Grounding Procedure; General; Conductive Pipeline - ABB K-MAG 10D1476 Instruction Manual

10D1476 K-MAG MAGNETIC FLOWMETER INSTRUCTION MANUAL

2.4 Grounding Procedure

2.4.1 General

Satisfactory operation of the magnetic flowmeter system requires that careful attention be paid to
proper grounding techniques. Meter grounding requirements are really 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 nothing more than insuring that the meter ground is in contact
with the process liquid at both ends of the meter body. Basically, the bonding procedure places an
electrical short circuit across the meter, thereby routing any stray current around the meter rather
than through it.
There are two basic types of piping systems:
• One of these is an electrically conducting pipeline in which the process liquid
comes in contact with the conductive pipe. This piping requires only that the
K-MAG bonding wires be attached to the adjacent pipe flanges.
• In the other case, the pipeline may be made of an electrically non-conductive
material or is lined with a non-conductive material. These nonconductive pipelines
require the use of metal grounding rings to bond the process to ground.
A good ground is one that is in contact with the earth over a large conductive area. An excellent
example of this is an iron cold water pipe that is buried in the earth for a considerable distance in its
distribution system. The water pipe laterals form a large conductive area of contact, that in turn
provides a low resistance connection to earth. Some systems in use today use plastic pipe and do not
provide a good ground system.
Select the applicable grounding procedure from Paragraph 2.4.2 or 2.4.3. Proper grounding of the
magnetic flowmeter is required for optimum system performance.
Regardless of which grounding system is used, the grounding pro-

2.4.2 Conductive Pipeline

If the magnetic flowmeter is included as part of a conductive pipeline that is not electrically insulated
from the liquid to be metered, the following grounding procedure should be followed. Refer to Figure
2-10 to supplement the text. Note that the grounding method shown in Figure 2-10 is applicable also
for meters supplied with sanitary fittings.
1. Drill and tap a blind hole on the peripheral surface of each of the two adjacent pipeline flanges (see
Figure 2-10 - INSET). These tapped holes should be placed so that they are within easy reach of the
bonding straps (2 supplied) attached to the ground lug on the meter housing.
2. Obtain a bright metal surface around the edges of both tapped holes with a file or burnishing tool.
3. Clamp the lug on the end of each bonding strap to the adjacent pipe flange, using a pair of 1/4" hex
head bolts and external tooth lockwashers (supplied by user).
4. The user must supply a sufficient length of grounding wire for connecting the meter grounding post
(ring lug supplied) to a good electrical ground. (Number 12 AWG, or heavier, copper wire may be
used for this grounding wire.)
2-14
NOTE
cedures given in this section must be followed.