Define the Various Grades of Carbon Steel Flanges

Carbon steel flange and end flange connectors are made of carbon steel. Common standards include ASTM A694, ASTM A105N (SA105N), MSS SP-44, DIN 2533. When you accompany, pressure ratings are from class 150 to 2500.

Carbon Steel flange

Carbon steel has a carbon content of up to 2.1% by weight. AISI defines it as:

  • No alloy element (minimum content) is required, as of Va, Ti, Ni, Mo, Cr, etc.
  • The specified minimum of Cu shall not exceed 0.04%.
  • Maximum Mn 1.65%, Si 0.06%.

As the carbon element content increases, the steel becomes more robust and complex after the heat treatment. On the contrary, it becomes less ductile. When without any heat treatment, higher carbon reduces weldability.

Carbon steel may include alloy steel in case it is not helpful as stainless steel.

Different grades of carbon steel flanges

The main component in manufacturing carbon steel flanges is carbon and iron steel. The forged carbon steel flanges help connect pumps, valves, or other equipment—the grade of steel changes on the material and its carbon content.

The different grades of carbon steel flanges are ASTM A350, ASTM A516, ASTM A694, ASTM A182, and ASTM A105. About 1% to 2% is the weight of the carbon in the carbon steel flanges.

The increase in carbon content in the element makes steel stiffer and sturdier. It also makes things less ductile. Higher carbon may reduce weldability if not treated with high heat.

Carbon steel A105 Flanges

Carbon steel A105 flanges are forged steel piping components that are useful for flanges, fittings, and valves in pressure systems at higher temperatures. You can operate on carbon steel flanges between 0 degrees to 550 degrees.

It is suitable for marine engineering and hydrocarbon processes. It has been helpful in gas, oil, and nuclear power plants equipment, valves manufacturing, petrochemical plants, pump manufacturing plants, and other places.

Carbon steel A350 LF2 Low-temperature flanges

Carbon steel A350 LF2 flanges are made with ring-rolled carbon flanges, forged fittings, low alloy steel forged, and valves for low temperatures. These flanges come with extensive pressure resistance, strength, and durability.

The type of carbon steel flange provides machinability when it is forged and hardened. It offers moderate strength. It is mainly in high demand because of its high hardness.

Carbon steel low Alloy A182 Flanges

The carbon steel grade is helpful for stainless steel pipe flanges, valves, and other high-temperature services. The type of steel suits the low corrosion applications. These flanges do not wear out quickly. These flanges are widely used, mainly in the petroleum, paper, and chemical industries.

The features of these flange types suit the most as it stays for a more extended period. It does not require repair after the installation. If you purchase these products from the right place, it will help you ensure their durability.

Carbon Steel A694 flanges

It is the most carbon stress-reliant steel flange material. It suits the high-pressure transmission of oil and gas piping. The products made with this steel are usable in the high-yield service.

The manufacturers of this steel need to build steel that can withstand cryogenic, high temperatures. The high carbon content with heat treatment makes it less ductile. If there’s a lack of heat treatment, it may reduce its ability to weld.

Forged carbon steel flanges

There are different ways you can manufacture flanges. The most prominent way is to forge and cast it. Flanges are plate-like devices that can be added at the end of the pipe; a valve and fitting can put a piping system altogether.


The manufacturers develop flanges that are useful in fittings and pipes. Forged steel has the best mechanical properties than any other product. It has excellent use for industrial purposes. It is often used with an attachment of a valve at the pipe end. It also functions for outlets and inlets.

Main Causes For Flange Leaks and How to Fix Them?

Piping systems play an essential role in worldwide infrastructure. These systems have been around for decades. Installing a piping system is not an easy task. If components like flanges are not properly selected and lack the right flange connection, corrosion and leaks could occur. When corrosion and leaks occur, a breakdown in the assembly can happen and cause a monstrous mess.

Below are few possible causes of corrosion and how to avoid it.

Bolt Stress

There are a lot of things that may put stress on the bolts. Vibrations that occur during the normal operating conditions tend to bolt movement leading to corrosion and leakage. Although the vibrations happen by normal operations, it is still something that you can avoid to a degree. Tightening the bolts seems to be an obvious solution, but you need to consider how often you need to check them.

Main Causes For Flange Leaks and How to Fix Them

Temperature also plays a part in how well bolts connect and whether they are successful in preventing leaks. Temperature fluctuations happen during an increase in temperature and cause bolts to become loose and not seal properly. Minimizing temperature fluctuation when possible is ideal.

Due to the usual operating procedures for high-stress environments, you can expect to tighten and check bolts due to temperature fluctuations. When bolts are tightened and checked, and the issue does not seem to be remedied, you may be dealing with another issue besides expected wear from normal operating procedures.

