Bài giảng công trình trên hệ thống thủy lợi valves and gates

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 ... 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... 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.):... on position: 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)