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Thermography is an easy and proven way to inspect electrical and mechanical components of a chilled water system in a non-invasive manner, without disruption to system operation. Like vibration monitoring, oil analysis and other forms of predictive maintenance, infrared thermography often spares facilities from minor periods of downtime at the least to catastrophic equipment failure at the worst. Early detection of potential, hidden issues improves overall HVAC system performance and also helps lower repair costs.
Infrared thermography uses infrared thermal imaging to detect and diagnose the thermal emissions of different components in the chilled water system. An increase in heat could suggest electrical and mechanical issues that can lead to component failure, unplanned outages and safety issues.
Typical problems that thermography can detect include finding loose electrical connections, cable wear, contactors and switchgear faults, and hot spots on PC boards. On mechanical machinery thermography I can be used to find overheating bearings, gearbox fault and shaft misalignments.
The thermography inspection method is based on the fact that most components in a system show an increase in temperature when malfunctioning. The table below shows thermal problem classification chart with comments and recommended actions depending on identified phase-to-phase temperature rise.
Thermal
problem classification chart : problem classification | Phase to phase
temperature rise | Comments |
Minor | 1°C–10°C | Repair during regular, scheduled maintenance. Little probability of physical damage. |
Intermediate | 10°C–30°C | Repair in the near future (2-4 weeks). During this time watch the load and change accordingly. Inspect for physical damage. Temperature rise indicates probability of damage in the component, but not in the surrounding components. |
Serious | 30°C–70°C | Repair in immediate future (1–2 days). Replace component and inspect the surrounding components for probable damage. |
Critical | Above 70°C | Conduct immediate repair (overtime). Replace component, inspect surrounding components. Repair should be done while IR camera is still available to inspect the component after the procedure. |
1. Low voltage inspection
Periodical infrared inspections is the best way to diagnose then to overcome the chiller electrical panels problems like:
· Poor electrical connections / contacts
· Loose connections
· Corroded connections
· Current overloading
· Electrical component degradation
· Damaged circuit breakers
· Worn contactors
· Damaged fuses
Thermal imaging cameras are commonly used for electrical inspections. As electrical connections become loose, there is a resistance to the current that can cause an increase in temperature which can then cause components to fail, resulting in unplanned outages and injuries. In addition, the efficiency of an electrical grid becomes low prior to failure, thus energy is spent generating heat, causing unnecessary losses.
2. Mechanical
inspections
Periodical mechanical infrared inspections to better prevent or identify
mechanical problems of HVAC system’s elements can be combined with vibration
analysis and oil analysis.
While most commonly used to find “hot spots” in electrical equipment, infrared technology has uses in plenty of other places in and around the plant. Particularly as more plants incorporate comprehensive predictive maintenance programs into their routines. Infrared technology can be used during different maintenance and check-up procedures: to scan conveyor systems, look for hot bearings in the rollers, production-wise or even for checking the buildings themselves.
A technician takes thermal images of the electrical and mechanical components of the chilled water system while it is up and running. The expert reviews thermal images, both past and new, and produces a detailed report of the current status of the pictured components, including possible reasons for any anomalies. Customers receive a detailed report generated by the computerized infrared scanner detailing the recommended repairs or improvements to avoid system failures and optimize reliability of the system. In detail, the report identifies and indicates:
· All areas photographed with visual and thermal images and their current condition
· Problem areas
· Clear description of expert evaluation of the identified issues
· Recommendations for next steps and solutions
· Repair priority among the identified issues
The Thermography technology is one of the service offerings that support the high performance buildings approach. Through this right approach high performance buildings meet specific standards for energy efficiency, system reliability, environmental sustainability and occupant comfort and safety.
L1
cable on the connector to the left shows overheating due to a bad connection.
This may be the result of a loose corroded connection. Recommended
action: repair and check afterwards if the overheating on the connection and
cable has disappeared. | |
The
connector to the right shows a higher temperature in all phases because of a
higher electrical load. Recommended
action: verify with a clamp that there is no overload. If the load is under
the nominal load, but the temperature is above the recommended (normally 70°C
for PVC cables), check with a power quality (PQ) meter the presence of
harmonics. | |
The
image shows clearly that the L3 phase on the third connector from the left is
overheated due to a bad connection. Recommended
action: guidelines provided by the InterNational Electrical Testing
Association (NETA) say that when the difference in temperature (DT) between
similar components under similar loading exceeds 15°C immediate repairs
should be undertaken. | |
Fuses
in L1 and L3 show overheating and non-uniform temperature. Recommended
action: check the loads for unbalance and if necessary replace fuses. | |
High
resistance electrical connection on L3. Recommended
action: check load and difference in temperature (DT) to the other phases to
determine severity (slight, moderate, severe or extreme). | |
Electrical system inspection to check for
loose connections. Load measurement shows 75 percent and temperature of only
45°C. Recommended action: repair at the next scheduled
maintenance. | |
The
temperature difference between L3 and L1 is 22.7°C which according to the
InterNational Electrical Testing Association (NETA) means an indication of a
serious issue. In addition to that, the temperature on the L3 cable is
84.3°C. According to European
Committee for Electrotechnical Standarization – CENELEC HD 516 – insulated
cable temperatures (PVC) should not exceed 70°C to avoid short circuits, interruptions and fires. Recommended action: replace L3 cable and check insulation on the
other cables. | |
Possible
issue when operating first compressor. The temperatures of the middle and
right compressors are 55-67 °C lower than the first compressor on the left. Recommended action: check working loads and compressor
operation to determine the reason for the significant temperature difference. | |
Loose
or high resistance electrical connections on all 3 phases. Measured current
is 80 percent of nominal which is the normal load in this case. Temperature on
the upper cables is about 20°C above the ambient temperature of 23°C.This is
still less than 35°C above ambient as per IEC 947-1 table 1. Recommended
action: there is no reason to assume the insulation on the cables has been
damaged. Repair and conduct another checkup within 3 months. | |
Bad
connections caused the temperature of the cables to be above 70°C. This is
above the limit recommended by European
Committee for Electrotechnical Standarization – CENELEC HD 516 for PVC
cables. Loads
at present are low, about 50 percent of nominal. It is unknown what
temperature the cables were exposed to when the loads were at near 100
percent. According to IEC60724, the short circuit current for a PVC cable
with a cross section <300mm2 is maximally 160°C for 5 minutes. Recommended
action: measure cable insulation and replace cables if necessary. |
The pictures are real-life examples of the early detection activities that can be done with the thermography service of Trane – examples are provided with the courtesy of Fluke.
About Ingersoll Rand and TraneIngersoll
Rand (NYSE:IR) advances the quality of life by creating comfortable,
sustainable and efficient environments. Our people and our family of
brands—including Club Car®, Ingersoll Rand®, Thermo King® and Trane® —work
together to enhance the quality and comfort of air in homes and buildings;
transport and protect food and perishables; and increase industrial
productivity and efficiency. Trane solutions optimize indoor environments
with a broad portfolio of energy efficient heating, ventilation and air
conditioning systems, building and contracting services, parts support and
advanced control. Ingersoll Rand is a $12 billion global business committed
to a world of sustainable progress and enduring results. For more information,
visit ingersollrand.com or trane.com. |
About FlukeFluke
Corporation is the world leader in compact, professional electronic test
tools. Fluke customers are technicians, engineers, electricians, and
metrologists who install, troubleshoot and manage industrial, electrical and
electronic equipment and calibration processes. Fluke is a registered trademark of Fluke Corporation. For more information, visit the Fluke website fluke.com. |
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