Flange Standard Guide for Valves

1. Introduction

In industrial pipeline networks, valves play an important role as critical unit nodes. The accurate and reliable connection between valves and pipelines is a crucial issue if safety and reliability are ensured.

Flange connection, as one of the important connection methods in pipeline construction, originated from the Industrial Revolution at the end of the 18th century and was initially mainly used for cast iron low-pressure steam pipelines. With the development of technology and the rise of the petrochemical industry, the requirements for flanges are constantly increasing with the increasing demand, and international standards are also constantly improving and unifying with this process. Various connection methods such as welding, threading, clamps, etc. also appear in pipeline systems.

Modern flange connections are mainly used for connecting valves, water pumps, water meters and other pipe components in large-sized main pipelines, mainly for the convenience of disassembly and replacement. The flange connection tightly connects the flange and valve together through bolts, and the gasket can fill the gap between the flanges to ensure sealing performance.

2. Flange Connection Standards

Flange connection standards are important bases for ensuring flange-to-flange connections. They are divided into globally universal standards and regional standards, specifying key parameters such as flange outer diameter, center distance, flange holes, inner diameter, and thickness.

2.1 Material Classification

Flanges are classified by material to adapt to different media and environments, including:

• Ductile iron flanges
• Carbon steel flanges
• Stainless steel flanges
• Alloy flanges

2.2 Surface Treatment

For economic and technical considerations, flange surface treatments are available in different types:

• Anti-rust paint coating
• Electro-galvanization
• Alloy material coating

3. Major Flange Standards

• EN 1092-1 Flanges
• Asme B16.5 Flanges
• GOST 33259-2015 Flanges
• AWWA C207 Flanges
• MSS SP-44 Flanges
• JIS B2212 Flanges
• GB/T 9114 (China)
• HG/T 20592 (China)
• BS 10 (UK)
• AS 2129 (Australia)
  
  
  
  

4. Valves for Flange Connection

Valves commonly used with flange connections include butterfly valves, Check Valves,flange gate valves, flange ball valves, and flange globe valves. The flange part of flange valves is designed in accordance with flange standards to ensure connection accuracy, especially for key parameters such as flange outer/inner diameter, number of bolt holes, and center distance.

In the conventional procurement process:

• Valve drawings will indicate flange standards and parameters as important reference bases.

• Purchasers will also provide flange standards as key technical documents to valve manufacturers or suppliers to obtain accurate quotations.

5. Flange Connection Methods for Different Valves

• Short-structure valves (e.g., Wafer Butterfly Valves,lug butterfly valves, U-type flange butterfly valves): Usually connected with a single bolt. Wafer butterfly valves, as a special type of valve, typically have only four mounting holes, so their side flanges can be designed with multi-standards to meet different flange standards simultaneously.
• Long-structure valves (e.g., flange Gate Valves): These have complex central parts and occupy large space, so two bolts are generally used to connect the flanges on both sides.

6. Application Scope

As precision-machined standard industrial products, flanges require selection of appropriate flange types, materials, and standards based on specific pressure, temperature, and media conditions. In actual installation, the connection method between flanges and pipelines varies depending on the pipeline material.

With advantages such as easy disassembly and installation, flanges are widely used in industries including petroleum, chemical engineering, metallurgy, electric power, construction, water supply, and drainage.