Mothballing requires more than mothballs
When economic or other circumstances require a production site to be shut down for an extended period of time, appropriate measures are necessary to ensure that the work can be reliably restarted . Otherwise, expensive problems may appear later. A strategic, tactical and documented approach is essential. Specialist Bernie Price shares his experience of how to adequately deal with this issue.
Bernie Price (81) graduated as a Bachelor in Mechanical Engineering from the University of South Wales in Newport. He gained his professional experience in the chemical process industry and in oil well drilling, mostly in the United States. Later, he founded Polaris Veritas. Today, he is semi-retired.
Price started ‘mothballing’ with oil rigs. His later experiences in the maintenance of chemical process plants made him very aware of possible pitfalls that await the unwary. The multinational he was working for had decided to temporarily close one of its production lines. When it tried to restart the line a few years later, it turned out that about a third of the parts (instruments, pumps, etc.) had disappeared.
“When a critical part was urgently needed to keep one of the other plants in operation, it was ‘stolen’.” Lower-level engineers and managers turned a blind eye to what was happening. Some years later, a restart was being considered and the uncomfortable truth was covered up.”
Lost count
During his career, which spans more than fifty years, Price has lost count of the number of plants that were shut down, not adequately cleaned and left without maintenance “because of the false logic that no immediate revenue means that expenses have to be reduced to zero.”
Such incidents made it clear to him that mothballing needed assigned responsibility and planned procedures along with the development of a structured approach. During the 1997 oil crisis, Price was tasked with doing just that for a Houston-based drilling contractor. The oil price had fallen so far that certain rigs and production platforms were no longer economically viable and had to be temporarily shut down. As it was obvious these procedures and the methodologies could also be used successfully in other sectors, they were shared with several organizations. Price started Polaris Veritas, not only for mothballing, but also to coach companies through the process of improving the reliability and operation of equipment.
Threats
While the issues are complex and varied, there are tools and techniques to solve all of them. Achieving optimum damage/corrosion reduction at the lowest cost largely depends on getting a good estimate of duration.
“Mechanical, electric, liquid, steam and gas handling systems and the combination of materials associated with these systems all require a concise approach to corrosion control which is of principal concern. In an idle plant, corrosion of these components occurs for several reasons . Idle plants and their equipment are subject to temperature fluctuations, condensation, weeds growing, vermin and other conditions that cause corrosion. Corrosion can occur very rapidly in certain combinations of conditions. Adequate, routine inspections are essential. Generally, it should cost only 5% or less of the ‘plant replacement value’ to reactivate a well-preserved unit. Restarting an inadequately mothballed plant will cost more than 20% of that value which in many cases becomes a deal-breaker.”
The maintenance costs aren’t limited to physical maintenance. “Attention should also be paid to the extension of all kind of permits and licences. After existing licences have expired, it can be very difficult to acquire new ones. During the shutdown, legal restriction can become stricter and NIMBY has an increasing tendency to appear .”
Possible scenarios
“First of all, you need to have a clear view of how to mitigate, if not defeat, the two primary foes, corrosion and mould. Much depends on local conditions and the microclimate. Then, you should award a single person the responsibility to sum up possible scenarios and give them enough clout (power) to implement the chosen strategy. The top of the company needs to be involved to make sufficient funds available, not only for the initial shutdown, but also for the preservation strategy. Sometimes, it takes a major effort to convince the upper management that a shutdown and its accompanying measures are necessary, because it is the kind of decision nobody wants to take responsibility for.”
Price insists on involving the mechanics and operators in the shutdown plan. “They can greatly improve both the quality of the shutdown plan and its execution. For the long-term caretaking of the equipment, select craftsmen with intimate knowledge of the equipment. all too often, security or ex-supervisory types are selected for this task. In a larger plant, they must ensure that no critical components are pirated for use elsewhere . It is good practice to take photos of the existing situation just before the shutdown. When dealing with very old equipment, examine what an upgrade would cost before spending money on the maintenance of depreciated components. It also important to speak with your insurance company about the implications of the operation for your risks and on your policies.”
Maintenance
“Examine every piece of equipment individually and write a specific mothball methodology for ongoing maintenance. Not only record but clearly and physically mark what has been done to preserve the item of equipment during deactivation. Make sure safety programmes and routine audits – e.g. every three or six months – are kept active to avoid accidents. Be aware that the reactivating crew will probably be a different group of people. They can easily miss that a filter, line blind or internal component has been removed or added. This can have serious consequences during a future start-up.”
Regulatory maintenance implies equipment tests.
“For some equipment, such as boilers, this is even a legal obligation in most countries.”
It also is essential to remove all process materials. “Even innocuous materials left in the unit can create costs that, in the long run, are many times more than at the time of the shutdown. Find experts to give advice on specific equipment preservation, to get your money worth.”
Corrosion
For the preservation of the equipment, several methods and applications are available.
“As temperature and humidity change, equipment actually breathes. Common driving forces for age-related deterioration are galvanic action, which needs a conducting medium or electrolyte and oxygen. The fundamental approach to stop or slow down deterioration is to remove one or more of those three. Simply put, separate dissimilar metal surfaces that could be attacked, dry out or remove the conducting medium and eliminate oxygen and sources of chemical or biological corrosion. In this context, you can open all the valves, because in many cases they contain different metals.”
Corrosion cannot occur when parts are stored in environments where the relative humidity is kept below 40%.
“The use of dry air/desiccants/gases should be considered before protective coatings. The obvious use of protective waxes and liquid PVC coatings is cost-based. These can be sprayed onto any clean and dry surface.”
Volatile phase/corrosion inhibitors (VPI/VCI) generate protective vapours even at room temperature. They are adsorbed into the enclosed metallic surfaces of equipment and can prevent corrosion for up to two years. Most VCI do not create safety hazards for the environment or employees, but some are suspected of being harmful. Vapour space inhibitors (VSI) are oily concentrates that evaporate and leave an oily coating. These can be added to lubricating oil systems, which ’should not be completely filled.”
Dry, clean and covered
“Heat-shrinkable plastic film containing desiccants is ideal for enclosing individual machines that have been cleaned and dried. VCI-covered polyethylene film is suitable for wrapping smaller, individual components. Chemical oxygen scavengers can be added to fresh water used to displace more-corrosive liquid in systems that can’t be effectively cleaned or dried out. Chemical inhibitors, when incorporated into liquids, prevent unwanted products from attacking the body of containers. Some antifreezes used in mothballing contain them. It is essential that tanks, pressure vessels and pipework be left as clean and dry as possible. Tanks that cannot be dried can be protected by sacrificial anodes. Biocides are used to prevent microbial growth in water and fuels.”