What are the Various Factors to Identify Suitable Flanges for Your Work?

It is crucial to choose the right flange for the application. If you want the flange to function, it must fit perfectly into the pipe joints. If you make one slight mistake while selecting the flange, it may affect the application and result in a costly error. For optimum usability, you can address the considerations relevant to choosing the right flange that goes well with the applications.


Flange Size

The flange size consists of several variables. These include the right pressure class, standards used, and right flange measurement. The inner diameter, outer diameter, number of bolt holes, the diameter of the bolt holes, and the bolt circle are influences. Flanges are available in many sizes ranging from 48″ (1200NB) to 1/2″ (15NB).

Flange Types

If you identify the flange type by its appearance, it is usually easy. Decide whether the flange has a socket weld, solder collar neck, lap joint, threaded bore, or flat face and that defines the basics.

You can start by choosing if it has a flat face that is completely raised or a flat face that is a slightly raised portion on the flange face with marked bottoms. There are many different types of flanges as indicated previously, in various material grades of carbon and stainless steel.

Flange Thickness

Define a flange by how it handles the high pressure. Apart from this, thickness plays a crucial role as thicker flanges can better handle higher pressures in an application.

Bolt Holes

The pressure class and size of the flange helps to determine this component. The actual size, pitch circle diameter, and the number of bolt holes, on the flanges, are the three variables that need consideration. The stronger and heavier bolt results in higher pressure that withstands the flange. The pattern must match up to the item the flange is bolting to.

Flange Standards

You can find a range in criteria that makes it tough to choose the flange standard. It is most likely that the choice is based on the standards and application of other components to which the flanges are linked. The three major standards used are JIS (Japanese International Standard), DIN (Deutsches Institut für Normung / European), and ANSI (American National Standards Institute).

Pressure Class

The pressure class is the nominal pressure quality that the product can safely work under or support. There are many pressure groups available for each standard, and it ranges from high-pressure tolerance to low-pressure tolerance. The pressure class of the items that operate together must be the same as the pressure class of the valves and pipes in the system to the ones they are connected. The pressure class of carbon and stainless steel flanges ranges from 2500#, 900#, 600#, 400#, 300#, 150#, and so on.

Flange Materials

It is crucial to select the right material for a flange. You must know the elements it will face in an application that uses the piping method is essential. Common materials include copper nickel, carbon steel, stainless steel, and steel. The supporting materials of these flanges, such as stainless Steel 317 flanges, are flange bolts, ring joining, and gaskets.

Other factors for selecting flanges

Consider the tolerances, flange dimensions, temperature and pressure ratings, and pipe materials to determine the appropriate flange material. ANSI ratings help to provide information on heat and pressure tolerances. The fitting type is one of the crucial things to consider. The material you choose must allow welding. For non-welded styles like lap joints or threaded flanges, weldability is not a major concern, and other requirements will take precedence.


Choosing the ideal flange for work refers to the standards required for your intended application. You must consider the pipe material that can connect to the flange and ensure that the flange material you choose is rated for the pressure and temperature it must withstand.

At Texas Flange, we offer all types of flanges for various systems. Our specialists can help you to identify the right flange for your equipment. If you want more information, contact us today!

The Manufacturing of Welding Flanges

The welding process for flanges helps to fix two pipes, equipment, or flange pipe fittings to form a union. First, put on a gasket between the two weld flanges, and use the bolts to complete the connection. Welding is a crucial process for the connection and construction of high-pressure pipelines. The welded type flange is easy to use and can withstand high pressure. Welded flanges are used widely in metallurgical pipelines, power stations, natural gas, petroleum, and other fields.

There are two main systems for international pipeline flange standards.

American pipeline flange system represented by American ANSI pipeline flanges.

European pipeline flange system represented by German DIN (including the former Soviet Union).

In addition, there are Japanese JIS pipe flanges, but they are usually used for public works in Japan or on Japanese fabricated vessels.

