Closure of a flood gate by means of two RACO Electric Actuators synchronized by RACOmatic® Control System

A small scale dam, or weir or levee, with a width of just over 156 feet (47.6 meters) and a backup height of nearly 20 feet (6 meters), needed a means to close a flood gate, safely and reliably. These flood gates are critical in minimizing future flood disasters. RACO International was a valued participant in this this project as more than 60 years of experience could be utilized in the design, manufacture and control of these high-performance electric actuators.

The demands were significant, so much that two smaller actuators were planned over just one very large actuator. Each individual RACO electric actuator required an actuation force of 80 tons (160,000 lbs) and a stroke of 4500 mm (14.76 feet). Since the electric cylinders were to be attached to the foundations by means of a Cardan suspension, exact calculation of the bending stresses . With the aid of the "Finite Element Method", RACO engineers checked the CAD data and confirmed the safety factors of the components which were within the stress flux pattern limits.

In order to enable the routing of the enormous volume of water in an emergency, heavy-duty RACO high-performance electric actuators had to withstand short term stroke forces of up to 805 kN, or over 180,000 pounds. These rugged RACO electric actuators were designed so that they guarantee a long operational life-span under extreme conditions. They are provided with special corrosion protection for hydraulic engineering steelwork. Furthermore, they require energy only when being used, which further enhances their energy efficiency at the site. A retention brake also latches the RACO electric actuators in their respective positions and in this way offers protection in case of a power failure. Additionally, the actuators can be quickly adapted to provide manual control in an emergency.

RACO, with their control technicians, also participated in the concept for the control of the entire system. In each case, two electric cylinders work in synchronization in order to move the weir gates. The micro-PLC from RACOmatic is provided with a full-text display and already includes the local control which is located in the switchgear cabinets, as well as the gangway over the flood backup gates. From there, communication to the control room is established in the machine house. This control is monitored for operation of the complete weir system and is provided with an emergency power-generating set.

The control scheme

The RACOmatic controller, provides for local and remote control functionality and was installed within sight of the flood backup gates.

The overall control concept required a couple key scenarios: In the case of a failure of the higher-level control in the operating house, the two weir gates needed to be activated autonomously with a separate local control in each case. Also a switchover of the local control of the operation for one flood backup gate to the other had to be possible. The semi-automatic and manual operation is provided both for the electric actuator pairs at their respective flood backup gate and for their interlocking cylinders. In case of power failure, an individual switchgear cabinet can be operated with a mobile emergency generating set (e.g. from the fire department).

Emergency manual operation

In accordance with local safety codes, in manual actuation, the main drive is automatically blocked electrically and, in case of multi-side-driven applications, all drive units simultaneously. In electrical operation, the manual actuation must also be isolated mechanically. The brakes of the main drive may be vented only after the coupling of the manual actuation, and must be closed again before decoupling. A controlled water overflow is thus enabled without a complete "lowering" of the weir valve in the fully-opened state being implemented through a simple release of the retention brakes.

For the manual operation of a weir valve with the two electric actuators, RACO additionally supplies two attachable gears with self-locking handwheel, which are flanged on the motor shaft end behind the brake housing. A mechanical brake venting of the electro-cylinder is implemented in this case "automatically".