過程裝備基礎(chǔ)chap.2 valve

1、After study this chapter, the student will be able to: Explain the purpose of valves in industrial manufacturing. Identify the basic components of a gate valve. Identify the basic components of a globe valve. Explain the operation and design of a ball valve. Identify the basic components of a check

2、valve. Describe the design and operation of a butterfly valve. Describe the design and operation of a plug valve. Describe the design and operation of a diaphragm valve. Describe the design and operation of a relief valve and safety valve. Describe the design and operation of a automatic valves. Cha

3、pter 2 Valve1Para 1: valves importance (2nd sent.)Primary purpose：（P23，line 3）Characteristics: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 with

4、stand pressure, temperature, and flow and can be found in homes and industry across the world.2Para 2: The types of valves The common valves found in the manufacturing environment are:Gate valveBall valveCheck valveButterfly valvePlug valveNeedle valveThree-way valveDiagragm valveRelief valveSafety

5、valveAngle valveMultiport valve globe valve3Classification of Valves:Process operators classify valves by:Flow-control element function Operating condition Gate valve Globe valve Needle valve Check valve Plug valve Adjusting valve Cut-off valve Three-way valve Hand-operating valve Safety valve Elect

6、ric-operated valve Pneumatic-operated valveConnecting manner Flange connection Threaded connection Clamp connection Welding connection 4Bridgewall Markings: some useful information specific to the valve.5Characteristics: most common tape;2.3 Gate ValvesA device that places a movable metal gate in th

7、e path of a process flow.Key termsdiameter line 6, P24erosion line 2, P25inch line 9,P246Bonnet 機(jī)罩Yoke 機(jī)架 The typical gate valve consists of a gate, body, seating area, stem, bonnet, packing, stuffing box, packing gland, and hand wheel. The gates are sized to fit the inside diameter of a pipe. 2.3 G

8、ate Valves7Very little restriction occurs when it is in the open position. Size: from 0.125” to several feet. Path: from “wide open” to “completely shut”. Should not be used to throttle flow. The gate can be wedge shaped or may consist of parallel discs. The gate is placed directly in the path of a

9、process flow when it is shut and is lifted completely out of the way when open. 8Common Gates: P26, Fig.2.3-2 spring line2 P26, Para4/this partSolid wedge 整體楔形閘板 should never be overtightened；Solid split gate整體開口閘板 high T；Parallel discs平行閘板 the higher the P, the more tightly the disc fits into the s

10、eat.Key terms9Gate valvesThe body is the largest part of the valve. The body can be connected to the process piping in three ways: flanges, threaded, or welding. 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 ar

11、ea 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 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 wh

12、en it is lifted out of the process flow.It is attached to the body permanently by welding or temporarily by threading or bolts. 103. Body largest part.4. Hand wheel is attached to the valve stem;Turn clockwise closes;Turn counterclockwise opened. 1112Gate Valve Materialscorrosive= erosion line 3,P27

13、Bronze 青銅 （ line 6, P27） 青銅原指銅錫合金，因顏色呈青灰色，故稱為青銅；但工業(yè)上都習(xí)慣稱含鋁、硅、鉛、鈹、錳等的銅基合金為青銅，所以青銅實(shí)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青銅(以青銅加工產(chǎn)品的形式供應(yīng))和鑄造青銅兩類。 13Brass 黃銅 line 7 黃銅是銅與鋅的合金。最簡(jiǎn)單的黃銅是銅鋅二元合金，稱為簡(jiǎn)單黃銅或普通黃銅。改變黃銅中鋅的含量可以得到不同機(jī)械性能的黃銅。黃銅中鋅的含量越高，其強(qiáng)度也較高，塑性稍低。工業(yè)中采用的黃銅含鋅量不超過45%，含鋅量再高將會(huì)產(chǎn)生脆性，使合金性能變壞。 Cast iron 鑄鐵（生鐵） line 9 cast

