At most chemical plants, plant management and operators face increasing pressures to improve the energy efficiency of their processes. A snapshot of just how well the industry is responding to these pressures could be seen in last October’s announcement by the American Chemistry Council (ACC), Arlington, Va., of the winners of its 2005 Responsible Care energy efficiency awards.
A total of 11 companies received 26 awards in recognition of company-wide and plant-level achievements in implementing a wide variety of energy efficiency improvements. “Since 1970, Responsible Care companies have reduced fuel and power consumption per unit of output by 46%,” says Jack Gerard, ACC president and CEO. “In the past five years, these companies have reduced their greenhouse gas intensity by more than 26% ... These awards show that our industry is doing its part to increase energy efficiency.”
Although many of the awards were given for specific process-improvement projects, the importance of plant utilities in the overall energy balance wasn’t overlooked. Among the citations, for example, were ones to DuPont’s Sabine River Works, Orange, Texas, for its site energy-reduction program, DuPont’s Belle Plant, Belle, W. Va., for powerhouse efficiency improvements, and ExxonMobil Chemical for a cogeneration project at its Baytown, Texas, olefins unit and for furnace energy improvements at its Baton Rouge, La., plant.
Focusing on site utilities for energy efficiency improvements may have benefited those companies but not everyone appreciates the potential gains to be made from investing in what is still considered by many as a non-earning part of the plant. Steam systems are a case in point, particularly when it comes to steam trap management.
“The problem in the chemical and petrochemical industries,” says Mike Acers of James D. Acers Co., Cloquet, Minn., “is the view that steam traps won’t make the company any money. They’re looked on as a necessary evil to keep the process running.” Acting as U.S. distributor for the bimetallic steam traps manufactured by Velan, Montreal, Quebec, and Leicester, U.K., Acers says it can take some time to convince people of the cost benefits of good trap management.
Recognizing the importance
Not everyone in the industry needs convincing, however. Dan Dvorak, a consultant in the energy engineering group of DuPont Engineering Technology, Nashville, Tenn., says that steam traps and steam trap management are “basically the foundations or building blocks for steam system management. We have hundreds of steam-consuming sites worldwide — from office complexes through research facilities to production sites — and we know that if we don’t take care of our steam traps on some routine basis, after a few years we could have anywhere between 25% and 35% of a site’s traps in some failed condition.”
That estimate may understate the situation at other companies, according to James Risko, president of steam specialist company TLV, Charlotte, N.C.: “For a site that has not had a proactive trap management program with annual surveys and repairs,” he has reported, “it is not uncommon to have 50% of the trap population (or more) in a current state of failure.”
DuPont adopts a best practice approach to looking after an installed base of traps that, says Dvorak, “is probably on the order of a quarter-of-a-million or so around the world.” That best practice depends very much on the installation and application. For routine maintenance, for example, the plants’ SAP enterprise resource planning system will prompt manufacturing areas to inspect traps. “The best practice may have them do that at some routine yet optimized frequency,” he says. “So, if you were just starting out and had critical process traps, you might inspect those — depending on whether you were using on- or off-line technologies — continuously or once a month. It just depends on the installation. Our best practice basically says get the right trap for the right application and have something in place to ensure they are inspected at some routine periodicity depending on the application.”
Dvorak stresses that DuPont’s approach to traps and trap management is quite pragmatic. “We know if we don’t take care of such systems we would impact our fuel bill by anywhere between 8% and 10% a year. We have data to support that.”
Acers also can provide data to show the value of good trap management, such as the results achieved at Murphy Oil’s Superior, Wis., refinery. Velan started work there back in 1998, analyzing the condition of the site’s 3,000 steam traps, and recommending upgrades and replacements of failed traps where necessary. The original work, including leak repairs and improvements to the condensate recovery system, took four months and a similar project has since become a biennial ritual — with significant energy savings as a result. The annual failure rate of Murphy’s steam trap population has dropped from 21% in 1998 to just 3.4% last year.
“When it comes to steam traps, people often ignore them,” says Bruce Gorelick, president of Enercheck Systems, Charlotte, N. C., an energy consultancy that works in collaboration with ultrasonic-testing-equipment supplier UE Systems, Elmsford, N.Y., to advise plants of the benefits of steam trap surveys. “There’s a complacency about them that is costing steam users much more than they realize,” he adds.
As Acers says, “steam traps are an old, old product,” which possibly explains, but doesn’t excuse, their relatively low profile at plants.
Although all traps are designed for the same function — basically to release condensate and non-condensable gas (air) from a steam system while preventing the escape of live steam — there are many types of traps for many different applications. (For selection guidance, read Find the perfect steam trap.)
The Velan bimetallic trap was introduced in the 1950s, but still is one of the more recent developments in trap design. The fixed orifice trap first was used in the 1850s, while the initial patent on a thermodynamic trap was taken out in the U.K. in 1878. Armstrong International, Three Rivers, Mich., pioneered the inverted bucket trap in 1911. Other popular trap types, such as the thermostatic bellows and capsule designs, arrived on the scene later, although still a long time ago in relative terms.
Bestobell Steam, Cincinnati, Ohio, for example, introduced the Delta Element trap more than 40 years ago. Karl Lutkewitte, product manager, says the single-blade bimetallic design was aimed at correcting “two age-old steam trap problems: inherent steam loss and steam loss on trap failure.” He points out that the traditional inverted bucket trap — “the workhorse for the steam industry for decades” — vents some steam, albeit a very small amount, with each cycle/discharge of the trap. Disc traps also lose live steam with every discharge and these losses can rapidly increase as the cyclic operation degrades the disc’s seating surface.
