Corrosion on valves can inflict serious costs that take plants by surprise.
Learning objectives
- Understand how corrosion on valves can create serious losses for manufacturers and end users.
- See how corrosion prevention can be easily incorporated into the hydrotesting, shipping and storage process.
- Learn how to create a rust removal station for rusty valve restoration.
Valve corrosion insights
- Thinking ahead about potential valve corrosion concerns and losses and taking simple steps to avoid them offers a significant return on investment.
- Fortunately, a few basic rust removal and prevention techniques can stop deterioration and loss of value at many steps along the way, at any point from the manufacturer to the end user.
It is more difficult to calculate the cost of โwhat-ifโ than โwhat-isโ in any industry, no less those that make or use valves. What if the next valve shipment rusts on the way to the customer and must be scrapped and replaced? What if that spare backup valve is corroded when the critical bypass valve needs to be switched out? What if the entire warehouse of spares rusts due to inadequate preservation?
The challenge of predicting the full cost of corrosion and its domino effect at any stage in a valveโs life cycle does not mean the exercise should not be done. A little upfront calculation of potential losses from rusty valves quickly shows that even small initial investments can add up to incredible savings that are worth the effort โ even if one never fully discovers the value of the time and money saved from emergencies avoided. In short, corrosion control at every stage from manufacturing to maintenance can have a significant return on investment for practically any plant that makes or uses valves.
Understanding valve hydrotesting and shipment
Valves are inherently critical components that must be manufactured with precision and reliability. Part of that process is hydrostatic testing to ensure valves can withstand the pressure of the fluids or gases that they will handle. The irony is that in seeking to confirm integrity, hydrotesting can undermine integrity by introducing corrosion-inciting moisture. Residual water must be completely dried to avoid flash rusting. Unfortunately, the intricacy of valves can make this step difficult.
Even without the threat of residual water, valves โ like any other metal component โ face corrosion risks on the journey to the end user. Shipping conditions can be unpredictable and uncontrollable, especially during several months of sea export through changing climates. Fluctuating temperatures and humidity can easily lead to condensation and corrosion that compromises the valve by the time the end user opens the package.
The natural response is to reject the components that no longer look new, forcing the manufacturer to incur time and labor costs to restore or replace the valves, while the customer may lose valuable time from project delays.
What-ifs of critical and operational spares
The cost of rust on critical and operational spares can also add up quickly. First, the plant loses the baseline value of the spares themselves, reflected in the amount of money spent to replace those spares (if not restored). This can quickly reach tens of thousands of dollars. For example, one water treatment plant in Canada spends approximately $6,500 (CAD) to purchase spare pumps. Losing a few of these to rust could quickly leave them with a price tag of close to $20,000 to replace these spares.
A more intangible but potentially much higher loss is the cost of plant downtime. If a major valve needs to be replaced but the backup cannot be installed because it is rusty, some or all of plant operations will be suspended until the valve can be restored or replaced.
Oil and gas facilities face some of the greatest potential losses. According to Siemens, the cost of one hour of unplanned plant downtime in the oil and gas industry was approximately $200,000 to $600,000 per hour over the 2019 to 2023 fiscal year period, fluctuating with the price of a barrel of oil. This could easily add up to $5 million in a 24 hour period, underscoring the importance of minimizing downtime.
The long and short of the equation is that when a plant cannot function due to rust, it cannot produce; when it cannot produce, it cannot generate revenue. The key then is to be able to return a facility to service as quickly as possible to minimize lost productivity and revenue. This makes storing critical and operational spares rust-free, in a manner that allows for immediate installation, even more important, not only for oil and gas facilities but for any manufacturing facility that can suffer from lost production while waiting for a replacement part.
Understanding the what-ifs of mothballing
Mothballing holds value like the layup of spares, but with a slightly different purpose. This term is typically reserved for plants that will be shut down temporarily or permanently. In the oil and gas industry, it is not uncommon to shut down operations for a couple of years.
In the meantime, idle equipment โ both spares and installed assets โ must be preserved or face the potential of gradual deterioration over time, especially if stored in harsh climate regions where warehousing is minimal or not climate-controlled. Without proper preservation, assets could lose their integrity and value by the time the plant restarts or the organization decides to sell them.
How to ship valves rust-free
Ideally, rust prevention should start with the manufacturer. Through proper foresight, the manufacturer can not only save the end user from unexpected delays and setbacks from rusted materials but can also spare themselves the serious headaches that would come from their liability to refund or replace rusty valves.
Hydrotesting is a prime time to add corrosion protection, especially when hydrotest additives include corrosion inhibitors that leave a protective layer behind. The higher the corrosion inhibitor dose, the longer the protection period will be (as much as two years after hydrotesting). This protects internal valve intricacies and eliminates the urgency of drying hard-to-reach valve internals.
