How can a plant improve its leak detection efforts? When leaks become large enough you can hear them. So, heighten awareness of people in each department. Ask them to report audible leaks. If you don’t already own ultrasonic leak-detection units, consider purchasing such equipment and training one or more individuals in each department to perform audits. Recognize these air/gas leak auditors as “energy conservation champions.”
How important is the quality of the detection equipment? Don’t stint on hardware. Investing in top quality devices makes your job easier and ultimately saves you time and thus money. In the end you will thank yourself for using a reliable instrument. Keep it properly calibrated and take all necessary steps to maintain it.
Find All The Leaks
It’s possible to feel or hear some leaks. Indeed, an easy way to confirm the existence of large leaks is to hold a slightly moistened hand near the leak site; the cooling effect will be immediately felt. To spot other leaks, rely on a device that detects the ultrasound produced by a leak.
Chemical processing facilities generally use a copious amount of nitrogen gas in addition to instrument air. Depending on the chemicals being produced, mandatory breathing-air hookup stations may be located at strategic points. Performing a leak audit may involve dealing with unique equipment and processes. For instance, to help prevent hazardous emissions, pumps may incorporate gas-lubricated double seals. These seals use dry nitrogen as a barrier gas to prevent process fluid leakage to the atmosphere. Pressurized stainless steel seal pots beside each pump have many fittings and connections that require ultrasonic scanning. Leaks may appear at threads, misaligned ferrules or where galling of stainless steel fittings has occurred. Because pressures are carefully regulated at each pump, there should be filter/lubricator/regulators — each needs to be scanned.
Tips and tricks. The Allen screw on the opposite side of a pressure regulator gauge can loosen, typically due to vibration or lack of factory-applied sealant, resulting in a leak. Other important areas to check include packing glands of small shut-off valves and shaft seals of air- or gas-operated process valves. In addition, carefully scan relief valves, nitrogen blanket vents, liquefied gas pumps, manhole covers on vessels, flange gaskets, solder joints, hoses, tubing connectors and quick-connect fittings. Don’t overlook overhead lines (Figure 2). Parabolic microphones can help there. They increase the range of standard scanners, enabling leaks to be pinpointed without climbing into labyrinths of overhead piping.
Unique challenges. The corrosive environments typical of many chemical processes can cause leaks. For example, a facility near the ocean discovered that piping for nitrogen distribution had deteriorated from the saltwater mist — leading to a whopping energy loss of $600,000/year from hundreds of pinholes.
Most chemical plants have extensive networks of steam and product piping beside cable and tubing trays. Many times contractors don’t properly secure tubing for compressed air or inert gas. If tubing touches un-insulated steam piping, it melts and creates a large leak.
Plastic tubing can experience a number of other problems. Sometimes small snap rings loosen at the connection points to air-operated valves. This can happen because too much oil or other contaminants are present in pressurized gas or because of vibration. Over time plastic tubing can develop pinholes or splits due solely to age or proximity to specific chemicals.