Pipe flanges in various countries

The assembly and the large flanges within the assembly are joined as per the requirements of the drawings. The large flange is divided into eight equal parts. With large grooves and thick flanges, multi-layer and segment symmetry welding is useful. The welding result is required to have the strength of the base metal at a minimum. The surface of the weld must be smooth and flat, and there must not be any defects like an undercut, slag inclusion, lack of welding, gas holes, etc. The residual height is usually to be less than 2 mm.

The Manufacturing of Welding Flanges

When it reaches the bottom, use J506 electrodes for manual surfacing and low current welding. Carry on the welding in strict accordance with the welding process. After each welding position, a level gauge is useful to clamp the deformation of the flange plane, and the welding seam must be hammered with an air hammer in the welding process to achieve the effect of elimination stress.

Technical requirements for flange welding

The inclination on both sides of the neck and head of the butt welding flange must not exceed v=7. The performance parameters of the butt welding flange need strict control in the welding and manufacturing process.

When manufacturing welded flanges, the selection of specific performance regulations and parameters helps to ensure that certain methods and basic principles can be promoted and applied.

Butt welding flanges are not easy to deform and come with good sealing performance. There are requirements for relative ductility and rigidity.  Butt welding flanges are applied to many fields. The horn-shaped structure is suitable for pipelines with great working pressure, great temperature, fluctuations, high-temperature, high-pressure, and ultra-low temperature pipelines. It is useful to connect pipelines and gate valves with PN exceeding 2.5MPa; it is also helpful for pipelines that contain explosive and flammable substances.

Does annealing temperature reach the required temperature?

Finalization of butt welding flanges after manufacture usually happens by heat treatment, quenching, and tempering. The temperature can range from 1120 to 1140 C as per industry standards. It is observable according to the inspection of the quenching furnace.

The butt welding flange generates water vapor in the forging furnace. Additionally, you can check whether the raw materials on the furnace wall are dry or not. During the furnace installation for the first time, the materials on the furnace wall must be air-dried. On the other hand, if you find holes in the flange pipe, check whether or not there are excessive watermarks on the flange pipe when entering the furnace. The presence of water must not be there otherwise as it will destroy the furnace’s atmosphere.


Butt welding flanges are used widely in pressure vessels, pharmaceutical facilities, industrial production, chemical plants, crude oil, power engineering, natural gas, etc. The price of carbon butt welding flanges are reasonable given the high pressure applications for which they serve.  Stainless steel butt welding flange is high-pressure, and corrosion and heat resistant as well, though at a higher cost.

You can contact Texas Flange for any inquiries related to the manufacturing of welding flanges.

How Are Flange Bolts Tightened?

Bolted flange joints are used widely in water mains. It is the reason why a proper bolt tightening sequence in flanged joints is a must. This precaution helps in controlling the stress variation in flange joint components. If not done right, the chances of leakage are higher at flanged pipe joints during the operating conditions.

There must be a correct bolt placement by tightening them properly and that of gaskets and their placement in a flanged joint that will help ensure a leak-free joint. With the help of proper bolt tightening, it will also help you make sure that there is uniform load distribution in all the bolts without injuring the gaskets. In this blog, you’ll learn how you can properly tighten the bolts of the flange.

Before you begin with the actual flange bolting, the bolts/nuts, gasket, flange need some observation.

Checking points of flange before bolt up

If there is any leakage through the flanged joint, the layout of gasket material prevents the flange surface from any type of imperfection and seals them. You can see the limitations that a gasket can successfully seal. You must review the flange surface thoroughly and make sure there are no gouges or dents. The flange surface finish must exist as per the recommendation of the manufacturer for particular gasket materials.

The recommended values of the flange surface roughness areas follows:

Metal or Jacketed Clad Gaskets: 63-80 rms
Spiral Wound Gaskets: 125-250 rms
Solid Metal Gaskets: 63-80 rms

The meaning of rms stands for root mean square. The specification of roughness is usually millionths of an inch as the average of valleys and peaks measured from the midline of the flange surface. The recommended radius of the flange is usually 1/16″, and the round-nosed tool must have 30-55 serrations per inch in a spiral or concentric pattern.

