Instrument wiring issue

1-to-1 configuration, facilitating later maintenance and reducing the number of contacts. However, the cost is slightly higher; using multiple cores requires the instruments to be placed relatively close together, as a too dispersed layout is not suitable.

Ideally, a 1-to-1 setup is of course the best option. However, if the scale of the project isn’t very small, from an economic perspective, as well as in terms of the amount of work required for installation and future maintenance, it’s better to use junction boxes:victory:

One-to-one is good; using junction boxes adds fault points and makes problems more likely to occur

I hope all fellow sailors will actively participate in the discussion and share their opinions.

Of course, 1-on-1 is good. However, if there are a large number of field instruments in one area and they are concentrated there, then using a 1-to-1 wiring method will result in a significantly increased width of the cable trays. Alternatively, the cable trays may need to be arranged in multiple layers, which increases both the cost of cables and the cost of the cable trays themselves. It also increases the load-bearing capacity of the process ductwork. Moreover, there are no strict regulatory requirements regarding the use of junction boxes; it depends on the actual conditions on site. The principle guiding the choice of wiring method in design is as follows: 1. When there are a large number of primary instruments on site and they are concentrated in one area, a wiring box is placed between these instruments, with cables used to transmit the signals to the terminals of the I/O cards ； 2. When the number of field primary instruments is small and scattered, a 1-to-1 wiring method is adopted.

Multi-core cables are better; when it’s necessary to add more instrumentation points on site, there’s no need to run additional cables

Generally, for small-scale use, a 1-to-1 setup is adopted； Large-scale systems use on-site junction boxes ；

For the construction party, it is better to use on-site junction boxes along with multi-core cables, which helps save costs； For the construction company, it’s better to use a one-to-one approach, which increases the volume of work.

What is the difference between a project owner and a construction contractor? Do you mean that the construction company is a subcontractor?

Both methods, which remain unchanged despite a decade of mature technology, can be adopted. In certain positions within chemical manufacturing units, significant changes can occur within just one or two years, and no method can keep up with such changes. With a shortage of staff and tight deadlines, using cables is convenient.

Personally, I favor a one-to-one format, as it reduces failure points and contributes to stable production.

For large installations with numerous points, it is advisable to use a main cable connected to branches through junction boxes, which helps save on material and installation costs. This is the approach used nowadays, and no problems have been encountered. For devices with few points, a point-to-point approach must of course be used.

Due to their relatively dispersed location, field transmitters, control valves, etc., are connected to the intermediate junction box using two-core cables； Multi-core cables are used from the intermediate junction box to the control room, allowing for a more centralized layout. Whether they are run in cable trays or cable ducts, it is convenient to arrange them in a centralized manner, and it also results in a better aesthetic appearance. This is a common practice.

For smaller quantities, a one-to-one approach is usually used; for larger quantities, junction boxes are generally employed. Each method has its advantages and disadvantages

Generally, a 1-to-1 installation configuration is used, which reduces the number of potential failure points in the instruments as well as the difficulty of maintenance.

It’s not possible to simply say which one is better; it mainly depends on the application area. For example, terminal boxes can be used for the purification of secondary brine in electrolysis processes, as well as for pressure swing adsorption in PVC production； For measurement points that are not closely clustered on site, a 1:1 scale is better.