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2.5 Electrical Connections
2.5.1 Grounding Procedure
Satisfactory operation of ABB Instrumentation Magnetic Flowmeter Systems 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 bur-
ied 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, and therefore,
its greater length of ungrounded path offers a less desirable ground bus. A metallic structural mem-
ber 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.
One of two similar, but distinct, grounding procedures applies to the Model 10DX3111 Magnetic
Flowmeter supplied. The selection of the applicable procedure is based upon the type of pipeline
in which the meter is to be mounted, as follows:
Case 1: Electrically conductive adjacent pipeline where the liquid to be metered comes in contact
with this conductive pipeline.
-or-
Case 2: Adjacent pipeline which is insulated from the fluid to be metered, such as ceramic-lined
iron pipe, plastic pipe or bituminous-coated cast iron pipe.
Perform the proper grounding procedure for the case which applies to your pipeline.
Grounding Procedure - Case 1
For the ABB Instrumentation Magnetic Flowmeter mounted in an adjacent conductive pipeline
which is not insulated from the fluid to be metered, the following grounding procedure must be per-
formed:
1) Drill and tap a blind hole on the peripheral surface of each of the two adjacent pipeline
flanges to accept a 1/4-inch hex head bolt. These tapped holes should be placed at that
point on the pipeline flanges that aligns with the 1/4" hex head bolts which clamp the 1/2"
wide, 6" long copper braid to the periphery of each meter flange. Obtain a bright metal sur-
face around the edges of each taped hole with a file or burnishing tool.
2) Securely clamp the lug on the end of each meter flange ground strap on the respective
pipeline flange surface with a pair of mating hex head bolts and external tooth lockwashers,
as shown in Figure 2-7.
3) If the pipeline is in itself not a suitable ground, interconnect the shortest practical length
of 1/2" wide copper braid from a meter flange ground strap bolt to a good ground as shown
in Figure 2-7. Copper wire #12 AWG or heavier, may be substituted for this ground connec-
tion if braid is not available.
2-10
10DX3111 INSTRUCTION MANUAL
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