by Alan S. Bandes, UE Systems, Inc.
According to Lt. Raymond Kay, Hazardous Materials (HAZMAT) Officer with the Orland Fire Protection District and HAZMAT instructor with the University of Illinois, “a single house fire is serious. But nothing compared to a leaking chlorine cylinder that jeopardizes the lives of 80,000 – 100,000 people.”
Lt. Kay is in charge of a regional response team that covers approximately 120 square miles in a 14-community area 25 miles from Chicago. “We respond to emergency or potential emergency conditions in public and private areas,” Kay said. “For example, an employee might call us about a leaking cylinder in a storage room. If the leak has the potential to affect the public, i.e. the leak travels outside the company’s fence line, our job is to go to the site immediately and mitigate the leak. Then it’s up to the company to make repairs.”
Lt. Kay’s HAZMAT team uses state-of-the-art ultrasound technology and a variety of other diagnostic instruments to pinpoint and identify the source of deadly leaks. Kay’s team has investigated everything from chemical spills at a chemical manufacturing facility to poisonous leaks at waterways.
Ultrasonics Pinpoints the Tiniest of Leaks
Lt. Kay discussed a recent call from an employee at an ice arena. “A series of pipes runs through the building and one of them was leaking,” said Kay. “We used our ultrasonic instrument (an Ultraprobe 2000 manufactured by UE Systems, Inc. in Elmsford, New York) to identify the location of the leak so the facility’s crew could isolate it and make repairs.”
An ultrasonic instrument quickly and accurately pinpoints leaks or other irregularities that are inaudible to the human ear. A portable, handheld unit, it is ideal for quick spot checks.
As any gas passes through a leak orifice, it generates a turbulent flow with detectable high frequency components. Ultrasonic instruments electronically translate these high-frequency sounds down to the audible range. By scanning the test area with the ultrasonic detector, an operator can hear a leak through a headset as a rushing sound and note it on the instrument’s meter. The closer the instrument is to the leak, the louder the rushing sound and the higher the meter reading. Should ambient ultrasonic noise be a problem, a rubber focusing probe may be used to narrow the instrument’s reception field and to shield it from conflicting ultrasounds. In addition, frequency tuning dramatically reduces background noise interference to provide ease of ultrasonic leak detection.
The strategy Lt. Kay’s team uses to detect leakage is straightforward. “Oftentimes, people are not sure what they’re seeing or smelling so they call us in to investigate,” Kay said. “We ask questions, look at material safety data sheets and floor plans, learn what the facility is used for, and what products are employed. If hazardous materials are involved, there’s the possibility of toxicity so we wear protective gear.”
“The first step at the ice arena, for example, was to identify what kind of product was leaking from the pipes,” Kay continued. “We spoke to the owner who told us that anhydrous ammonia, which is corrosive, was used as a refrigerant. Our next step was to take our ultrasonic instrument and move along close to the pipeline where the leak was reported, noting turbulence or change in flow on the unit’s meter. Within an hour the team had isolated the leak and the facility made the necessary repairs.”
Before Lt. Kay and his team enter a potentially dangerous area, they must be certain that the situation is under control and does not threaten the safety of the response team. For example, escaping steam from faulty steam valves can cause third degree burns. Kay said they use the Ultraprobe equipped with contact probe attachment to verify that Lock-Out and Tag-Out procedures (a process for controlling hazardous energy) have been properly followed.
To verify that a steam valve is working, an operator touches the ultrasonic instrument upstream of the steam valve and takes a reading. Then he touches downstream of the valve and compares intensity levels. If the sound is louder downstream, the fluid is passing through. If the sound level is low, the valve is closed and leaking.
Distinguishing Toxic Leaks From Nuisance Leaks
Lt. Kay’s HAZMAT team employs a combination of technologies to distinguish nuisance leaks, i.e. air leaks and hydraulic oil leaks, from toxic or flammable potentially life-threatening leaks, i.e. chlorine and sulphur trioxide that maybe stored under pressure in cylinders or in various piping systems. To detect leaks of methane (obtained commercially from natural gas), and other combustible gases, Kay’s team uses infrared thermography, pH paper and Wheatstone bridge (a circuit for measuring an unknown resistance by comparing it with known resistances, aka a combustible gas indicator) technologies.
“Not all chemicals have only one associated hazard,” Kay said. “For example, anhydrous amonia, a common industrial refrigerant, will burn and can explode; it is also corrosive.”
According to Lt. Kay, ultrasonics is becoming an increasingly popular technology with HAZMAT crews. “The technology also is proving to be valuable when responding to potential threats to the environment or in the event of terrorist attacks,” he concluded. “Some of the agents that terrorists use need to be deployed in aerosol form and a tool like ultrasonics could help us identify the source of the potentially lethal material. A HAZMAT team’s objective is to prevent injuries and save lives. If we can stop a leak before disaster strikes, we’ve done our job.”