In the face of rising energy costs, steam waste is becoming even more of an issue for chemical plants. Traditional manual surveys are time consuming and expensive. Even when audits are carried out annually, up to 15% of steam traps will fail between surveys, says Emerson Process Management. A two- or three-year gap between inspections can push this figure up to 30%.
Failed steam traps can do more than waste steam. For example, a trap failing closed, instead of open, can lead to water hammer and physical damage to a facility — with potentially catastrophic results.
However, many steam traps are in hard-to-access or potentially dangerous locations that make surveying them hazardous.
Fortunately, wireless monitoring systems can ease the checking of steam traps at chemical plants. Vendors offering such systems include Spirax Sarco, Cheltenham, U.K.; Cypress Envirosystems, San Jose, Calif.; Emerson Process Management, Round Rock, Texas; and Armstrong International, Three Rivers, Mich.
NOW ATEX APPROVED
Spirax Sarco's new STAPS wireless steam-trap monitoring system, which was developed at the company's global R&D center in Cheltenham, currently is undergoing beta testing at the company's own sites around the world and with a major food manufacturer. Beta testing at chemical plants was hampered by lack of ATEX approval. However, this approval came in the last week of February. "We can now offer two versions, the standard one and the ATEX-approved one, and we anticipate trial sites in the chemical industry will be forthcoming," explains Simon Geuley, group product manager for condensate management.
The main driver for investment in steam trap monitoring is heat loss, says Geuley. The numbers associated with such losses can be dramatic. For instance, if roughly 10% of the steam traps fail annually at a process plant with 200 traps and the plant has an average trap size of DN20, steam pressure of 14 barg and operates 24/7 for 50 weeks/year, the cost of ignoring the failures would be £89,000 (about $150,000), he notes. This is equivalent to well over one million liters of fuel oil plus 3,000 metric tons of carbon dioxide released to the environment, he adds.
Wired monitoring systems are an option but can be expensive to install and maintain. "There are issues with intrinsic safety, particularly within the chemical industry. So, there has been a huge move to wireless solutions, particularly in the field of condition monitoring," Geuley explains.
The heart of the system is a head unit assembly that is mounted on the pipe upstream of the trap to be monitored and that is powered by a lithium battery that can last for up to ten years. It features vibration and temperature sensors as well as an advanced processor to carry out calculations. The head unit "listens" to the sound signature of the trap (Figure 1). This sound signature is categorized and transmitted via a 2.4-GHz wireless network.
The system also includes a receiver that the head unit communicates with and a repeater. These create a network and can communicate with each other and pass on the steam trap data to a supervisory PC that determines the trap condition and calculates any steam loss.
The monitoring is semi-continuous — occurring a minimum of every 15 minutes depending upon the customer's requirement. The information appears in a very simple format on the PC: green denotes "good," amber is "caution" and red indicates a leak. Two other displays show battery condition and wireless signal strength. The latter also notes when the last successful communication took place in case there's a problem with the wireless network.
STAPS' leak-detection intelligence differentiates it from other wireless steam-trap monitoring systems, says Geuley. Using information from the tens of thousands of steam trap installations it has worldwide, the company has developed a device that can account for the operating principals of different types of steam traps — Spirax's offerings include bimetallic, fixed temperature discharge, ball float, inverted bucket, sealed thermostatic and thermodynamic traps — plus their respective loads and pressures. "So our algorithm is very difficult to replicate," he claims.
The wireless steam trap monitor (WSTM) from Cypress Envirosystems mounts non-invasively onto existing steam traps in minutes and uses a proven algorithm to detect trap failures, particularly expensive steam leaks. It has been designed to augment manual audits to detect failures in a timely manner.
One of its most successful applications has been at the main technology center of a major U.S. pharmaceutical company. The center includes a number of manufacturing buildings, each supplied with steam, chilled water and compressed air from a dedicated utility plant. Each building is responsible for its own energy consumption and is billed separately by the utility plant. Overall, the center houses more than 2,400 steam traps, many operating in hazardous locations where temperatures can reach up to 500°F.
The utility plant installed WSTMs to continuously monitor the steam system — to provide transparent accountability for each building and close the loop on energy reduction goals for the company as a whole. The payback on this project was under 12 months.
The WSTMs perform monitoring and diagnostics, and transmit health status wirelessly to a central server for trending, graphing, alarming and historization. Installing each WSTM takes less than half an hour and doesn't involve breaking seals, leak checks, or production downtime. Whether traps fail open or closed, the WSTMs provide alarm notification, enabling timely maintenance to increase safety and reliability in addition to saving energy.
The WSTM has a built-in "zero footprint" web-based user interface that enables any user on the company Intranet to view historical trends, graphs and alarms/notifications. It also provides comprehensive reports with an energy summary that shows steam loss and its associated cost for analysis and auditing — no new software or operator training is required, says Cypress.
Existing automation systems easily can integrate the WSTM data via open system interfaces. The pharmaceutical company uses OPC to bring the data into its Wonderware utilities management system; Cypress has a technology alliance with Invensys to ensure operability between its products and Wonderware software.
In a second application, a pharmaceutical company in New England has installed WSTMs on its 550 steam traps.
