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all enclosures should be specified as metallic or with a conductive coating rather
than the basic polymer enclosures.
Wiring shields should be terminated on both ends to the enclosures’ ground lugs
– not to circuit common.
TV&C – Prophetstown recommends that all wiring be enclosed in electrical
metallic tubing (EMI) and that drip loops are established at each enclosure entry
point. Spiral wrap cable conduits (e.g. Greenfield, BX) should not be used.
2.3 Location of the Electronics
The section on Startup and Operation, Sensitivity Control (Section 3.2) explains
how to set the sensitivity range according to the conductivity of the water in your
application. Water with a low conductivity requires a higher sensitivity and
consequentially has greater noise susceptibility. The highest sensitivity (<1-10
μS) range limits the shielded cable distance between probe and electronic
module to 80 ft. [25m]. The intermediate sensitivity range
(10-100 μS) places an upper limit of 165 ft. [50m] for the shielded cable distance.
The lowest sensitivity greater than about 50 μS allows the shielded cable
distance to be up to 500 ft. [150m]. The coolest, most accessible location for
mounting the electronics is preferred, usually on an outside wall. Dimensions of
enclosures are shown in fig’s 2 and 3.
2.4 Water Column (Refer to Water Column I.O.M. for complete details)
The water column is fixed to the steam drum either by being welded directly to
the isolating valves or welded to flanges that mate with existing flanges on the
steam drum tapping points. A steam inlet line must be installed to provide a free
flow of steam to the Model 12B column. The steam line must slope down toward
the column (a slope of 2% is recommended). When globe valves are used as the
isolation valves, they must be installed with the stem horizontal. Ideally, the
return water leg should be horizontal. This leg may, however, be sloped down to
the drum, in which case it must be insulated. In no case should the steam line be
insulated.
Water Columns with three maximum pressure ratings are available –
850 [58 bar], 1800 [124 bar] and 3000 psi [206.9 bar] design. The fittings on
steam generators of lower pressure usually have a lesser rating. As a result, the
overall rating of a system is governed by the lowest rating of any of the
components.
The metal probe covers should be removed from the water column after it is fully
plumbed into the system and remain off until the system is in service and a
satisfactory inspection of all the probes and the associated wiring is completed.
! W A R N I N G !
The nature of the electronics, the harsh operating environment and the
potential hazards associated with live steam require that only qualified
personnel install and maintain this equipment. Without adequate qualifications,
an operator could allow live steam to escape which may cause property damage
or severe
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