Home Magazine Mothballing – a guide

Mothballing – a guide

A result of the coronavirus crisis is that across much of industry, valuable equipment could lie unused for months. Bernie Price, president of Polaris Veritas, explains how to preserve it so that you can reactivate production quickly and without undue cost when the time comes

The Covid-19 virus has wreaked havoc with the global economy, forcing closure and immobilisation of plant and equipment worth billions of dollars. Typically most organisations’ actions have been taken hastily as a knee-jerk reaction to the crisis. This can result in diminished value, or even destruction of the value of assets, which can preclude the possibility of reactivating them once business rebounds.

However all is not lost if a little informed action described here is taken.  A contingency plan can be made even if we don’t know the duration of this forced shutdown.

Here’s how to go about mothballing your equipment so it can readily be reactivated when the time comes.

Primary action

Write and communicate a mothball plan based on time – one month; six months; 12 months; three years and so on.

Engaging in a well-planned process of deactivation/mothballing can pay off whether the intention is to  reactivate or sell the assets. If properly prepared for shutdown, the equipment and facilities (including buildings, distribution systems and even organisational teams) can retain most of their value with just a little forethought.

 Be aware of the need for routine reporting of “fitness for purpose” and condition of safety systems. Remember the odds are that the facility or plant will be restarted by some third party, not you.

In my experience through three boom/bust phases in the process industries and energy over 40 + years, 75% of idled facilities and plants were reactivated in some form.

Key facts about a one-year mothball plan

  • It typically cost less than 0.5% of the replacement value to set up
  • It should cost 5% or less of the replacement value to reactivate a well-preserved unit
  • Restarting long-idled facilities without mothballing cost 20+% of replacement value. (This often is a deal breaker and they are never restarted).          

Let’s look at what should be done and describe specific products and techniques. These concepts are not new or experimental – they’re based on 40-plus years of documented experience.

The approach

The enemy: –

  • Galvanic/ Bio Corrosion,
  • Mould, Mildew, etc.
  • Moisture
  • Loss of time-based data/knowledge.

(Though much depends on local conditions, wetter and colder environments pose greater challenges for handling humidity, while blowing dust is an issue in desert regions).

Avoid common mistakes

Here are ten frequent errors that can damage or even doom a facility, organisation or plant’s prospects:

  • 1. Treating news of an impending shutdown as a “knockout” blow rather than a “knock-down” one. In today’s global marketplace, pitfalls and setbacks are almost everyday events, and organisations have to become adept at handling them to survive: this is part of that pattern. With adequate preparation, it can be turned into just another setback.
  • 2. Not allocating responsibility to an individual beforehand for writing a list of possible scenarios during tough times. This person should have enough clout to implement the chosen strategy whether the fateful scene develops suddenly or slowly unfolds.
  • 3. Despite massive pressure, not making sufficient funds available to execute the initial shutdown and preservation strategy.
  • 4. Not choosing the right type of long-term equipment caretakers. Those selected often are security or ex-supervisory personnel rather than experienced operators or craftsmen with intimate knowledge of the equipment.
  • 5. Failing to maintain operating permits – “grandfathered” ones might be unobtainable in the future if allowed to lapse.
  • 6. Not removing all process materials. Dealing with even innocuous materials left in a production unit in the long-term is likely to cost five times as much as at initial shutdown. Plus the current operations people are familiar with all the hazards, while those in the future might not be.
  • 7. Not seeking expert advice on equipment preservation, resulting in not getting the best value for money.
  • 8. Not involving the hourly workforce in the shutdown and mothball plan. Experience has shown that involving operators and mechanics can very much improve both the quality of the shutdown plan and its execution.
  • 9. Failing to keep good records and not clearly marking and keeping track of what has been done to preserve an item of equipment during deactivation, making it too easy for the reactivating crew (a different group of people) to miss the fact that a filter, line blind, or internal component has been removed or added, with serious consequences at start-up.
  • 10. Not keeping safety programmes and routine audits active to avoid accidents. Idle plants with small maintenance crews operating at a very relaxed tempo can be dangerous places.

