knowledge

Types of filter edges and their applications

November 17, 2025
admin

In the oil, gas, and petrochemical industries, flanges   are    essential components for connecting and sealing pipes, tanks, and process plants. They ensure fast, reliable, and easily detachable connections between pipes and plant components. Given the high pressures, temperature fluctuations, and corrosive environments in refineries, selecting the correct flange type is crucial. This article describes the flange types used in refineries, their properties, standards, and applications.

What is a lip?

A flange is a round or square component typically mounted at the end of a pipe or piece of equipment. Its main function is to create a tight seal, withstand pressure, and prevent fluid loss. Flanges are usually fitted with gaskets and fastened  with     bolts and nuts  .

General quality standards in oil refineries

Flanges are designed and manufactured according to international standards. The most important of these are:

  • ASME/ANSI B16.5     : The most widely used standard for steel sidewalls up to 24 inches in size.

  • ASME B16.47     : Applies to flanges with a diameter greater than 24 inches.

  • API 6A and 6B     : For use in the oil and gas industry under high pressure.

  • DIN and ISO     : European Standards.

The selection of the appropriate standard depends on the design pressure (class 150–2500), the type of fluid and the operating conditions.

Lip types depending on the type of contact

1. Welded end flange

  • It has a conical neck that is welded to the pipe.

  • Thanks to its uniform pressure distribution, it is ideally suited for high-pressure and high-temperature conditions.

  • It is frequently used in the main pipelines of oil refineries.

2. Sliding lip

  • The pipe is passed through the flange and then welded.

  • The installation is simpler and less expensive than with a neck flange.

  • Suitable for medium and low pressures.

3. Blind lip

  • This is a plate without a central hole.

  • Used to seal the end of a pipe or device.

  • Widely used in hydrostatic testing and repairs.

4. Socket welding flange

  • Insert the pipe into the lip recess and weld it in place.

  • For small high-pressure lines.

  • This is more secure than a retractable closure.

5. Threaded flange

  • The pipe is connected to the flange by means of a thread.

  • Suitable for low-pressure and welding conditions.

  • Especially on routes or temporary facilities with a high fire risk.

6. Loose lips

  • Used with a short   end  .

  • The screw holes are easy to adjust.

  • Suitable for pipes made of expensive materials (e.g. stainless steel), as the flange itself can be made of cheaper materials.

  • aerodinamica pressure relief valve V 185. V85

Edge type depends on the sealing surface (end type)

  • RF (Facial Convex):     The most common variant with an increased surface area for filling.

  • FF (flat):     flat surface,    suitable    for low-pressure devices and cast iron.

  • RTJ (Ring Connection):     Contains an annular groove for a metal seal; suitable for extremely high pressures and temperatures.

  • Tongue and groove connection/plug and sleeve connection:     for  a more precise  seal and to prevent joint movement.

By-products used in oil refineries

  • Carbon steel:     The most commonly used material for oil and gas pipelines.

  • Stainless steel:     resistant to corrosion     and     high temperatures.

  • Special alloys (Inconel, Monel, Hastelloy):     suitable for highly corrosive liquids or extreme temperatures.

  • Cast iron and bronze:     are mainly used in the auxiliary industry for low voltage.

Criteria for the selection of oil refinery lips

  1. Pressure and temperature:     should be selected according to the design level.

  2. Fluid type:   Corrosion-resistant     alloys are used in acidic or corrosive fluids.

  3. Ease of maintenance:     Some edges, such as overlapping joints, are easier to maintain.

  4. Cost:     Ring rims are more expensive but last longer, while slip-on rims are cheaper.

Use of lips in oil refineries

  • Pipelines for crude oil and petroleum products.

  • Pumps, compressors and heat exchangers can be easily installed and removed.

  • Check and inspect the pipes regularly.

  • Use blind edges to    temporarily or permanently block the flow path.

  • Improved safety during repair and maintenance work.

Advantages and disadvantages of using cable ties

Special feature:

  • The device can be disassembled quickly.

  • Ability to withstand high pressure and high temperatures.

  • Unity and high diversity.

Shortage:

  • Requires more space than direct welding.

  • If the seal is not installed or selected correctly, leaks can occur.

  • The initial costs are higher than for permanent welded joints.

Finally

Flanges are     a critical component of refineries and the oil and gas industry, playing a crucial role in connecting, sealing, and securing pipelines and equipment. Flange selection depends on operating pressure, temperature, medium, and operating conditions. The following flange types are commonly used in refineries:     pilot flanges, union nut flanges, blind flanges, weld flanges, threaded flanges, and cross flanges     . Furthermore, the surface finish (e.g., RF, FF, RTJ) and the material used significantly influence performance and service life.

Ultimately, correct design, proper dimensioning and correct flange installation ensure the safe and efficient operation of the wastewater treatment plant.