TOPIC: Entrained Gas Contamination in Lube Oil System of Large Gas Compressor
ASSET: Acetylene Gas Compressor
DATE: July 13, 2015
At a large Petrochemical facility there was ingression of Acetylene Gas through a leaking seal into the 3,000 litre lube oil system of a Gas Compressor. High concentrations of light end hydrocarbon gases (including H2S, Benzene, Toluene, and Acetylene) drive down the flashpoint of compressor oils to very low and dangerous levels, and they also adversely affect the viscosity of the ISO VG 32 compressor oil, inhibiting its ability to act as an effective lubricant.
Because the Gas Compressor could not be shut down to fix the seal leak without incurring a tremendous cost in manpower and down-time, and because the next scheduled turn-around was not until 2017, operators at the plant were “sweetening” the oil on a regular basis in an effort to maintain a proper flashpoint and viscosity. New oil was introduced through the fill port while old oil was drained off of the bottom. The cost to purchase new oil is very expensive (roughly 5,700 litres per month at $6.32 per litre = $36,000 per month x 12 = $430,000 per year), with an additional labour cost involved as well.
As an alternative, the plant decided to implement a trial 20 GPM Vacuum Dehydration Oil Purification System (VDOPS) to re-circulate the lube oil reservoir in a kidney-loop configuration and continuously remove entrained gases from the oil as the compressor was running. The VDOPS needed to be suitable for Class 1, Division 2, Groups B, C & D hazardous locations, and the gases that were removed from the oil via “vacuum distillation” had to be plumbed to a flare from the discharge of the vacuum pump. While the VDOPS was recirculating on the reservoir, excellent results were achieved and well documented.
Return on Investment:
Due to the implementation of a 20 GPM Vacuum Dehydration Oil Purification System on this Gas Compressor, and because of the successful performance and results, the plant no longer needs to “sweeten” the oil at a cost of $430,000 per year. After the trial, a new fully equipped VDOPS was put in place within weeks.