Materials, equipment and techniques

A useful analogy in developing a mothballing strategy is to consider how plants fend off fire hazards by eliminating one of the fire triangle’s three elements – that is, heat, a fuel source and oxygen. Similarly, in mothballing, at least one of the three enemies of age-related deterioration mentioned above must be removed – 1. galvanic action, 2. a conducting medium or electrolyte, and 3. oxygen.

In simple terms the aim is to do the following:

  • separate dissimilar metals
  • protect surfaces that could be attacked — with a covering (even if only a few molecules thick)
  • dry out or remove the conducting medium (electrolyte – air or gas): corrosion can’t occur when parts are stored in environments with relative humidity below 40%); and
  • eliminate any oxygen and sources of chemical or biological attack.

Covering the suface to be protected

Materials and equipment that can be used for covering or protecting surfaces are:

  • Simple liquid protective waxes and liquid polyvinyl chloride (PVC) coatings. These can be sprayed on to any clean, dry surface to protect it. Light waxes are chosen for surfaces where subsequent removal process such as high-pressure washing might damage the substrate. PVC will form a tough, flexible and waterproof skin that will withstand temperature extremes, thermal shock, differential substrate movement and impingement, even when sprayed onto webbing to form a cocoon.
  • Heat-shrinkable desiccant plastic films. Such films containing desiccants are ideal for enclosing individual machines that have been cleaned and dried.
  • VCI-covered polyethylene films. These suit wrapping individual smaller components.
  • Volatile phase/corrosion inhibitors (VPI/VCIs). Such materials generate protective vapours even at room temperature. They come in a number of convenient forms, including time-release vaporisers, sprays, plastic bags and films, powders, oil additives (see VSIs below) and coatings. They are adsorbed (just a few molecules thick) on metallic surfaces of equipment and can prevent corrosion for up to two years.

They actually have surprisingly low vapour pressures and are solid or liquid at room temperature. Though there are many chemical compounds in use, the most common form of VPI is a salt of an amine (such as the carbonate salt of dicyclohexylamine) and a weak acid. Research has shown that they work by disassociation of the amine and the acid; the two volatile components then recombine on the metal surfaces.

While most VCIs are environmentally friendly and create no safety hazards for employees, some are suspected of being harmful. Most contain no toxic substances such as nitrates, chromates or volatile organic compounds (VOCs). (Note: products containing VOCs shouldn’t be used in combination with a desiccant.)

  • Vapour space inhibitors (VSIs). These concentrates can be added to lubricating oil systems (in internal combustion engines and the like) when equipment isn’t going to be completely filled. They essentially boil at ambient temperatures to exclude air, leaving an oily residue.
  • Chemical inhibitors. Incorporated into liquids, they remove unwanted products while preferentially inhibiting their attack on the body of the container. (Anti-freeze sometimes used in mothballing contains them.)
  • Biocides. Such materials prevent microbial growths in water and fuels such as gasoline and diesel fuel.

Electro-chemical protection

Separation of dissimilar metals is the simplest approach

Sacrificial anodes: Best known for their use on ships these are usually made of materials such as magnesium or aluminium. In industry these are used in tanks that can’t be drained of their contents.

Removing oxygen

Chemical oxygen scavengers. These compounds are added to fresh water used to displace more corrosive liquids in systems that can’t be effectively cleaned or dried out

Removing moisture (Conducting medium)

Removal of moisture stops or reduces corrosion or chemical deterioration. If the stoppage is anticipated to be very short-term, start with desiccants. These are placed in an enclosed space which can be sealed.

Desiccants. Numerous solids can be used to absorb water from gases (air) or liquids.

Dehumidifiers. Such equipment removes moisture by one of two methods, the refrigeration principle or two-cycle rotary (wheel) heated desiccant absorption. These are simple from an engineering point of view but tactically complex to implement.

As a simple example of how effective dehumidifiers can be, friends who have left one running in older homes vacated for the winter report a 100% improvement in the condition of their properties on return in spring.

Because the individuals doing the initial deactivation often aren’t those who’ll be doing the reactivation, take pictures, encourage the team to visibly identify various components and equipment condition, even if this is just by using chalk or felt tip pens.

