HT PIPE supply all different types and scales of flanges. Please feel free to contact us for further product information and pricing.
Threaded flanges (also referred to as companion flanges or screwed flanges) are bored to match the internal diameter of the pipe, but feature internal NPT (National Pipe Thread) threads conforming to ASME B1.20.1.
A Class 900 pressure rating is a powerhouse classification. It signifies a nominal pressure threshold capable of handling environments exceeding 2250 psi (approximately 155 bar) at ambient temperatures, depending on the metallurgy (e.g., ASTM A105 carbon steel versus ASTM A182 stainless steel).
Why Threaded at 900lb Rating?
In most piping designs, as pressure ratings ascend, welding becomes mandatory. However, the Class 900 threaded flange is strategically deployed where:
Post-Weld Heat Treatment (PWHT) is Impractical: In operational facilities or remote fields where field-welding and subsequent stress-relieving heat treatments are logistically impossible.
Explosive/Hazardous Atmospheres Exist: Maintenance environments where open flames or welding arcs pose an immediate ignition risk.
Dissimilar Materials Require Joining: Applications where a transition between safe, un-weldable alloys or hardened components is necessary.
Thread Engagement Mechanics
Effective Thread Length: The depth of the internal thread must accommodate full engagement with the external pipe thread to guarantee seal integrity.
The Sealant Equation: Because NPT threads rely on metal-to-metal wedging along the crests and roots, high-pressure 900lb applications often require specialized anaerobic thread sealants or structural sealing welds (seal welding) performed on the external lip, assuming the environment permits it.
Material Selection Criteria for High-Pressure Environments
The dimensions outlined above remain identical regardless of the material used, but the pressure-temperature envelopes vary drastically. Choosing the right material grade ensures the flange can handle the structural demands of Class 900 service.
ASTM A105 (Forged Carbon Steel): The default material for ambient to high-temperature oil, gas, and hydrocarbon processing lines.
ASTM A182 (F316/F316L Stainless Steel): Selected for high-corrosion environments or low-temperature cryogenic applications. The lower yield strength of stainless steel at elevated temperatures requires careful pressure de-rating.
ASTM A350 LF2 (Low-Temp Carbon Steel): Essential for projects located in geographic regions experiencing extreme sub-zero winters (such as the Canadian oil sands or Siberian transport lines).
ASME B16.5 Class 900 Threaded Flange
