Temperature Measurement


A powerful argument for infrared windows

July 2014 Temperature Measurement

A regional power generation facility in the USA was required to perform regular preventive maintenance on the switchgear within its facility. Unfortunately, regular downtime is not a practical option for this industry and the processes required hazardous live inspections that required significant manpower and resources. In addition, the pressure of the requirements of NFPA 70E was causing management to rethink the strategy since inspections of energised equipment were becoming more restrictive and costly.

After some research, it was decided that infrared windows should be considered as an alternative method of conducting safer, standards-compliant inspections and it was determined that a reduction in hazard liability and maintenance costs could be attained.

As stated in NFPA 70E: “Under normal operating conditions, enclosed energised equipment that has been properly installed and maintained is not likely to pose an arc flash hazard.” The use of IR windows for routine inspections would therefore:

* Maintain an enclosed state for the switchgear and keep energised components in a guarded condition, in NFPA terms. The hazard/risk category would be equal to that of reading a panel meter etc.

* Eliminate the need for a supporting cast of electricians to remove and reinstall panel covers.

* Allow critical personnel to perform other tasks which were often being outsourced.

* Provide the ability to perform more frequent inspections for critical applications to ensure more plant uptime.

A site inspection was performed by IRISS to ascertain the optimal number and position of windows to give thermographers the desired visibility of relevant targets. Previously, none of the primary switchgear or transformers had been included in the sites inspections due to the inherent safety hazards associated with their being safely inspected while energised. The review showed that some of the plant’s critical assets were never inspected during the annual survey. The primary goal of Phase I was to bring this equipment into the standard inspection routes.

Typical cost analysis of standard inspection

The client had been using a contract thermography company for some time and the survey crew consisted of two in-house electricians and one contract thermographer.

The hourly wrench time (time spent on productive labour) rate for the electrician was calculated at $62 (R650), and the contract thermographer’s rate was $150 (R1575) per hour. Typically, the equipment being considered for Phase I would require 19 days to survey during a standard inspection. The cost for such an inspection was calculated as (R650x2 + R1575) x 8 x 19 = R437 000.

After analysing the time studies, management was astonished to learn that over 90% of the total project time for the traditional open-panel surveys was non-productive due to suit-up, suit-down, thermographer wait-time (waiting for electricians to complete their work) and electrician wait-time (waiting for thermographers to complete their work).

Infrared windows

In search for an alternative approach that was both safer and standards-compliant, the corporate reliability engineer investigated how infrared inspection windows (IR windows) might be utilised. It was determined that use of IR windows would:

* Provide nonintrusive access to electrical applications.

* Allow surveys to be conducted during periods of peak-load without elevating risk to either plant assets or processes.

* Eliminate the need for a supporting cast of electricians to remove and reinstall panel covers. These critical personnel would then be available to perform other tasks which were often being outsourced.

* Eliminate high-risk tasks during inspections.

* Improve inspection efficiency and allow increases in inspection frequency for mission critical applications.

Investment

The facility’s 95 applications with 147 inspection compartments required 203 infrared inspection windows, representing an investment of $48 841 (R513 000). The installation of the inspection panes was conducted during a shutdown, using two installation teams. The majority of the windows were installed while equipment was de-energised, in what NFPA terms an ‘electrically safe work condition’. However, some installations involved energised gear and needed to employ the traditional safety measures such as use of PPE, energised work permits, etc.

Cost analysis with windows

After the installation of the IR windows, there was no requirement to remove panels or wear increased levels of PPE. In addition, inspections were now performed on applications that had previously been considered impossible. Finally, the entire task became a one-man job, which increased efficiency and economy of motion.

Total man-hours to complete an inspection dropped to just 33. As a result, the cost of a survey dropped from R437 000 to just under R52 000. Because of the efficiencies achieved, the facility saves R385 000 per inspection.

After just two inspections the capital costs are recovered and every inspection after that saves R385 000.

Conclusion

The new inspection process using infrared windows brought significant ROI to the plant in just two inspection cycles, while reducing the risk of catastrophic failure among the plant’s critical power distribution systems. Other benefits to management include:

* Increased safety.

* Inspection of previously ‘impossible’ equipment.

* Increased the frequency of inspection – while saving money.

* Safeguard of profitability by eliminating high-risk behaviour.

In the future the facility is planning to purchase its own IR camera and training for the maintenance engineers, which will quickly pay dividends and allow the plant to improve the maintenance programme while operating in full compliance with the requirements of NFPA and OSHA.

IR windows provide a cost-effective and safer alternative to traditional open-panel inspections.

For more information contact R&C Instrumentation, 086 111 4217, info@randci.co.za, www.randci.co.za



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