14、 steel1415Rising Stem and Nonrising Stem Q6Rising（RS，升桿式，即明桿）: the hand wheel countclockwise open stem (in the center of the hand wheel) rises. Look at tellNonrising （NRS，非升桿式，即暗桿） :a collar cannot look at can not tell.Maintenance (HW)16Characteristics: 截止閥2.4 Globe valvesGlobe valves are the second

15、 most common used in industry. A globe valve places a movable metal disc in the path of a process flow. This type of valve is most commonly used for throttling service. The disc is designed to fit smugly into the seat and stop flow.Process fluid enters the globe valve and is directed through a 90o t

16、urn to the bottom of the seal and disc. 17Globe valves must be installed properly to work well.If the valves is installed backward it will tend to wear unevenly and push the flow-control element down. 2.4 Globe valves18 (1) 結(jié)構(gòu)比閘閥簡(jiǎn)單，制造與維修都較方便。(2) 密封面不易磨損及擦傷，密封性好，啟閉時(shí)閥瓣與閥體密封面之間無(wú)相對(duì)滑動(dòng)，因而磨損與擦傷均不嚴(yán)重，密封性能好，使

17、用壽命長(zhǎng)。(3) 啟閉時(shí)，閥瓣行程小，因而截止閥高度比閘閥小，但結(jié)構(gòu)長(zhǎng)度比閘閥長(zhǎng)。 2.4 Globe valves19The typical globe valve consists of:discbodyseating areastembonnetpackingStuffing boxPacking gland Hand wheel Structure:20The disc is attached to the stem in three ways:Slip joint Threading One-piece manufacturingThe disc can be classified

18、as plug, ball, composition, or needle shape. 2122The hollow ball rotates into the open or closed position.A ball valve does not lift the flow-control device out of the process stream.Ball valves provide very little restriction to flow and can be fully opened with a quarter turn on the valve handle.I

19、n the closed position, the port is turned away from the process flow. In the open position, it lines up perfectly with the inner diameter of the pipe.Ball valves take their name from the ball shaped, movable element in the center of the valve.2.5 Ball valves23Characteristics: Fig.2.5-1Ball valves ar

20、e not designed for excessive temperatures.It should not be used for throttling service.Ball valves do not generally seal as well as globe valves in high-pressure service.Some ball valves (multiport valves) are designed with multiple ports, so an operator can switch fluid sources without stopping flo

21、w. The ball valves only require one-quarter turn on a handle.24Material: plastic-coated material-the seats. specifications 技術(shù)要求Key term25Para 1: Primary function2.6 Check ValvesA check valves is designed to prevent reverse flow and to avoid possible contamination or damage to equipment.26Para 2: 4 t

22、ypes of check valvesSwing check valve旋啟式止回閥：Flow lifts the disc and keeps it lifted until flow stops or reverses.A typical check valve design is the swing check, which has a hinged disc that slams shut when flow reverses.2.6 Check Valves272. Lift check valve升降式止回閥：Another design is the lift check, w

23、hich has a disc rests on the seat when flow is idle and lifts when flow is active. Special guides keep the disc in place.2.6 Check Valves28Lift checks are ideal for systems in which flow rates fluctuate.Like the swing check, it is designed to close when flow reverses.The lift check is more durable t

24、han the swing check.In the horizontal or vertical lift check design, a piston or ball is lifted up and out of the seat by process flow. Characteristics:2.6 Check Valves29Ball check valve落球式止回閥 ：Special guides keep the ball disc in place；Flow rates fluctuate or the fluid contains some solids；More tha

25、n the 1st, as the 2nd；Stop check valve切斷式止回閥： Of a lift check and a globe valve. Deference from Lift check valve: The degree of lift can be controlled. P3230Para 3: pay attention gravity line1 horizontal vertical line 2 1. We can see from the figure that they all operate by gravity;2. The 4 types of

