Flare line cleaning”on-line” restores efficiency
The Germany-based facility of this global oil and petrochemical complex refines crude oil and produces a variety of hydrocarbon products, including ethylene, propylene, benzene, toluene, xylenes, and methanol. Combustible waste gases from all processes are offloaded into a single flare line for burn-off. Bespoke ‘fast clean’ technology was developed by Tube Tech in order to clean a severely fouled refinery flare line in Germany. The flare line cleaning was completed on-line and the back pressure in the line reduced to safe operational levels.
- Back pressure levels exceeded allowable limits during emergency blow down in the 150 metre refinery flare line as resistance to flow increased.
- The flare line was restricted by approximately 40% overall pyrophoric and sulphurous sludge deposition.
- Client’s own inspections suggested there were substantial sections of the pipeline badly restricted by this soft, mud-like sludge.
- Taking the flare line off-line for cleaning meant the entire refinery would have to shut down.
- Operational and cost implications of complete shutdown would be substantial.
- Client hoped to limit any such impact by conducting the accomplished during the shutdown.
- Tube Tech surveyed the flare line and the client provided digital images, isometrics and inspection records.
- Surprising the client Tube Tech reported that the flare line could be cleaned online.
- If it could be achieved, while addressing all safety issues, it would be a world first for the oil industry.
- The flare line clean could then be taken out of the shutdown and be done at the client’s convenience.
- Tube Tech demonstrated their technology on a full-scale mock-up of key sections of the flare line at its UK operations centre.
- The client’s consultants witnessed a successful on-line trial, which demonstrated multiple fail-safes.
- A bespoke seal coped with temperatures and pressures inside the flare line and prevented oxygen and spark ingress and the escape of toxic gases.
- The major technical difficulty was to design seals to access 25mm valve ports located at intervals along the length of the flare line.
- Ultimately, only two points of entry were used.
- Cleaning was carried out using pulsed high-pressure jetting lances designed to be heat and scratch resistant when fed into the small 25mm entry points.
- All three systems devised for the project were trialed on the life-sized mock-up.
- Locating the deposits and establishing their level and density before cleaning was carried out by Tracerco, using gamma ray-based inspection before, during and after cleaning.
- Intrinsically-safe video probes were used by Tube Tech through the 25mm ports to take digital images before and after cleaning.
- The objective was to reduce the deposition level within the flare line by removing as much sludge as possible, to level the remaining deposit and achieve an 80% cleanliness level in order to reduce excessive back-pressure.
- Some entry points turned out to be corroded shut or obstructed by weld intrusion, but Tube Tech’s ‘design-on-the-run’ reputation came to bear and equipment was modified to accommodate this unforeseen additional challenge.
- In just five days the cleaning standard had been achieved.
Tube Tech Comment
Mike Watson: “Based on the client’s sample analysis, we came prepared for soft, mud-like deposits. Actual samples found during removal were concrete-like lumps, commonly known as ‘sulphurcrete’ and not just sludge! We were, however, still able to wash loose concretion downstream to an interceptor tank. Whilst our objective had been achieved, we offered to return with appropriate equipment and a personal guarantee to all remaining concretion at some future date.”
Mike concluded: “This was the first time an on-line clean of a flare line had been accomplished. We have already designed more powerful equipment, capable of tackling any unexpected deposits, just in case another similar opportunity presents itself anywhere in the world. A considerable digital video archive of information and knowledge was built up during the exercise, which means we can repeat the exercise any time in the future.”