Pipeline isolation solution, what else can we use besides blind flanges

introduce

In the industrial sector, blind flanges are often used for pipe isolation and are one of the most common isolation methods. However, in some specialized applications, blind flanges are not used, leading to the emergence of other isolation methods.

Double valves are also a common isolation method. Therefore, when designing and repairing piping systems, it is important to select the optimal isolation solution based on the specific application.

This article focuses on blind flanges and common isolation methods, hoping to provide some helpful advice.

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What is a blind flange

A blind flange is a disc-shaped flange without a central through-hole. It connects to a mating flange via bolts to seal and isolate the ends of a pipe. Unlike conventional flanges, a blind flange does not function as a fluid passage, but rather serves as a “pipeline endpoint.”

Classification of blind flanges

Based on their structure, blind flanges can be categorized into two types: flat-plate blind flanges and butt-weld blind flanges with necks.

Flat-plate blind flanges are solid circular discs with uniform thickness. They are low-cost and easy to process, suitable for low-pressure and normal-temperature environments.

Butt-weld blind flanges feature a tapered neck structure that allows for butt-welding of the pipe. They offer enhanced pressure-bearing capacity and are commonly used in high-pressure and high-temperature environments.

Material of blind flange

The performance of blind flanges is directly dependent on the material used. Common materials include:

Carbon steel (Q235, A105): Economical and practical, suitable for general media such as water and air;

Stainless steel (304, 316L): Highly corrosion-resistant, suitable for use in chemical corrosive media;

Alloy steel (16Mn, CrMo): High-temperature and high-pressure resistant, suitable for use in power plants and petrochemical projects;

Special materials, such as titanium alloys and nickel-based alloys, are suitable for use in extreme operating conditions.

Standard specification for blind flanges

American Standards: ANSI B16.5 (pressure rating 150 lbf to 2500 lbf), API 6A (for wellheads);
European Standards: EN 1092-1 (pressure range PN6 to PN100);
National Standards: GB/T 9124 (nominal pressure PN0.25 to PN16), HG/T 20592 (chemical industry standard).

Four common methods of pipeline safety isolation

Pipe blocking method

Pipe plugging is a common method for safely isolating pipelines, often used for rapid sealing in emergency situations. Before plugging, the pipeline must be fully emptied.

A plug is then selected based on the pipe material and diameter, installed, and secured.

Cutting off the pipe method

Cutting the pipe is a common safety isolation method. Generally, specialized pipe cutting equipment is required. Before cutting, the pipe must be drained.

A pre-cut safety inspection is then conducted, and the pipe material, strength, and location are comprehensively considered before determining the cutting location and method.

Valve installation method

Valve installation is a relatively mature method for pipeline safety isolation.

Installing valves on pipelines allows them to be opened or closed at any time, preventing adverse environmental, health, and property impacts during pipeline maintenance interruptions or emergencies.

Installing Isolation Valve Method

Installing an isolation valve is a relatively safe and reliable method for isolating pipelines.

The isolation valve has an independent connection to the pipeline, separating different media in the pipeline and effectively isolating the pipeline during cleaning and maintenance.

Common types of isolation valves

Globe Valve: A globe valve is a common isolation valve that completely shuts off a fluid medium.
Ball Valve: Ball valves are widely used in many applications. They control the flow of fluid by rotating the ball.
Butterfly Valve: A butterfly valve controls the flow of fluid in a pipeline by rotating the butterfly disc.
Check Valve: A check valve is a valve used to prevent backflow of fluid, also known as a non-return valve.
Gate Valve: A gate valve is an advanced shutoff device. Since it only moves up and down, the seal formed on the valve seat surface is more reliable.

What is a double valve

A double valve is a valve structure that consists of two independent valves. The double valve structure generally consists of an inlet valve and an outlet valve.

The two valves are synchronized by a synchronization device to achieve synchronous movement, thereby controlling and regulating the pipeline flow.

The difference between double valve and blind plate

Both double valves and blind plates are devices used to isolate pipes. However, they operate differently.

A blind plate is typically a single plate that needs to be removed and installed, while a double valve consists of two valves that directly control the opening and closing of the valves.

There are some differences in their use.

First, double valves can be operated in the pipeline, while blind plates require the pipeline media to be removed before they can be removed or installed.

Second, double valves make pipeline maintenance and operation more convenient. Finally, double valves reduce pipeline leakage and provide better sealing performance.

Can double valves replace blind plates?

Double valves can replace blind flanges in some situations, but not all. Blind flanges are more reliable than double valves in pipelines involving high pressure, high temperature, toxic and hazardous media, or where rapid shutoff of the fluid is necessary in unexpected situations.

In these situations, blind flanges offer greater flexibility in pipeline control and are safer and more reliable.

Furthermore, blind flanges are indispensable for some pipeline maintenance and operation. In some cases, openings in the pipeline are necessary, and blind flanges can provide effective isolation.

Summarize

Through the above introduction, we believe we have a clear understanding of the applications of blind flanges and double valve isolation. Understanding the differences between each pipe isolation method can help us better solve pipeline problems.

This knowledge is extremely important for both pipeline repair and installation.

If you would like to purchase steel pipes or pipe fittings, please contact our engineers, who will provide more thoughtful service based on your needs.