The Use Of Pipe Fittings

The Use of Pipe Fittings

With the development of petrochemical industry, the engineering construction tend to be larger and more complicated, pipe fittings used in piping engineering according to different working condition, the pipes are also varied. Which is used to change in the direction of piping branch or different sizes of the pipeline and pipe connection pipe, its usage environment is far more demanding than straight tube. Pipe materials used can be a pipe, plate, forgings, castings, rods, etc. The processing method can be welding, stamping, casting or forging. Usually, pipe material and thickness depends on the used tube material, shape, size, and the conveying fluid medium, pressure and other factors.


(1) The elbow and mitre elbow are often used in pipe bending parts, in order to change the course of the pipeline. Commonly used with 45° elbow and 90° bend. Bending radius of about 1.0 times of the pipe diameter is called short radius elbow; and the bending radius is about 1.5 times of the pipe diameter is called long radius elbow. In the pipeline system, general appropriate to choose long radius elbow connection, and the short radius elbows are usually used in piping installation position or more compact situation in order to reduce the cost. When using short radius elbow, the maximum working pressure should not be commonly 0.8 times more than the same specifications of the long radius elbow. Miter elbows are normally used for low pressure (design pressure s 2.0 MPa), water and similar fluid conditions of large size which has a more moderate line. When the direction angle of the miter elbow of the single section is greater than 45, it should not be used for toxic, flammable medium pipeline, or under vibration, pressure pulsation and due to temperature change of alternating load line.

(2) The reducing joint and short reducing joint is used for short straight connection of the two pipes of different size pipe to change the diameter of the pipe. There are concentric sloper and eccentric sloper. The centre line of the two tubes connected by the concentric reducing joint lines on a straight line, mainly used in vertical pipeline. Eccentric sloper mainly used in horizontal pipeline. With straight section of sloper, GB12459 (DN20x 15 ~ 500 ~ 300) made by the seamless steel tube; Without a straight section of sloper, GB/TI MOI (DN350 x 300 ~ 1200 x 1000) made by steel plate or steel belt. Usually, large diameter pipe connection with reducing joint using steel plate or steel belt to make the price cheap, economy but elbow without straight section reducing joint, the welding groove in the alignment of more difficult than with straight segment sloper. In small diameter pipe (below DN50), also often use nipple diameter instead of reducing joint for pipe diameter changes. Reducing nipple also has the branch of concentric and eccentric. 

(3) The pipe coupling is to lead a branch pipe from the main pipe, and it includes tee, cross pipe, branch pipe, half coupling, etc. Tee is used for the joint of main pipe and branch pipe, usually have equal tee, reducing tee and tee. Oblique tee usually instead of tee is used to transport solid particles or pipe erosion which is more serious.

(4) pipe connection is used for straight line connection of instrument, and the connection includes socket weld or threaded connection. It is mainly used for small diameter of low pressure pipeline, for the part which often need to install and tear down, or as a final adjustment using threaded pipe line. Structure is better to adopt metal surface contact seal structure, and the structure of gasket seal is typically used for the general piping for conveying water, oil, air, etc. In addition, the usage and the price also is the relative factor.

(5) The pipe cap is used for the pipe with closed end closed. For the same purpose, blind flange is also often used, so that good for the pipe purging and cleaning. Generally, according to the requirement of the size of pipe connection, and considering the possibility of future expansion on economics or engineering requirements to determine the cap or blind flange. Pipe cap form of connection includes screw thread, socket and butt welding.