How Are Flange Bolts Tightened

Now here are a few points to check before the flange bolts are installed.

Ensure proper cleaning of the gasket seating areas before insertion. In case of serration damage, re-serration is a must.
In the case of ANSI B31.3 not meeting the requirements, do not forget the rectification of the piping components.
According to clause no. 335-C in ANSI B31.3, permitted tolerances are as given below:

1. The alignment of the flange faces must be as per the design plane within 1 mm in 200 mm (1/16 in./ft) measurement across any diameter.
2. The alignment of the flange bolts must be within 3 mm (1/8 inch) maximum offset.

Check if the flanges are co-axial or parallel before you insert the gasket in between the flange pipe.

Checking points for the gaskets before tightening flange bolts

Examine the gasket making sure it is free from all defects.
The location of the gasket must help to ensure the full sealing. For instance, the gasket that is on the tube sheet of the exchanger requires a proper location so that the outer periphery of the gasket can match with the OD of the tubesheet at every point.
Make sure that the gasket is of the right dimension with the usage of specified materials.

Bolts for pipe flanges

Bolts must create compressive pressure on the gasket and flanges so that you can prevent leakage. So when you want to select, the temperature variations in service are considered.

Do not avoid the usage of short bolts on the flange joints.
The bolt’s lubrication with molybdenum disulfide is recommended, especially in all the bolts of size 7/8″. You can check the application as the bolt load is developed by torque and depends on the lubrication of threads.
The cleaning of nuts and bolts with suitable solvents is advisable, such as CTC/Diesel with the use of a wire brush, especially in the threaded portion.
Make sure that the material of all the nuts and bolts is specified.

Procedure for flange tightening

It is essential to tighten all the bolted joints in a uniform and diametrically staggered pattern.
In the case of pipe flanges from 12″NB to 8″NB and a pipe with spacer piece with at least two gaskets, the distance measured between the two flanges must be at four locations like 6’o clock, 9’o clock, 12’o clock, and 3’o clock positions and require equal distance for even tightening.
The stud bolts of 7/8″and above can be tightened with the use of a torque wrench. Make sure that the tightening load to every bolt is applied uniformly as possible. You can carry the tightening in three to four stages in the steps of 70, 50, and 30 percent of the final torque value. The fourth stage uses 70 percent again for the final torque value.
For the exchange of heat, final torque can value up to 100, 70, and 30 percent of the final torque value.
Follow the guidelines by the manufacturer wherever you can find the recommendation to use the hydraulic tensioner for bolt tightening.

Wrong practices for tightening flange bolts

There are many times when the plant operators end up following wrong practices for the flange bolt tightening. These are as follows:

Usage of rusted/dirty fasteners without lubricating
Usage of ordinary fasteners and not high tensile ones
Using a lot of gaskets for filling larger gaps between the flanges
Improper storage of gaskets
Reusing old gaskets
Improper sequence of bolt tightening


Flange bolt tightening is not an easy task. You must take care of all the elements required to understand the proper flange bolting, be it flange thickness, bolt sizes, or any other. Also, make sure not to go forward with wrong practices as it’ll put you at risk later.

If you need assistance to know more about the flange bolt tightening or choosing the right type of flange, contact Texas Flange today!

Use of ASME B16.5 Standards for Flange Pressure Ratings

Engineers rely on ASME/ANSI standards and codes. The construction of the piping system helps to make sure that they meet the prescribed requirements of pressure integrity. The standards and codes help to determine the characteristics of pressure integrity and simplify the design rules.

The difference between the codes and standards is helpful for the designers with detailed flange specifications and designs for the components. Here are the frequently encountered rules and standards:

1. Minimum wall flange thickness

2. Permissible materials for construction

3. Allowable work stresses

Structural behavior is due to the effects of thermal expansion, live loads, seismic loads, deadweight, internal pressure, and other imposed external or internal loads.

