Dimension standards for DN15~DN40 reducers (butt-welded)
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The dimensional standards for elbows of sizes DN15~DN40 (for butt welding): some companies use GBT12459, while other companies (within certain industrial complexes) use GBT14383 for this size range; in that case, socket welding is employed, and there is no option for butt welding. Yet some other companies (large enterprises) use SHT3419. Since GBT12459 does indeed specify elbow dimensions for this range, why don’t these industrial complexes use it? I don’t know what the situation is at Haiyou’s company?
The shape of 12459 can be achieved using forgings; it would thus be considered a custom product, although the cost is much higher than that of 12459
Does the teacher mean that SHT3419 is much cheaper than 12459? DN10–40
No, these two are the same. The forgings you requested need to be welded together as well; only then will they tell you to create the welding joint according to the forging design.
There are various types of horizontal reducer fittings for DN15~DN40: 1. The reducer coupling type, which uses an eccentric pipe clamp, can be used. The end can be a socket type or a threaded type. It is a socket pipe clamp when it has a socket connection, and a threaded pipe clamp when it has a threaded connection. The standards are GB/T 14383, SH/T 3410, ASME B16.11, etc. 2. The swaged nipple type can be used. The ends can be flat, beveled, or threaded, or a combination of the above three, meaning that the connection styles at the two ends are different. The standards are SH/T 3419, MSS SP-95, etc. 3. A reducer, which is a type of reducing fitting (size change fitting), can be used. The end is in a groove shape. The standards are GB/T 12459, SH/T 3408, ASME B16.9, etc. It is worth noting that: 1. GB/T 14383, SH/T 3410, and ASME B16.11 all pertain to forged pipe fittings, and the raw material must be forged. 2. Both SH/T 3419 and MSS SP-95 are seamless products; the raw materials can be seamless pipes, as well as bars or forgings. 3. GB/T 12459, SH/T 3408, and ASME B16.9 all apply to seamless or welded components; the raw materials can be seamless pipes, welded pipes, sheets, bars, or forgings. The specific type of diameter change to be used should be determined based on the operating conditions. The main factors to consider include the following: 1. For ease of disassembly, threaded pipe clamps can be used, such as for instrument air pipelines ； 2. Considering harsh operating conditions, fittings of the butt-weld type must be used. Such as high temperature, low temperature, high pressure, severe cyclic operating conditions, severe corrosion conditions, etc ； 3. When purity requirements are considered, socket-welded pipe fittings such as those used for lubricants should not be used. 4. When considering the installation size requirements, under the premise of meeting the operational conditions, it is advisable to choose those with smaller installation sizes. 5. Compared to a reducer, a swaged nipple has a section of straight pipe at its end that can be inserted into a socket or thread, whereas a reducer does not have such a section at its end and can only be welded. Typically, pipeline material engineers specify the requirements for using reducers in the grade tables.
The chemical industry generally uses GBT12459, while SHT3419 is the industry standard for the petrochemical sector. When making a selection, it is necessary to consider the specific operating conditions. If it is to be used in the chemical industry, then the GBT12459 standard should be adopted; if it is to be used in the petrochemical industry, then SHT3419 should be chosen