Gates and Valves for Flow Control (Part - 3) - Civil Engineering (CE) PDF Download

Deep seated gates 

1. Vertical gate Similar to that used for crest type gates (Figure 1), but usually for deep-seated purposes like controlling flow to hydropower intake either the ones with roller wheels (Figure 13), or the sliding-type without any wheels (Figure 14), are used.

Figure 13. Typical Arrangement of Vertical Liftgate with Wheels with Hydraulic Hoist 

Figure 14. Slide Gate (Vertical Lift} With Hydraulic Hoist Mechanism

According to the Bureau of Indian Standards code IS: 5620 “Recommendations for structural design criteria for low head slide gates”, slide gates may be classified into the following three types depending upon their service conditions. 

• Bulk head or stop-logs These are usually located at the upstream end of river outlet conduits or penstocks where in addition some other equipment is used to cut off flow and are subjected to relatively high heads. 
• Emergency or guard gates These are designed to be operated under unbalanced head, that is, with water flowing through the conduit or sluice but are not meant for regulation. These are kept either fully opened or fully closed and are not operated at part gate opening. 
• Regulating gates These are used for regulating flow of water. These are also operated under unbalanced head condition and are designed to be operated at any gate opening. 

2. Deep-seated radial gates These are low level radial outlet gates. These gates have sealing on top apart from on all sides. They are located at sluices in the bottom portion of dam (Figure 15). The hoisting arrangement is usually at the top but could also be provided near the elevation of top seal to reduce hoist stroke. 

Figure 15. Deep Seated Radial Gate with Hydraulic Hoist

3. Disc gates A gate, which is in the form of disc, and rotates about an axis of its plane to control the flow of water. 

4. Cylindrical gates A gate in the form of a hollow cylinder placed in a vertical shaft. These gates are used usually for intake towers, upstream of dams for shutting off the water to penstocks and control values. These may also be used in outlet works (Figure 16). 

5. Ring follower gates These are gates with a slide gate with a circular ring (a leaf with a circular hole) extending below the gate leaf. The diameter of the circular hole is equal to the diameter of the conduit. When the gate leaf is raised above the conduit, the circular hole forms an unobstructed passage for the flow of water in the conduit. When the gate is lowered to shutoff the flow, the circular ring fits into a recess below the invert of the conduit. It is used as emergency gate upstream of a regulating or service gate and is operated either in fully closed or fully open position (Figure 17). 

FIGURE17. RING FOLLOWER GATE

6. Jet flow gates A high pressure regulating gate in which the leaf and the housing are so shaped as to make the water issue from the orifice in the form of a jet which skips over the gate slot without touching the downstream edge of the slot (Figure 18). They are adopted when very fine control of discharge is desired. 

Figure 18. Jet Flow Gate

7. Ring seal gates A roller or wheel mounted gate in which the upper portion of the gate leaf forms a bulkhead section to stop the flow of water and the lower portion forms a circular opening of the same size as the conduit so as to produce as unobstructed water passage with the leaf in the open position. Complete closure of the leaf in the lower position is made by extending a movable ring seal actuated hydraulically from the water pressure in the conduit to contact a seat on the leaf. This type of gate is usually used as either service or emergency gates in the penstocks or other conduits (Figure 19).

FIGURE 19. RING SEAL GATE (INSTALLATION OF 2 GATES)