Questions about gas pipeline valves
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I have a project here where I need to create a DN1400 opening in a DN2400 gas pipeline. I would like to know how much length of pipe should be left ahead of the newly created opening for installing a DN1400 butterfly valve Also, is it best to leave a blind flange in front of the valve? Please ask those who know to help. Thanks first
What kind of flanges and gaskets are generally used for gas pipelines? Is it necessary to install a vent pipe? Drain pipe? What medium is used for pressure testing?
There is no specific requirement regarding the length of pipe to be left in front; it is sufficient if there are two to three hundred millimeters of length in front of the flange. Valves that are resistant to sulfur corrosion should be used.
It is necessary to install a blind plate in front of the valve.
The length to be left in front of the valve depends on the site conditions; the most important factor is to meet the requirements for installing and removing the valve, ensuring that the bolts can be removed. As for whether the blind plate should be installed before or after the flow of fluid, it depends on whether maintenance is carried out more frequently on the process before the valve or after it. If maintenance is done more often before the valve, then the blind plate should be installed there; if maintenance is done more frequently after the valve, it should be installed there instead.
According to the construction specifications, this length should be greater than 100 mm; however, if it is possible on site to use shorter pipes, the length of such sections can be calculated based on the length of the tee – generally, it is 1.5 times the diameter of the pipe. For a DN1400 pipe, it is recommended that the length of such sections be around 700 mm. Regarding blind plates, the characteristics of downstream users need to be taken into account – whether frequent shutdowns for maintenance are necessary – and this is an issue that should be considered by the designers or the users.
Are there gate valves of DN1400? What kind of opening mechanism? I usually use butterfly valves
Gas pipelines are generally pressurized with steam, which allows it to be determined whether there are any leaks in the pipeline (when a leak exists, steam will be emitted from the location of the leak, enabling quick detection). Venting is generally necessary to empty the gas in the pipes during shutdowns for maintenance. Gas pipelines need to be equipped with traps at their lowest points to prevent water accumulation within the pipes. Generally, a nitrogen pipeline is also required on coal gas pipelines for purging during shutdowns.
In gas pipelines, a butterfly valve + blind flange serves as a reliable shut-off mechanism!
It is recommended to use eight-character blind plates.
It’s impossible to use gate valves for such large diameters. Just think about how big the valve disc itself has to be, and then how large its actuator needs to be as well. Even if it were possible to produce them, I doubt there would be enough space to fit them
When the pressure is not high, a telescopic disc valve can be considered, which makes it easier to insert and remove blind flanges. There is no specific requirement for the reserved length; it just needs to be convenient for construction and for replacing the valve in the future.