The Castair 120HD200 is a 120-gallon horizontal ASME air receiver tank rated to 200 PSI, built with an extended 17"x85" top plate specifically for duplex compressor installations. The "D" designation stands for duplex — this tank is engineered to support two complete compressor pump and motor assemblies mounted directly on top of the tank, with enough top plate length (85 inches) to accommodate both units side by side with proper spacing. If you are building a duplex compressor system, this is the tank you need. Weight is 445 lbs empty — 90 lbs heavier than the standard 120H200, reflecting the larger top plate.
Tank Specifications
- Capacity: 120 gallons
- Orientation: Horizontal
- Tank Dimensions: 24" diameter x 68" length
- Top Plate Size: 17" x 85" (extended duplex plate)
- Maximum Working Pressure: 200 PSI
- Weight: 445 lbs (empty)
- Construction: Power coded, ASME certified
- Part Number: 120HD200
What Makes This Tank Different: The Duplex Top Plate
The standard 120H200 has a 17"x44" top plate — enough for one compressor unit. The 120HD200's 17"x85" top plate is 41 inches longer, providing the mounting surface for two separate pump/motor assemblies. In a duplex installation, both compressors sit on this shared tank, alternating on and off to equalize run time and maintain system pressure. The extended plate keeps both units properly aligned, at the correct mounting height, and on a rigid surface that controls vibration.
Duplex Installation Notes
- Requires two complete motor/pump assemblies (motors, pumps, pulleys, belts, belt guards)
- Requires duplex alternating controls — either an alternating pressure switch or a full magnetic starter alternating panel
- Vibration pads (VP100, 4 per motor base) recommended at each motor mounting point
- Right From The Start duplex kits (RFS001D, RFS002D, RFS003D) cover oil, vib pads, ball valves, flex hoses, and filter elements for 10 HP, 15-20 HP, and 25-30 HP duplex builds respectively
ASME Certification
Power coded and ASME certified — required for commercial and industrial installations. All Castair tanks carry the ASME stamp, meaning they meet the material, welding, and inspection standards for pressure vessels. This is not a nice-to-have; it is a code requirement in most jurisdictions for tanks above a certain capacity in workplace environments.
120H200 vs. 120HD200: Which Do You Need?
- 120H200 ($1,755.83): Single-compressor horizontal tank, 17"x44" top plate. For standard simplex installations.
- 120HD200 ($2,305.53): Duplex horizontal tank, 17"x85" top plate. For installations with two pump/motor assemblies sharing one tank. The $550 price difference is the cost of the extended top plate and structural reinforcement to support two motors.
- 120V200 ($2,338.57): Vertical, single-compressor, 17"x44" top plate. Takes less floor space but more ceiling height than horizontal options.
What's in the Box
- 1x Castair 120-gallon horizontal ASME duplex air receiver tank, 200 PSI rated
- Extended 17"x85" top plate (integral)
- Channel base supports (integral)
Note: Safety valve, pressure gauge, drain valve, motors, pumps, and alternating controls are sold separately.
When Does a Shop Need This
You need the 120HD200 specifically when you are building a duplex compressor system and want both pumps sharing a single 120-gallon tank. Shops that cannot afford downtime — automotive dealerships, production facilities, paint booths running continuously — typically specify duplex for redundancy. The extended top plate is not optional for duplex; the 85-inch length is what allows both motor/pump assemblies to mount properly. For a single-compressor system, buy the 120H200 instead.
Why Buy From Air Compressor Factory Direct?
We specialize in industrial air compressor systems and components. We can help you plan a complete duplex installation — tank, motors, pumps, controls, and accessories — and make sure everything is compatible before it ships. Free shipping (freight), free technical support at 866-217-0063, full manufacturer warranty on all Castair equipment.
Call 866-217-0063 for quick answers and help!
