edge of alleviating the problem.
Whilst this may seem a daunting proposition, I believe that carbon footprint concerns open the door for engineers seeking to design and install the most effective pumping plant based on the ‘whole life cost’ approach.
Various methods exist to measure life-cycle cost and these are currently being incorporated into the carbon footprinting models being developed. However, there are two fundamental problems with this approach in practice:
1) Investors in companies are looking for short term gain that drives a low capital-cost approach;
2) Pumps are actually bought by contractors, not the end-users - and, again, capital cost becomes the most significant issue in any competitive tendering situation.
From a designer’s perspective, we need to ensure that the significance of pumping design is recognised by both project managers and civil designers.
Pumping stations are often designed as if they are a relatively insignificant part of a larger project. The fact that this can result in a disproportionally high influence on whole life costs, emissions and the rest is sometimes lost. The design of a pumping station should be driven by the pump’s requirements - not vice versa.
When a major UK water company undertook a performance review, it discovered that around one in five new pumping stations did not perform efficiently. This represents a significantly high amount of power being wasted over their 20-year lifespan.
Many UK water and sewage pumping stations are run at lower than optimum efficiency because of the monitoring and maintenance regimes in place. A regular monitoring regime should be installed for all major stations, with the thermodynamic method proving an excellent way to trend pump performance.
A simple example of the need for better maintenance would be the utilisation of pump wear rings. In the water industry they are generally specified for machines of a reasonable size, but many have not been adjusted since the pumps were commissioned.
For high load pumps, a spare impeller, or full rotating element, stored on site and fitted at shortened intervals could be considered. It is not too difficult to calculate pay-back time. For example, one water company’s practice is to replace impellers on their main feed pumps every 18 months. This is good practice in this particular case, where virtually all of the company’s OPEX is power.
Unless mechanisms are produced which ensure that the lowest life-cycle cost designs and machines are selected, then the required improvements in energy consumption will prove highly elusive.
With regard to the interaction between clients and contractors, partnership is becoming more common. However, these relationships need to be fully established before the mutual trust required to realise the potential benefits materialise. Use of the New Engineering Contract could help here.
Another option would be for the client to ‘free issue’ the most appropriate pumps to the contractor to install. Here the problem is one of risk — or more accurately, the perception of risk. If the contractor is to take the risk, then he is entitled to the rewards — particularly when he embraces the best engineered solutions rather than just the cheapest.
