Q: Could you briefly explain your role, involvement and experience with regards to pumping systems?
Peter Carless, Yorkshire Water (PC): As the Engineering Manager for Asset Integrity within Yorkshire Water, the department covers aspects of design, installation, operation and maintenance through to optimisation of pumping systems for clean and wastewater systems. This range of activities enables a holistic understanding of how different systems are required to operate in order to meet their intended design and operational purpose. Yorkshire Water operates a grid-pumping system for balanced distribution of raw water across the Yorkshire region. This network requires constant system optimisation whilst meeting increasingly variable supply and demand peaks due to seasonal and climatic conditions.
Ron Palgrave, Sulzer Pumps UK (RP): I have more than 55 years’ experience in the hydraulic design of centrifugal pumps in roles from Development Engineer to Director of Engineering. My experience spans 7 major pump manufacturers, including their subsidiary companies. I am currently semi-retired. Three pump-related patents have been granted in my name. I am the author of the textbook “Troubleshooting Centrifugal Pumps and their systems”. I have delivered a number of papers and magazine articles dealing with the art of pump hydraulic design.
Paul West, Torishima Europe Ltd (PW): I have worked for large pump manufacturing companies since graduating from the University of Aberdeen in 1985. In the intervening, almost, 35 years, I have worked in many facets of the business, including in M&E Project Sales. This was the ideal learning environment in terms of complex Water Systems, covering head calculation, multi-pump operation / changeover points and the potential benefits of variable speed operation. I say potential because this was in the early 1990’s and harmonics from VFDs were still an issue and the powers available much lower!
Martin Richardson, ABB (MR): I’m a Water Framework Manager for ABB, in the variable speed drives part of the business and been involved in pumping systems for 14 years. My day to day activities include helping customers to use variable speed drives to optimise pumping systems and promote the advantages that VSD’s can bring. ABB play an active part with organisations such as the BPMA and The Pump Centre, both of which support pumping systems and the pumping industry.
Daniel Griffiths, WEG Motors (DG): I have been with WEG for 12 years and within the industry for over 20. Although my background is mainly electrical and motor control, I have worked on many projects for Pump OEMs and for the major Water Utilities. I am the current chair of the Variable Speed Drives working group within the trade association GAMBICA and have also attended the Pump Centre and BPMA Technical meetings for a number of years providing expert advice to those groups wherever possible.
Brian Conway, Pumps & Systems Ltd (BC): I have been involved in application of pumps and analysing pump systems for over 25 years, covering oil and gas, petrochemical, mineral processing, industrial and for the last 15 years, water and wastewater.
I have two main functions:
- An advisory capacity to water companies and other industries on methodology for assessing pump and system performance
- A lead engineer role to Tier 1 and Tier 2 contractors in design and build of pumping station optimisation upgrades
Q: What are the main challenges caused by pumping inefficiency?
PC: Pumping inefficiency can present itself in several forms such as mechanical, electrical, process (that is system) and in a less recognised but commercially important form, in way of whole life cost which is associated with the maintenance of the pumping assets. The main challenges of these various forms of inefficiency present common consequences which are; increased operational costs, reduction in process and asset performance and increased capital costs for asset replacement due to reduced asset life.
RP: 1) The laws of physics obliges centrifugal pumps of relatively low flow and relatively high head, when driven at normal speeds, to be inherently inefficient. Typically, in such pumps the impeller passage width at outlet might [say] 3 to 5 % of the impeller diameter. The inherent parasitic losses cannot be overcome without complexity. One challenge is to shatter the illusion that pumps of such geometry can EVER be much more efficient, though small gains are quite feasible.
2) Once the system has been decided in terms of static lift and friction losses, then the efficiency of the lowest cost and simplest configuration has implicitly been decided – within 3 or 4 percentage points. But making a binary selection from 2 pumps on the basis of efficiency alone might not assure the lowest total lifetime power use. One pump may have a “steeper” curve than the other and so be lower in efficiency - but under the same liquid conditions it will appear to wear out more slowly than the more efficient and usually slightly cheaper pump. The steeper curve pump will have lower power at runout which may lean towards smaller motors - perhaps even non-overloading power characteristics. So, developing a non-binary perspective would be useful.
PW: The most obvious is clearly the increase in power consumed by the pump and the associated increase in energy bills. The increased losses are going somewhere, usually internal recirculation, and that leads to increased noise and vibration, and subsequently reduced component life. It has a knock-on effect on other system components, particularly valves which may require to operate partially closed, permanently, and of course, on the process itself. If the process is not getting the fluid it requires, then the cost of production can go up and/or quality can go down. Desalination is an area where the challenge is clear. The contractors sign contracts on the basis of a rate per m3 of potable water. The electricity cost is a huge portion of the cost side and small changes affect their bottom line.
