Carbon Steel Orifice Flange — Factory Direct Supplier | Huaxia-Steel

Carbon steel orifice flanges are precision-forged fittings designed to hold orifice plates, flow nozzles and venturi tubes for flow measurement and restriction in oil, gas, petrochemical and power-generation piping systems. Unlike standard weld-neck or slip-on flanges, orifice flanges incorporate jack screws, paddle spacers and tap holes that allow differential-pressure transmitters to be connected without penetrating the pipe wall.

Huaxia-Steel supplies ANSI B16.36 orifice flanges in raised face (RF) and ring-type joint (RTJ) configurations, manufactured from ASTM A105, A350 LF2/LF6 and A694 F52–F65 forgings. All flanges are heat-treated, hardness-tested and dimensionally inspected before shipment. This product page provides specifications, material options, dimensional data and procurement guidance for engineers and buyers sourcing orifice flanges for new construction or retrofit projects.

Product Overview

Orifice flanges are always supplied in pairs — one upstream and one downstream — with the orifice plate or flow element clamped between them. The flanges are thicker than standard ASME B16.5 flanges of the same pressure class to accommodate the tapped holes for instrument connections and to provide sufficient stiffness for accurate differential-pressure measurement.

Huaxia-Steel produces orifice flanges by closed-die forging on 3,000-tonne hydraulic presses, followed by normalising or quenching-and-tempering heat treatment. CNC machining guarantees face flatness within 0.05 mm and tap-hole positional tolerance within ±0.25 mm. Every flange is marked with heat number, grade, pressure class, bore diameter and Huaxia-Steel traceability code.

Specifications and Dimensions

Parameter	Specification
Standard	ANSI B16.36, ASME B16.5 (compatible)
Pressure class	150, 300, 400, 600, 900, 1500, 2500
Size range	1/2" – 24" NPS (larger on request)
Facing	Raised Face (RF), Ring-Type Joint (RTJ), Flat Face (FF)
Bore type	Standard bore, reduced bore, spectacle blind bore
Tap holes	1/2" NPT or 3/4" NPT, 2–4 holes per flange pair
Jack screws	2–4 sets per flange pair, ASTM A193 B7 or A320 L7
Surface finish	RF: 125–250 AARH; RTJ: 63 AARH max
Coating	Black oxide, rust-preventive oil, hot-dip galvanized

Dimensional tolerances conform to ANSI B16.36 Table II and ASME B16.5 Table II-8. For critical flow-measurement applications, we offer precision-bored orifice flanges with bore concentricity within 0.10 mm and surface roughness Ra ≤ 1.6 μm on the sealing face.

Material Grades and Selection Guide

Grade	Standard	Service Temp.	Typical Application
ASTM A105	ANSI B16.36	−29°C to 425°C	General oil & gas, water, steam
ASTM A105N	ANSI B16.36	−29°C to 425°C	Normalised for better toughness
A350 LF2	ANSI B16.36	−46°C to 345°C	Low-temperature hydrocarbon service
A350 LF6	ANSI B16.36	−46°C to 345°C	Arctic LNG and cryogenic piping
A694 F52	ANSI B16.36	−29°C to 260°C	High-strength pipeline service
A694 F65	ANSI B16.36	−29°C to 260°C	High-pressure gas transmission

For sour service (H2S > 50 ppm partial pressure), specify A105N or A350 LF2 with NACE MR0175 / ISO 15156 hardness limitation of 22 HRC max. Huaxia-Steel provides NACE-compliant orifice flanges with mill hardness reports for every heat.

Manufacturing Standards and Quality Assurance

Forging: Closed-die forging on 3,000-tonne press, minimum 3:1 forging ratio
Heat treatment: Normalising at 870°C–900°C or Q&T per grade requirement
Machining: CNC turning, drilling and tapping on VMC centres
NDE: 100 % ultrasonic testing (UT) per ASTM A388 for forgings above 2"
Hardness test: 10 % random sampling, HRC or HB per ASTM E18/E10
Dimensional inspection: CMM verification of OD, bore, bolt-circle diameter and face flatness
Positive material identification (PMI): XRF alloy verification on every heat

Applications

custody-transfer flow metering in oil and gas pipelines
steam flow measurement in power-plant boiler feedwater lines
chemical injection and produced-water measurement in offshore platforms
compressor station fuel-gas measurement and control
refinery process stream balancing and allocation metering
water-treatment plant influent and effluent flow monitoring

Packaging and Shipping

Orifice flanges are shipped in matched pairs with the paddle spacer and jack screws bundled together. Each pair is wrapped in VCI polyethylene film and secured to a wooden pallet with steel banding. Pallets are fumigated and marked with handling instructions, heat numbers and project references. Sea-freight containers include desiccant packs and moisture indicators.

For urgent projects, air freight is available to any international airport with customs-bonded warehousing. Typical lead time is 3–4 weeks for standard sizes and 5–6 weeks for special bores or high-alloy grades.