Technical Specification
FAV Air Cooler Header Plugs (commonly designated as Fin Fan Plugs, Shoulder Plugs, or Air-Cooled Heat Exchanger Plugs) are high-integrity threaded closure components manufactured in accordance with API 661 / ISO 13706 and ASME Section VIII Div 1 standards. Installed directly opposite each process tube in the plug boxes of air-cooled heat exchangers (ACHE / Fin Fan Coolers), these plugs provide dependable high-pressure fluid containment while allowing fast individual tube access for mechanical cleaning, eddy-current inspection, hydrostatic testing, and tube plugging without dismantling header boxes. Each plug features a heavy hexagon driving head with an integral precision-machined shoulder flange designed for positive sealing against soft iron, copper, or stainless steel gaskets. Available in standard 12-UNF thread sizes from 1" up to 2-1/2"—including popular stock sizes such as 1-7/8" x 12 UNF (TL: 1-5/8") in normalized ASTM A105N carbon steel with 100% Heat Number traceability (EN 10204 3.1 MTR).
API 661 / ISO 13706 Compliance: Designed specifically for air-cooled heat exchanger header boxes across refinery and petrochemical applications
Precision 12-UNF Unified Fine Threads: Class 2A thread fit ensures smooth make-up, consistent torque-tension transfer, and galling resistance
Integral Sealing Shoulder: Precision face-machined perpendicular to thread axis for leak-tight compression against soft iron or metallic ring gaskets
100% Heat Number Traceability: Permanent laser or stamped marking on hex head with Manufacturer/Client (ATH), Material (A105N), Thread (1-7/8" x 12 UNF), Thread Length (TL: 1-5/8"), and Heat Number (e.g. H.N: 2730)
Engineering & Selection
Select nominal thread diameter, thread engagement length, material grade, and companion sealing gaskets.
Model Code
Inspect the header box counterbore sealing face thoroughly before plug insertion. Remove all old gasket remnants, scale, and particulate buildup.
Always install a new soft iron or metallic gasket when reinstalling header plugs. Never reuse crushed gaskets.
Apply a high-temperature nickel or molybdenum-disulfide based anti-seize lubricant to plug threads and shoulder face to prevent thread galling during torquing.
Tighten plugs using calibrated torque wrenches in progressive increments according to the cooler manufacturer's bolt-up torque matrix.
In air-cooled heat exchangers (Fin Fan Coolers), process fluid circulates through hundreds of finned tubes expanded into heavy forged or fabricated header boxes. Because header boxes operate as high-pressure vessels under continuous thermal cycling, accessing individual tubes for inspection, tube rolling, cleaning, or emergency plugging requires specialized removable closures.
FAV API 661 Header Plugs solve this requirement by positioning a precision-threaded shoulder plug directly opposite each tube opening. Tightened against a companion soft iron gasket seated in the header counterbore, the plug forms a hermetic metal-to-metal primary pressure boundary that withstands intense vibration from overhead induced-draft fans.
Eliminates the requirement to unbolt entire header cover plates or cut welded bonnet enclosures during maintenance turnarounds
Allows technicians to use high-pressure water jet lances, mechanical tube cleaners, or eddy-current probes through individual plug ports
Integral shoulder provides controlled gasket seating stress, preventing gasket extrusion or thread stripping under torque
Engineered thread relief groove ensures full thread engagement without bottoming out against the header box face
In critical refinery and petrochemical environments, material verification is paramount to plant safety. Every FAV Header Plug supplied by ATH Performance undergoes high-precision fiber laser etching on its top hex driving face to guarantee permanent legibility even after years of atmospheric exposure and high-temperature service.
