Working Towards a Net Zero Future with Pumps
The UK has released a target of Net Zero Emissions by 2050, meaning any emissions generated must be balanced by schemes offsetting an equivalent amount of gas emitted. While this could be performed through carbon offsetting programs, companies are ideally looking to reduce, reuse or recycle more to meet these objectives before carbon pricing comes into force.
The timer has started. How can companies work towards achieving Net Zero with pumps?
By Simon Hooton, Technical Product Manager, North Ridge Pumps Ltd.
One method to reduce pump related carbon emissions, and improve efficiency, is to reduce the amount of power consumed, decrease the amount of wastage and lubricants spent, and spare the parts consumed by the unit during operation.
In order to do this, more efficient practices need to be looked at. Finding an alternate practice is fairly easy if looking at a single pump or application. It quickly becomes more complicated however, if working with a variety of applications that have varying liquids according to process demands.
High Efficiency Pump Design
In a high efficiency pump design, the pump imparts a maximum amount of energy onto the fluid which exits the pump. The pump's head internal tolerances are also very close, to ensure that energy is not lost through recirculation within the pump head. The types of pumps that typically have these designs include: end suction centrifugal pumps, multistage pumps, and piston/plunger pumps. As tolerances for these pump types are fine, viscous or solid laden fluids cannot be accommodated. This is turn means that the pump's efficiency is limited to low viscosity clean fluids.
Efficient designs incorporate variable speed drives, which enables the models to produce a wide range of flow and pressures, to accommodate varying demand in process. This technology is prevalent in applications where pumps are running continuously. For example, in cooling, when circulating water continuously, or when pressure boosting, this technology can save up to 50% of the energy required to transfer fluids. Eco versions of pumps have pump head design optimized for efficiency, and casing wear rings to improve efficiency.
With viscous or dry fluids, lowering spare part consumption enables equipment to operate more efficiently and at a lower cost. Peristaltic or progressing cavity designs, which rotate slowly, especially with abrasive media, ensure that a pump part’s lifespan is drastically increased.
Hose pumps can operate as slowly as 1rpm, which drastically reduces wear when media such as grout, dehydrated sludge, or digestate are transferred. As the only wearing part is a hose, spares holding is significantly reduced, maintenance times improved, and the main hose can be recycled reducing impact on the environment. Peristaltic pumps are seal-less, which can wear, degrade, or cause clogging.
Other designs, such as air operated diaphragm pumps, have been refined through R&D to contain fewer internal parts. Having fewer parts ultimately reduces the time needed for maintenance and allows the unit to work more efficiently, as there are fewer parts to maintain.
Another method of increasing efficiency is by using self-priming pumps as opposed to submersible pumps. As the pumps are not immersed within a fluid, the amount of equipment, personnel, and frequency of inspection is reduced.
To become more efficient with certain process fluids, such as chemicals, there is another aspect of the process that needs to be looked at; reducing wastage.
Reducing the amount of wastage can be achieved by ensuring that the bulk containers, in which most blends of liquids are delivered, are completely emptied. A 99.98% Barrel Emptying Kit ensures almost all of a containers’ liquids are emptied. Normal designs typically only empties 95% of a containers’ contents. Where fluids are expensive, units can pay for themselves within only a few months of use.
Image 1: ECO Design of Pump.
Efficient Component Selection
An expeller seal design is when a rotary disc shaped device, similar to an impeller, rotates as the pump shaft rotates. With this type of design the pump does not require a seal flush to maintain sealing. The expeller creates an area of low pressure around the shaft, effectively creating a dynamic seal. The benefits of such a design is that a continuous fresh water supply is not required. This is important in applications such as mining, as mines are typically located in remote areas, where water is scarce. An expeller seal design therefore reduces water use, as well as operational costs.
To maximize optimum operation of a pump and system the following should be checked:
Pipework Routing & Size
The number of bends, material, diameter, and length of pipework directly effects the pressure losses within the system and the amount of energy required to overcome such pressure losses. A common mistake is to size pipework according to the pump inlet diameter, or according to existing equipment. Pipework should be sized according to the required flow, ensuring that the pressure loss does not create a velocity in the fluid above 2m/s in the suction pipe, or 3m/s in the discharge pipework. Ideally head loss should be no more than 6%. Incorrect pipework size selection can create water hammering and damage the pipework.
Filtration & Strainer Clogging
Filters and strainers can become clogged during operation and go unnoticed for periods of time leading to higher power consumption in pumps, and in a worst case scenario, cavitation. The use of self-cleaning strainers ensures filter mesh is always kept free from debris and produces very little pressure loss. Pressure differential switches provide a visual and audible indication of the strainers becoming clogged, therefore ensuring any issues are addressed before escalation.
