The Olefin VI ethylene cracker has been operating at ICI's Wilton, Teeside site since 1979. It is 20% owned by BP Chemicals. The plant is normally shut down for maintenance every three years - an operation that lasts 5-6 weeks and incurs costs of £6-8 million as a result of lost production time and product wastage as well as the cost of maintenance itself. Some 1,000 contractors are typically employed.
The 1990 overhaul was "a particularly difficult one", Dr Jim Whiston, ICI's Safety, Health and Environment Manager told a Confederation of British Industry conference on greening the supplier chain in April.
By the end of the project, the plant was leaking at 1,000 points from poorly fitted joints and flanges. The result was that several hundred tonnes of gases, including methane, ethylene and propylene, had to be burned in a flaring operation that, in Dr Whiston's words, "lit up the skyline".
ICI usually aims to ensure that flaring does not go on for longer than a day, though it has been known to last up to a week. In 1990, it received "very many" complaints from the local community about the light and noise of the flare. Dr Whiston concedes: "There was major community concern. We were not a good neighbour then." The value of the gases needlessly burned was around £2,000 per tonne.
Gases are flared when leaks are found in the equipment during start-up. Although there may be no more than a whisper of a leak, the plant is under several hundred pounds of pressure, thus magnifying the effect. Material and pressure loss caused by leaks interferes with the cracker's process dynamics, so that any product made at that stage has to flared off.
Following the troubled 1990 operation, ICI decided to treat the 1993 overhaul as a major project, with potential problems elucidated and debated before work began. In addition, environmental concerns were placed at the top of the list alongside health and safety.
ICI management carried out a post mortem of the 1990 operation with managers of the contracting firms that were to be involved in 1993. A project team subsequently designed a series of training modules for the engineers and other personnel who would be carrying out the work. Training took place over two to three months.
Dr Whiston says that the education process was more a matter of "re-training" than teaching contractors anything new. He told ENDS: "It was a question of re-emphasising to people the importance of the job in hand, explaining why the job has to be carried out very carefully, and what the consequences would be otherwise. All the right tools have to be used and more care should be taken than with a normal job. These fellows get a lot of jobs to do during the operation and you have to get it into their minds that every job they do is the most important of their lives."
A system of mutual auditing was also established, with contractors auditing each others' work to ensure it had been carried out satisfactorily. An overall audit team for the first time had an eye to environmental impact as well as the safety and health features of the project.
More emphasis was also placed on better communication between contractors carrying out different activities, by publishing a health, safety and environmental newsletter every day of the operation. In addition, the local community was warned of the operation in advance.
The result was that the number of leaks experienced during the 1993 overhaul was reduced to just 20, the amount of gas flared off was halved, and not a single public complaint was received.
Dr Whiston stressed that there were no fundamental changes to the mechanics of the 1993 operation, simply a revision of the way in which contractors worked together. He declined to give the exact costs of the 1990 and 1993 operations, but noted that savings of a few million pounds were not an unrealistic estimate of the benefits of flaring less material. The cost of the training exercise was insignificant by comparison.