EHM replaced the aging 1937 vintage chain-drive machinery gate hoist systems for 8 spillway gates on the Emsworth Lock and Dam at the headwaters of the Ohio River. These original mechanical systems were failing and getting increasingly difficult to maintain. The replacement systems are state of the art hydraulic drive systems with PLC electronic controls which allow the spillway gates to be operated either locally or from remote locations. Emsworth spillway dam controls water pool levels for the downtown area of Pittsburgh, Pennsylvania. Most of the downtown area street level is at elevations less than two feet above the average water level. The city is strategically located at the confluence of the Monongahela and Alleghany rivers. These two rivers meet at the pinnacle of downtown Pittsburgh and form the beginning of the Ohio River. Emsworth Dam is the first lock and dam structure for the Ohio River located just Northwest of Pittsburgh. One very unique aspect of the hydraulic drive design is the capability to raise the gate a total of 40 feet with 30 foot stroke hydraulic cylinders. The Corps used a custom made cylinder with trunnion pin mountings in two locations (see attached pdf). This dual pin design allows the entire cylinder to be lifted by itself to the secondary trunnion location for the additional 10 feet of required gate travel. A typical gate is lifted 29 feet where it is rested on dogging beams which are hydraulically extended underneath each side of the gate. Lifting cylinder trunnion pins are then released from the upper cylinder trunnion position such that the cylinder can now be pushed upward to the secondary or lower trunnion position. Once located in the secondary trunnion position the cylinder trunnion pins are reinserted with hydraulic cylinders and the lifting cylinder is ready to raise the gate an additional 11 feet. Now that the total 40 feet of gate movement has been accomplished the gate is rested on hooks that are automatically extended and the gate lowered into the hooks for storage as required. EHM crews fabricated, installed, and commissioned complete working systems that are anticipated to carry this important water control structure another 75 years.
Emsworth Dam Spillway gate hoist rehabilitations - USSD Paper 2012