陜西科技大學過程裝備與控制工程過程裝備雙語過程裝備基礎-Chap.2_Valve

1、Chapter 2 ValvePara 1: valves importance (2nd sent.)nPrimary purposenCharacteristics:2.2 Valve Applications and Theory of OperationValve a device to direct and control the fluids by starting, stopping, and throttling (restricting) flow to make processing possible. Valvesare designed to withstand pre

2、ssure, temperature, and flow and can be found in homes and industry across the world.The common valves found in the manufacturing environment are:Gate valveBall valveCheck valveButterfly valvePlug valveNeedle valveThree-way valveDiagragm valveRelief valveSafety valveAngle valveMultiport valve globe

3、valveProcess operators classify valves by:Flow-control element function Operating condition l Gate valvel Globe valvel Needle valvel Check valvel Plug valvel Adjusting valvel Cut-off valvel Three-way valvel Hand-operating valvel Safety valvel Electric-operated valvel Pneumatic-operated valveConnecti

4、ng manner l Flange connection l Threaded connection l Clamp connection l Welding connection A device that places a movable metal gate in the path of a process flow.line 9,P24Bonnet 機罩Yoke 機架 The typical gate valve consists of a gate, body, seating area, stem, bonnet, packing, stuffing box, packing g

5、land, and hand wheel. The gates are sized to fit the inside diameter of a pipe. Very little restriction occurs when it is in the open position. l Size: from 0.125” to several feet. l Path: from “wide open” to “completely shut”. l Should not be used to throttle flow. The gate can be wedge shaped or m

6、ay consist of parallel discs. The gate is placed directly in the path of a process flow when it is shut and is lifted completely out of the way when open. Gate valvesThe body is the largest part of the valve. The body can be connected to the process piping in three ways: flanges, threaded, or weldin

7、g. The seating consists of two fixed surfaces or rings inside the body of the valve that the gate closes against to stop flow. The seating area falls into two categories: replaceable or fixed. The stem is a long, slender shaft attached to the gate, bushing, or wheel.When the hand wheel is turned, it

8、 transmits rotational energy to the stem, causing it to rise to open or lower to close. The bonnet provides a housing for the gate or disc when it is lifted out of the process flow.It is attached to the body permanently by welding or temporarily by threading or bolts. 3. Body largest part.4. Hand wh

9、eel is attached to the valve stem;nTurn clockwise closes;nTurn counterclockwise opened. corrosive= erosion line 3,P27Bronze 青銅青銅 （ line 6, P27）青銅原指青銅原指銅錫合金銅錫合金，因顏色呈青灰色，因顏色呈青灰色，故稱為青銅；但工業(yè)上都習慣稱含鋁、硅、故稱為青銅；但工業(yè)上都習慣稱含鋁、硅、鉛、鈹、錳等的銅基合金為青銅，所以青銅鉛、鈹、錳等的銅基合金為青銅，所以青銅實際上包括有錫青銅、鋁青銅、鈹青銅等。實際上包括有錫青銅、鋁青銅、鈹青銅等。青銅也可分為壓力加工

10、青銅青銅也可分為壓力加工青銅( (以青銅加工產品以青銅加工產品的形式供應的形式供應) )和鑄造青銅兩類。和鑄造青銅兩類。Brass nRising Stem and Nonrising Stem Q61.Rising（RS，升桿式，升桿式，即，即明桿明桿）: the hand wheel countclockwise open stem (in the center of the hand wheel) rises. Look at tell2.Nonrising （NRS，非升桿式，非升桿式，即，即暗桿暗桿） :a collar cannot look at can not tell.nMa

11、intenance (HW)lGlobe valves are the second most common used in industry. lA globe valve places a movable metal disc in the path of a process flow. lThis type of valve is most commonly used for throttling service. lThe disc is designed to fit smugly into the seat and stop flow.lProcess fluid enters t

12、he globe valve and is directed through a 90o turn to the bottom of the seal and disc. lGlobe valves must be installed properly to work well.lIf the valves is installed backward it will tend to wear unevenly and push the flow-control element down. The typical globe valve consists of:discbodyseating a

13、reastembonnetpackingStuffing boxPacking gland Hand wheel The disc is attached to the stem in three ways:Slip joint Threading One-piece manufacturingThe disc can be classified as plug, ball, composition, or needle shape. lThe hollow ball rotates into the open or closed position.lA ball valve does not

14、 lift the flow-control device out of the process stream.lBall valves provide very little restriction to flow and can be fully opened with a quarter turn on the valve handle.lIn the closed position, the port is turned away from the process flow. In the open position, it lines up perfectly with the in

15、ner diameter of the pipe.lBall valves take their name from the ball shaped, movable element in the center of the valve.lBall valves are not designed for excessive temperatures.lIt should not be used for throttling service.lBall valves do not generally seal as well as globe valves in high-pressure se

16、rvice.lSome ball valves (multiport valves) are designed with multiple ports, so an operator can switch fluid sources without stopping flow. lThe ball valves only require one-quarter turn on a handle.Material: plastic-coated material-the seats. specifications 技術要求技術要求nPara 1: Primary functionlA check

