temperature.
2.12.2.5
Control Drive
Control drives shall be pneumatic type. The term "control drive" refers to
a power actuator which is primarily used for positioning another device
such as a damper, in response to signals from a control system. Select
each control drive size as required to provide adequate capacity for the
existing loads and conditions. Each control drive used for modulating
service shall positively position its controlled device accurately and
without fluctuations with the existing load conditions and at any position.
The time required for full-stroke travel in either direction shall be 15
seconds. Provide speed control to allow adjustment of full-stroke time
from ten seconds to one minute. Provide couplings, adapters, linkages,
clevises, ball joints, drive arms and damper arms required. Furnish
control drives and handwheels, dual-pole-dual-throw limit switches for open
and closed indication, on open-close drives, and 4-20 mA dc position
outputs on modulating drives. Position shall be sensed electronically
without the use of a slide wire. Provide control drives except the induced
draft fan inlet damper drives with current-to-pneumatic positioners to
accept a 4-20 mA dc control signal. The induced draft fan inlet damper
drives shall be furnished with a pneumatic positioner to accept a 3-15 psi
signal from a current-to-pneumatic signal converter furnished by the
Contractor.
2.12.3
Digital Control Systems
Digital controls shall be relay logic, solid-state programmable logic.
Baghouse sequence control shall be wired solid-state logic or solid-state
programmable logic. Digital logic associated with analog process controls
shall be as specified in paragraph entitled "Electronic Control Modules."
Control circuits shall be 120 VAC maximum. Higher voltage power shall not
be brought into a control system cabinet or control panelboard.
2.12.3.1
Wired Solid-State Logic
Components shall be highest quality industrial grade devices. Logic
elements shall be integrated circuits. Components shall be subjected to a
rigorous quality assurance inspection. Circuit cards shall be burned-in
and tested in the completed system a minimum of 170 hours continuous
operation. Logic elements shall be assembled on circuit cards to perform
specific operational functions. Different types of circuit cards shall be
minimized to reduce stocking of spares and to facilitate maintenance by
card substitution. Logic cards shall be arranged in functional groupings
for individual pumps or sequences. Failure of a single logic circuit or
compartment shall not affect more than one pump or separate functional
sequence. Power supplies shall be as specified for Analog Control Systems.
System electronics shall be buffered and protected from external power
sources by optical couplers or reed relays. Logic shall be documented by
2.12.3.2
Solid-State Programmable Logic
Components shall be highest quality industrial grade devices. Components
shall be subjected to a rigorous quality assurance inspection. Circuit
cards shall be burned-in and tested in the completed system a minimum of
170 hours continuous operation. Small systems requiring a minimum of
memory elements may use nonvolatile programmable memory. Larger systems
shall use software programmable memory with nonvolatile memory for program
SECTION 15864N
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