Another great option for internal protection is the use of vapor corrosion inhibitors (VCI) that diffuse throughout an enclosed space, forming a protective molecular layer on metal surfaces. VCIs can be applied by fogging a valve internal or placing a VCI emitting material (e.g., a breathable pouch containing VCI) inside the valve and closing all openings. VCI bags or shrink film work well for this purpose while adding an additional dose of VCI to the package. All materials are relatively easy to remove before installation.
Steps to reclaim rusty valves
Valves that have already rusted โ whether just during the trip overseas or after years of deficient storage โ can often be reclaimed through a simple rust removal process if the rust is not deep enough to compromise valve integrity. Setting up a rust removal station is a great way to restore multiple parts over a brief or extended period (see Figure 2).
Step 1: Select three containers large enough to hold the valves or components that need to be cleaned. These could be anything from small pails or dishpans to large tubs or tanks. Using portable containers is a great idea for large facilities that might have rusty parts on opposite ends of the warehouse.
Step 2: Choose rust removal materials. A biobased rust remover can be a great way to introduce sustainability into the project, although stronger chemistries often act more quickly. Still, large preservation projects have found biobased rust removers to work well for hundreds of parts.
Step 3: Clean the valves. It is important to remove any existing grease or rust preventatives to avoid contaminating the rust removal solution and to allow direct contact with the metal.
Step 4: Soak the valves in the rust remover solution. This may take 20 minutes to 24 hours depending on the severity of the rust. The best strategy is to check the part periodically to see how rust removal is progressing. If needed, workers can speed the process by warming or agitating the solution. (A scrub pad and gloves can also be used for extra abrasion if needed.)
Step 5: Rinse valves in clean water. This helps remove corrosion products and avoid contaminating the final rinse solution.
Step 6: Rinse valves in an alkaline cleaner that offers flash corrosion protection. In addition to providing temporary protection from re-rusting, this also neutralizes the acidity of the rust removal solution.
The same rust removal solutions can often be reused many times before they need to be topped off or replaced.
One manufacturer in India used a process like this to restore valve inserts that had been rejected by the customer due to rust, despite previous application of a moisture-displacing rust preventive. Short on time, the manufacturer set up a rust removal station with three tubs: one for the rust remover solution, one for water and one for the alkaline cleaner/neutralizer/flash corrosion inhibitor. (A fourth tub was added to dip the parts into a wet film corrosion inhibitor for the preservation stage.) After going through this assembly-line process, the components were like-new and arrived rust-free at the customerโs location. The whole restoration process was completed in three days, with some parts taking as little as two minutes to clean.
How to preserve valves
Restoration and preservation often go hand in hand. Restoring valves without preserving them can leave them rusty again. Preserving valves without restoring them does not eliminate the rust that has already occurred. Therefore, every restoration project should end with preservation and any preservation activity must first take place on clean, rust-free surfaces.
Preserving critical and operational spares or mothballing entire plants follows similar principles to those of preparing valves for shipment. The main differences are that the valves may not be new and may require a longer term of preservation โ perhaps two to five years instead of two months.
Once again, VCIs play a major role in the success and ease of preservation projects. Thanks to their diffusion, VCIs work well for protecting intricate valve internals where a coating would not be appropriate or easy to apply. As for shipping, workers can fog VCI into the package or place a breathable VCI-emitting pouch inside, making sure to close all openings by capping them with VCI film or entirely shrouding the valve in a VCI bag or VCI shrink film. Thicker films should be used for longer storage periods, with ultraviolet (UV) additives included for durability in outdoor storage.
A great example of this valve preservation routine is the process one oil and gas supply company follows to preserve surplus valves of all sizes: Place a VCI emitter inside, fog with VCI and cover openings with VCI film. Some valves are so large (30- to 42-inch ANSI 600 class trunnion ball valves) that they must store them outside in UV resistant VCI bags that are 36×600 inches.
Due to their critical need for integrity, the company practices careful documentation โ both for valves themselves and for the preservation process. This underscores an important practice among preservation crews: providing quality assurance to the next project owner by providing evidence of proper preservation. With traceable preservation, one team can hand off the valves to another team with greater confidence in and confirmation of their reliability and integrity.
The valve life cycle is full of what-ifs โ many possible points at which rust could enter the picture and send the entire plant reeling with hundreds to millions of dollars of loss. Fortunately, preventing those what-ifs from happening is relatively easy with a little foresight and good restoration and preservation habits. The key is to think about these what-ifs before they become โwhat isโ to save significant time and money.
