Control What You Can Measure

Asia Wireless for Asset Uptime

Source: Control Engineering Asia magazine

You’ve likely heard the phrase, “You can’t control what you don’t measure.” Emerson’s Jonas Berge, in a Control Engineering Asia article, Wireless for Asset Uptime, notes that many plants were built years ago with the minimum amount of instrumentation required for control. Often it’s difficult to go back and add instrumentation if the cables, junction boxes, cable trays, and other infrastructure is not already in place. Jonas writes:

The good news is that older plants can now easily be modernized by installing wireless instrumentation to supply the missing measurements and intelligence.

Jonas describes several examples where the addition of wireless measurements can improve unit utilization, improve energy efficiency, reduce maintenance costs, and mitigate safety and environmental incidents. These examples include essential asset management, heat exchanger monitoring, pump health monitoring, and steam trap monitoring. In yesterday’s post, Business Case for Essential Asset Monitoring, I highlighted the essential asset management example.

Jonas cites issues with heat exchanger fouling:

…downstream fired heater has to make up the process heat requirements, increasing fuel cost. At the point the heater reaches its maximum capacity, it is necessary to slow throughput to meet process temperature requirements resulting in underutilization of the unit.

Cleaning the heat exchanger may require a process shutdown. Without the measurements in place, plant personal must perform reactive maintenance when the fouling is visible. Through the use of wireless transmitters to measure:

…hot and cold fluid inlet and outlet temperature using single or multi-input wireless temperature transmitters on each heat exchanger.

With these measurements:

…wireless heat exchanger monitoring can be used to initiate actions which reduce energy loss and prevent throughput drop. The maintenance shutdown period is shortened by optimizing heat exchanger cleaning, and maintenance costs are reduced by avoiding unnecessary cleaning and disposal costs of chemicals. In addition, overheating damage to heat exchangers can be avoided and severe plugging of heat exchangers can be prevented, eliminating the cost of decoking.

A second example I’ll highlight from the article is steam trap monitoring. Jonas explains:

A steam trap has a life expectancy of four years. Therefore, with yearly inspection, as many as 25 percent of steam traps in a plant may have failed and should be replaced or possibly repaired… A typical plant could have thousands of steam traps. Depending on the steam trap size and steam pressure, failed steam traps may cost the plant millions of dollars annually.

Manually checking these traps is difficult. Automatic monitoring is possible through a [hyperlink added]:

wireless acoustic transmitter, a non-intrusive multi-variable instrument strapped onto the outside of the pipe at the trap inlet. The acoustic transmitter “listens” for the ultrasonic noise created by steam or condensate. A temperature sensor built into the wireless acoustic transmitter measures the temperature at the steam trap inlet.

Jonas shares that the [hyperlink added]:

…temperature tells the [steam trap] software if there is cool condensate or hot steam at the steam trap inlet and can thus detect if the steam trap has failed “cold” blocking condensate discharge. The status of all steam traps is displayed in software for easy review by technicians, allowing them to make decisions as to which steam traps to replace.

Give the article a read if your plant is missing measurements that could help improve efficiency, performance, and safety.

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