Pipe Flange Selection Standards and Specifications

(Website News Article for Cangzhou Yunxinda International Trade Co., Ltd.)

Introduction

Correct flange selection is the foundation of safe, leak-free industrial piping systems. Improper specification matching often causes assembly failure, medium leakage, pipeline shutdown and potential safety risks. Engineers and purchasers must follow systematic selection standards and confirm all core technical specifications before ordering. This article sorts out complete selection principles, applicable standards and essential specification parameters for industrial pipe flanges.

1. Priority Confirmation of Applicable Manufacturing Standards

Different regions and projects adopt independent standard systems. Do not mix different standards arbitrarily, as bolt circle, outer diameter and sealing face dimensions cannot match.

American Standard System

ASME B16.5: Pipe flanges & flanged fittings, NPS 1/2 ~ NPS 24, Class150, 300, 600, 900, 1500, 2500. Widely used in oil, gas, petrochemical and overseas energy projects.

ASME B16.47: Large diameter steel flanges, NPS 26 ~ NPS 60, Series A / Series B.

European Standard System

EN 1092-1: Steel circular flanges for piping, PN pressure grades, DN nominal diameter system, mainstream for European, Middle East municipal and industrial projects.

Other Common Standards

JIS B2220: Japanese standard flanges, popular in Southeast Asia.

GB/T 9113 ~ GB/T 9124: Chinese national standard flanges for domestic engineering.

2. Core Specifications to Be Confirmed During Selection

① Flange Type (Connection Mode)

WN Weld Neck Flange: High temperature, high pressure, critical circulating pipelines

SO Slip On Flange: Low & medium pressure, normal temperature general pipelines

SW Socket Weld Flange: DN50 and below small-bore high-pressure piping

TH Threaded Flange: Welding-prohibited sites, fire protection pipelines

LJ Lap Joint Flange: Stainless steel pipelines requiring frequent disassembly

BL Blind Flange: Pipeline end blocking, equipment opening closure

② Nominal Size

ASME system: NPS (Nominal Pipe Size, inch)

EN / GB system: DN (Nominal Diameter, metric)

Must correspond with matching pipe size.

③ Pressure Rating

ASME: Class150, Class300, Class600, Class900, Class1500, Class2500

EN / GB: PN6, PN10, PN16, PN25, PN40, PN63, PN100

Important rule: Flange allowable pressure declines as temperature rises. Select pressure class with sufficient safety margin; never use lower pressure grade instead of design requirement.

④ Sealing Face Type

RF Raised Face: Most universal for medium & low pressure

FF Flat Face: Cast iron equipment, low-pressure water supply system

RTJ Ring Type Joint: High pressure, high temperature heavy-duty pipelines

MFM Male & Female Face / TG Tongue & Groove Face: Medium pressure, toxic and flammable medium

Prohibition: Do not mate RF flange directly with FF flange.

⑤ Material Standard

Common forged flange material specifications:

Carbon steel: ASTM A105, A350 LF2

Stainless steel: ASTM A182 F304, F316, F316L

Alloy steel: ASTM A182 F11, F22

Material must be compatible with pipeline medium, temperature and corrosion environment.

3. Systematic Flange Selection Procedure

Clarify working conditions: maximum operating pressure, maximum temperature, medium property (water, steam, oil, acid, gas etc.)

Confirm project execution standard: ASME / EN / JIS / GB

Select nominal size NPS/DN according to pipe outer diameter

Determine pressure class or PN grade with pressure-temperature table check

Choose flange connection type based on installation space and load condition

Select proper sealing face matching gasket type

Confirm material grade and required heat treatment, NDT test requirements

Verify complete specification to avoid dimension mismatch during site installation

4. Complete Standard Specification Example

WN RF Class300 NPS6 ASTM A105 ASME B16.5

Explanation: Weld Neck Flange, Raised Face, Class300, NPS6, Material A105, manufactured per ASME B16.5

About Cangzhou Yunxinda International Trade Co., Ltd.

Cangzhou Yunxinda International Trade Co., Ltd. supplies full-series standard and customized flanges and supporting pipe fittings. Our product range covers WN, SO, SW, TH, LJ, BL flanges in carbon steel, stainless steel and alloy steel, complying with ASME B16.5, ASME B16.47, EN1092-1, GB and JIS standards.

We provide professional technical support for flange parameter confirmation, standard comparison and model selection. Material Test Reports (MTR), dimension inspection and third-party testing services are available. Matching butt-weld fittings including elbows, tees, reducers, pipe caps and crosses can be supplied as one-stop solution.

Our piping products serve petrochemical, natural gas, power generation, water treatment and construction projects worldwide. Global importers, engineering contractors and distributors are welcome to send drawings and inquiries for quotation.