Where there is steam in an industrial plant or facility, there are steam traps to recapture condensate. When they work well they’re great, but they can also be a maintenance headache.
In the Sep-Oct 2018 issue of InTech, Tom Bass addresses the problem in his article titled Steam Trap Monitoring Enables Predictive Maintenance. He makes the point that these simple devices have an enormous influence on the efficiency of the entire steam generation and distribution system.
Producing steam is energy intensive, and an ineffective distribution system can be wasteful. Boiler designs can be highly efficient, but this efficiency can be rapidly lost with a poor distribution system.
Condensate is water, but it is very valuable water and needs to be recaptured, as Tom explains:
Condensate is sent back to the boiler as feedwater, which makes it valuable for two reasons. First, boiler feedwater is heavily treated with expensive chemicals to avoid boiler fouling, so any that can be recaptured saves money. Second, condensate is usually hot, which reduces the amount of energy needed to turn it back into steam. Consequently, condensate collection is critical for overall system efficiency, and it depends on steam traps.
The situation is clear enough: poorly performing steam traps cost money. Given how expensive steam is, a steam trap leaking steam could waste its original purchase price many times over. So how and why do they fail, and how can maintenance teams determine which ones need attention? As Tom points out, they tend to fail open or closed, either leaking live steam or shutting off entirely so they don’t release condensate. The good ones are just right.
Finding these "Goldilocks" units performing correctly, and tagging the bad actors for maintenance, requires an appropriate tool to evaluate temperature, such as an infrared viewing device. These can do the job, but a technician has to get to wherever the steam trap is and make the evaluation. Unless manual rounds by a very highly qualified and experienced technician happen regularly and frequently, one or many steam traps can malfunction for quite a while.
Another approach is monitoring a trap with a permanently mounted temperature sensor, but Tom points out there is a better way to implement data collection and analysis, providing a better evaluation of performance.
An acoustic transmitter mounted on the pipe adjacent to a steam trap can listen to the noise it makes. It is sensitive to ultrasonic frequencies, so it can hear the cycling, and an algorithm can be applied to learn the characteristic activity for each trap. Data can be sent from the transmitter via WirelessHART to a central data collection and analysis platform, where operators can see how the steam traps equipped with acoustic transmitters in all parts of the plant are performing.
The acoustic transmitter Tom has in mind is the Rosemount 708, communicating via a WirelessHART network. Take a look at the full article because he goes into more detail on how the data can be collected and analyzed using Plantweb Insight to find the Goldilocks units mentioned earlier, along with those acting more like a grumpy bear. He also includes an interesting case study about how one snack food manufacturer saved $27,800 in steam production costs by monitoring just 12 steam traps.
You can find more information like this and meet with other people looking at the same kinds of situations in the Emerson Exchange365 community. It’s a place where you can communicate and exchange information with experts and peers in all sorts of industries around the world. Look for the Asset Management group and other specialty areas for suggestions and answers.
Posted by Deanna Johnson, Rosemount Measurement & Analytical Global Marcom Manager, Emerson Automation Solutions