MR: Inefficiencies in pumping systems ultimately cost money. The obvious cost is energy, but the inefficient running of a pump or system also has an impact on asset life, maintenance intervals, reliability and risk of failure. Whilst costs are important for users and operators of pumps, the environmental impact of running inefficiently should not be ignored. On a global level, a huge proportion of the world’s electrical energy is consumed by pumps and they are the single biggest user of electricity in the EU, so the opportunity to make a difference in CO2 savings and energy reduction is massive.
DG: Poor selection, control and maintenance are key areas which present the most challenge to pump users, as the plant equipment can often be in remote or inaccessible locations or have such a wide and changing requirement that it can be difficult to keep a pump system running at its optimum. These factors often result in expensive, rushed repairs and an overreaction for highly sophisticated control and monitoring solutions.
BC: Modern pumps, and even pumps designed and installed more than 50 years ago are very efficient, and if they are selected correctly for the system, they will provide and maintain almost as-new efficiency and long-term reliability of wearing and non-wearing components (routine maintenance permitting!). When a pump is taken outside of its preferred operating zone, then you are inviting increased stress, vibration, wear, recirculation, etc. as compound interactive issues, which will increase maintenance costs and reduce reliability. If we look outside of the effect on the pump, the annual energy cost over the life of the pump is a hidden cost, often not seen within the budgets of those that can affect it.
Q: Where do you think the solution to pumping efficiency lies?
PC: In my opinion the most important starting point is to establish the design or intended purpose of the pump and the system in which it has been installed. For example, the pumped media and diurnal flows associated with wastewater systems are fundamentally different from optimised grid flows for raw or clean water pumping systems. The next step is to define the relevant categorisation of efficiency for the pump and system, that is; electrical energy consumption or mechanical process efficiency or whole life cost efficiency etc. Once these parameters are established, a relevant whole life cost efficiency can be assessed.
RP: 1) The hypnosis with efficiency and inefficiency masks the real practical issue which is power consumption. There is little point in selecting [say] a pair of high efficiency pumps to [say] run in parallel if, when system demands reduce, both pumps are just throttled back, when instead the installation would consume less power if one pump were just switched off. Plant designers presume the latter will happen whereas site operators usually override this and follow the first route, because it is more convenient.
2) In perhaps two out of three cases, an even more efficient selection solution is yielded by a two stage or even multistage pump. If lifetime power consumption costs were the criterion rather than efficiency - then often a different pump selection would result.
PW: I think the solution lies in monitoring and feedback from processes to adjust pump operation. This is much easier said than done as it requires investment either up front or as a retrofit. When we see power plants where 2.5MW boiler feed pumps don’t have flow meters installed, the hurdles of installing them for 200kW water pumps become a little clearer. Developments in instrumentation, data gathering, and analytics will smooth the path. Processing of ‘Big Data’ will negate some of the shortcomings in the information that is available. In addition to improving efficiency by optimising the operating range, data analysis can improve efficiency by minimising the non-operating time by optimising maintenance activities.
MR: Society generally sees technology as the solution and there is no doubt that technology is advancing. It is allowing us to increase efficiency at a component level, but we sometimes are obsessed with ‘new stuff’ and tend to focus on that rather than utilising the tools that we already have. I think the biggest gains in terms of gaining efficiency from pumping systems actually come down to how these systems are really operated and used. The interaction of components and how individual items can be combined to increase efficiencies is important, but designers often have limited control over how the system actually operates after it is commissioned.
DG: A simplistic and practical approach to any pump solution is often the most effective at maintaining an efficient system, asking good questions about the requirements of the pump system, planning for expansion, redundancy and duty control and understanding the demand profile are vital to creating an efficient control system which matches the requirements of the system.
BC: Being able to understand the interaction of pump characteristics with system characteristics to enable intelligent design and intelligent control and operation. Pumps are almost at their peak in terms of efficient design, but there is a long way to go in terms of a sustainable optimised and reliable system. Match the pump to the system, either through confident engineering methodology, or practical system testing and analysis, and intelligent operation. Many in industry that operate pumps do not understand what they are operating because they haven’t been given the training. Investment in training will provide enormous benefits to intelligent, operational pump efficiency.
Q: What are the developments in technology to watch for when it comes to improving pump efficiency?
PC: With the advent of Industry 4.0 based technology and the use of connected data systems, there is an increasing opportunity to understand the performance of a pump and pumping system in a way that would have been previously not possible. This means that the interaction of pumps on a network when overlaid with event driven information such as weather, seasonal or city-based activity variations will enable designers to size pumps and electrical drive units for maximum optimal efficiency. The wastewater world will continue to present optimal challenges due to the nature of the pumped media which, for the foreseeable future may continue to focus on mechanical and process efficiency to maintain its intended function.
RP: The laws of physics dictate that the machine with highest efficiency will have an impeller passage width between 20 and 25% of its diameter. Often this impeller diameter is insufficient – even at two pole speed - to generate the necessary head. Multistaging becomes necessary. Compact high-speed motors would reduce the need for multistaging. An infinitely variable speed capacity might eliminate the need for control valves and allow better matching of pump to system.
