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Separating Instrumentation, Controls, and Power Cabling
Looking for a source or standard to reference concerning the separation of analogue, discrete, and communications cabling from 120 VAC and higher voltage cabling as well as co-mingling instrumentation.

Looking for an ISA source or standard to reference concerning the separation of analogue, discrete, and communications cabling from 120 VAC and higher voltage cabling as well as co-mingling within the instrument and controls realm. NEC calls out Classifications which can be referred to however the verbiage in the NEC Code Book has caused considerable debate between Engineer, and Contractor. My typical note on the first sheet of a drawing set: "Keep 4-20mA Analogue wiring, 24 VDC Discrete Control Wiring, 120 VAC wiring and Power Cabling in separate conduits and raceways. Dedicated conduits and raceways must be provided. Keep Intrinsically Safe wiring in separate conduits and raceways from all other wiring." This is the truncated version for simplicity. Additionally, in the drawing set distances between conduits and raceways are called out. Look forward to hearing back from fellow readers if a reference is available to list in the design document specifications and drawings.

Thank You.

By W.L. Mostia on 6 November, 2018 - 4:53 pm

IEEE 518-1982 "IEEE Guide for the Installation of Electrical Equipment to Minimize Electrical Noise Inputs to Controllers from External Sources"

API 552 - "Transmission Systems"

William (Bill) L. Mostia, Jr. PE
ISA Life Fellow,
Winner of the 2018 ISA Raymond D. Molloy Award
Sr. Safety Consultant
SIS-SILverstone, LLC.

"No trees were killed to send this message, but a large number of electrons were terribly inconvenienced." Neil deGrasse Tyson
Any information is provided on a Caveat Emptor basis.

Sir,

Thank you for responding. Both standards will be most beneficial for quoting as reference.

Thank you
Paul Dackermann

Sidhu Associates Inc.
Wholly owned subsidiary of C.C. Johnson & Malhotra, P.C. (CCJM)

Most plants with cable trays with mixed wiring separate or grouped separately, power and instrument cabling. Some require a divider plate between the two groups to avoid mixing.

Intrinsically safe categories apply to the instrument/wiring to devices in the hazardous area. If the tray and wiring are rated for the hazardous area, the same practice is common.

In some refineries where there is definite fire risk and severe out comes, all intrinsic safe wiring is brought to suitable termination cabinets outside the hazardous area for remote I/O and network tie ins.

Safety is a mandatory requirement.

d,

Thank you for noting the key points.

I am in a situation where I am coming in on the midnight hour of a construction project and there are a few areas in the design documents that could be construed as conflicts. By that what is meant between the P&IDs, Plans, Schedules, ECDs, Diagrams, Risers etc. something may be shown on one or many but not all. There is other legal verbiage that can handle the overall outcomes. With that back to the construction installation.

”Most plants with cable trays with mixed wiring separate or grouped separately, power and instrument cabling. Some require a divider plate between the two groups to avoid mixing.”

Thank you and this being accomplished; however, in some instances there are some transition issues between tray and conduit as well entering into a structure form either ductbank or conduit to tray. Fixes are in the works.

“Intrinsically safe categories apply to the instrument/wiring to devices in the hazardous area. If the tray and wiring are rated for the hazardous area, the same practice is common.”

Fortunately the Classified installation is being performed with a firmer understanding.

“In some refineries where there is definite fire risk and severe out comes, all intrinsic safe wiring is brought to suitable termination cabinets outside the hazardous area for remote I/O and network tie ins.”

Though the installation is not a refinery all of the IS wiring is brought to the safe area for the enclosure with barriers tie in.

“Safety is a mandatory requirement.”
Yes, that is always paramount.

Greatly appreciate your responding.

Thank you
Paul Dackermann

Sidhu Associates Inc.
Wholly owned subsidiary of C.C. Johnson & Malhotra, P.C. (CCJM)