hi everyone,

can anyone send me the wire marking philosophy for termination of instrument cables at instrument side, junction boxes, panels side.

thanx

 

I do not think people have a philosophy so much as a standard or practice.

A lot of places label it with the instrument tag designation.

I do mostly PLC work and it is not unusual in my world to label the cables and/or its conductors with the I/O address or some derivitive thereof.

Some people give it a number based on an index that is generated from either the sheet number of a drawing set or some other criteria (such as the first cable is #1).

 

I agree with Bob Peterson. Almost EVERY site or manufacturer has its own standard or practice. ("The best thing about standards is that there are so many to choose from!"--from a control.com Fortune.)

Some larger companies (utilities; refiners; process plants) have wire-marking standards that they provide with Requests for Quotes/Proposals for new equipment that they expect will be followed during the construction and installation of new equipment in order to have a single wire-marking standard across the plant or organization.

But, it's basically left up to individuals at sites or the manufacturer as to how wires are to be marked. I've encountered just about every kind of wire-marking scheme and the only one I dislike is the one that requires the location where the wire is terminated to be the only information on the wire marker. Some other sites insist that wires which--if disturbed--can trip the equipment or interrupt the process to have special markings or be of a certain colour. (This one is very maddening as well when troubleshooting a plant that has been in operation for decades and where a lot of modifications have been made--and no one changed or removed trip indications from wires which no longer had the same effect on the equipment/process.)

And, the most maddening wire-marking standard is the one that individuals in the plant refuse to follow or feel that it's their prerogative to alter to suit their own personal "requirements" which are different depending on the circuit or the location or the process.

The best wire-marking "standard" is the one that is explained in the legend/notes area of the respective drawing so that when someone is troubleshooting the equipment it can be consulted and used to speed up the resolution of problems, or the upgradation (love that word!) of the control system.

The guiding philosophy for any wire-marking standard or procedure should be that every wire in a circuit is uniquely marked so that a circuit can be traced from location to location without detailed drawings. For example, if a pressure switch is terminated in a sub-junction box, which is then connected to a larger junction box, which is then connected to a marshaling panel which is then connected to a control system I/O card, every wire used to connect the NO contact of the pressure switch to the control system I/O card should have the same wire/circuit/conductor marker (say 115 for example). If every wire in that same circuit has a different marker (say TB1-2 in the sub-junction box, and TBL-7 in the junction box, and HLTB14-12 in the marshaling panel, and R2S4-9 at the control system I/O card, it's virtually impossible to trace that signal from device to I/O card without a detailed set of drawings. If one finds 115 at the device and can follow the conduit from the sub-junction box to the junction box, and then to the marshaling panel A single circuit conductor with four different wire-markers on the wires used to interconnect the device to the control system is about the most frustrating thing in the world at 3:14 am in the morning when trying to troubleshoot a problem when no one in the plant can find the drawings for the equipment.

Clear, concise, unique markers for every circuit--whatever the decision might be about what the markings should be--is the proper philosophy. The standard or the procedure should be developed with the philosophy that circuit conductors are uniquely marked along their entire length for easy tracing/troubleshooting.

 

As a Technician I have used and experienced several iterations on wire label philosophy. From no labels at all (fun mystery) to sticky quick labels to nice printed shrink wrapped labels. The philosophy I have used and so far like the best is a modification on german DIN wire labels. The wire will have two printed lines, the first line is the termination point where the wire is terminated locally and the second line is where the other end of the wire is terminated. Then the other side of the wire has the reverse information. Example a wire that terminates at terminal block 2 terminal 14 on one end and PLC input card 3 channel 4. One end of the wire will be labeled TB2:14 IO3:4 and the other end will be labeled IO3:4 TB2:14. That way all of the wires could be disconnected and re-connected easily.

Have fun,
AMW