17、 valves is designed to prevent reverse flow and to avoid possible contamination or damage to equipment.nPara 2: 4 types of check valves1.Swing check valve旋啟式止回閥旋啟式止回閥：lFlow lifts the disc and keeps it lifted until flow stops or reverses.lA typical check valve design is the swing check, which has a h

18、inged disc that slams shut when flow reverses.lAnother design is the lift check, which has a disc rests on the seat when flow is idle and lifts when flow is active. Special guides keep the disc in place.lLift checks are ideal for systems in which flow rates fluctuate.lLike the swing check, it is des

19、igned to close when flow reverses.lThe lift check is more durable than the swing check.lIn the horizontal or vertical lift check design, a piston or ball is lifted up and out of the seat by process flow. 4.Stop check valve切斷式止切斷式止回閥回閥： Of a lift check and a globe valve. Deference from Lift check val

20、ve: The degree of lift can be controlled. P32gravity line1 horizontal vertical line 2 1. We can see from the figure that they all operate by gravity;2. The 4 types of check valves come in horizontal and vertical designs. Para 4: MaterialsFunction: PVCPVC蝶閥蝶閥lButterfly valves are commonly used for th

21、rottling and on/off service. The body of this type of valve is relatively small when compared with other valves. It occupies much less space in a pipeline.nStructure: a smaller body than other valves, (Fig.2.7-1) and a metal shaft extends through the center of the disc and allows it to rotate one-qu

22、arter turn.lA one-quarter turn is all it takes to fully open or close the valve.nPay attention: the handle connects the disc, and it should be carefully secured(穩(wěn)固）穩(wěn)固）, otherwise the flow will cause it to open when the handle is not latched（閂鎖）（閂鎖） into position.lDuring a throttling operation, a but

23、terfly valve handle should be carefully secured. They have non-uniform flow characteristics. lThey are designed to be operated at low temperature and low pressure. nSeat material: because it can be only operated at low T and P, the seat can be made of natural gum rubber or suitable plastics.nMechani

24、sm:lPlug valves provide very little restrictions to flow and can be opened 100% with a one-quarter turn on the valve handle. lThe plug valve takes its name from the plug-shaped flow-control element it uses to regulate flow.lQuick-opening, one-quarter turn plug valves are very popular in the process

25、industry.nApplication (Design): slurry 漿料，泥漿漿料，泥漿 line 2 6 basic situationslThe plug valve is designed for fuel gas piping systems, low-pressure situations, slurry and lubrication, on/off, low-temperature service. nOperation: nPay attention: it is not for throttling, if needed a wear. （last Para. P3

26、4)nMaintenance: wear 磨損磨損 line 1, para 2 grease 潤滑脂潤滑脂 line 3, para 2lPlug valves depend on a lubricant inside the body of the valve. The lubricant helps the valve provide a leak-free seal. Application Para 13 : flexible 柔性的，可彎曲的柔性的，可彎曲的 line 3 membrane 薄膜薄膜 line3 setting 調節(jié)調節(jié) counter-count line 3 n

27、eoprene 聚氯丁烯聚氯丁烯 counter-count line lIn a chemical plant, a variety of slurries, corrisive or sticky substances, are transferred from place to place.lStandard valves would have a difficult time with this type of product.lDiaphragm valves are specially designed for the job. lUltra-pure substances e.g

28、. demineralized boiler feed water.（P35）lThe stem is attached to a device called the compressor. lDiaphragm valves use a flexible membrane and seat to regulate flow.lThe compressor pushes on a flexible diaphragm. lThe internal parts of the valve never come into contact with the process material. lThe

29、 diaphragm valve seats are made of chemical-resistant plastic, rubber, or neoprene. lDiaphragm valve can handle corrosive fluids. nMechanism:nPara 2StructurenWeirFig.2.9-1nNon-weirFig.2.9-2nWe can see that the diaphragm conforms to the setting on the hand wheel.Relief Valves relief valve 減壓閥減壓閥 pred

30、etermined 預先設定的預先設定的 line 2, p35 前綴前綴pre- 預先預先 pretreatment 引申：后綴引申：后綴 post- posttreatment pressurized 增壓的增壓的 line1, para2, p36 velocity 速度速度 line 7, para2, p36 fraction 分數(shù)，分餾分數(shù)，分餾 line12,para2, p36 lift-off 提升提升 counter-count line2,para2 spindle 主軸，轉軸主軸，轉軸 line4,para3nFunction and application:High

31、velocity gas would do damage to the seats and disc.lRelief valve is to respond automatically sudden increases of pressure in liquid services. They do not respond well in gas service.lA relief valve is designed to open at a predetermined pressure. StructurelIn the valve a disc is held in place by a s

32、pring that does not open until the system pressure exceeds operating limits.nComponents: (Fig.2.10-1)nAdvantages: lThe two advantadges of relief valves are that they will reseat as soon as the pressure drops below the relief pressure and the spring tension is adjustable. When a system overpressures, safety valves respond to allow excess pressure to be vented to the flare header. They are designed to respond quickly t