| Engineering Services: Automated Damage
Control System Development
CHILLED WATER REDUCED-SCALE ADVANCED
DEMONSTRATOR (CW-RSAD)
The Chilled Water
Reduced-Scale Advanced Demonstrator (CW-RSAD) is a small-scale replica
of DDG-51 Class chilled water system and is located at the Naval Surface
Warfare Center in Philadelphia, PA. The RSAD was originally constructed
to investigate the use of component-level intelligent distributed
control system (CLIDCS) technology to achieve reliable, unmanned
operation of shipboard auxiliary systems. The RSAD features a
vertically offset main loop (1-inch nominal pipe size) that distributes
chilled water to 15 cooling coils via 8 branches. Each of the two
air-conditioning plants contains a 30-gallon expansion tank and has the
capacity to deliver 20 gpm of chilled water flow at 120 psig. Seven
pairs of electrically actuated ball valves installed in the main loop
divide the main loop into 6 zones. Fairmount Automation developed and
integrated the DLSM for the 100+ programmable LonWorks control nodes
that monitor and control the more than 50 sensors and 80 actuators
(i.e., smart valves and pumps) present in the RSAD system. The RSAD DCN
consists of 14 LonWorks Free Topology subnets and a single Ethernet
channel that serves as a high-speed backbone. Fairmount also developed
the HLSM-DLSM interface for communicating feedback and commands between
the LonWorks control nodes and a high-level control system executing on
a Unix workstation.
Fairmount Automation
used the RSAD facility as a testing ground for its rupture detection and
isolation algorithms. Fairmount Automation upgraded selected valves on
the RSAD main loop with an enhanced flow inventory algorithm capable of
rapidly detecting and isolating piping system damage. Testing
demonstrated the ability of the smart valves to detect and isolate leaks
and rupture within 10 seconds (this includes the 5 second valve stroke
time) of the damage event. During this project, Fairmount Automation
developed a novel method for determining the smart valve flow estimation
model, which is a set of mathematical expressions used by a smart valve
to compute an estimate of the volumetric flow rate and to calculate the
corresponding uncertainty in the flow estimate. The enhanced flow
inventory logic uses the uncertainty predicted by the flow estimation
model to reduce the probability of false detection without compromising
detection performance. Additionally, this method may be applied without
the need for manual biasing and tuning after the valves are installed in
the shipboard piping system. This addresses a critical weakness in
other smart valve systems, such as those implementing hydraulic
resistance logic, which require significant in-place tuning of pressure
and flow setpoints so that the activation of fluid services (e.g., heat
exchangers, fire plugs, or water mist nozzles) does not prompt the false
detection of a rupture condition.
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