Air supply

Published Sept. 21, 2012
By Mike W. Ray
Tinker Public Affairs

TINKER AIR FORCE BASE, Okla. -- If you can hear a leak of compressed air, inert gas or steam, "That's probably not good," says Paul Garnaas, Resource Efficiency Manager of the 72nd Air Base Wing Civil Engineering Directorate.

Compressed air is used to perform a myriad of functions at Tinker Air Force Base. It operates machine tools that are used to install and remove fasteners and rivets. It powers winches, robotics, and aircraft paint sprayers. It's used in hydraulic scaffolds that mechanics employ to repair jet engines and military aircraft, for cleaning benches and other work areas, for clean-up of parts, and in heating, ventilation and air conditioning controls.

This is, after all, an aircraft maintenance depot. Consequently, leaks are a continuous problem, "something we fight all the time," Mr. Garnaas said. Objects such as hose connectors, flexible hoses, equipment connections and elbows wear out, he noted. "These are common points of failure."

Compressed air is easy to control and simple to operate, but it's one of the most expensive utilities, "way above chilled water," Mr. Garnaas said. "You expend about eight times the energy for every pound of work produced from compressed air," he said.

Compressed air costs an estimated 23 cents per 1,000 cubic feet, Mr. Garnaas said. In comparison to compressed air, argon and helium cost $22 per 1,000 cubic feet, and nitrogen costs $56 per thousand cubic feet, Mr. Garnaas said. Consequently, repairing a leak quickly can result in a substantial avoided cost.

Even at that nominal cost, an air leak of 3 cubic feet per minute multiplies to 1.5 million cubic feet per year, at an estimated cost of $350 per year. It all mounts up. So far this year the 76th Maintenance Support Squadron has repaired leaks saving approximately $335,000 in compressed air cost and $210,000 in Argon gas cost.

A leak of compressed air or inert gas can be costly in more than one way. A leak also allows outside, humid ambient air to enter the system causing water to building up in the hoses and lines, and thus fouling machines and tools. Mr. Garnaas pointed out that even with Tinker's complex drying system where the compressed air is dried with refrigerated or desiccant dryers, a leak will allow moisture to enter the system.

According to Allen Logan, a Predictive Maintenance technician in the 76th Maintenance Support Squadron, leaks in argon and compressed air lines that were found by the PdM unit in 2010 and then repaired saved an estimated $800,000 - and resolved at least one perplexing production problem.

In an Oklahoma City Air Logistics Complex welding shop, several welds performed by veterans who'd been welding for 20 years or more were deemed unsatisfactory. The mystery was solved when an ultrasound device was used on the welding system; a leak found in an argon gas line was pulling in air and moisture that spoiled the welds, said David Robinson, chief of the Equipment Engineering Flight in the 76 MXSS. Repairing the leak improved the welds and derailed plans to purchase an auxiliary argon gas storage tank, he said.

Ultrasound equipment is used to detect various leaks such as vacuum, steam, inert gases and compressed air leaks, all of which are "big money losers," PdM Technician Mike West said.

Safety first, however. Do not use your hands to inspect an air, gas or steam leak, Mr. Garnaas warned. A high-pressure compressed-air leak could easily damage your flesh, and leaking steam can burn you.

An air or gas leak should be reported to Tinker Support Services at 734-3117, "or tell your supervisor," or write a maintenance work order, Mr. Garnaas advised.

"The biggest issue we have is simply getting people to notify someone when they hear one of those leaks," he added. "Periodically check your area. If it's hissing, it probably shouldn't be doing that."