Pearl Harbor Naval Station and Hickam Air Force Base have grown up together around the historic port known as Wai’Momi, adjacent to Honolulu. Pearl Harbor Naval Shipyard (PHNSY), located at Joint Base Pearl Harbor-Hickam, is a one-stop regional maintenance center for the Navy’s surface ships and submarines. It is the only intermediate maintenance facility for submarines in the Middle Pacific.

Of the four dry docks at Pearl Harbor, numbers 1, 2, and 3 are located in the Controlled Industrial Area (CIA), and are primarily used for repairing and maintaining nuclear submarines. These are graving-style dry docks comprised of a narrow basin with access to deep water through a floating caisson gateway. To access the dry dock, a ship is floated into the basin, the caisson is positioned at the seaward side, and the dock basin is dewatered with large vertical turbine pumps. As the basin empties, the pressure of the sea against the caisson creates a water-tight seal and allows the ship to come to rest on a dry platform. Dry dock operators manage this process, known as evolution, with a staff of engineers, electricians, and operators responsible for the safe movement of equipment and water in order to ready the dry dock for ship maintenance and repair.

The CIA dry dock operation has been automated using supervisory and data acquisition systems (SCADA) from PcVue. The SCADA is primarily controlling a network of Limitorque actuators assembled on large gate valves. The assemblies are known as Motor Operated Valves (MOVs). The SCADA communicates with the MOVs using redundant Modbus IP networks connected to a redundant gateway. A Modbus serial 485 loop connects the actuators with the gateway. Each dry dock is controlled by 19 MOVs with 16 I/O points monitored and controlled per actuator. This fault tolerant system opens and closes valves to precise percentages and adheres to specific dry dock operational valve position protocols for safe control of water flow. The dry dock operators are prohibited by the SCADA from performing valve movement until receiving the Ready for Operation indicator. This indicator is a synthesized status derived from monitoring multiple alarm points including power off, over-temperature, over-torque, jammed valve, and other actuator alarm conditions. PcVue’s event historian keeps an ongoing log of the control actions as an audit trail.

Triton Marine Construction Corporation was awarded a task order for improvements to dry dock 1, including upgrading the actuators and installing a valve control system. PcVue was commissioned for this purpose in 2012. Dry dock 1 was the last of the three CIA dry docks to have a valve control SCADA installed. Previously, a system based on a different SCADA platform had been in operation for dry docks 2 and 3. Dry Dock Operations had not been satisfied with the safety, reliability, and performance of their existing control system. These concerns prompted the discontinuation of that system, and had forced the dry dock operations personnel to go back to more labor-intensive manual operations. Upon completion of the dry dock 1 project, and after firsthand experience with PcVue, the Navy was able to confirm that the reliability and performance issues were mitigated. Most importantly, the PcVue system had eliminated the safety concern. While safety is important in any process, at the dry dock, the large amount of water flowing through chambers puts dry dock personnel and shipyard workers in harm’s way if not carefully controlled.

Subsequently, the shipyard elected to retrofit the SCADA in dry docks 2 and 3. An RFP was issued for the troubleshooting and upgrading of the control system. The system integrator replaced the SCADA and was able to leverage the object-oriented reusability features of PcVue and minimize the bid cost by using common objects developed for dry dock 1. The retrofit for dry docks 2 and 3 was completed in a matter of a few weeks in 2013.

PcVue was configured to be identical to the previous dry dock 2 control system. It was important that they should not have to change the operational processes to accommodate the new system, but rather be able to illustrate their processes in the way that the operators are certified. The team that configured the application also benefited from PcVue’s objected-oriented project methodology. They developed objects to PHNSY standards including animated graphical objects known in PcVue as symbols and mimic templates, which provided a consistent graphic and navigation look and feel.

This article was contributed by PcVue Inc., Woburn, MA. For more information, Click Here .

Motion Control & Automation Technology Magazine

This article first appeared in the December, 2014 issue of Motion Control & Automation Technology Magazine.

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