tubing. All copper instrument single connecting lines shall be provided
with brass, ASTM B 61, 20.7 MPa 3000 psi rating, forged body screws or tube
ends.
3.1.9.1
Tubing Supports
PVC-coated expansion metal troughs or epoxy-coated vertical unistrut racks
shall be used as tubing supports. No elbows, tees, or crosses shall be
used. Where the trough branches or changes direction, a suitable gap for
the transition will be acceptable. The tubing shall be unsupported over
the gap.
3.1.9.2
Air Supply
Instrument air supply headers shall be as shown. Instrument air shall be
distributed through the area at nominally 620 kPa 90 psig. Pressure shall
be reduced to that required at the instrument by a local regulator. An air
set unit shall be furnished and installed for each instrument that has a
pneumatic output signal (e.g., transmitter, transducer, controllers,
positioner, and relay). Air set units shall have a filter regulator with
integral drip-well and drain cock and output gauge.
3.1.10
Electrical
Instrumentation and power-interconnecting wiring shall be as [shown]
[recommended by the manufacturer] and as specified in NFPA 70. All
external wiring to the control panels shall terminate on terminal boards or
on devices in the panels. All cable wire and cable runs shall be carried
in conduit or wireways. All signal wiring used for alarm or measurement of
control circuits shall be run in conduit separate from power circuits.
Direct current signals used for electronic transmission may be run in
multiconductor cables. Wiring for control, shutdown, or interlock circuits
may be run in the same conduit with power wiring as shown. Instruments
shall not be fed from lighting branch circuits. Termination of all wires
on instrument binding screws shall be made with solderless insulated
shoulder ring-tongue lugs of the proper size for the wire and binding
screw. Lugs shall be properly and securely crimped to the wire using the
tool recommended by the lug manufacturer. Any termination that is made
improperly shall be cut off and a new lug installed. Stripping of all wire
shall be done with an approved stripping tool or in such a manner as not to
damage the conductor.
3.1.10.1
Cable Conductor Identification
Identification shall be permanently attached to each wire terminating on a
terminal board or binding screw to facilitate maintenance. Identification
shall be by means of plastic sleeving with printed markings, permanently
attached stamped foil markers, or other approved means. Wire numbers shall
correspond to wire numbers shown.
3.1.10.2
Relays
Industrial relays shall be provided for interlocking circuits.
Contacts
and coils shall be accessible for cleaning and replacement.
3.1.11
Steam Flowmeter Installation
Transmitters shall be mounted at the orifice flanges. Impulse lines shall
be sloped to eliminate liquid or gas pockets. Meter manifolds shall be
SECTION 15846A
Page 62
Previous Page