Thermal Stress

The temperature of the product (inside a tube heat exchanger and shell for example) can vary. However, the distortion caused by the rapid change from cool to hot solutions is inevitable in few cases. If this is the case, it is essential to ensure all parts of the exchanger are designed to account for temperature distortion. Alloys are considered carefully by engineers for this very reason.

If you want to determine your requirements, special considerations need to be made regarding the flange dimensions. Next, determine the temperature of a high load area within the tube and a random area on the shell side. Calculate the difference between the tube side outlet and inlet and the difference between the random area on the tube side and the shell side.

Other Stresses

Many things can produce stress on the bolts of the flange connections, but one, in particular, is the stress on both sides of the flange assembly point. When circumstances happen to cause one side to be tightened more than the other, the gasket becomes damaged, resulting in leakage. It can happen by improper bolting procedures during the initial installation.

Sometimes these pipes are assembled in small spaces, making it hard to reach specific bold to tighten them. It can lead to some bolts being properly tightened while the others are not as tight. The same amount of pressure needs to be applied to all bolts. It helps to hold the gasket securely in place due to corrosion and leakage.


It may not be easy to spot imperfections. Sometimes warped surfaces can lead to improper installation. If the flange face is warped or has other deformities, improper seals tend to occur. While the issue may not cause direct interruptions in the flow, it can cause corrosion and leaks. Just like other pipe fittings, flanges usually need to work in conditions free from any defects to work properly. Some of the defects are easier to notice than others. A welded face may be harder to recognize, and it could easily get overlooked. Flange face re-machining is a common remedy in these cases.

Need Of Additional Hardware

A recurring problem in a tube and shell heat exchanger, bolts need to stay secure, despite efforts to tighten them using the proven techniques. Even after hydraulic tensioning and hot torquing, the bolts would loosen and cause problematic leaking in the plant.

Researchers identified two problems: gasket scuffing and excessive bolt load. The excessive bolt load happens due to temperature differentials. If you want to combat this issue, install disc spring washers before you replace the bolts. They found that these were more capable of handling the load to the bolts without allowing flange deformation in most cases.

The second issue of gasket scuffing was likely due to movement during operation and caused enough damage to the gasket, that even with adequate bolt tightness, it would continue to leak. The gasket needs replacement, but the problem also needs to be addressed so the new gasket would not also fall into disrepair. If you want to avoid this, a weld ring consists of two separate halves of the gasket ring welded together to contain the gasket material and prevent any deformation.


If you are experiencing gasket leaks in your tube and shell heat exchangers, it could indicate that something is amiss in your equipment. The staff at Texas Flange are happy to help point you in the right direction and recommend the right sourcing for your assembly hardware needs along with the usual flange and fitting products we provide our customers every day.

Difference Between ANSI and ASME

American Society of Mechanical Engineers (ASME) and American National Standards Institute (ANSI) are important organizations in the flange industry. Each of them plays an integral role in developing the standards and codes that govern the industry.

Many people usually fail to understand the difference between the two or realize that these organizations are technically two distinct non-products that work separately and impact the flange industry.

Here in this blog, we’ve tried to make it clear about the difference between the two. Before that, we must explain the meaning of each term.

Meaning of ANSI

ANSI was established in 1918. The focus of ANSI is to oversee standards for services, systems, processes, and products offered in the US. The organization consists of members from organizations and corporations, as well as scholars from different academic fields, companies, and government agencies.

The primary purpose of ANSI is to work in a way to solidify the position of the US in the global market by establishing the standards for services and products. The goal is to ensure that the performance and feature levels of items created in the US are consistent and up to par.

Adding on, ANSI accredits organizations that train personnel and produce products to meet their established requirements and standards. They always keep an eye on and check if the services and products are meeting their standards well. They need to consider and update these performance requirements as per the need. They also play a huge role in some initiatives about environmental conservation.

Meaning of ASME

ASME was founded decades before ANSI in 1880 and is one of the oldest standards to develop the organizations in existence. The establishment of society happened after numerous failed occurrences of steam boiler pressure vessels that were devastating. The main focus is to create standards and codes for mechanical equipment.

In the industry, especially the ASME code, it is also called ASME Boiler & Pressure Vessel Code. The main reason for its establishment is to regulate the manufacturing, development, and design of the boilers utilized in various industries.

ASME serves as one of the leading international developer codes and standards to regulate the mechanical engineering industry. It is one of the private organizations to promote multidisciplinary engineering, science, art and encouraging collaboration across engineering disciplines. ASME also involves various industry and periodicals publications, education courses, professional development, and conferences.

How ASME and ANSI differs

At the first look, you can see that ASME and ANSI seem to play similar roles in the industry. But in reality, many things set them apart. You can see it from the description above. Now here are a few crucial distinctions that set the two apart:

1. The foundation of ASME happened decades before ANSI came into existence. ASME was founded in 1880, while ANSI was founded in 1918.

