Given the global rise in energy costs, there has never been a better time to review and evaluate the performance of your pumping systems – regardless of their size, complexity or scope.
In this article, Gary Wilde, Technical Services Officer at the British Pump Manufacturers Association (BPMA), offers essential information and guidance on purchasing, maintaining and designing pumping systems for optimum energy efficiency, CO₂ reduction and payback time for capital expenditure .
Pumped systems are responsible for 20% of global electricity demand and between 25% – 50% of electricity consumption in certain applications. Pumps are the largest consumer of electricity in industry across the European Union, consuming over 300 TWhpa of electricity, which in turn accounts for over 65 Mton of CO₂ emissions.
It is also well documented that rotodynamic pumps, which make up 80% of the installed base, are between 20-30% larger. Therefore, there is great potential for energy savings if rotodynamic pumps are properly sized and operated.
Where to start – Assess the savings potential
Understand your pump system:
To determine if the pumping system is correctly sized, perform the following checks;
• Are you losing fluid flow?
• Are you creating additional pressure?
• What is the monitoring and control philosophy?
• Are oversized pumps installed for your required duty?
• Are there used old pumps in the system?
• Is there excessive noise in the system?
• Are there throttling valves installed in the system?
• Is the correct size piping installed?
• Inadequate maintenance reduces the efficiency of the pumping system, so what maintenance procedures are in place?
• Do you adopt a proactive equipment replacement program in accordance with current EU legislation
Available technology – Choosing the right equipment
Understanding Drive Technology:
Use the latest EU regulations to achieve the best possible drive efficiency;
• Variable speed drive (vsd)
• Integrated control and monitoring
• Permanent magnet technology
Choose your provider – Make the right choice
This article does not recommend or advertise any vendor or technology. However, he recommends choosing a supplier who is a member of the BPMA, and as such offers the assurance that they are working within the organisation’s agreed standards and Code of Practice.
The majority of existing pumping systems in operation today were not originally designed with energy conservation as a primary consideration. If pumping systems are initially designed on an energy efficient basis and the pumps are correctly applied and sized, energy savings will often be over 50%.
In order to design an energy-efficient pumping system, all of the following criteria must be considered:
• Basic plant layout
• Pipe size, configuration and limitations for limited pipe operation losses
• Information about the liquid (viscosity, density, aggressiveness, temperature)
• System characteristics and pump selection
• Pump/system management
• Avoid large pump unit sizes
• Selection of the most energy efficient pumps at the most efficient point
• Mounting of VSD to suit the design and demand of the system
Reduced energy costs are a direct result of choosing the right pump and matching it to the system.
When choosing a pump, it is important to determine the required flow rate and pressure generated by the pump. The flow rate can be determined by a process requirement, by the heating or cooling required in the system, or by the peak utility water demand. The required pressure may be to lift the fluid in the system or to overcome pressure losses in the system created as the fluid passes through it.
It is important to know as much as possible about the pumping system and create a pressure/flow profile for the system. The energy required to drive the pump is directly related to the required flow and pressure. Generating high pressures usually results in designs that may be inefficient, so it is important that neither the flow rate nor the pressure is above set.
Variable speed drives can save energy
It is estimated that significant energy savings have already been made by using variable speed drive and high efficiency motors. Typically, variable speed drives are used to continuously adjust the pump speed as needed.
Savings can be determined by the laws of affinity:
Q = flow, H = head, P = power and n = rotational speed
When building a new pumping system, most pumps are selected with a “safety factor” to allow for potential future increases or to allow for pump wear or system fouling. There are often many different parties involved in specifying and building a system, and the safety factor can grow exponentially. This results in the pump delivering much higher flow rates than required. There may also be a need to change the flow due to process conditions or different heating and cooling needs in buildings.
Traditionally, throttling is used to regulate flow in a pumping system. While throttling reduces the flow, the motor is still running at full speed and working even harder because it has to work against a restriction. By reducing the speed of the motor, the variable speed drive ensures that no more energy is used than necessary to achieve the required flow. A centrifugal pump operating at half speed consumes only one eighth of the energy compared to a pump operating at full speed. Using a variable speed electric drive is the simplest and most economical way to control the pump and coordinate it with the pumping system.
