Automated fuel handling prevents spills, aids efficiency

Ralph Shealy -- Control Engineering, 7/1/2000

To lessen risk of spills or other accidents at deep water, marine front terminals and other fuel handling and storage sites, the SPAWAR (Space and Naval Warfare) Systems Center (SSC, Charleston, S.C.), a U.S. Navy corporation, recently began to automate and standardize its distribution and handling facilities.

The Automated Fuel Handling Equipment (AFHE) program seeks to improve control and inventory accountability; provide continuous monitoring and fail-safe engineering for spill prevention; and increase efficiency. AFHE focuses on marine terminals and bulk Defense Fuel Support Points because they would immediately affect surrounding environments if fuel were accidentally released.

To improve DESC sites in Virginia, Florida, California, and Washington, SSC evaluated existing facilities and checked tanks, piping, pump/motor configuration, and valves for instrumentation to ensure compatibility with controllers and other supervisory control and data acquisition (SCADA) equipment.

SCADA software for the new AFHE system is USDATA's (Richardson, Tex.) FactoryLink enterprise control system, configured to match site designs. FactoryLink was tested under all combinations of normal and emergency operations, and approximated 85-90% of functional capability over three weeks.

SSC engineers installed piping, pump, and valve modifications; system cabling and related electrical work; and system instrumentation, integration, and training. The new AFHE system integrates fuel handling functions, but also enables monitoring and automation of all motor-operated valves. For example, valve position data allow the system to notify operators if a valve setup is incorrect. .

The AFHE system's instrumentation indicates timing and routing of fuel between tanks and tracks fuel volumes-essential for accountability and spill prevention. During a recent recent fuel transfer, the system alerted operators that less fuel was arriving than was being pumped, revealing a potentially disastrous spill through a manual pressure relief valve. The spill was immediately minimized and contained within acceptable boundaries.

The AFHE system is integrated as well with the sites' other fuel handing, storage, and distribution functions, such as fuel tanks, pipeline arrays, pier operations, rail car and truck rack facilities, and connecting equipment.

The AFHE system's configuration is based on an open architecture, fully redundant control layout. The system's network scheme (see figure) has three tiers, each with redundancy and independence. Redundant Unix or Microsoft Windows NT operating systems are used for the AFHE workstations, which are networked to administrative peripherals.

For redundancy, primary and secondary Modbus Plus networks interface to control devices, such as PLCs and bridge MUX equipment. These devices and a Modbus network, using RS-232 and RS-485-based communications, provide monitoring and control of motor-operated valve master stations, flow computers, and remote I/O devices. This bottom-tier Modbus is a master-to-slave network that directs motor-operated valves and monitors several parameters.

For more information on USDATA, visit www.controleng.com/freeinfo.

Primary and back-up workstations in the Automated Fuel Handling Equipment (AFHE) system's layout are also networked to AFHE control devices via Modbus Plus, a peer-to-peer, LAN system.