Steam leaks are completely unnecessary but unfortunately quite common, according to Kelly Paffel, technical manager at Swagelok Energy Advisors. “If you do your job incorrectly, you will have leaks. If you do your job correctly, you will not have leaks,” he said during his presentation today at the 2014 Ultrasound World X conference hosted by UE Systems in Clearwater Beach, Florida. Paffel shared the risks, causes, and costs of steam leaks and offered suggestions on how to quantify and avoid them.
Steam leaks have multiple negative effects on steam-based plant operations, including energy losses, increased emissions, loss of reliability, production issues, and safety, Paffel explained. “Steam leakage is a major energy loss and we accept it as normal, but it’s not normal. You can also save tons of CO2 by changing steam systems to reduce leaks,” he said. “Steam will erode and the leak will increase, which means you need to be very proactive in stopping it.”
Safety is an obvious concern, because steam leaks can cause severe burns and even death. “A high-pressure leak that is invisible and generates only a whistling sound can cut and cauterize you if you walk into it,” cautioned Paffel. Dripping condensate and foggy conditions also are safety issues. Water hammers cause 67% of component failures in a steam system, and they can be audible or silent, and they can be deadly. Production is also put at risk. Leaks will cause a pressure loss in the system, lowering temperatures, which can create problems in the tracer system.
He believes that to avoid steam leaks, you must be willing to accept change. Requirements specifications, design, installation, start-up procedure, and shutdown procedure are all potential contributors to leaks. Although accepting and implementing change may seem difficult, steam leak fixes create instantaneous savings and a high payback. By comparison, the savings gained by stopping a compressed air leak depends on the compressor.
Estimating the leakage is difficult to do because the orifice is not perfectly round. Measuring the diameter only can be done by visual inspection because physical measurements will cause burns. The plume length is highly dependent on the pressure of the leak, and volume is dependent on the diameter and pressure. Taking a surface temperature with an infrared unit will provide a relative temperature, and with a steam table, you can get an estimated steam pressure. If it’s on the downstream side of a process, the pressure will vary.
|Kelly Paffel, technical manager at Swagelok Energy Advisors, noted that steam leaks have multiple negative effects on steam-based plant operations, including energy losses, increased emissions, loss of reliability, production issues, and safety.|
“Calculations are a best guess, but you have to give it a number,” Paffel said. He has been working on a more precise method of estimating steam leakage for seven years, and the results are becoming more and more repeatable. He is hoping to have a technical paper on it ready in the first quarter of 2015.
The primary causes of steam leaks include piping and tubing connections and erosion, as well as failures of steam components such as valves and steam traps. Paffel believes that steam lines should last 200 years and condensate lines should last 30 days. Hoses should never leak.
Valves are a prime source of steam leaks. Paffel showed how one leaking valve can cost $11,000 per year. The primary reason valves leak is because they are purchased based on price rather than the leak rate. Even a brand new valve will leak if it is not suited for the application. “A Class 1 valve leaks like a river. Class 6 valves have the tightest shutoff,” he said. “If a cheater bar is used to turn off the valve, run! If it breaks the valve, you have 1 nanosecond to avoid a crisis.”
He offered several recommendations. For instance, pipe should never be threaded, because the thread is the weakest part of the pipe. Threaded connections are at risk of expansion and contraction from steam system startups and shutdowns, and subject to CO2 erosion and carbonic acid. Paffel recommends following the piping code and using welding or flanges instead of threaded connections.
|Sheila Kennedy is a professional freelance writer specializing in industrial and technical topics. She established Additive Communications in 2003 to serve software, technology, and service providers in industries such as manufacturing and utilities, and became a contributing editor and Technology Toolbox columnist for Plant Services in 2004. Prior to Additive Communications, she had 11 years of experience implementing industrial information systems. Kennedy earned her B.S. at Purdue University and her MBA at the University of Phoenix. She can be reached at firstname.lastname@example.org.|
“Steam traps are an option. However, the No. 1 failure of steam traps is people who don’t understand the system,” he said. “Steam traps won’t be effective if they’re undersized or installed incorrectly. My standard operating procedure for steam trap testing is 90 pages.”
When designing a steam system, you need to counter the corrosion effects on the condensate of the system, and counter the acid so you don’t have failure. Vent the air out of the system to avoid oxygen corrosion. Use ball valves, butterfly valves, or other types in lieu of packed valves. New types of expansion joints are leak free. Gasket material today has improved technology but you need to follow the torque pattern recommended.
Predictive technologies such as thermal imaging and ultrasound are effective for finding conditions such as steam leaks under insulation. “Where the moisture is dripping out is not necessarily where the leak is located,” said Paffel.
Root cause analysis (RCA) also is essential in the steam world, although it isn’t often done. “Start with the steam trap to determine the causes of failure,” Paffel recommended.
In summary, eliminating steam leaks and steam loss to the atmosphere requires changing in multiple areas:
- product selection
- system design
- installation design
- operation (follow SOPs)
- root cause analysis (a “must”)
- tube connectors and welded joints vs. threaded connections
- valves that will eliminate packing leakage
- valves that do not excessively leak internally
- stainless steel vs. carbon steel.
“Stop what you’ve been doing since 1941 and change,” he recommended. “It may cost more, but there will be no leaks. With steam, there’s only one way to do it, and that’s the correct way, period.”
|Roger Earley, Lubrizol|