On-site instrument grounding
Thread Content
This post was last edited by zhoudingshengs on 2023-11-13 at 16:10. Discussion: The grounding design specifications for instrument systems state that the enclosures of field instruments need to be grounded – does this mean that all instrument enclosures in the field must be grounded? How exactly do I connect it?
Grounding in explosive environments: The enclosures of intrinsically safe instruments do not need to be grounded, while the metal enclosures of non-intrinsically safe instruments must be grounded； Grounding in non-explosive environments: The enclosures of instrument equipment with a voltage of 36V or higher must be grounded, while those of instruments with a voltage below 36V do not need to be grounded
Well summarized; please have a professional give it a review.
My current workplace uses an explosion-proof system; the instrument enclosures, as well as the valves, all have grounding terminals. 4-square millimeter single-core stranded wire is used to make connections via explosion-proof flexible tubes to galvanized steel pipes. Bridging is provided at all couplings and junction boxes of the galvanized pipes, with grounding carried out at the locations where grounding is available. It was done by the construction team during the construction period. Haven’t seen it before either. Some experts have suggested that even the air supply pipes for control air should be electrically bonded, as there should be no separate metal components, as this could lead to static discharge. To be honest, in my opinion, depending on the environment, I think it’s completely unnecessary in ordinary Zone 1 or Zone 2 settings. It’s also possible that the level of chemical exposure I’ve experienced is relatively low, so the risk level is low as well.
“The term “grounding the instrument enclosure” is not precise enough; instruments that use electrical signal transmission for control and display require electrostatic grounding. It is mainly installed to prevent interference from static electricity. For reference.
That’s not the case; devices that are not intrinsically safe require a protective ground connection. Some devices such as electromagnetic flowmeters and radars are powered by 220V AC, and in the event of a leakage current, it can pose a risk to human safety. Even with 24V DC, there can be issues such as leakage and short circuits, which can generate sparks or high heat in explosive areas and lead to explosions.
Summary of grounding for chemical process instruments; I think this covers it quite comprehensively
It’s better to connect it; experts say that the issue of not having a ground connection is a penalty factor
In non-explosive hazardous environments, the metal enclosures of field instruments, metal protection boxes, and metal wiring boxes with a supply voltage of less than 36V do not require protective grounding; however, those that may come into contact with equipment operating at voltages higher than 36V must have protective grounding. In explosive hazard environments, the metal enclosures, metal protective boxes, and metal wiring boxes of field instruments in non-intrinsically safe systems shall be provided with protective grounding, while those of field instruments in intrinsically safe systems need not have protective grounding. The metal enclosures of field instruments, metal protection boxes, and metal wiring boxes used for lightning protection shall be provided with protective grounding. Refer to the \"Code for Design of Instrument Grounding in Petrochemical Industries\" SH/T 3081-2019