PW: There are limits (Steppanoff!) to what can be done with pump design. If I consider the equipment that I saw on my first day in Weir Pumps and that I see now in Torishima’s main factory, whilst there are differences, they are not that marked. Improvements in design (CFD) and manufacture (tolerances/surface finishes) and materials (corrosion/erosion resistance) and non-metallic components (composite wear rings for reduced leakage losses) have optimised pump efficiency.
For big wins nowadays, the scrutiny has to be on the system, matching the pumps to the system and then monitoring them. For the last of these, this comes down to data collection and analysis. So, the developments to watch for are those that make this faster, more efficient and, probably most importantly, more cost-effective. For matching the pumps to the system, reduction in costs for MV VFDs will see them applied more and more, with significant benefits.
MR: From an electric motor perspective, motor technology is changing a little bit. The induction motor has almost hit its design limit in terms of efficiency. Therefore, other motor types such as Permanent Magnet and Synchronous Reluctance motors are being used to help increase motor efficiencies. These are different technologies, so they have different challenges, but certainly can help increase the efficiency from the electro-mechanical perspective.
DG: Improvements in motor efficiencies, control and process analysis and the inclusion of IOT/Industry 4.0 will all assist the system designers in creating adaptive and efficient pump systems.
BC: The efficiency gains now being made can only be marginal as hydraulic design is well engineered from old school engineers and well developed in terms of software. The solution is to run a pump or multiple pumps at best efficiency point (BEP), or very close to it. It requires a good understanding of system demand variation, if any, and a detailed process description, followed by intelligent selection of a pump, or multiple pumps to operate at BEP. There is now a great opportunity for data gathering, and the facilities for AI cloud-based systems, but there are very few providing real-time intelligent control to maintain assets at their optimum.
Q: Why do you think it is important for engineers to join in the discussion around pumping systems?
PC: Engineering is a broad church and often pumps and pumping systems refer only to the electro-mechanical aspects and even then, not always in a complementary fashion. For example, it is not uncommon for variable speed drives to be fitted to pumps for flow control without mechanical consideration of the impeller design for the best efficiency point which has a consequential impact on component service life and performance. The decision-making process for both designing and operating pumping systems requires an increased multi-disciplined engineering collaborative approach in order to achieve optimal efficiency. This would deliver a true whole life costed efficiency and optimised carbon footprint (built and emissions).
RP: Under current practice the communication flow seems largely one way. Pump conditions of service seem “slid under the door” of the manufacturer, and a response awaited. A much better understanding of the interdependence of pump and system flow characteristics under both normal and abnormal operation would produce more robust solutions. For example; most if not all, pump data sheets only ever give the manufacturer the pump head at duty flow. They do not give head at say zero flow. So, the manufacturer has no sense of whether it is a largely static head system or a largely frictional. Knowing this would help the manufacturer select curve shapes that are less vulnerable to wear. And it might steer the system designer in the same direction too!
PW: Because pump people know pumps but don’t know (all the) processes and vice-versa. I had worked as a Senior Noise and Vibration Engineer in a pump company for more than 5 years before I learnt what made a pump operate where it operates – clearly a switch in role was involved!
Torishima sees requests for pumps to operate at 10% of BEQ, because that is where the process requires it on certain occasions. We see CEPs running at around 60% BEQ as a design point, because there is an emergency condition that requires them to produce almost double the flow. The pump manufacturer sees the solution as an additional pump, the EPC contractor sees that as an additional cost. The end user pays the increased power and maintenance bill. All involved parties have a stake in the discussions.
Developments with IoT mean that analytics will have a huge role to play going forward and engineers working on data collection and processing must be also involved in determining the future.
MR: It’s important that we all contribute and collaborate to share best practice in pumping systems. It helps save businesses money, but it also ensures we are making a positive difference to the environment. Engineers hold the key to using, designing and creating products that will work more efficiency and sustainably.
DG: Pumping systems are a vital part of our modern society, from drinking water and sanitation to their use in many modern industrial processes. We must address the pressures of an expanding global industrialisation on our natural resources and deliver effective and efficient solutions for the future.
BC: It is a very interesting, but very small part of engineering that you can spend a lifetime learning. Mechanical engineers need a far greater understanding of instrumentation and software, and likewise, as I have found, training software engineers in the mathematics of pump and system hydraulics will provide them with an entire lifetime of interesting engineering.
Pumping Systems 2019 conference will take place on 11-12 December 2019 at the Manchester Conference Centre.
Join this event to:
- Gain insight into the growth of the use of condition monitoring technologies and how to use them to make efficiency savings at your organisation
- Hear about cutting-edge pump designs to improve the performance of your pump
- Learn about the latest vibration monitoring techniques to ensure your rotating equipment is operating optimally
- Network with pump design, operations, performance and maintenance engineers as well as wider systems and plant managers, and monitoring and modelling experts
To book your place, please visit www.imeche.org/pumpingsystems.