《机械密封基础知识一》由会员分享，可在线阅读，更多相关《机械密封基础知识一（75页珍藏版）》请在金锄头文库上搜索。
1、2007新进员工技术培训资料之三,机械密封基础知识（一）,主要内容,机械密封的典型结构、组成部分 机械密封的布置方式,离心泵结构,rotating seal unit,two flat sliding surfaces, which maintain a close running clearance while separated by a fluid film,stationary seal unit,什么是机械密封？ What is a mechanical seal?,机械密封的结构,机械密封的基本组成,Loose ring set screwed to the shaft 动环靠紧钉
2、螺钉传动与轴一起旋转,1,机械密封的基本组成,O-ring prevents leakage through the bore O型圈防止通过间隙泄漏,2,机械密封的基本组成,Spring ensures automatic adjustment 弹簧确保动环能够自动补偿,3,机械密封的基本组成,4,机械密封的基本组成,5,机械密封的基本组成,O-Ring O型圈,Shaft轴,Mating Ring 非补偿环,Primary Ring补偿环,Snap Ring卡环,Anti-X Ring 挡环,O-Ring O型圈,Disk推环,Springs弹簧,Retainer传动套,Set Screw
3、定位螺丝,机械密封的基本组成：小结,机械密封由以下部分组成： 1. A wearable, stationary, primary sealing element 一个耐磨,静止的密封件 2. A wearable, rotating, primary sealing element 一个耐磨,旋转的密封件 3. A secondary sealing element 二次密封 4. A mechanical loading device to press primary sealing elements 1 and 2 against one another, and 使件1和件2相互贴合的
4、机械装置 5. Auxiliary components to complete seal 辅助密封,机械密封的结构 主密封,主密封 Primary Seal,SPRING FORCE FLUID PRESSURE,fluid film (3 - 5 microns),a thin film of liquid forms the primary (dynamic) seal between the rotating and stationary elements,FILM REACTION,主密封 Primary Seal,- Higher pressure on outside diame
5、ter - Higher pressure holds faces closed - Fluid is forced between faces to lubricate - Springs keep faces closed when no pressure,Faces lapped flat to within 1 - 3 light bands. 密封面研磨后平面度1-3个光带,主密封膜厚度Primary Seal Film Thickness,主密封膜厚度Primary Seal Film Thickness,Fluid film thickness is very important
6、膜厚很重要 too thin - wear, causing early seal failure 太薄磨损，早期失效 too thick - visible leakage 太厚泄漏量大 Must be:必须： present - beware dry running 存在避免干运转 stable 稳定 clean - beware abrasive wear symptoms 干净避免磨粒磨损 reasonable viscosity 合理的黏度 temperature controlled 控制温度 acceptable pressure 压力可以接受,主密封膜厚度Primary Sea
7、l Film Thickness,Lubricant 润滑剂,Separation分离面,Magnified Surface A 放大面,Magnified Surface B 放大面,Heat 热量,密封面 The Sealing Interface,Lubrication Purpose: 润滑目的 Separate surfaces 分离两个面 Prevent contact of high surface points 防止出现面接触 Reduce friction/heat generation 减少摩擦/生热,流体在两个面之间充当润滑剂的过程 Process Fluid Acts
8、as Lubricant Between Faces,Gland 密封端盖,Pump Housing 泵腔,Process Fluid 工艺流体,Invisible Leakage: 不可见泄漏 Fluid Evaporates Upon Reaching Atmosphere 微量的泄漏在大气侧蒸发,Primary Ring 补偿环,Mating Ring 非补偿环,主密封平面Primary Seal Face Flatness,If faces not flat, contact generates heat Excessive wear - short life 如果密封面不平，摩擦生热
9、，过度磨损，寿命短,1 light band = 0.0003 mm 1光带=0.0003mm,Gland 密封端盖,Pump Housing 泵腔,No Fluid Or Dry Running 没有流体或者干运转,Primary Ring 补偿环,Mating Ring 非补偿环,没有润滑干运转导致过热 Without Lubrication, Faces Run Dry And Overheat,稳定液膜 Stable Fluid Film,主密封总结,A mechanical seal is self-adjusting for wear Has three main parts :-
10、 Primary Ring (narrower running face) Mating Ring (wider running face - harder) Spring Force Usually the mating ring is stationary & the primary ring rotates with the shaft The liquid film between the primary ring & mating ring is only 0.5 - 3.0 microns thick There are three main sealing areas :- Pr
11、imary Seal - Primary Ring & Mating Ring Secondary Seal - Primary Ring & Shaft Tertiary Seal - Mating Ring & Housing,机械密封的结构 二次密封,二次密封 Secondary Seal,二次密封 Secondary Seal,Three basic forms o-rings wedges bellows elastomer metal formed 冲压成型 edge welded 焊接 PTFE,Two groups Pusher推进式 sliding o-rings Wedge
12、s 楔形环 Non-pusher非推进式 bellows,Teflon Bellows 聚四氟乙烯波纹管,Elastomeric Bellows 橡胶波纹管,Half Convolution 半波,Welded Metal Bellows 焊接金属波纹管,V Rings V型圈,U Cup 杯型,Wedge 楔形,Encapsulated O Ring 包覆 O型圈,O Ring O型圈,二次密封元件Secondary Sealing Elements,Pusher 推进式,Non-Pusher 非推进式,O-ring secondary seal must slide along shaft
13、 as seal face wears O型圈二次密封在密封面磨损的时候必须能够沿轴滑动,Bellows secondary seal expands to accommodate face wear. Bellows tail is stationary against shaft. 波纹管伸长能够补偿密封面磨损,波纹管尾部与轴保持静止,vs.,推进式/非推进式 Pusher vs. Non-Pusher,二次密封：推进式 Secondary Seal: Pusher,As the face moves forward to take up wear, the o-ring moves fo
14、rward with the face, pushed by the hydraulic and spring pressures,二次密封：推进式 Secondary Seal: Pusher,Typical pusher seal - low emission duties 典型的推进式密封,二次密封：推进式 Secondary Seal: Pusher,Advantages sudden failure very unlikely higher pressure capability - face not stressed wide choice of materials for all
15、 components field repairable Disadvantages hang-up (not likely where o-ring is well isolated) permanent set / pressure problems (cause hang-up) excellent shaft surface finish required maximum temperature +260C,推进式密封：卡滞 Pusher Seal: Hang-up,Product leakage solidifies / crystallises / polymerises Prev
16、ents o-ring pushing forward - leakage increases 泄漏的介质凝固/结晶/聚合阻止O型圈移动，造成泄漏增加,An external quench will prevent hang-up 外部冲洗可以避免卡滞,二次密封：O型圈 Secondary Seal: O-Ring,二次密封：楔形环 Secondary Seal: Wedge,二次密封：非推进式 Secondary Seal: Non-Pusher,Bellows flexes to take up wear, misalignment and axial play 波纹管伸缩弯曲，补偿磨损，不