“By contrast,” says Lutkewitte, “bimetallic thermostatic/thermodynamic steam traps and some thermostatic bellows and capsule traps don’t lose or use any live steam during operation.” This is because they do not cycle to discharge condensate, but instead modulate the condensate flow at a rate relative to its formation. This smooth modulating action, coupled with fewer moving parts, results in the Delta Element trap lasting three to four times longer than traditional cyclical discharge traps, claims Lutkewitte.
Spotting problems early
But, as Lutkewitte says, steam traps do wear out at some point. Unfortunately, users don’t always recognize when that occurs. “Traps that have failed completely open are easy to detect but the object is to find failing traps before they fail completely,” explains Gary Mohr of UE Systems. “Ultrasonic testing can do that. Technicians who use ultrasonic detectors on a daily basis can achieve accuracy [of detection] that exceeds 98%.”
One such detector is the hand-held TM5 ultrasonic and temperature-testing instrument that forms part of TLV’s TrapMan computerized trap-management system. The other part is TrapManager software, which enables extensive data analysis of a plant’s entire trap population. By comparing the test results obtained from the instrument with stored data from TLV’s laboratory analysis of similar traps in a controlled environment, the system is said to be able to diagnose trap performance within 15 seconds, an obvious attraction to plants that number their traps in the thousands. In its automatic referencing mode, the TM5 can be used by personnel with little trap-testing experience or training, TLV says.
Later this year the company plans to introduce to North America the PT1 Pocket TrapMan, a compact diagnostic instrument, also based on ultrasonic and temperature detection, that will enable the more skilled technician to make quick basic judgments as to the condition of traps and valves. The small hand held device can store the results of up to 100 trap/valve and 100 bearing inspections in its internal memory. TLV already offers PenCheck, a pocket-PC-based management system for small- to medium-sized populations of up to 1,000 traps.
Other steam trap monitoring and management systems on the market include the TrapMaster software from Yarway, Blue Bell, Pa., the SteamEye and SteamStar systems from Armstrong International, and Bestobell’s Steam Tector 2 hand held ultrasonic leak-detection device.
Claiming to offer the world’s widest range of steam traps — comprising the six main trap designs in sizes from 1/4 in. to 4 in., pressures to 1,940 psig, and capacities to 300,000 lb/h — Spirax Sarco, Blythewood, S. C. and Cheltenham, U.K., employs its own STMS computerized steam-trap management system to conduct plantwide trap surveys for customers. Failed traps are highlighted and steam losses automatically calculated to give payback times for replacements of the failed traps.
Sensors right at the trap
Spirax Sarco currently is involved in a collaborative project to develop an acoustic performance sensor that will be low enough cost to make it viable for attaching to most traps on the market, according to Richard Carmichael, head of central research in the U.K. That’s for the future, but for now the company’s equally innovative Pivotrol PTF4 condensate pump has been proving its worth on many condensate recovery systems (Figure 1). “This was designed in response to specific customer requirements,” says Carmichael, “such as high reliability and low maintenance, because if the condensate pump fails, the whole steam system fails.”
Figure 1. Reliable unit is crucial for keeping the whole steam system from failing.
One sensor that already is mounted on a trap itself is Yarway’s SmarTrap. Designed solely for the company’s Series 711/721 UniBody Plus disc traps, which are used on light loads such as steam tracing, the non-invasive electronic SmarTrap monitor comes permanently attached to the bonnet of the trap or its replacement capsule. Two LEDs (red and green) on the monitor alert inspection personnel in the area to the trap’s condition without them having to check the trap itself.
Inspectors need not be in the field, though, with Armstrong’s SteamEye system (Figure 2) for remote trap monitoring. “The basis of the system is a wireless transmitter — using either ultrasonics or conductivity monitoring — that reports to a receiver in a central location in the plant; this then web-enables the information to report on the plant’s intranet system,” says Tom Henry, the company’s director of global marketing. “What it reports is the condition of the trap at every moment of its operation.”
Figure 2. Wireless sensor and software enable monitoring of all steam traps from plant intranet.
Mounted just upstream of the inlet of any make or style of steam trap, SteamEye detects fluctuations in steam flow and temperature and, working in tandem with the web-enabled SteamStar “measurement platform,” can give remote warning of a failing trap. “Users can log on from anywhere in their company’s network through a password-protected interface,” explains account manager Chris Gibbs, “and monitor via the Internet the performance of their traps from an individual site or a host of different global sites.”
Armstrong plans to extend the SteamEye/SteamStar principle to additional points of monitoring around the steam system, notes Henry. “We’re looking at safety relief valves and monitoring condensate pumps,” he explains, “so you will know instantly the moment a condensate pump fails and begins to back up condensate.”
“There is a general trend in chemical plants at the moment to look at using wireless equipment to monitor plant equipment and provide more information on actual operating conditions,” says Henry, echoing what CP recently reported, (Where is wireless going?). Armstrong’s system is certainly capable of that, although DuPont’s Dvorak sounds a note of caution about automatic monitoring in general. “We do use ultrasonic detectors and automated diagnostic devices from several of the leading suppliers,” he says, “but with caution. That’s not to knock any particular product. It’s to maintain a principle whereby we believe that the people doing the testing need to know what it is they’re testing. The technology is great but they are tools — they should not be the mindset. It’s up to the user to understand why the device is there and how it is functioning.”
All the users — and suppliers — then have to do, of course, is convince others of the benefits these tools and good steam-system management in general can bring to the overall energy efficiency of the plant. But, like steam traps themselves, that’s an old, old story.