I have a question regarding the method of taking pressure samples using the pressure lead in pressure transmitters
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This post was last edited by purelove310 on 2009-6-5 at 16:55. I have a question: on the installation diagrams, I see that for some pressure transmitters installed on pipes, there is a socket-welded pressure tapping flange attached to the pressure tap tube, while for other pressure transmitters, the tapping is done directly by welding. Is there any regulation regarding this? Under what circumstances is a flange necessary? As for the equipment itself, it’s even more confusing – on some devices, the pressure transmitters don’t come with flanges; instead, two socket-welded flanges are used in the manufacturing process, along with a short pipe, with the pressure tap tube being connected directly to this short pipe. Other pressure transmitters, on the other hand, come with a flange that connects them to the equipment. It’s really confusing; I hope an expert can help answer this. Thank you!
Pressure transmitters come in two types: direct pressure sensing and capillary pressure sensing. Capillary pressure transducers are generally connected via flanges. Threaded connections and flanges can both be used for direct pressure measurement. I suggest you take a look at Rosemont’s samples and you’ll understand.
The issue mentioned upstairs is quite clear; in fact, the problem with flanges stems from the division of tasks within the design institute. Generally, the flanges related to process operations are designed by the process engineering team, while those related to instrumentation are designed by the instrumentation team. Medium and high-pressure systems are usually connected using high-pressure flanges, whereas other connections are made through welding. As for the instruments installed on equipment, it’s often the case that the main design institute doesn’t bother much about them – the equipment manufacturers handle their design, so there’s no need to delve too deeply into this matter.
Thank you for the reply above, but I’m not referring to flanged pressure transmitters; I’m talking about ordinary pressure transmitters. For these types of transmitters, there is no need for a diaphragm seal to transfer pressure – the pressure is directly transmitted through pressure conduits. What I don’t understand is that sometimes these pressure transmitters are connected by welding directly, while at other times the pressure conduits are connected to two flanges on the pipeline using socket welding. When taking pressure readings from such equipment, sometimes two flanges are connected by a short pipe, and other times they are connected directly to the flanges. I’m confused about the differences between these approaches.
Thank you. I have a question: what pressure level is considered low enough that flanges are not required? Also, for process applications, socket weld flanges are always used – what regulations govern this?
Take a look at the installation diagram of the transmitter in the HG21581－1995 automatic control installation manual; it contains specific details
Generally, for taking pressure readings from pipes, a primary valve is used, which is directly welded to the pipe through a short tube. On equipment, an installation flange is usually welded during manufacturing, so as to avoid welding on the equipment at the construction site; therefore, most equipment is connected using flanges.
Take a look; just put on Rossmont’s pressure suit and you’ll know
Generally, welding should not be carried out on pressure vessels at the joint openings; therefore, a 25*3 pressure gauge connector is usually welded to the flange of such vessels. The gauge is typically installed by direct welding to the pipeline, but when the pipeline pressure exceeds 6.4 MPa, direct welding for installation is not recommended.
I agree with what was said on floor 7: generally, interface flanges are used on pressure vessels to ensure the appropriate pressure rating. If this flange is intended to connect to a pressure pipe, then another matching flange will be used along with the pipe.
2# yangq4725 The installation of compressive strain measurement is divided into two types: direct measurement and indirect measurement. Direct measurement is divided into side-flange type, direct-installation type, and immersion type. The first two are the most common in the market. Indirect measurement methods are divided into double (single) flange remote transmission type, threaded remote transmission type, snap-ring remote transmission type, and insertion tube type.