Fittings is a collective term for all the connective elements, installed in branching points, contractions and bends. These devices allow sealed blocking of traffic flow and, at the same time, simplify the process of assembling and disassembling the pipeline. A fitting may be made of metal or of softer materials; threaded, welded and tube fittings are the most common models, while flanges form a special group.
The article is kindly prepared by butt weld fittings UK manufacturing expert, Alexander Comley, a Birmingham-based firm with long years of successful experience under the belt.
The flange and its use
A true to type flange is a flat rectangular or round plate with holes for bolts throughout the perimeter. The main objective of the flange is ensuring strong and tight connection of pipes; flanges may also be used for connection of shafts and rotating parts. Flanges are produced in different shapes and sizes, though they are always mounted in pairs. To ensure the reliability and tightness of the connection a gasket is installed between the flanges. The shape and type of gasket, which is laid between the flanges depends on the pressure the pipeline is designed to deal with. Flat gaskets are used at a low pressure up to 4 MPa, while metal or asbestos pads are installed to withstand pressure up to 20 MPa. From time to time the seals are needed to be changed.
Flanges manufacturing technologies
Basically, there are three ways to produce steel flanges. In the first case, the flange is produced by hot stamping. A more innovative method of producing stainless steel flanges, practiced at AlexanderComley facilities, is gas cutting. Some flanges are made through bending and welding steel bands. Each method dramatically influences the quality of the final product and the cost of the finished flange respectively. However, much depends on the form needed to be delivered: thus, bespoke flanges of sophisticated forms demand pretty much technological effort to be manufactured; thus, e.g. tube sheet production, as claims Birmingham-based firm, one of the most resource-intensive processes.
Basic Parameters Of Flange Fasteners Described
The part covers the technical characteristics of flange fasteners; the set of characteristics focused on is applicable to both standard and bespoke flanges.
Operating pressure stands for the pressure under which the fluids (gas, vapor, etc.) are transported. Therefore, the higher system operating pressure is, the higher strength characteristics should be. In turn, the required strength characteristics are provided by the correct choice of fastener material, thermal treatment and etc. Thus, in the temperature range from -40 to + 400 ° C at a pressure of 100 kgf/cm2 it is recommended to make use of fasteners made from c35 steel type, while increasing the pressure up to 200 kgf/cm2 requires the use of fasteners made of steel 20X13.
Operating temperature is another crucial flanges parameter. Basing on the temperature of the medium, defined by the type of transportation as well as the external environment, the steel type is selected. Each steel grade has a certain temperature range in which a fastener can provide robust and reliable connection.
For example, at the same nominal pressure at a temperature not lower than -30 ° C it is recommended to use of c35 steel studs, while at the intended operating temperature of -70 ° C making the choice in favor of cold-resistant steel fasteners is a more reasonable option.
There are two main characteristics of the working environment to point out: temperature and chemical properties (aggressive or non-aggressive composition). In accordance with the above indicators flanged fasteners should be selected. For aggressive media the hardware that can withstand the devastating impact of the negative environment is selected.
All the threaded fasteners feature internal (nuts) and external (studs and bolts) thread diameter. Depending on the purpose and specifications under which the products are manufactured, the thread can be metric and imperial.