ACEEE Summer Study: Updating Steam Trap Savings Calculations

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The Need to Update Steam Trap Savings Calculations

By Cameron Kinney, ERS for Zondits, June 7, 2018

Steam trap repair and replacement projects are currently the fourth-largest natural gas energy savings measure in Massachusetts. Program administrators (PAs) have been increasing their promotion of the measure in recent years due to its cost-effective nature, but evaluators have observed that steam trap realization rates for both custom and prescriptive savings vary widely at the project level. As gas efficiency programs grow and participant volume increases, PAs will need a more consistent and practical method for estimating savings. Unfortunately, the complexity of steam systems makes standard M&V procedures anything but practical.

The good news is that some of the current processes are working. For example, a good deal of the information that vendors need to collect on-site is already standardized, and current templates do not deviate far from this existing setup.

But there is always room for improvement. Ensuring that vendors and applicants are populating a consistent workbook structure will allow for more uniformity in record keeping and can give way for trap inventories to be aggregated into a master archive, which could be used to assess steam trap demographics at a program level. Additionally, the structure will provide a platform to conduct further research and analysis on the program trap population if decision makers choose to do so.

Calculating steam trap losses (i.e., savings) is essentially a two-step process: 1) determine the theoretical steam flow through the trap orifice, and 2) apply a number of conversion and corrective factors to establish the theoretical savings potential. The merits to using one empirically derived equation over another are rooted in small differences in the expected error of the estimate as well as the curve shape of the relationship between pressure and steam weight. Regardless of the group’s preference for 100-year-old empirically derived equations, a consensus needs to be reached.

Moving forward, consistency and updates are needed. More importantly than the base equation used, the correction factors applied need to be carefully reviewed and agreed upon. While there are inputs and conversion factors that need to be included in the savings equation regardless of any industry professional’s preference, the real attention needs to be focused on the more ambiguous factors that may be applied to the savings equation. Reaching a consensus on which factors to include in the savings algorithm is important, as it will allow for uniform comparison among similar traps serving various end uses at different facilities. It doesn’t matter which parameters are selected; consistency is the key.

Even with the right tools to establish savings estimates, interpreting the operating status of a steam trap tends to be an art rather than a straightforward science.
Even with the right tools to establish savings estimates, interpreting the operating status of a steam trap tends to be an art rather than a straightforward science. Temperatures and pressures can be measured, but the burden of interpretation for most traps lies in ultrasonic measurement. Auditory testing is not an exact science, but it can provide the necessary data for a surveyor to interpret a trap’s status. PAs should ensure that vendors are trained to use a (relatively) consistent method for not only identifying defunct traps, but also establishing the mode and magnitude of failure.

To head off potentially erroneous trap analysis results, PAs should direct resources toward the review of projects at the processing phase. There are spot checks that PAs can conduct prior to approving site savings using little more than the information provided from a survey. PAs should also make an effort to compare the estimated savings with the annual utility bill consumption. Additionally, PAs should review the facility’s history of steam trap maintenance and understand how the facility uses steam at the facility.

Increasing both consistency and oversight will be key to improving the accuracy of steam trap savings calculations. This fact should not deter PAs from this rich source of savings; rather, it should serve to focus their efforts on the proper steps that maximize the effectiveness of program dollars allocated to steam trap improvements.