Pumps in Parallel
To ensure maximum efficiency of pumps operating in parallel, within a closed loop circulation system, pumps of the same type, model, and with the same speed ratio should be operated with controls in place to make certain that the minimum number of pumps are operated.1
Reuse: Recycled or Dry Fluids
Another way to reduce the carbon footprint of companies undertaking processes such as: jet washing, hydro demolition, paint projects, plastic or rubber removal from metal components for recycling, is to evaluate whether fluid recycling or reuse can be implemented.
Pump designs are available that utilize recycled water. Historically high-pressure jets of water are used to remove layers of a media or material by the pumping of fresh clean water, with water which has been spent, drained away or disposed of. The use of recycled water allows jetting fluids to be recycled and recirculated within the pump head, vastly reducing water use.
A device such as the North Ridge Hull Cleaner, which can be adapted for similar processes, does not utilize grit or other media to remove coatings. Using hydro-blasting as an alternative eliminates the costly use of sand or grit, the worlds’ second most consumed natural resource, is quieter, and ensures rebar is not damaged.
Hydro-blasting is also far more efficient. It can cover up to 30-40sqm an hour, as opposed to sand blasting which can only cover up to 10sqm an hour.
Recycle: Energy Recovery
High pressures can often harm equipment and can sometimes lead to pipeline failure and fluid escape. As a result, excess pressure in a pipeline is often wasted. Excess pressure in a process is often reduced by using pressure reducing valves. These types of valves reduce pressure and leave the excess energy unused.
Using a pump as turbine enables this otherwise wasted excess energy to be converted into energy. The unit runs in reverse by rotating a generator as the impeller rotates from excess flow and pressure. Unlike turbines, the payback can be as little as 2-5 years, and their uncomplicated design enables maintenance to be performed without special tools, knowledge or expertise. The unit can also function as a pump if required.
Image 3: Multi stage Pump.
13 Checks to Make Within Your Plant Today
1. Excessive throttling of pumps by valves.
2. Continuous use of bypass lines leading to excessive amounts of fluid recirculation.
3. Frequent spare part replacement of bearings, mechanical seals, and gaskets.
4. Cavitation with pumps operating noisily and consuming higher power than required.
5. Wear ring clearances. A 50% decrease in wear ring clearance can increase efficiency between 2-4% and reduce the risk of cavitation.
6. Oversized pumps with units being frequently operated away from duty point.
7. Pumps with IE1 / IE2 motors running continuously. Utilizing a pump with a VFD can reduce energy consumption by up to 50%.
8. Air Leaks which can lead to savings of between 20-50%.
9. Check whether heating of fluids will enable easier and lower energy methods of transfer, reduce pump wear and increase recovery rates from containers.
10. Check whether containers are being returned to suppliers which are still partially filled.
11. Check whether pumps operating in parallel are utilizing inverters and appropriate technology to meet the required duty points against the system curve. Alternatively, if one pump is in operation, check whether a second in parallel will improve pumping efficiency reducing overall power consumption.
12. Check pipework is sized correctly and renewed periodically to keep friction losses at a minimum.
13. If pump maintenance is reactive rather than proactive leading to downtime, and product wastage. Check whether the 6 to 1 rule is being followed.
Image 4: Progressing Cavity Pump for Sludge.
Although the UK Net Zero target is not due to be implemented until 2050, the goal for many is to achieve this goal as soon as 2030.2 It is likely that increasing pressure will be placed on manufacturers and plant operators to work towards decarbonization sooner. With restrictions of oil and gas funding by major financial institutions,3 we could see a similar situation for financial investments in firms not working towards Net Zero.
With consumers increasingly believing that the private sector must make substantial improvements in corporate social responsibility,4 although the target may appear to be a mere speck on the horizon, the journey towards Net Zero begins today.
1. efficient_driving_at_variable_speeds_world_pumps_vol_2013_issue_4.pdf World Pumps April 2013.
3. Restriction of oil and gas funding https://cleantechnica.com/2020/10/28/global-financial-institutions-plan-for-major-oil-gas-lending-exits/.
About the Author
Simon Hooton is a Technical Product Manager at North Ridge Pumps Ltd. He has operated in the pump industry for over 10 years. Simon is a specialist in a wide range of process applications from simple transfer or circulation applications to dewatering, chemical injection and energy recovery. He is frequently involved in projects across the industrial and marine industries worldwide. For more information, visit www.northridgepumps.com.