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CHAPTER VALVES AND GATES INTRODUCTION What are valves and gates? Which types are valves and gates classified? 1.1 Definition Valves and gates play as a part of hydraulic structures; are installed at outlets of the structures to control water level on reservoir and adjust discharge at the outlets 1.2 Classification 1-Based on function: Service, maintenance, emergency gates 1.2 Classification (cont.) 2-Based on pressure transmission: to piers or abutments to gate sill a) ®) b) e) c) g) d) h) 1.2 Classification (cont.) 3-Based on mode of operation: to let water out under the gate to let water out over the gate Combination between the above types a) b) c) 1.2 Classification (cont.) 4-Based on form of gates: Plain, radial, drum, flap, roller, fabric gates 4-Based on form of gates (cont.): Radial gate 4-Based on form of gates (cont.): Drum and sector gates 4-Based on form of gates (cont.): Flap gate 4-Based on form of gates (cont.): Roller gate 1.2 Classification (cont.) 5-Based on moving mechanism: Gates are movedelectrically mechanically automatically by water pressure 6-Based on material: Gates made of steel, reinforced concrete or other synthetic materials 1.2 Classification (cont.) 8-Tidal barrage and surge protection gates CALCULATION OF PLAIN GATE (VERTICAL LIFT) 2.1 Forces acting on the gate Hydrostatic pressure; Hydrodynamic pressure; Weight of the gate; Frictions; Forces caused by floating objects 2.2 Necessary driving forces to open or close the gate a General formulas: Opening driving force: P1 = K1G + K (T1 + T2 ) − K '.G d Closing driving force: P2 = K1.G d + K (T1 + T2 ) − K '.G G- Weight of the gate; T1- Friction between gate and abutment; T2- Friction at watertight components; Gd –Weight of counterpoise; K1, K2, K’: Safety factors: K1 =1,1; K2 =1,2; K’ =0,9 b Specification of items *Calculation of G: (for gates made of steel) G = g.H.l0 (N) g- averaged weight of the gate/unit (N/m2) H- Height of gate (m); l0- Width of gate (m) g was determined based on catalogs of gates or experimental formulas *Calculation of Gd : depend on the designer *Calculation of T1- Friction between gate and abutment: b Specification of items (cont.) *Calculation of T1- Friction between gate and abutment: + If gate slips against abutment: T1 = f.Wo f- Friction factor; Wo- total water pressure acting on whole gate + If gate moving is supported by wheels: R- Radius of wheel; W ( f r + f1 ) T1 = R r- Radius of axle of wheel; f- Sliding friction factor between axle and wheel; f1- Rolling friction of wheel; W: total water pressure on each of wheels; b Specification of items (cont.) *Calculation of T2- Friction at watertight components; T2 = f2.W f2- Friction factor W- Total water pressure acting on whole gate In case of crest gate: T2 = f2.a.γγh a- width of watertight component; h: water depth 19 2.3 Structural analysis of the gate a Structure of the gate: Principal beams; Sub-beams; Inner columns; Border columns; Braces; Watertight surface plate 2.3 Structural analysis of the gate (cont.) b Determination of principal beams: Method: Choose the number of principal beams (n); Divide the diagram of water pressure into n parts which has the same amount of total water pressure; Position of each beam is the centroid of each part of water pressure, correlatively A h1 H h3 h2 yk a A b a) a H/n b' d' f' A H/n d H h2 yk h1 H/n f C D b' d' B H/n b) a: In case of crest gate; b: In case of submerged gate D' b d BC/n BC/n BC/n For crest gate: ( H 3/2 3/2 yk = k − (k − 1) n ) yk- the distance from water surface to k-principal beam n- number of principal beams; H- water depth For submerged gate : yk = [ H (k + β)3 / − (k − + β)3 / n+β ] na β= H − a2 a- the distance from water surface to crest of submerged gate 22 CALCULATION OF RADIAL GATE 3.1 Forces acting on the gate Hydrostatic pressure; Hydrodynamic pressure; Weight of the gate; Frictions; Forces caused by floating objects 3.2 Necessary driving forces to open or close the gate a General formulas: T2 T1 Opening driving force: T0 P1 = K1.To + K2.(T1 + T2) W l4 α Closing driving force: Q G P2 = K2.(T1 + T2) - K’.To g0 h1 W To- force to win weight of the gate (G); T1- force to win friction at the hinge; T2- force to win friction at watertight components; K1, K2, K’: Safety factors: K1 =1,1; K2 =1,2; K’ =0,9 l3 b Specification of items T0 = G T2 T1 l3 l4 T0 f Q.r T1 = l4 W l4 α Q G e f P R + 2 T2 = l4 h1 l4- tay đòn lực T Q- lực tác dụng tổng hợp khớp quay r- bán kính trục quay f- hệ số ma sát khíp quay g0 W l3 f2- hƯ sè ma s¸t thiết bị khít nớc P- tổng áp lực lên thiÕt bÞ khÝt n−íc e- chiỊu réng thiÕt bÞ khÝt nớc R- bán kính mặt van cung b Specification of items *Calculation of G (To): Experimental formula of Berezinzki G = 1500 F4 F (N) F- area of watertight surface plate (m2) *Calculating total water pressure acting on whole gate W = W12 + W22 W1 = 0,5.γ.H21 L W2 = γ.Ω2.L VALVES and GATES INTRODUCTION 1.1 Definition 1.2 Classification CALCULATION OF PLAIN GATE 2.1 Forces acting on the gate 2.2 Necessary driving forces to open/close the gate 2.3 Structural analysis of the gate CALCULATION OF RADIAL GATE 2.1 Forces acting on the gate 2.2 Necessary driving forces to open/close the gate 2.3 Structural analysis of the gate 27 REFERENCES Tài liệu tham khảo: Bài giảng Công Trình Trên Hệ Thống Thủy Lợi-ĐHTL; Hydraulic structures-P.Novak; http://www.pancanal.com/eng/index.html The Manchester Ship Canal-David Owen,1983; 28 ... on form of gates (cont.): Radial gate 4-Based on form of gates (cont.): Drum and sector gates 4-Based on form of gates (cont.): Flap gate 4-Based on form of gates (cont.): Roller gate 1.2 Classification... Crest and submerged gates a) b) ®) c) e) i) d) g) k) h) l) m) Types of crest gate a) Plates; b) Vertical lift gate; c) Radial gate; d) Roller gate; ®, e) drum and sector gate; g) Roof gate; ... gate 2.3 Structural analysis of the gate 27 REFERENCES Tài liệu tham khảo: Bài giảng Công Trình Trên Hệ Thống Thủy Lợi- ĐHTL; Hydraulic structures-P.Novak; http://www.pancanal.com/eng/index.html
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