After an oil leak, a large U.S. supplier of industrial, medical and specialty gases took another look at the risk it faced with the oil/water heat exchangers it uses to cool compressor lubricating oil at its various plants.
Its heat exchangers have oil on one side and cooling water on the other. Some of the plants have open-loop once-through cooling systems that discharge back to a river or lake, and if a heat exchanger were to leak oil to the water side, it potentially could pollute the environment and violate the company’s discharge permit. The company’s other plants are closed-loop with cooling towers, and an oil leak could cause decreased heat transfer efficiency from resulting bacteria growth, increased chemical costs and more frequent blowdown. Also, the oil could evaporate to the atmosphere or be discharged through blowdown to the environment.
After the recent oil leak, the gas supplier reviewed its heat exchanger maintenance practices company-wide, with the goal to be proactive and reduce the risk of unmonitored discharges. Early in the review, the company decided to immediately install continuous oil-in-water monitors. Some of the aging copper heat exchangers would eventually be replaced with titanium to help prevent corrosion, but that was going to be a lengthy and costly effort. Continuous monitoring would help each plant continue without the early added expense of replacing heat exchangers.
The company chose Turner Designs Hydrocarbon Instruments’ TD-1000C online oil-in-water monitor. Reasons cited for selecting the Turner unit include its high sensitivity to compressor lube oil and its low maintenance record in similar applications. Turner’s applications lab tested the Mobil DTE oil to a detection limit of 0.4 ppm, which gave the customer the confidence to purchase.
Because the TD-1000C detection limit is much lower than the discharge limit of any of the company’s compressor plants, the monitor can provide early warning of a leak before it becomes a major problem. Further, in plants with multiple heat exchangers on a single loop, if an oil leak is detected at the discharge end of the loop, strategic samples from each heat exchanger can be injected directly into the TD-1000C with a provided syringe to quickly locate the leak.
Monitoring Cooling Water for Leaks
August 18, 2009