Thermal Spray Tungsten Carbide Coatings Applicator Develops Proprietary Process

A proprietary coatings process, capable of tungsten carbide coating surfaces as flat as 12 millionth of an inch and finishes finer than 1Ra, has been developed by Longevity Coatings, Allentown, PA, for valve components used in oil and gas drilling wellhead equipment.

The finished products—valve sealing tungsten carbide rings and slab gates—are capable of a service life two to three times those produced by competitive coaters and even those of Original Equipment Manufacturers, said Mark Purington, owner and general manager of Longevity.

Wellhead valves are critical components in the drilling process, noted Purington. The wellhead –the structure on the surface of a drilling site— controls the flow of gas or oil during production. Valves in the wellhead are subject to pressures that can reach as high as 20,000 psi. Failure to maintain pressure control at the wellhead could lead to a well blowout.

Purington pointed out that typical wellhead valves have two critical components: the sliding slab gate, which opens and closes to permit passage of fluids, and its mating opposite, the seat or sealing rings. Because of the intense high pressure brought to bear on the valves, the two opposing components cannot employ the types of non-metallic seals often used in industry in similar situations. “Both components are metal, with no intervening sealing materials. Because of this metal-to-metal contact, the surfaces of both the slab and seat must be perfectly flat to ensure there is no possible leakage.”

When the valve components become worn, wellhead operators routinely replace or refurbish them. Longevity can refurbish a slab or seat at a cost as little as one third that of purchasing new components, Purington estimated. “We have all the in-house technology required to take your gate, strip off the old coating, apply a new tungsten carbide coating of high quality tungsten carbide, apply our proprietary flat-finish process—free of any scratches-- and return them in a reasonable time frame.” The final product, he added, is a coating surface as flat as 12 millionth of an inch and a finish finer than 1Ra ---well above the industry standard. Installed, he added, “they will function at or above OEM quality.”

Although Purington sees wellhead service contractors as the primary market for Longevity’s flat-surface process, “We anticipate that some OEMs—wishing to improve still further the service life of their newly manufactured valve components—might want to utilize our services as well.”

Founded in 2005, Longevity Coatings, offers thermal spray coatings services for many parts and equipment components used in the mining and oil/gas drilling industries, including new and rebuilt drive shafts, slurry blenders, fracturing plungers, high pressure pumps, pump plungers and pistons, augers, valves, valve seats, valve tips and valve assembles and impact rings.

The company’s Allentown plant is equipped to apply diffusion bonded metal, ceramic and carbide coatings to virtually any type or size of mining apparatus or accessory, noted Purington. The company’s largest coating handling system can swing parts in excess of 18’ at a diameter of 50". In addition, “our multi-axis computer- directed motion control systems and mechanical multi-spindle setups provide the handling apparatus for processing shafts, sleeves, plungers, valves and numerous other coating applications.”


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