However, the piping codes provide no design rules for standard in-line components like standard valves and flange fitting components. The designing of these classes of elements happens through the reference to the industry standards.

1. Pressure-integrity standards: The standards help in providing uniform minimum-performance criteria. The designing and manufacturing of the components to the same standards will be helpful to function equivalently.

It helps to remember that pressure integrity is not entirely synonymous with leakage integrity. During the operation and test, pressure integrity is one assurance when it comes to the leak-tight condition and does not account for the entire risk profile to the structural stability of the pressure boundary or added stresses.

2. Dimensional standards: The standards provide the configuration that helps in controlling the parameters for components. The primary purpose of these dimensional standards is to ensure that the manufacturing of similar parts by different suppliers will be physically interchangeable.

Conformity to the specified standards of ASME flange dimension during manufacturing a product doesn’t imply that the configuration of all such similar products will provide equal performance.

There are many different ASME standards for piping components that provide pressure-temperature ratings in their included “Reference Codes and Standards” sections.

As per the ASME B16.5, 2017, there are:

a. 16 nonferrous metal groups

b. 10 high-alloy steel material groups

c. 8 low-alloy steel and carbon material group

If you want to check the complete lists and tables, you can check them on ASME B16.5, 2017. (Standard: “Pipe Flanges and Flanged Fittings: NPS ½ through NPS 24 Metric/Inch Standard”.)

The flanges with any material in the same group can easily carry the same pressure class of ASME flange and have the same pressure-temperature rating for almost any single material group.

The ASME B16.5 standard provides the 7 pressure classes for flanges. These are – 2500, 1500, 900, 600, 400 (less common today), 300 and 150. Class 75 also exists in ASME B16.47 Series B large diameter.

The rating for flanges in terms of pressure temperature represents all the material groups organized within 44 tables. One table includes the ASME B16.5 2017 ed, for every material sub-group or group.

Table B2.1 is the adaption from ASME Standard B16.5 and is typical of the 34 flange rating tables that provide the pressure-temperature ratings for the flanges in the 2.1 material group.

The tables you will find below are organized as per the pressure classes that you can find at the top. At the left-hand border, you can also find the maximum working temperatures.

During the practice, using ASME B16.5 to determine the rating of the flange is relatively easy. Below is the recommended three-step process:

a. Determine the maximum temperature and operating pressure required for the flange.

b. You can select the material of the flange from the material groups of the 44 listed materials. Be aware of the qualifying notes that concern maximum operating temperatures for various materials that may influence the final material selection.

c. You must consult the right group table of material. You can start with the temperature listed in one increment higher than the desired maximum operating temperature. Try to start with the Class 150 column and then proceed to the right until you find the proper pressure rating for the desired temperature, exceeding or equal to the required operating pressure.

The specified column that can satisfy the requirements can dictate the required pressure class and determine the actual pressure-temperature rating of the flange.

ASTM A182 is one of the chrome-based material specifications from material group 2.2.

If you consult Table B2.2 at a temperature of 650°F (343°C), a Class 600 flange has a rating of 890 psig (6136 kPa gage) at 650°F (343°C).

Table A1.1 Materials Used for ASME B16.5 Flange Construction (Partial Listing)

ASME B16.5 Flange Construction
Table B1.1 Pressure-Temperature Ratings for ASME B16.5 Flanges Made from Material Group 1.1 Materials

Table B1.1 Pressure-Temperature Ratings
Table B2.1 Pressure-Temperature Ratings for ASME B16.5 Flanges Made from Material Group 2.1 Materials

Table B2.1 Pressure-Temperature Ratings
Table B2.2 Pressure-Temperature Ratings for ASME B16.5 Flanges Made from Material Group 2.2 Materials

Table B2.2 Pressure-Temperature Ratings

If you still have any doubts about how to select flanges and what to look for, do let us know in the comment section or call us today!