The company's traditional annual audit was taking about 140 man-hours, costing $20,000 and requiring a calendar month to complete. The pharmaceutical firm replaced all failed steam traps uncovered during the audit. However, before the next audit, around 15% of the traps would fail and start to leak. On average, it took six months before the leaks were detected, at a cost of $375,000 in lost steam.
Installation of the 550 WSTMs has reduced steam leakage by 95% and cut audit labor costs by 70%. Payback was achieved in less than a year.
"Although we are more focused on our healthcare market at the moment, we are absolutely considering the chemical industry and it's definitely a market that we want to grow into," says David Roberts, vice president of marketing.
FOOD FOR THOUGHT
A major food manufacturer based in the southeast U.S. also has benefited from wireless trap monitoring. The company had developed a preventive maintenance (PM) schedule for steam traps at a large plant that makes multiple product lines. It took a maintenance crew at least an hour to properly check each of the nearly 100 steam traps, which limited the PM to an annual exercise.
To meet its demand for automatic online monitoring of steam trap performance, together with real-time alerts to minimize the need for PM and energy losses, the company installed nine Rosemount 708 wireless acoustic transmitters from Emerson (Figure 2).
The plant already had a self-organizing wireless network for the Rosemount 3051S DP wireless flow meters it was using to monitor compressed air flow. Adding the non-intrusive wireless acoustic measurement devices was easy. "Wireless greatly reduces installation cost, and we use those savings to purchase more instrumentation to extend utility monitoring in our plant," notes the site's project engineer.
The nine transmitters were put on steam lines throughout the plant and integrated into the existing Smart Wireless Gateway, which communicates to a plant host. The acoustic transmitters monitor a variety of types of steam traps and work equally well on all of them, says Emerson; one transmitter even keeps tabs on a steam-driven pump to give early indication of problems. The network was easy to expand; the new transmitters just strengthened the mesh. There's a lot of concrete between the transmitters and the gateway and high EMF, but the wireless communications are strong and reliable, adds the company.
"Manual monitoring of temperature did not give us enough information to conclusively target a steam trap for replacement when we saw water-hammering," explains the project engineer. "But when we installed the wireless acoustic transmitter, we could tell immediately which steam trap was stuck." It was quickly fixed, and a trend of the new trap showed normal acoustics and temperature.
"We found 22% of our traps needed to be replaced during our last PM check. By installing wireless acoustic transmitters, the plant will prevent steam loss with early detection of steam trap failure. Not only will this minimize energy loss, but it will free up maintenance to focus their time and attention on things that need to be fixed, to further improve our productivity," the project engineer notes.
BUILDING UPON EXPERIENCE
The AIM system from Armstrong International provides intelligent wireless steam-trap monitoring that's designed to tackle the three constant challenges faced by plant and maintenance engineers: identifying a failure, evaluating its scope and measuring its impact. AIM (Figure 3) relies on a mix of methods, including acoustic and temperature monitoring, integrated into a smart wireless device that can deliver immediate failure notifications and pinpoint their locations.
Armstrong's biggest differentiator is the knowledge it has gained in over 100 years of steam system work, says Kerry Phillips, global manager, smart services group. "We've designed, tested, constructed and maintained more steam systems than any company. This gives us an advantage to not only know how to apply proper technology for maintaining steam traps, but also the ability to provide and execute the solution when problems are identified," he notes.
The chemical industry only is at the early adopters' stage when it comes to wireless steam-trap monitoring technology, says Phillips. "Based on experience, the industry's biggest concerns appear to be with reliability and cyber security. Old behavior has been to manually survey the steam traps, but as wireless technology becomes more accepted, the behaviors will change to automate steam trap testing. Wireless steam-trap monitoring is real-time, whereas manual surveys are typically done once per year. Real-time monitoring enables companies to identify the failure immediately so action can be taken. Most like to focus on the critical steam traps such as the high energy wasters and critical process."
As a result, Armstrong's successes so far in the chemical industry have mainly been in high-cost application areas. "For example, a chemical company with 2,000 steam traps will typically monitor the high-steam-pressure applications as well as any steam traps that are critical to their process. Armstrong is able to identify the worst offenders, to really focus down into the areas that are affecting efficiency and costing money."
This, he says, is particularly important to process and maintenance engineers who these days are under pressure to achieve more with fewer resources. "However, as energy costs rise, so does the need to stay on top of steam leaks. One steam trap failing open can lose upwards of 500,000 lb/yr of steam. Depending on your cost of steam, this could be wasting up to $8,000 per year — just for one steam trap! Typical chemical process facilities will have in excess of 1,000 steam traps, so the energy losses can add up quickly if they are not maintained regularly."
Phillips cites examples at three customers to illustrate the point. The first boosted performance and profits after using the system to identify failed steam traps on high-pressure steam lines. The second had steam traps 105 ft off the ground in the middle of a pipe rack with no scaffolding support. AIM has enabled this customer to reduce downtime and reallocate valuable maintenance man-hours. The third experienced multiple steam-trap problems that caused condensate to back up into its steam turbine. Using wireless steam-trap monitoring decreased downtime and increased plant performance.
Seán Ottewell is Chemical Processing's Editor at Large. You can e-mail him at firstname.lastname@example.org