Today’s weak global economy is forcing closure and immobilization of plant and equipment worth billions of dollars. Unfortunately, such actions usually are done hastily and typically against a background of acrimony. Even worse, they can diminish or even destroy the value of assets and preclude the possibility of reactivating them once business rebounds.
Two major plant dismantling/second-hand equipment vendors recently told me that when the decision to shutdown comes most companies remove anything that could present an immediate danger and essentially close the doors and walk away from millions of dollars worth of equipment. Leaving assets “as is” to deteriorate can make them suitable only for scrap in just a matter of months. Yet, it’s a fact that an unused plant — if properly prepared for shutdown and left in fairly good condition — can retain much of its value. Engaging in a well-planned process of deactivation/mothballing can pay off whether the intention is eventual reactivation or sale of assets.
In my experience through three boom/bust phases in the process industries and oil well drilling, 75% of idled plants or rigs eventually were reactivated in some form. The bottom line is that while it only should cost 5% or less of Plant Replacement Value (PRV) to reactivate a well-preserved unit, restarting an inadequately mothballed plant will cost 20+% of PRV. This often is a deal breaker.
So here, we’ll look at what should be done and describe specific products and techniques. None of these are new or experimental — there’re 40+ years of documented experience for some.
It’s essential to have a clear view of how to mitigate if not defeat the constant foes of galvanic/bio corrosion, mold, mildew, etc. While much depends on local conditions, wetter and colder environments pose greater challenges for handling humidity, while blowing dust is an issue in high desert regions.
A useful analogy in developing a strategy is to consider how plants fend off fire hazards by eliminating one of the fire triangle’s three elements — i.e., heat, fuel source and oxygen. The three corresponding elements for age-related deterioration are a driving force such as galvanic action, a conducting medium or electrolyte, and oxygen. The fundamental approach to stopping or slowing deterioration is to remove one or more of the three.
In simple terms we aim 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.
Materials and equipment we can use are:
Liquid protective waxes and liquid polyvinyl chloride (PVC) coatings. These can be sprayed onto any clean dry surface to protect it. Light waxes are chosen for surfaces where a 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.
Volatile phase/corrosion inhibitors (VPI/VCI). Such materials generate protective vapors even at room temperature. They come in a number of convenient forms, including time-release vaporizers, sprays, plastic bags and films, powders, oil additives (see VSI below) and coatings. They are adsorbed (just a few molecules thick) onto metallic surfaces of equipment and can prevent corrosion for up to two years.
They actually have surprisingly low vapor pressures and are solid or liquid at room temperature. While there are many chemical compounds in use, the most common form of VPI is a salt of an amine (e.g., 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 VCI 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 (VOC). (Note: products containing VOC shouldn’t be used in combination with a desiccant.)
Vapor space inhibitors (VSI). These concentrates can be added to lubricating oil systems (internal combustion engines, etc.) when equipment isn’t going to be completely filled. They essentially boil at ambient temperatures to exclude air, leaving an oily residue.
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.
Chemical oxygen scavengers. These compounds are added to fresh water used to displace more-corrosive liquid in systems that can’t be effectively cleaned or dried out.
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.)
Desiccants. Numerous solids can absorb water from gases (air) or liquids.
Biocides. Such materials prevent microbial growths in water and fuels like gasoline and diesel fuel.
Sacrificial anodes. Made of materials such as magnesium or aluminum, they are used in tanks that can’t be drained of their contents.
Dehumidifiers. Such equipment removes moisture by one of two methods, the refrigeration principle or two-cycle rotary (wheel) heated desiccant absorption.
You must couple a long-term strategic approach with a series of medium-term tactics; detailed plans are needed. First guesstimate how long the shutdown is probably going to last and whether the plant most likely will be restarted, sold as a complete unit or disposed of piecemeal.
Consider every item or class of equipment individually and detail a specific initial storage/mothball technique plus a methodology for ongoing maintenance.
The individuals doing the initial deactivation often aren’t those who’ll be doing the reactivation — so encourage them to visibly identify various components and equipment state, even if this is just by using chalk or felt tip pen.
Before we go further into mothballing, permit a small digression about the practice of “pirating parts” from an idle unit. It can wreak havoc or worse. I vividly recall the impact on a major U.S. chemical manufacturer I was involved with. After it shut down a product line in the 1960s, other operations on site began to purloin parts. 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. So, in your preservation plan explicitly prohibit removal of parts.
Now, let’s get into how to properly deal with specific equipment and hardware. For purposes of this article, let’s consider a plant in the central U.S. or Europe that could restart in from six to nine months to perhaps several years. What follows is only a guide and isn’t intended to be comprehensive and detailed.
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 pressurized (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 (e.g., 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 either long-term dry or wet hydrazine methods. The latter involves leaving the wet-side — i.e., boiler, economizer 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) and 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 minimize 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, etc., 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 minimize 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 powder wherever possible — they won’t adversely affect electronics.
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 — desiccants and 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 reqular monitoring of motor/generator internal resistance (meggar), 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 — fires are common in dried-out wooden cooling towers. If batteries normally 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 Assets
It makes sense to think strategically about plant deactivation. Proven techniques can preserve the functionality and value of assets. Proper mothballing can pay off substantially whether an operating company aims to eventually restart, sell or dismantle a plant.
Bernie Price is CEO of Polaris Veritas Inc., a Houston-based consulting group. E-mail him at Polarisver@aol.com.