Commissioning; Instrument Coupling To The Torque Tube - GE Masoneilan 12420 Instruction Manual & Safety Manual

7. Commissioning

This section is based on the following assumptions:
♦ 12400 head has previously been mounted on a torque tube without coupling adjustment.
♦ Torque arm is mounted according to site requirements, if calibration has previously been done at workshop.
♦ Instrument is powered.
The steps described in the following pages for instrument settings and checking are done with the three pushbuttons and the
LCD display.
To perform 12400 commissioning through HART communication ValVue* software or handheld terminal, consult related
instruction manuals. Setting and calibration procedures are similar as based on the same philosophy.
Perform the following actions in the order given. They are also used for maintenance purposes. Several calibration procedures
are provided to cover available solutions at workshop and on site.

7.1. INSTRUMENT COUPLING TO THE TORQUE TUBE

NOTE: It is necessary to know the mounting direction (right or left) in order to correctly adjust the torque arm. See figures 7 and
23.
a. Remove the screw (106), the covers (104 & 107) of the connection and mechanism compartments, and the plug (190)
located at the bottom of the instrument.
b. Required level of liquid for coupling:
b1. At workshop with weights:
Coupling between torque tube and mechanism is achieved by simulating a half level of a 1.4 specific gravity liquid with
weights. Attach to the torque arm a weight equivalent to that of a displacer half immersed in a 1.4 specific gravity liquid
according to the following calculation:
Simulated weight =
Actual displacer weight –
i.e. 1362 – 907 x 1.4 / 2 = 727.1 g for a standard displacer
b2. On site with the process liquid(s):
Two situations may occur:
•
If the specific gravity (or the difference of the density in case
of an interface service) of the available liquid is between 0.7
and 1.4:
Simulate half level h (1.4) of a 1.4 specific gravity liquid with a
calculated value h (d) of the available liquid (refer to chart
Figure 14).
•
If the specific gravity (d3) (or the difference of the density in
case of an interface service) of the available liquid is below
0.7:
Perform the coupling at high level
(immersed displacer) or at high level of the highest spec
gravity liquid in interface application.
CAUTION: In this situation, the instrument must
be used for specific gravities (or the difference
of SG) ranging from 0.15 to 2xd3.
22 | GE Oil & Gas
(Actual volume displacer X 1.4)
2
in liquid service
Figure 14
Curve of Half Level Simulation in a Liquid with S.G.
between 0.7 and 1.4
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