Here are some key considerations when looking to optimize energy use in pumping systems:
Has an alternative configuration been considered?
In some cases, switching from an existing pump arrangement to an alternative one can offer energy saving opportunities.
Is the pump performance monitored?
By looking for early signs of pump wear, which may include increased noise, vibration or power consumption, major energy and maintenance savings can be achieved.
Is ease of maintenance enabled?
Ease of future maintenance requirements should be considered when designing or replacing pumps.
Variable speed drive considerations
When fitting a VSD to a pumping system, consideration must be given to outlet and inlet filters, along with isolated motor bearings.
Support
When maintaining pumping systems, it is recommended to use original manufacturers’ recommendations and parts.
Reliability / Security
Efficient, well-maintained pumps are more likely to be reliable and less likely to fail prematurely, causing loss of production or services.
Valves
Valves are considered to lose energy in the pumping system, but if installed, they should be checked for proper operation.
The pumps are not used
Standby pump sets or non-demand pumps should be switched off to save energy.
Is the pump operating near its best efficiency point most of the time?
Rotodynamic pumps operating far from BEP not only waste energy, but also reduce pump life expectancy.
System changes
When upgrading, changing or expanding a pumping system, demand may have changed and existing pumps may not be the most efficient solution.
Buying the right pump kit
When buying a pump kit, price should not be the deciding factor. If the pump is sized correctly, the return on investment is shorter, likewise if the pump is oversized and wastes energy going forward, you will have these additional costs for the expected life of the pump set.
Has an energy audit been performed on existing systems?
Under the UK’s ESOS regulation, all non-SME organizations are mandated to carry out energy audits, and pumped systems can offer significant energy savings.
When choosing a new pump, ask for a high-efficiency motor to be installed. If you are replacing or rebuilding a motor, then consider the cost of fitting a high efficiency motor, remembering to factor in the savings in labor that will pay for any increase in cost. Invest in an energy audit. Review your utility bills and understand the energy you use. Audit if:
• Your energy bills are high
• You have continuously running pumps
• You have many pumps in the system
• You have processes with different flows
• You have throttled pumps
• You have pumps that are on bypass
• You have noisy valves or pipes
• You have critical systems that have been subject to failures
The purpose of the energy audit is to reduce operating costs by reducing energy use, and the government has estimated that most companies can reduce energy use by 10% to 20%. Energy audits conducted by BPMA members have shown that savings of 30% to 50% are not unusual. When deciding whether or not to carry out an energy audit, a good starting point is to assume that you will save at least 10% of your current energy consumption. By reviewing your utility bills, you can get an indication of the savings you need to make and the investment you should be willing to make in the audit process.
In most industrial sites, about two-thirds of the total energy consumption is used to power electric motors. Furthermore, the total costs associated with operating these major pieces of equipment over their lifetime can be broken down as follows; 5% is the initial purchase/installation cost, 10% for ongoing maintenance and a whopping 85% for the energy used to run them. It is clear that any reduction in the energy consumed by electric motors is important, and with modern designs this reduction can reach up to 30%. It is also evident that many pumps and motors are constantly running at full power regardless of process needs, and so across the installed base there is potential for significant energy savings; savings that in turn can trickle down to the bottom line and increase the profitability of any business.
BPMA participation
Given the amount of energy consumed by pumps in their normal operation and the potential to increase energy efficiency within pumping systems, the BPMA is working to develop a Certified Pumping System Auditor (CPSA) Scheme.
Through CPSA, pumping engineers are trained to properly evaluate the efficiency of pumping systems and provide appropriate recommendations to improve the efficiency of those systems. CPSA accreditation is achieved by successfully completing a four-day placement course followed by satisfactory completion of a pumping system audit. Only then can the status of “Certified Pump System Auditor” be achieved.
Within the full ESOS guidance document, the ISO/14414 Pumping System Energy Assessment standard is listed as an audit methodology that can be adopted by ‘lead assessors’ approved by the Environment Agency. Accordingly, we hope that CPSA accredited individuals (who are trained to IS0 14414) will be recommended by lead assessors to undertake the pumping system elements of company-wide energy audits.
The next CPSA training course is scheduled for the 7thth-10th November, with the next session already scheduled for 9th-12th May 2023. For more detailed information, please visit http://www.bpma-cpsa.co.uk.
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