2. The main focus of ANSI is to strengthen the US market position, while the focus of ASME was to develop solutions to mechanical engineering safety issues and problems.

3. ANSI accredits and established quality and performance standards for services and products in a huge variety of sectors, while the primary focus of ASME is on pressure vessels and boilers.

4. ANSI works towards strengthening the position of the US in the global market, whereas ASME works towards finding the solutions to real-time mechanical engineering problems.

5. ASME has developed 600 standards and codes for various mechanical devices, while ANSI has designated approximately 9500 standards.

6. The ASME members include engineering professionals and individual volunteers from other organizations as its members. On the other hand, ANSI members are chosen individuals from organizations, academic fields, government agencies, and corporations.


It is essential to know the difference between ANSI and ASME before anything. If you order a flange fitting at Texas Flange, you will get products that adhere to ASME B16.5, B16.47, or B16.9 per your project requirements.

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!

Guide to Properly Measure Flanges

Flanges are the best and easiest way to connect pipes, pumps, and valves. They come in different types and shapes. Flanges are in high demand and are the most convenient and cost-effective components in the piping system.

Flanges and their Advantages:

Flanges are ring-shaped devices designed to substitute for welding in various piping system components. A flange is integrated into the piping system either by welding or screwing. Flanges are highly flexible and can be easily fixed or removed if any modification is required. So the industries that require frequent maintenance rely on this piping system component. While purchasing flanges, make sure they possess high-pressure ratings and a good capacity to tolerate extreme temperatures if your application requires this.

Flange Faces and Its Types:

Before moving on to the different flange types, it will be productive to know about the different flange facings.

Flat face

Raised face

Ring-type joint face

Pipe flanges are made up of materials like stainless steel, cast iron, aluminum, bronze, brass, and even plastic. The most preferred material is the forged carbon steel. Each flange is different and has different characteristics, and so when choosing a flange, always double-check to make sure that it meets the specific requirements.

Flanges are available in different types, and so it is easy to choose according to your specific needs. Most commonly they are blind flanges, slip-on flanges, and welding neck flange, and less often they are socket welding flange, threaded flange, lap joint flange, and custom. Among these, welding neck flange is preferred in piping systems of a more complex nature.

How to Find Out the Right Flange Dimensions?

It is common knowledge that flanges can join the pipes to other parts of your assembly or vessel, but to get the best out of flanges, you must ensure that the flanges are correctly measured. Only then, the rest of the process can be done smoothly. Finding the apt flange dimensions is the primary and essential step.

A few efforts are required to get the right flange dims. The right measurement is completely dependent on understanding the accurate pressure ratings and the size of the corresponding pipe.

First, to measure the standard pipe flanges, measure the outer diameter of the flange (O.D.). It can be achieved by measuring from the outer edge of the flange to the opposite outer edge and then measuring the flange’s inner diameter from these two outer reference points.

Similarly, while taking flange dimensions, you should consider the flange base thickness too. For this task, you only need to analyze the thickness of the attaching outer rim (the base where the bolt pattern is located).

Calculating the Flanges Weight:

While calculating the weight, it is necessary to understand that the construction of pipe flanges is directly connected to the material grade and the pressure it can handle.

The weight calculation of pipe flanges is based on the model of the flange. Now calculating the flange weight is pretty simple as most of the manufacturers have provision for this. Just providing few details like outside diameter and inside diameter, the thickness of the base, number of drill holes, the diameter of the holes, and chamfer can easily help calculate the flange weight in seconds.

Measuring Flange Thickness:

Flange thickness calculation can be achieved through some techniques. In standard flanges, by understanding the design conditions, especially the pressure and temperature of the piping system and the kind of piping material, the thickness can be found. In this situation, no calculations are required to find the flange dims. All you need is to check the ASME pressure vessel design calculations and determine the ratings that match the design condition. Once you find out the flange rating (class), it is easy to find the standard flange dimensions from the ASME B16.5 table.

Flange Specifications:

Many standard flange specifications are available depending on the variety of industries. Flange specifications indeed vary according to the industries and their applications. Most of the standard manufacturers offer popular flange specifications like ASME/ANSI flanges, DIN flanges, API flanges, and AWWA flanges. ANSI standout best and most popularly used among the various flange specifications because of its ubiquitous mechanical designs amongst ASME engineers.

ANSI Flange and its Dimensions:

ANSI (or the American National Standards Institute) is the most standard flange specification and the most preferred flange in various industries. The standardized ANSI flange dimensions are 150, 300, 400, 600, 900, 1500, and 2500, in sizes NPS 1/2 through NPS 24. Furthermore, ANSI B16.47 covers pressure classes ranging from 75 to 900.