Figure 147.-Intermediate stems and coupling hooks for the 13.96-by 22.45-foot fixed-wheel gate. P557-D-37604. the gates 14 inches for conduit filling with maximum unbalanced pressures on the gate; and in an emergency, to close the gates with full flow to the turbines under a maximum head of 255 feet. The cylinder size for the hoists was determined by the sum of the weights of the gate and stems, plus maximum downpull, minus friction of the coupling hooks sliding on the concrete guide surface, and minus one-half the gate wheel and seal friction. This load would produce a cylinder pressure of approximately 1,200 pounds per square inch during emergency closure; however, normal balanced operations or conduit filling will require a maximum cylinder pressure of less than 600 pounds per square inch. The hoists and stems were designed for a relief valve setting of 1,000 pounds per square inch, using normal factors of safety. The pressure switch setting of 750 pounds per square inch provides a minimum lifting force at the hoists of 437,000 pounds which exceeds the 392,000-pound force required to open the gate for conduit filling. The hoists were designed to lower the gates, without operating the pumps, by bypassing oil from the underside of the piston directly to the top of the cylinder. The design time selected for opening the gates balanced was about 20 minutes, and for closing unbalanced less than 2 minutes, based on normal oil temperatures. The closing time will increase slightly as the oil temperature drops, and decrease slightly when the gate is subjected to downpull forces during emergency closure. A hanger stud is provided in the upper cylinder head of each hoist to engage the piston stem and support the weight of the stems and gate in the open position during gate installation or removal. During normal operation the hanger stud will not be engaged, as the piston was designed to support the gate and stems on oil confined under the piston. Two constant-delivery pumps, having a combined delivery of 49 gallons per minute at a pressure of 1,000 pounds per square inch and a pump speed of 1,800 Figure 148.-Hydraulic hoist and intermediate stems for the 13.96- by 22.45-foot fixed-wheel gate. P557-D-37603. revolutions per minute were selected for each cabinet to open the gate within the predetermined design time. Two 15-horsepower motors, using 440-volt, 3-phase, 60-cycle current were required to drive the pumps. The two independent pump units were used to provide protection against failure of a single pump unit. A 110-volt transformer was used to provide power for most of the control circuits and the cabinet heater; however, the control was designed to use a separate source of direct-current power from the powerplant to close circuit and the the operate emergency solenoid-operated, four-way valve which directs the flow of oil to open, close, or stop the gate. The control was designed for gravity closure of the gate with the closing speed controlled by a throttle valve in the bypass piping from the bottom to the top of the cylinder. A restoring cycle was incorporated in the controls to maintain the gate automatically within close limits of the open position. A penstock pressure switch was included to prevent opening the gate until the penstock is full and the pressures on either side of the gate are essentially balanced. Gate position indication was provided in the cabinet using a vertical scale with a pointer driven by a stainless steel cable connected to the piston stem. The control was designed for normal gate operation by pushbutton from the control cabinet and for emergency gate closure by selector switch or automatic protective devices from the powerplant. The emergency close circuit was designed to override all opposing signals initiated from the control cabinet. Normal clearance SECTION B-B * * * SECTION A-A SHOWING RELATION BETWEEN GATE. GATE SEATS, AND GUIDES SECTION C-C 1664 3-xi Slotted SHOP NOTE: All holes in seal clamps 6. 7. 8.ond 2 Seal projection 19 Spaces 6-9-6" SEAL CLAMP STEEL TWO REQUIRED -14-92 -29 Spaces @ 6 = 14'-6". Gate shall be shipped with small parts attached unless otherwise noted. Seat bases shall be welded in place before machining as Beams shall have ends cut square before assembling. Any variation in the depth of the 181 or 18[ sections, if BULKHEAD GATE LIST OF DRAWINGS ASSEMBLY-LIST OF PARTS-DETAILS. GATE LEAF.. DETAILS.. $57-D-1903 527-0-1964 $97-0-1965 SHEET OF ASSEMBLY Holes- SECTION E-E Bor 2xf DRAWN..AM 9) TRACED. Figure 149.-Turbine draft tube 12.42- by 15.95-foot bulkhead gate assembly. 64. TURBINE DRAFT TUBE BULKHEAD GATES. (a) Description.-Twenty-four bulkhead are provided to seal the turbine draft tubes from the tailwater in the event that it is necessary to unwater the turbine units for inspection and maintenance of either equipment or structure. The 24 bulkhead gates and related equipment (fig. 149) were furnished under invitation No. DS-5341. A gate having nominal dimensions of 12.42 feet wide by 15.95 feet high is available for each of the draft tube openings. The gates and lifting frame operate in steel guides embedded vertically in the concrete structure. The gates are raised and lowered by means of a 10-ton gantry crane. An automatically engaging lifting frame is used for raising and lowering the gates. The gates are normally stored in the upper portion of the gate slots. The gates are supported by latches so located that the lifting lug on the gate is just below the deck slot covers and is therefore easily accessible from the deck. The latches consist of hinged bars which will automatically engage the gate guide lugs during the raising cycle, and may be laid back out of the path of the gate guide lugs to allow the gate to lower. Inasmuch as the gates must be raised and lowered only under balanced head conditions, a filling valve is incorporated in the gate lifting stem of each gate for the purpose of creating the balanced head prior to raising the gates. In the event that high-pressure penstock water is unintentionally admitted to the turbine and draft tube while the gates are in place, a gate will blow off of its seat, shearing the bolts which fasten the lower guide lugs to each side of the gate. The top guide lugs are rigidly fixed to the gate, enabling the gate to swing out in the event that the lower guide lugs shear. The estimated weight of the 24 gates is 396,000 pounds. (b) Design.-Maximum stresses are calculated on the basis of a dry draft tube and maximum tailwater surface, the maximum head being 78 feet. Under these conditions the combined stresses of the faceplate and beams are permitted to reach 24,000 pounds per square inch. Other stresses conform to the American Institute of Steel Construction. |