Finishing Pipe Spools, Valves and Fittings

Handling Spools, Branches and Heavy Castings

Handling is the first problem to solve. Straight spools can roll on stands or turning rolls so the blaster and painter can rotate them and reach all sides. Branched spools often hang from a monorail or overhead crane, or sit on custom stands that support them at flanges. Valve bodies and large fittings are frequently placed on turntables or rotating fixtures so one operator can blast and coat the full casting without lifting it again. Small fittings and flanges can be hung on racks or run through a conveyorized system, which opens the door to powder coating for some product lines.

• Write down the range of shapes, the largest spool envelope and the heaviest casting.
• Pick handling that lets the part rotate rather than making the operator climb.
• Plan where parts wait between blast and coat so they stay dry and clean.

Sizing a Blast Room and Booth Around the Spool Envelope

Booth and blast room sizing for spools is driven by the envelope of the largest assembly, not its pipe diameter. A short spool with a long branch can need more width than a long straight run. Measure the overall length, width and height including flanges and supports, then add space for the operator and handling equipment on every side. Many piping fabricators choose a long crossdraft booth or a side downdraft booth because they fit flat floors and accept long parts through end doors. A drive-through arrangement with a cart or rail lets spools move from blast to coat to cure in a straight line. Blast rooms for piping often use partial floor recovery or sweep-in trenches because media collects inside pipe bores and needs to be cleaned out before coating.

Protecting Flange Faces and Machined Surfaces

Flange sealing faces, threaded ends, valve seats and machined bores must not be blasted or coated. Plan a prep area with good lighting and benches for applying caps, plugs and masking before blasting, and again before coating if needed. Blowing out pipe bores and valve cavities after blasting matters as much as the blast itself, because trapped media will contaminate the coating and the line it eventually goes into. A dedicated prep station with its own dust control keeps this step out of the booth.

• Separate masking and unmasking areas so clean parts do not mix with prepared parts.
• Provide compressed air blow-off stations with good dust control.
• Light the prep area well enough to inspect inside bores and cavities.

Liquid Coatings, Powder and Cure for Piping Products

Many pipe spools and large valves receive liquid coatings such as epoxies and polyurethanes applied in a booth, then air dry or cure with heat. Smaller valves, fittings and flanges can be well suited to powder coating, especially when volumes are steady and parts can hang on a conveyor. Heavy castings take longer to heat in a cure oven, so oven sizing and air movement have to account for part mass. A batch cure oven fits shops with mixed sizes, while a conveyor oven suits repeat parts running on a line. Infrared heating is sometimes used for quick cures on surfaces that can face the emitters. Whichever route you choose, the booth or oven connects to exhaust ductwork, make-up air, fuel or electrical service and controls that all need room on the roof or wall and a clear path through the building.

Ventilation and Site Details for a Piping Coating Area

Piping shops are often busy fabrication buildings with welding fumes, grinding dust and crane traffic. The coating area needs make-up air that keeps the booth slightly controlled without starving the rest of the building. Locate the booth exhaust stack and the blast dust collector exhaust away from make-up air intakes. Coordinate fire suppression, interlocks and electrical classification with your fire code authority and insurer. For a first site visit, gather drawings of your largest spools and valves, building drawings with crane coverage, and the location and capacity of gas, electrical and compressed air service.