Titanium Flanges and Piping
Flanges are common elements used to connect components within a piping system. Titanium piping and any other piping require a way of connecting the different components that form part of a pipeline, such as the pipes themselves, valves, pumps, filters, among other equipment.
Moreover, different elements have different materials and demand specific connection types. Therefore, there is a wide variety of flanges to choose from. The question is, how to choose the right option. Keep reading to discover it.
What are flanges?
Flanges are normally defined as a protruding ridge or rim which is intended to increase the strength of an element or distribute the load applied on it.
When used to connect elements in a piping system, a Titanium flange is usually a protruding rim which is welded and/or bolted to the elements requiring the connection.
Generally, each of the elements being connected will have a flange attached so the joint is done by bolting the two flanges. To guarantee the sealing of the connection, a gasket is placed between the flanges.
Types of flanges
As mentioned above, there are different types of titanium flanges. Here are the most common types and when they are recommended:
Weld neck flanges
These flanges require butt welding for installation, hence the name. The tapered hub on one end of the flange is welded to the end of the pipe or fitting. These flanges provide high temperature and high-pressure operation, which is why they are recommended for process piping, especially those with repeated bends and pipe diameter changes.
Socket weld flanges
For the installation of these flanges, the pipe is inserted into the flange and then a fillet weld is done to secure it against a shoulder located at the bottom of the flange. This installation is simpler than the other welded types and helps avoiding the limitations of threaded ends. However, it has its own limitations since these flanges are only recommended for use in small diameter pipes working at low temperatures and low pressures. The best feature of this type of flanges is that it results in a smooth bore and improved flow.
Threaded flanges
Sometimes called screwed flanges, they have a female thread inside the bore for easy installation of male-threaded piping or fittings. These are commonly used when welding wants to be avoided, but they cannot be used in high temperature and high-pressure applications.
Slip-on flanges
These are similar to socket weld flanges with the different that they do not have the shoulder for the pipe to rest on, so it requires welding on both sides. The main advantage is that there are many sizes and materials available, which makes them a good choice for systems with high flow and production rates.
Lap joint flanges
These flanges are formed of two pieces, a stub end and a backing flange. There are two requirements for the installation, butt welding the stub end to the pipe and sliding the backing flange over to achieve the flanged connection. The backing flange is the one that provides the holes for bolting the lap joint flange with the other flange in the connection. This type is recommended for confined or reduced spaces.
Blind flanges
There are some cases where a system requires isolation or termination of certain sections. Here is where blind flanges are relevant. These flanges are basically blank plates that can be bolted to another pipe flange and provide the needed sealing when combined with appropriate gaskets. They are recommended for their easy installation and removal when or if needed.
How to select the right flanges?
Apart from the type, you have to pay attention to some important characteristics when selecting the best flange for your specific applications. These include the size, the pressure class and the material.
Let’s take a closer look to some of them.
Selecting the size
To select the flange size, you need to refer to ANSI/ASME standards. These standards provide the sizing of the flange for the specific pipe diameter that will be connected to the flange. They usually include tolerances together with requirements and recommendations for flange bolting and flange gaskets.
Pressure class
The pressure class makes reference to the pressure and temperature capacity of the flange. The term is used interchangeable with others, such as “pressure rating”, “class”, “#”, “Lb” or “Lbs”. ANSI/ASME standards are also applicable, and according to ANSI/ASME B16.5, there are seven flange pressure classes: 150, 300, 400, 600, 900, 1500, and 2500.
These values are tightly related to sizing too. While two flanges may have the same bore size and the same material, having a higher class means it is bigger, heavier and more robust to withstand higher temperatures and pressures depending on the material.
For example, ASME B16.34 takes care of the class for the most common flange materials which are carbon, alloy and stainless steels.
Selecting material
The usual recommendation is to use a flange made of the same material as the pipes and fittings that will be connected to the flange or at least a compatible alloy. For example, in the case of titanium piping, the best choice would be titanium flanges or zirconium flanges.
The idea is that the chemical composition of the materials does not create undesired reactions, especially when in contact with process fluids. ASTM standards apply for the specifications and requirements of the materials. ASTM standards assign a grade for easy identification of the material and describes the chemical composition in percentages.
Common ASTM specifications for flanges are A105, A182 and A350. For titanium flanges, the ASTM standard gives specifications such as B363 and B381.
Flanges and titanium piping
All that is described above applies for titanium flanges and piping. However, being a special material with special capabilities, flanges and titanium piping will provide great capabilities for almost any and every application.
Of course, each application requires a proper analysis to optimize results from the flange selection. If you are not sure on which type, class or grade of flange works best for your titanium piping, the recommendation is to consult an expert to make sure you get the highest return on your investment.