Hurricane Harvey stalled over Houston in August 2017 creating what has been called the most extreme rain event in U.S. history. The storm dropped more than 50 inches of water on the city. What’s more, it was the third 500-year flood Houston experienced in as many years, and while much of the city is well into the rebuilding process, it will no doubt take years for the damage to homes and businesses to be fully calculated and corrected.
Among the millions of damaged components in homes, factories, refineries and petrochemical plants are valves and the actuators and controls that manage their operation. The city’s woes undoubtedly provide a very good lesson in what happens when valves get wet.
VALVES, ACTUATORS AND CONTROLS IN SERVICE
Many of the valves in service handle material much more dangerous than water, Mitch Copeland, business development manager of United Valve, pointed out. Those valves might not be directly affected by an influx of water that, through water ingress, can threaten both the externals and internals of other valves.
The same cannot be said of actuators and controls, however.
If not properly installed, “Electric actuators if they are submerged could be at risk,” Copeland said. “I know of one company that had a local actuator company pulling and going through more than 150 actuators [after the flood]. Most of these needed motor rewinding due to the flooding.”
The loss of electricity during flooding is another big problem for electric actuators, said John Barr, metallurgist with Watson Grinding & Mfg.
“You lose the ability to open and close the valve,” he pointed out.
On the other hand, when pneumatic actuators are in place, no real problem exists if the actuators have a receiver with enough air to cause the valve to open or close when the air supply “fails” or is shut off. “The valves themselves do not care if they are dry or wet to my knowledge,” he added. Meanwhile, “Internally they are wet with product, which can be vastly more severe than water!”
Still, in many cases water can cause significant damage to valve internals.
When valves and controls are handling natural gas or propane, a slightly different story exists. According to the Pennsylvania Department of Environmental Protection (EPA), natural gas furnaces and boilers all have gas valves and controls that are especially vulnerable to water damage from floods.
“Corrosion begins inside the valves and controls, and damage may not be readily visible even if the outside of the device is clean and dry. At a minimum, this damage can result in reliability problems. More severe consequences could be fire or explosion,” according to Pennsylvania’s EPA. The department’s recommendation is that all gas valves and controls be replaced if they are flooded.
When asked about possible danger if flood waters meet various chemicals in valves already in service, Ron Rayman, lead engineer at Watson, explained that, “Flood waters meeting various chemicals could cause some problems, depending upon what level of concentration may develop.”
Still, “if valves in service are designed for severe service, they should withstand any attacks by chemical mixtures,” he added.
He also noted that, when valves have been flooded, his company performs standard tests, then repairs or replaces parts as dictated by the valve’s performance in the test. The main test his company is called upon to use is API [American Petroleum Institute] Standard 598–Valve Inspection and Testing. Once tested and repaired, the life of the valves shouldn’t be affected by the water influx, Rayman pointed out.
Meanwhile, when a flood alert comes in, all electrical and pneumatic actuation should be moved to a location that would not be affected by the flood waters, he warned. If they are flooded, they must be totally rebuilt, he pointed out.
United Valve’s Copeland noted that, with respect to valves carrying chemicals, “Only water-sensitive applications would be affected.”
Still, even in this situation, valves covered with water and not dried out promptly are threatened by rust, which “would set in fairly quickly,” meaning sealing areas may have to be re-machined.
VALVES IN STORAGE
For valves not yet in service that are stored in a warehouse or plant, damage can occur to all exposed surfaces. For example, what happens with seats or seals is a real concern when flooding occurs.
Donald Polasek, a member of the Valve Repair Council and North American Service Manager for ValvTechnologies, explained that, “As one will quickly learn when speaking to a valve manufacturer, repair shop or modification shop, valves that spend time in storage before they are placed into service do not always get the best care or remain protected with end protection installed prior to shipment.”
Why is this important in regard to flood situations?
“When valves are readied for assembly, whether it be at the manufacturer, repair or modification shop, the internals are cleaned to remove all dirt, grit, shavings, oils, etc., that will cause damage to the seating surfaces,” he explained.
These surfaces in many valves are made with some type of hard material or metal that can handle high friction loads when fully seated against the seat (which is flat polished or lapped surfaces.)
Because of this configuration, “Foreign material entering the valve and getting on the seating surfaces can and will cause scratches or galling, resulting in seat leaks,” he pointed out.
Valves that were flooded in storage will likely have foreign material that is not supposed to be in the valve, leading to seat leakage, he said. Also, the largest population of valves are made of some form of carbon steel, which leads to concern about oxidation of the valve internals that over time, can cause rust particles that get large enough to come loose and damage the seat.
Polasek recommended that valves subjected to flood waters be disassembled and inspected for damage. “Any oxidation will need to be cleaned prior to re-assembly and testing to verify the valve performs as designed,” he said.
He suggested contacting any Valve Repair Council member company [or the valve manufacturer] for guidance on a particular type of valve.
ANOTHER RUST CONCERN
After the waters receded from Houston, Watson Grinding and Mfg. received several valves that had been flooded in storage at a refinery. While some of the valves were undamaged or suffered minor damage by the flood waters, the company found that plastic protectors were missing on a few flanged valves. In those cases, the unprotected equipment’s raised face on the carbon steel body was already rusting. In another case, even though the plastic protector was partially open, flood media was able to exit, and very little damage was apparent.
Assuming all the submitted valves were stored in the same way, it may be best to remove a cap on the valve end and leave the other one partially open to allow flood media to escape, Watson suggested. However, that would also potentially allow ingress of foreign particles so it’s not a permanent solution.
That having been said, it is difficult to make any kind of conclusive statement as to the best way to protect valves in storage, except to move them to a safer, drier place.
While most valves in service are not going to be rendered useless by flood waters, actuators and controls are very susceptible to damage. Also, most valves in natural gas or propane service will likely need to be replaced. For valves in storage, ideally, they could be moved to higher ground. However, this may not always be possible.
If the Houston and other recent floods accomplished anything, it was to throw even more questions into the picture—questions that can only be answered by studying what happened.