In your preservation plan explicitly prohibit removal of parts, essential systems or people familiar with the facility: you will have a head start over the opposition. I vividly recall the experience of a major US chemical manufacturer after it shut down a product line in the 1960s. Other operations on site began to purloin critical parts to keep themselves going. When the market recovered four years later, little of the plant was left to restart. The company was forced to exit the market for that product.


Now, getting into the detail of specific equipment and hardware in use. Consider a plant in Europe or the central US that could restart in from six to nine months to perhaps several years. Please note this is only a guide and isn’t intended to be comprehensive in any way.

Tanks, pressure vessels and pipework. In all cases ensure these are as clean and dry as possible. Insert line blinds to create manageable zones that can be slightly pressurised (0.5+ psig) using nitrogen or dry air. Provide a small flow and arrange for some simple telltale mechanism to show pressure, flow and level of humidity (such as indicator cards).

For large enclosures, use an appropriate-capacity commercial dehumidifier or maybe even consider a total “tented” enclosure. For vessels, tanks and containments that must be kept full of liquid, employ some form of oxygen scavenger or anti-biological growth chemical (see Boilers). If a pipework system contains any traps, remove their internals and clear all strainers.

Boilers. These can be laid up using one of two methods either – long-term dry or wet hydrazine. The latter involves leaving the wet side of the boiler, economiser and superheater – full of treated feed water (dosed with 15% hydrazine, a proprietary solution, and then pH adjusted to raise alkalinity to a minimum pH of 8.3) while supplying the fireside with heated air with desiccant as a backup.

Both waterside and fireside points should have new gaskets, except for furnace hot-air entry inspection and exit points.

Pumps, engines, compressors and machinery. To minimise internal corrosion, close off all vents and openings and completely fill the casing with the manufacturer’s recommended lubricant. Alternatively, add VPI in the correct proportion to the lubricating oil.

For large compressors, turbines, and the like, use a portable filtration cart with water-absorbing elements to remove any free water in existing oil soon after shutdown.

For diesel and gasoline engines, drain fuel systems and add biocide to remaining fuel to prevent growth of bioslime.

To minimise external corrosion, spray either a light wax or liquid PVC on unpainted surfaces.

Instruments and controls. Maintain the driest possible conditions for both electronics and external field devices, including sensors, transmitters and valves, by strategically placing desiccant packages and sealing the enclosures. Supplement this by putting small containers of VCI.

Instruments that would normally be in contact with process materials should be removed, cleaned, protected and marked for immediate local storage.

Electrical enclosures. Seal and insert bags or wraps of desiccants or containers of VCI. Alternatively, heat using individual strip or built-in heaters.

Motors and generators. Clean exterior, grease and apply protective covering. Lift carbon brushes from commutators/slip rings. Where sleeve-type bearings are fitted, add VPI concentrate to the lubrication system. Include packets of desiccants if completely sealing a unit.

Periodically – nominally monthly – exercise equipment by rotating it several times and leaving it at a different (90°) angle. Where humidity controls have been set, monitor these at least weekly; where chemical controls are used, check these every three months. In addition, long-term lay-up requires regular monitoring of motor/generator internal resistance (megger), as well as tank oxygen and humidity levels.

Auxiliaries. Don’t forget that in most cases fire protection systems and alarms still need to be maintained and powered up. It should be noted that fires are common  in dried-out wooden cooling towers. If batteries are used, disconnect them and smear terminals with petroleum jelly. Fully charge vented-type lead-acid batteries, then drain and flush them with distilled water.

Don’t squander your assets

It makes sense to think strategically about deactivation. Proven techniques can preserve the functionality and value of assets for a small outlay, albeit at a time of extreme financial pressure. Proper mothballing can pay off substantially, whether an operating company aims to eventually restart, sell or dispose of its assets.

Bernie Price is president of consultancy Polaris Veritas Inc. His current activities include assessments of organisations and plant related to Due Diligence, Error Proofing and Organisational Efficiency for several chemical process plants.