Warm Stack Or Cold Stack? This May Be The Wrong Question

“Cold stacked rigs” is a bad name. “Preservation to Milspec Standards” may be a better term; it reflects a more positive mindset

As the offshore service sector continues to head south, the question of how to stack idle expensive offshore assets is on the minds of many Oilpros. “Stack” is rig slang for “layup.” The two words have the same meaning.

Warm layup (or warm stack) is the practice of keeping a small layup crew on a vessel to run equipment and carry out protective maintenance on the hundreds of systems found on a modern offshore rig or vessel.

enter image description hereShown here is a group of cold stacked jackups clustered together offshore collecting rust (there were 3 others out of the frame in this particular “boneyard”) (Photo from oilpro.com)

Cold Layup is the practice of mooring the vessel with only watchmen and not running systems during the layup period.

Although cold preservation technologies are well understood and widely accepted in other industries, the term “cold stack” has a deservedly bad name in the offshore industry. During the last cycle of rigs laid up in my main area of operations (the Singapore Straits), I observed a standard of preservation close to zero.

During my career of operating and managing offshore marine assets, I’ve spent more than a few project years reinstating barges and rigs from a fairly poor cold stacked condition. Here is a quick rundown of some lessons I have learned.

The Road To Cold Stack Hell Is Paved With The Best Of Warm Stack Intentions

First, the best intentions of men can turn sour.

At the start of an industry down turn, when there is still some money in the bank, everybody in the company agrees that this downturn won’t last long, so partially crewed warm stacked rigs are the best way to get back into the market, because cold stacked rigs have a bad name in our industry.

Second, the harsh reality of good intentions.

As time drags on and cash gets low, it is time to cut costs. Experienced warm stack rig crews are replaced with lower cost less skilled labor. Top line reliable supervisors are laid off. Later, fuel & lube oil to run engines and equipment are cut back. The end result is laid up equipment with no proper cold preservation, because the funds to do so were spent during the preceding years of warm stacking.

The Solution

There are good arguments to go for cold stacking from day one, with proper preservation to known standards. For some reason, knowledge of best preservation practices is not well understood in the offshore industry.

The basics are not hard to understand – used, proven techniques are known to protect critical surfaces from oxidation. Other industries that have to lay up expensive equipment, e.g. the military, have a good handle on what needs to be done. With so much literature in the public domain, it is not hard to learn about how to effectively cold stack complex modern equipment.

Cold Preservation to MILSPEC Standards

Before the rig is idled (meaning while the crew is still on board) the owners should make and implement two big decisions rather quickly.

Firstly, the people in your company have to overcome their prejudice against cold stacked rigs. Somehow, they need to be persuaded that it is not uncommon for other industries to cold store expensive equipment, in nearly perfect condition, for years.

If you think about it, a large proportion of high tech military equipment is in a permanent state of “cold stacked but ready to use” condition. For example, the military does this all the time.

Not only could rig marketing people replace the term “Cold Stacked” with “Preserved to MILSPEC Standards” but the entire offshore industry will benefit from adopting the military’s cold preservation mindset.

Secondly, the rig’s own crew, while it is still on board, is the best qualified team to do a top line cold stack preservation job (under supervision from third party specialists). There are some things the preservation contractor’s people cannot do regardless, such as stand back the top drive, remove the pipe handler, lay down the traveling blocks, de-reeve the drilling line back onto the storage spool, reposition and open the ram bonnets on BOP stacks, etc. Get these things done before the crew disappears.

Effective Preservation Practice Is Heavily Based On Modern VCIs

VCI – Volatile Corrosion Inhibitors (or VpCI – Vapour Phase Corrosion Inhibitors) slowly emit protective vapours into confined spaces. The more tightly confined the space, the longer the protective vapours last. Add VCI fluid to oil systems, find and seal off breathers, heavily grease bearings and joints, add special electrical VCI tablets inside electrical junction boxes, etc.

After preservation fluids are applied internally, entire top drives, mud pumps, anchor winches, engine gensets can be wrapped in VCI impregnated cling film, which keeps the protective vapors in and fresh moist air out. So long as there is no air exchange and the base VCI deposit is adequate, idle equipment can be preserved in a near-new corrosion free condition for years – even in the tropics.

Dehumidifying Enclosed Spaces – Hulls and Living Quarters (LQ)

Not everything can be shrink wrapped in VCI plastic, The rest of the hull and LQ can be stacked in a dry dehumidified condition by running desiccant wheel dehumidifiers. The drier is put at one end of a space and at a high level; the dried discharge air is run through flexible trunking through open doors to the furthest and highest point. Dry air is heavier than moist air. Dry air self seeks and replaces moist air. One dehumidifier can keep a large number of open interconnected spaces, dry and mold free. For smaller spaces e.g. crane cabs, a window air conditioner left running inside the space is an effective air drier. Pipe the water from the AC’s evaporator to the nearest drain.

Adopting Preservation Practices On Still-Running Rigs

Volatile Corrosion Inhibitor chemicals really work and they are not used enough on working equipment, e.g. inside electrical junction boxes and panels. An example could be anchor winches on jackups, which may go years without being used. There are VCI oil additives that can be added at a low concentration to little used equipment such as the hydraulic oil reservoirs of lifeboat davit winches, even lifeboat engines and fuel systems. Outdoor electrical panels give less trouble when suitable VCI compounds are deployed inside enclosures.

Getting Cold Preservation Accepted

Make sure your preservation contractor’s procedures meet a recognized standard e.g. NORSOK Z-006, MIL-STD-2073, SFLC 6310, GL222012-04. Have a third party inspect and certify that preservation practices meet the desired industry recognized standard. Offshore contractors’ marketing people need to discuss with clients.

But today’s offshore contractors’ equipment is so electrically automated and complicated that the cold preservation techniques so widely used and accepted in the military must inevitably become our new standard of care. Using modern VCIs, the military can now mobilize a mothballed tank or truck in an hour instead of a day. Remove the plastic wrapping, connect the batteries, tighten vee belts, check fluid levels, start and run. No need to remove the VCI tablets. No need to change coolants or oils or remove protective coatings.

Anybody who wants their skills to remain relevant in these economically depressed times, may be doing themselves a favor by learning how to manage the application of modern cold preservation technologies.

Preview Part Two:

Preservation issues related to ballast tanks, spud cans, seawater piping systems, fresh water cooling systems, lifeboats & FRBs, cranes, seawater piping, electric panels, wire rope, BOPs , BOP controls, jacking & fixation gearboxes, mud pits and HP piping, hydraulic tubing under the rig floor and in the derrick. Not how to preserve these items, so much as what to think about when planning to preserve. Many preservation techniques are worth immediately applying to working rigs too.

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