A predictive maintenance road map to energy savings
The connection between maintenance and energy savings is not well understood. In fact, many of us view energy savings as just an electrical issue rather than a holistic approach to all energy usage. We need to consider energy measurement as part of a predictive maintenance system; to save time, money and energy throughout the facility.
All facilities tend to lose energy (cost involved) through overheated electrical distribution systems, overloaded and misaligned rotating assets as well as lose expensive compressed air and steam through leaking pipes/fittings. We need to improve equipment reliability by fully leveraging predictive maintenance (PdM) technologies.
Step 1 – Assets Listing
It is crucial to gain a complete picture of all assets within a reliability program or at least the equipment targeted in the pilot project. Keep in mind that from an electrical standpoint, many organizations don’t breakdown the electrical systems to the component level (i.e. relays, breakers, and lighting panels).
If you are finding information gaps while compiling the assets lists, the best way to get the full is by walking through the facility with a simple facility layout drawing and notebook to capture asset name plate data.
Step 2 – Get the Energy Bill
This step requires review and analysis of energy invoices for two to three years to establish consumption patterns. The consumption pattern need to be broken up for all the specific major energy using equipment groups (HVAC, Compressors, Ovens, Blower groups etc) and groups geographical or logical location (Utility group / Data center / Paint shop / Pharmaceutical production modules / Major office floor / Lunch room etc
Step 3 – Prioritise Your Efforts
A simple prioritisation approach is to divide the gas, electric and oil bills into two usage categories; by building type or use and by equipment types which are common to a variety of process and applications, compressed air, pump and fan systems, etc.
The facility may have hundreds of fractional horsepower motors that cumulatively consume a lot of energy, but the labor, analysis and reporting costs of deploying PdM to each is more than the replacement costs. The PdM approach will be cost-effective on lesser number of critical equipment.
An asset criticality ranking process creates weighted scores based upon probability of failures, failure severities, value impact on associated personnel, systems, buildings and the overall organisation.
Ultimately, you end up with a comprehensive site equipment list and corresponding criticality score that can be easily sorted to identify the most critical equipment by asset classification, building, and cost center.
The list will be used to identify which equipment to focus on first with specific maintenance strategies. Equipment having a high-ranking will likely have more advanced PdM equipment strategies and analysis performed; whereas equipment having the lowest ranking may have a lower maintenance strategy such as “run-to-failure”.
Each organisation has a different profile. For example, industrials have a higher number of process related motor loads, pharmaceuticals more HVAC loads and commercial buildings more focus on the electrical, HVAC and roofing systems.
Step 4 – Calculate the Energy Savings
Electrical Savings – The key process requires capturing power consumption measurements taken when an anomaly is identified and after equipment is put back into service. The savings in energy will give us the annual cost savings for a given maintenance effort.
Steam savings calculation will involve the collection of large data covering boiler efficiency, loading, losses, number of boilers, fuel cost per 1,000 BTU, steam pressures, water treatment chemical costs, labour burden, etc. Further costing for PdM efforts to critical boiler components could be made to achieve cost-effective maintenance with equitable energy savings.
Electrical distribution Systems
Electricity and electrical distribution systems are the backbone of any infrastructure. The issue at hand is that much of the electrical generation and distribution systems age without too much maintenance effort at sub assembly or component levels. Many sub systems cross the designed life and become susceptible to failure and low reliability. Some of the problems faced are:
- Unstable utility supply / line surges
- Transient voltages
- Unbalanced and overloaded transformer banks
- Short circuits
- Unidentified single-phase ground faults
- Faulty power factor correction equipment
- Upstream and downstream relay faults and tripping
- Un-calibrated relays and meters
The above variables are often hidden but can manifest themselves as single phasing, shorted windings, overheated transformer banks and partially tripped over current protection. Such component level failures are caused due to lack of maintenance.
IR thermography captures thermal anomalies and variances in temperatures. It is ideal for capturing high resistance, overload, phase imbalance and loose electrical connections that cause overheating and wasted energy.
Ultrasound scanning of steam, fire fighting water and compressed air systems will help in identifying leaky components such as isolation valves, traps etc, without physically opening the systems for maintenance.
Thus PdM initiatives will work towards holistic infrastructure energy savings.
Adapted from an article by Dale Smith, CMRP, in Plant Maintenance Aug 2010 Issue