How to Select 4-Inch Flange Cast Iron Gate Valve: Key Points and Practical Guide

4inch flange cast iron gate valves are widely used in industrial piping systems due to their pressure resistance, corrosion resistance and long life, such as water treatment, petrochemical, HVAC and other fields. However, there are many types of products on the market with varying quality. How to correctly select a valve requires a combination of technical parameters, usage scenarios and quality control. The following is a detailed selection guide:

一、Identify key specifications

1. Diameter and flange standard

Nominal diameter (DN) : Four inches corresponds to DN100 (GB) or 4" (ANSI). Please confirm that the pipe size matches.

Flange standards : Common standards include the national standard GB/T 9119, the American standard ANSI B16.5, the Japanese standard JIS B2220, etc. It must be consistent with the pipe flange specifications (such as the number of bolt holes and spacing).

2. Pressure level : Select the nominal pressure (PN) or Class level (such as PN10/16 or Class 150) according to the system working pressure. A safety margin must be reserved to avoid overpressure risks.

3. Structural length : The structural lengths of national and American standard valves are different (such as GB/T 12221 and ASME B16.10). They need to match the pipeline installation space.

二、Material and process requirements

1. Valve body material : Cast iron material must meet the standards to ensure tensile strength. Check whether the casting process has defects such as sand holes and pores.

2. Material selection for key components

Valve stem : Stainless steel (such as 2Cr13) is preferred, which is corrosion-resistant and has high strength.

Gate : It is recommended to choose ductile iron or copper-clad cast iron to improve sealing and wear resistance.

Sealing surface : copper alloy or EPDM rubber (for low temperature water medium), stainless steel hard seal can be selected for high temperature environment.

3. Anti-corrosion treatment : If used in a humid or corrosive environment, the valve body must be epoxy coated or galvanized.

三、 Application scenario adaptation

1. Medium type : non-corrosive media such as water, steam, oil, etc.: standard cast iron gate valve is sufficient.

Acid and alkali media: Choose rubber-lined or all-stainless steel valves to avoid cast iron corrosion.

2. Temperature and pressure range : The applicable temperature of cast iron gate valves is usually -20℃~200℃. The heat resistance of the material needs to be confirmed in high temperature environments. It is recommended to upgrade to cast steel material for high pressure systems (such as Class 300 and above).

IV. Quality Inspection and Certification

1. Factory inspection report : Suppliers are required to provide pressure test (1.5 times the nominal pressure holding test) and sealing test (no leakage) reports.

2. Industry certification : Confirm that the product complies with the ISO 9001 quality management system, or industry-specific certification (such as API 600, CE, etc.).

3. Appearance and detail inspection : The flange surface should be flat and free of scratches, and the bolt holes should be aligned without deviation.

The handwheel rotates flexibly and the valve stem can be raised or lowered without obstruction.

5. Installation and maintenance suggestions

Install

1. When flanges are butt-jointed, gaskets (asbestos rubber gaskets or metal spiral wound gaskets) must be installed and the bolts must be tightened evenly diagonally.

2. The valve installation direction must be consistent with the medium flow direction (usually marked with an arrow on the valve body).

Maintenance precautions

1. Operate the valve regularly to prevent rust and jamming, the cycle is 1-2 times every quarter.

2. Check whether the valve stem sealing packing (such as graphite packing) is leaking, and tighten or replace it in time.

Summarize

The selection of four-inch flange cast iron gate valves requires comprehensive technical parameters, usage scenarios, quality certification and cost budget. It is recommended to give priority to products from regular manufacturers with test reports. Aival Intelligent Fluid Equipment has 25 years of manufacturing experience. Each valve is tested by professional equipment before and after manufacturing to ensure the quality of each valve. Factory test reports and certification reports are also provided.