26、 check valves come in horizontal and vertical designs. Para 4: MaterialsKey terms31 Function: PVC蝶閥2.7 Butterfly ValvesButterfly valves are commonly used for throttling and on/off service. The body of this type of valve is relatively small when compared with other valves. It occupies much less space

27、 in a pipeline.32Structure: 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-quarter turn.A one-quarter turn is all it takes to fully open or close the valve.2.7 Butterfly Valves33Pay attention: the handle connects the

28、 disc, and it should be carefully secured(穩(wěn)固）, otherwise the flow will cause it to open when the handle is not latched（閂鎖） into position.During a throttling operation, a butterfly valve handle should be carefully secured. They have non-uniform flow characteristics. They are designed to be operated a

29、t low temperature and low pressure. Seat material: because it can be only operated at low T and P, the seat can be made of natural gum rubber or suitable plastics.34Mechanism: 旋塞閥2.8 Plug ValvesPlug valves provide very little restrictions to flow and can be opened 100% with a one-quarter turn on the

30、 valve handle. The plug valve takes its name from the plug-shaped flow-control element it uses to regulate flow.Quick-opening, one-quarter turn plug valves are very popular in the process industry.35Application (Design): slurry 漿料，泥漿 line 2 6 basic situations The plug valve is designed for fuel gas

31、piping systems, low-pressure situations, slurry and lubrication, on/off, low-temperature service. Key termOperation: When close: the port is turned away from the process flow;Open: the port lines up with the Di of the pipe.2.8 Plug Valves36Pay attention: it is not for throttling, if needed a wear. （

32、last Para. P34)Maintenance: wear 磨損 line 1, para 2 grease 潤(rùn)滑脂 line 3, para 2Plug valves depend on a lubricant inside the body of the valve. The lubricant helps the valve provide a leak-free seal. Key terms2.8 Plug Valves37 Application Para 13 : flexible 柔性的，可彎曲的 line 3 membrane 薄膜 line3 setting 調(diào)節(jié) c

33、ounter-count line 3 neoprene 聚氯丁烯 counter-count line 2.9 Diaphragm Valves 隔膜閥Key termsIn a chemical plant, a variety of slurries, corrisive or sticky substances, are transferred from place to place.Standard valves would have a difficult time with this type of product.Diaphragm valves are specially d

34、esigned for the job. Ultra-pure substances e.g. demineralized boiler feed water.（P35）382.9 Diaphragm Valves 隔膜閥The stem is attached to a device called the compressor. Diaphragm valves use a flexible membrane and seat to regulate flow.The compressor pushes on a flexible diaphragm. The internal parts

35、of the valve never come into contact with the process material. The diaphragm valve seats are made of chemical-resistant plastic, rubber, or neoprene. Diaphragm valve can handle corrosive fluids. Mechanism:39Para 2StructureWeirFig.2.9-1Non-weirFig.2.9-2We can see that the diaphragm conforms to the s

36、etting on the hand wheel.40 Relief Valves relief valve 減壓閥 predetermined 預(yù)先設(shè)定的 line 2, p35 前綴pre- 預(yù)先 pretreatment 引申：后綴 post- posttreatment pressurized 增壓的 line1, para2, p36 velocity 速度 line 7, para2, p36 fraction 分?jǐn)?shù)，分餾 line12,para2, p36 lift-off 提升 counter-count line2,para2 spindle 主軸，轉(zhuǎn)軸 line4,para

37、32.10 Relief and Safety ValvesKey terms41Function and application:High velocity gas would do damage to the seats and disc. 2.10 Relief and Safety ValvesRelief valve is to respond automatically sudden increases of pressure in liquid services. They do not respond well in gas service.A relief valve is

38、designed to open at a predetermined pressure. 42StructureIn the valve a disc is held in place by a spring that does not open until the system pressure exceeds operating limits.2.10 Relief and Safety Valves43Components: (Fig.2.10-1)Advantages: (last Para)The 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. 44When a system overpressures, safety valves res