Norsork E-001:2016
"System 2 and system 3 cables can be installed on same field tray from branch to single equipment".
System 2 is 230VAC cable and system 3 is instrumentation cable.

I am trying to figure out how far that branch should be from the equipment in question. From this statement, its seems ambiguous and likely to bring unnecessary discussions late in the project. I would appreciate some guidance if anyone has come across a standard that gives a specific distance maximum distance of tray sharing.

 

@Jonte,

I applaud you for being proactive in this regard!

There is a saying that goes, "The good thing about standards is there are so many of them to choose from." And truer words were never spoken.

In my experience (almost 40 years in the field commissioning electrical power generation equipment, it's the buyer and the site that "chooses" the standard for such things. Whatever is in effect at the plant or other plants owned/operated by the buyer is THE standard to be met.

It's not so much about the voltage levels of the non-instrumentation cables (though that does figure into consideration for higher voltage levels--but read on), it's more about the amount of current that is switched on and off that flows through the cables. It's really about the current flow (and the resultant flux generated) AND the instantaneous currents when the device is started and stopped that cause the most problems for instrumentation cables. If it's just lighting circuits being powered with the 230 VAC and the total load of any circuit isn't too great, then it's still a very good idea to have as much separation in the cable tray as possible. Large(r) motors and other loads, well, that depends on the available space in the cable tray to separate the instrument and non-instrument cables.

And, I agree--this "standard" seems ambiguous at face value, but we don't know the nature of the loads, the currents, etc.

Most instrument cables have foil shields with drain wires, so if they are properly installed (meaning the installers have had proper training and understand what they're doing--or they have proper supervision--or they have good drawings and installation instructions AND proper supervision then as long as the currents flowing in the non-instrument cables aren't excessive, especially when the device is being switched on and/or off it shouldn't be too much of a problem. BUT, it's still a very good idea to maintain as much separation between the instrument and non-instrument cables as possible in the cable tray.

But, again, the equipment supplier may choose a standard they have worked with many times before, but when the site inspectors/technicians see how the equipment was built and/or is being installed they may scream loudly if it doesn't match the way it's done on the site or other plants/installations owned/operated by the buyer. (And, believe me--they go around LOOKING for these kinds of issues, which you may already be painfully aware of, from the sounds of your enquiry....)

Anyone can point you to a standard or regulation, but we don't know where the equipment is being installed in the world, AND we don't know if the buyer has their own standard.

Again, the great thing about standards is: There are so many of them to choose from. And without more information it's really impossible for anyone to recommend one that fits the particular situation and locale where the equipment is being installed.

I wish it weren't so, but it is. And site technicians and supervisors just LOVE to find fault with the equipment being installed (they think it makes them look good to management).

The best answer is to ask the buyer what their standard is, presuming the equipment is bespoke (custom) or built to order. If it's a commodity and you have the opportunity to ask the buyer that's always a good idea--the best idea. But all situations are not the same, and, again, we don't really know about the equipment and the process/application.

If this standard was given to you by the buyer then it's prudent to ask them for clarification--in writing. You can also say, "This is our standard for these types of cables, and with some clarification we can accommodate your standard, but without clarification by [a certain date] we will build it to our standard and the cost of re-working it during installation/commissioning will be the responsibility of the buyer." Better, as you say, to get it out in the open and resolved sooner rather than later. You may want to ask your supervisor if they can provide guidance or history in similar situations (and maybe just hand this off to them to sort and get back to you with some kind of resolution).

Best of luck!

 

@WTF?
Thank you for this guidance. This is for offshore fixed installations. I can bet the buyers' teams has been quite dramatic over simple engineering.
I would seek their clarification on these too.

 

I'm certain you would win that bet, too.