Grounding Procedure; General - ABB 3000 Series Instruction Manual

2.5 Grounding Procedure

2.5.1 General

Satisfactory operation of the flowmeter system requires that careful attention be paid to proper
grounding techniques. A good ground is one that is in contact with the earth over a large conductive
area. An excellent example of this is a cold water pipe which is buried in the earth and travels many
miles in its distribution system. A great number of pipe branches form a large conductive area of
contact which provides a low resistance connection to earth. A hot water or steam pipe must first
return to a boiler before it becomes a cold water pipe, therefore, its greater length of ungrounded path
offers a less desirable ground bus. A metallic structural member of a building, such as a supporting
"I" beam, may be a good earth ground, but it is a second choice to a cold water pipe.
If selecting a cold water pipe for meter grounding purposes, the
user should be aware that is becoming more common to use
sections of PVC piping in the cold water piping system. It is the
user's responsibility to make certain that there is electrical
continuity between where the meter is grounded on the copper
cold water pipe and where the copper cold water pipe actually
Meter grounding requirements are a combination of standard grounding methods and a bonding of
the meter body to the process liquid. The most important of these is the process bonding, which is
insuring that the meter body is in contact with the process liquid at both ends of the meter body. The
bonding process places an electrical short circuit across the meter, thereby routing any stray current
around the meter (rather than through it).
From the point of view of grounding there are two basic types of piping systems:
• electrically conductive pipeline: the process liquid comes in contact with
conductive pipe. This piping requires that each meter flange be connected with a
bonding wire to the adjacent pipeline flange. The grounding procedure to use with
conductive pipeline is described in 2.5.2.
• non-conductive or electrically insulated pipeline: the pipeline may be made of an
electrically non-conductive material (plastic, concrete, etc.) or lined with a
non-conductive material (rubber, TEFLON, etc). These non-conductive pipelines
require the use of metal grounding rings or grounding probes to bond the process
to ground. The grounding procedure to use with nonconductive pipeline is
described in 2.5.3.
Proper grounding of the meter is required for optimum system
10DS3111A INSTRUCTION MANUAL
NOTE
enters the earth
NOTE
performance.
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