REFRIGERANTS
Predictive maintenance is the future
Klas Berglöf, chief executive of ClimaCheck Sweden explains how predictive maintenance is becoming increasingly essential.
T
here is an increasing pressure on property owners to reduce energy consumption. ‘Green Recovery’ has become a mantra and the
Kigali Cooling Efficiency Program (K-CEP) recently stated “Effective optimization, monitoring, and maintenance of cooling equipment could deliver substantial electricity savings of up to 20% (700 TWh)”.
Property owners are enrolling energy managers/ controllers to benchmark the use of energy to reduce cost as well as carbon footprint. and global investors are changing focus to sustainable investments. It is not just ‘green wash’ anymore, it is about profitability and development as well as the possibilities opening up with IoT, Industry 4.0 and artificial intelligence (AI) evolving business and moving the focus towards ‘predictive maintenance’. I have heard property owners state satisfaction as “their maintenance contractor comes quickly when there is a problem”. Today this is not a quality mark – quality is when issues and deviations are detected and the equipment owner is contacted before they are aware of the problem. Most issues can be pin-pointed long before they cause breakdowns/ performance drift and impact temperatures in building/goods or increase the energy bill. The saving potential is huge in reduced failures and downtime, but it is claimed that the owners only focus on lowest initial cost and are not prepared to invest to save in the future. This results in a vicious circle – if owners do not focus on efficient operation there is no incentive for commissioning engineers and maintenance contractors to build analysing competence. The industry has a responsibility to inform the equipment owner of the saving potential documented by K-CEP and many others and how measuring performance will help find saving opportunities in every plant When a failure has occurred, it is often challenging
to pinpoint the root cause and many plants have repeated issues as only the symptom is dealt with it. Failures and trouble-shooting are important business for the service sector. However, predictive maintenance will be where the future growth is, as it lowers operational cost for equipment owners. In due course, the focus will shift to actual performance
20 December 2020
after installation not only high rating in specification. Experience from thousands of documented performance inspections and continuous monitoring show that saving opportunities of 20% as described in the K-CEP information mentioned above is conservative rather than exaggerated. Unless responsibility to document performance is assigned to a specific person after installation it will not be done.
Enter the future Key Performance Indicators (KPIs) must be checked at different loads and operating conditions. This is no problem today as data can be logged and analysed during ‘normal’ as well as extreme conditions Modern HVACR systems are often supplied with
controls that have most pressure and temperature sensors required to analyse performance but it remains only data points as performance is not analysed. The BMS/SCADA systems can add missing sensors and send data to state-of-the-art performance analysing platforms through gateways or APIs. Manual analytics of performance can be done but is time-consuming and costly even to do it for one timestamp. The future is already here – analysing all KPIs in real time in the cloud and giving early warning as soon as a deviation occurs. There are almost the same KPI’s to monitor in a chiller/heat pump or refrigeration plant even if level of the KPIs for a good system will vary somewhat with application. KPIs should primarily be benchmarked within similar technologies. KPIs are unbiased and based on physical parameters/thermodynamics, but in-spite of hundreds of pages of operating manuals, they are rarely specified onsite even if they are essential for maintenance and troubleshooting. The example below is for air-cooled chillers: Evaporator performance KPIs Evaporator efficiency is a powerful tool as performance is compared to an evaporator without temperature differences – an ideal evaporator. The efficiency will be much less affected by differences in operating conditions and flow than approach but it will be higher at part load when
the heat exchanger is relative larger.
Evaporator approach means the temperature difference between supply chilled water and evaporation temperature. This is a direct indicator of the performance of the evaporator but the challenge is that this will vary with capacity, supply water temperature, dT between supply and return water and if there is any glycol/brine in system. It will be affected by superheat as well as flow and if there are issues such as air bubbles, foaming or fouling in evaporator.
dT of chilled water – Normal, min and max help to validate ‘correct flow’ and the flow over each evaporator is often not available unless performance analysing is implemented but when performance is verified, the dT is a good KPI. Variable flow offers reduced pumping power – if flow is reduced to 50% the power consumption will be reduced to 12.5% of full flow and chiller performance at a given supply temperature will improve if dT is maintained within the recommended flow range for chiller.
Superheat at high and low temperature lift and high and low capacity. Superheat is an important KPI and depending on design it varies significantly over the operating envelope.
Setpoint- chilled water temperatures should be seen as a KPI. Design setpoint and normal for the specific site and minimum and maximum has a significant impact on energy consumption and design setpoint should not be seen as the optimum setpoint to maintain. Few sites require 12°C return and 7°C supply chilled water year around – the fixed setpoint and flow are in most cases extremely wasteful as energy consumption increase with 3-5% per degree lower chilled water supply. Most sites operate most of the time on part-load that allow for a higher set-point and lower flow when air handling units/beams only need to deliver part of design capacity – required dehumidification also needs to be considered. Floating chilled water supply temperature offer a significant saving at most sites. Condenser performance KPIs
www.acr-news.com
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44
