As an important connecting component in piping system, flanges are widely used to connect pipes, equipment, valves and so on. According to different needs, there are different types of flanges, among which Blind Flange and Ordinary Flange (e.g. Weld Neck Flange, Socket Weld Flange, Slip On Flange,etc.) are the two most common ones. This article will analyze the difference between blind Flange and normal Flanges in detail.
ZIZI specializes in the generation of flanges in various materials and types, in strict compliance with international standards (e.g. EN 1092-1, ASME B16.5, etc.), and provides high-quality piping connection solutions to customers all over the world.
Core Definitions and Underlying Concepts:
Blind Flange：
Blind flange (BL) is a kind of solid disk-shaped parts without a hole in the middle, with the edge of the matching flange with matching bolt holes, mainly used for permanent or temporary blocking of pipeline ends or equipment interfaces.
Normal Flanges：
Normal flanges are connecting parts with through-hole in the center, which is bolted to fasten two pieces of flanges together to realize the detachable connection between pipelines, valves or equipments. According to different connection methods, normal flanges can be divided into weld neck flanges (WN), slip on flanges (SO), threaded flanges (TH), socket weld flanges (SW),lap joint flanges(LAPJ)and other types.
Blind Flange and Normal flanges Material Selection:
Blind flanges and normal flanges are basically the same in the selection of base materials.
| Carbon Steel | ASTM A105/A105N |
| low temperature steel | ASTM A350 LF2/LF3 |
| Pipeline steel | ASTM A694 F42/46/52/56/65/70 |
| Alloy steel | ASTM A182 F5/F9/F11/F12/F22/F91/F92 |
| Stainless steel | ASTM A182 F304/304L/304H、F316/316L、F317、F310S、F321、F347、F904L |
| Duplex stainless steel | ASTM A182 F51/53/55/60 |
Blind Flange VS Normal Flanges：
| Item | Blind Flange （BL) | Weld Neck Flange (WN) | Socket Weld Flange (SW) | Threaded Flange (TH) | Slip-On Flange (SO) | Lap Joint Flange (LAPJ) |
| Definition | Used to seal pipe ends | Welded pipe connection | Inserted into pipe, welded | Threaded connection, easy to dismantle | Welded to pipe | Removable flange, often for stainless steel |
| Applications | Pipe end closure | High-pressure systems | Low-pressure pipes, HVAC | Low-pressure, cooling systems | High-temperature, high-pressure | Clean or corrosive environments |
| Structure | Closed, no hole | Long neck design | Inserted inside pipe | External threads | Flat connection | Inner and outer ring design |
| Sealing | High sealing | Good, requires weld | Good, needs gasket | Thread seal, for low pressure | Good, uses gaskets | Good, easy to dismantle |
| Installation | Bolt-fixed, simple | Requires welding | Easy welding installation | Threaded, quick install | Welding, long-term use | Simple installation, easy to remove |
| Pressure Resistance | High-pressure, high-temperature | Medium to high-pressure | Low to medium-pressure | Low-pressure | Low to medium-pressure | Medium-pressure |
| Cost | Low cost | Medium cost | Low cost | Low cost, fast install | Higher cost | Medium cost |
| Maintenance | Moderate, sealing issue during removal | Requires professional welding | Easy to install and remove | Simple maintenance | Regular weld inspection required | Suitable for frequent removal, easy maintenance |
BL Flange Advantages:
✅High sealing: Suitable for high pressure piping to prevent leakage.
✅Simple installation: easy to install by bolting.
✅Lower cost: simple design, lower production cost.
✅High reliability: High-pressure and high-temperature resistant, ensuring safe operation of pipelines.
Blind Flange Application Areas:
•Petrochemical Industry
•Power & Energy Industry
•Marine & Offshore Engineering
•Water Treatment & Municipal Engineering
•Pharmaceutical & Food Industry
Frequently Asked Questions：
Can a blind flange be reused?
Yes, but check the sealing surface for wear or corrosion, replace the gasket and recalibrate the bolt torque if necessary.
We are professional in manufacturing and exporting flanges in various materials.
