Help with PID diagram

1. The basic form and design concept are similar. 2. In terms of details, the types of manual valves before and after the control valve differ. 3. Whether heating is provided or not. 4. Or are there any differences in the interlocking and control mechanisms for these two control valves? ? ? Put this in quotes.

I have a few more questions: 1. Is there a significant difference between the design with two check valves connected in parallel for venting in the first diagram, and the design with a single ball valve used for venting in the second diagram? 2. In the first diagram, what two pipes are the white color coding applied to?

The first issue is that these two valves aren’t very useful in this location: firstly, the space available in this area isn’t large enough; secondly, these two valves are mainly used to prevent leaks, serving as a double safeguard. Generally, two drain drains are often used between the boundary valves of the main pipeline. As for the second question, I can roughly understand that what you’re referring to is the change in pressure level between the front flange and the pipeline behind it; however, the tag number you’ve used seems to be incorrect, right? I really haven’t seen any that start with Q. . . . The 1B behind it indicates that the pressure rating is 1.25 MPa for manganese steel

There should be no problem with the one that starts with Q; in this drawing, Q seems to stand for low-temperature carbon steel, as this is a process design related to LNG.

Mm-hmm. Here where I’m working, there is low-temperature propane, but the PID diagram here does not show the pressure level changes starting with Q. LNG natural gas might be a bit special. . . :D

The first one is a remotely controlled pneumatic valve with interlock, and the second one is a pneumatic interlock valve; both are designed for emergency shutdown. Hope this can help you

This post was last edited by yourp on 2020-8-11 at 11:32. First image: The pressure in front of the control valve is relatively high; using two valves for drainage provides a double layer of protection, as required by the standards. The control valve is used to reduce the pressure from Q1B (6.4 MPa) to M1B (1.6 MPa). The pipeline grade is determined after the shut-off valves in all branch lines; the pipeline before the valve in a branch line is of Q1B grade, while that behind the valve is of M1B grade. Second diagram: The pressure difference before and after the control valve may not be significant; for example, it might go from 1.6 MPa to 0.6 MPa. In such cases, there is no need for as detailed a separation as shown in Diagram 1 – the same type of pipes and material grades can be used. In Figure 2, if the pressure is not high and the medium poses no danger, one valve for the drain is sufficient.

Could you explain the differences between the two in a bit more detail?

Thank you for such a detailed explanation; I now understand a lot more

I’m new to this field; could you let me know what the standards are? :handshake