1、裂解气压缩机机械密封失效的原因分析摘要 ： 阐述了机械密封零部件损坏的现象，从原理上分析了密封油泄漏的原因和机械密封元件损坏的原因。关键词： 离心式压缩机 ； 机械密封； 泄漏；喘振中图分类号 TH452 文献标识码： B Reason Analysis of the Invalid Mechanical Seal in Cracked Gas Compressor Abstract: This paper has specified the damage phenomenon of mechanical seal components and theoretically analyzed t
2、he reasons of seal oil leaking and damaged mechanical seal components. Key words: centrifugal compressor; mechanical seal; leaking; surge 1 机械密封简介和失效判断1 introduction of mechanical seal and failure judgement http:/ http:/ 1996 年装置兴建时引进意大利新比隆公司的设备。该设备为超高压蒸汽轮机驱动，压缩机分高、低压缸两缸，低压缸 3MCL606 ，高压缸 2BCL459 。该机
3、组轴端密封型式采用的是德国伯格曼公司生产的机械密封和浮环联合密封，低压缸 3MCL606 使用的机械密封的型号为 SH1/200-E1 ，单端面、平衡式、双转动机械密封，在密封腔的外侧装有浮环（节流环） ，通过浮环径向间隙起第二密封作用 ( 见图 1) 。密封油的压力为 900 650kPa, 油气压差即密封油与密封气的压力差控制在 350 200kPa 。为了使机械密封得到良好的润滑和冷却作用，密封腔内必须有充分的密封油，如果油气压差偏低或密封气的压力高于密封油的压力密封腔内充满气体，密封端面就会发生干磨，产生大量热量，在很短的时间内机械密封就会烧坏。本机械密封的密封油最小流量为 32 L
4、/min ，密封油大部分通过机械密封外环即动环外侧腔体流出并带走密封端面产生的热量，极少量的密封油通过密封端面流出进入静环内侧的腔体，最后进入油气分离器，平均最大漏油量为 50 L /d 。高压缸 BCL459 使用的机械密封的型号为 SH7/117-E1 ，单端面、平衡式、双转动机械密封。密封油的压力油气压差与低压缸的要求相同，密封油最小流量为 10 L /min ，进入油气分离器的平均最大漏油量为 13 L/d 2 。Ethylene joint workshop olefin plant of lanzhou petrochemical company http:/ http:/ cra
5、cking gas compressor unit, for the 1996 introduction of Italy during the construction of the new equipment than long company. The device for the super high pressure steam turbine driven, compressor is divided two cylinder, high and low pressure cylinder 3 McL606 low pressure cylinder, high pressure
6、cylinder 2 bcl459. Is the unit shaft end seal with German bergman company produces the mechanical seal and floating ring seal, low pressure cylinder 3 McL606 type mechanical seal to the use of the SH1/200 - E1, single, balance type, double rotating mechanical seal, on the outer edge of the sealed ca
7、vity filled with floating ring (throttling ring), through the radial clearance on the floating ring seal effect (see figure 1). Seal oil pressure is 900 650 kpa, oil and gas differential pressure oil seal and seal gas pressure difference control in 350 200 kpa. Get good lubrication and cooling to ma
8、ke mechanical seal, seal chamber must have adequate seal oil, if oil and gas differential pressure is low or the seal gas pressure is higher than the seal oil pressure seal cavity filled with gas, the seals will occur dry grinding, produce a lot of heat, mechanical seal in a very short period of tim
9、e will burn out. This mechanical seal of the seal oil minimum flow for 32 L/min, seal oil, most of the mechanical seal ring by ring outer cavity flow and take away the heat generated by the seal face, very small amounts of seal oil flow through the seal face into the static ring inside the cavity, a
10、nd finally into the oil and gas separator, the average maximum flow rate of 50 L/d. High http:/ http:/ cylinder BCL459 type of mechanical seal used for SH7/117 - E1, single face, balance type, double rotating mechanical seal. Seal oil pressure, oil and gas differential pressure is the same as the re
11、quirement of low pressure cylinder, the sealing oil minimum flow of 10 L/min, into the oil and gas separator maximum size of the spill to an average of 13 L/d 2. 低压缸东、西两侧进入油气分离器的回油管线的密封油流量突然增大， 2009 年 8 月 3 日 约损失 10 桶润滑油，回油管线的温度升高约 70，高压缸西侧密封的回油管线的流量从 7 月 28 日就突然变大、温度也突然升高，为了实现油气分离才扩大了回油孔。初步制定低压缸两侧和
12、高压缸西侧机械密封失效即密封端面脱开或偏磨严重。由于工艺操作工况的变化发生喘振，机组振动大，可诱使机械密封端面间的液压膜厚度变化，当静环（弹簧装在静环座上）的补偿性变差时，两密封端面就脱开或发生倾斜，可导致密封泄漏量大，密封失效。 2009 年 8 月 2 日因外界蒸汽压力波动10：0510： 10 喘振一次，8 月日夜班 0 ：160 ：18 1 ：361 ：39 机组转速均有波动（约 80r/min ） ，从最近的几次喘振看，每http:/ http:/ 但随着工况的波动泄漏量在不断变化，不可避免地使裂解气通过回油孔进入润滑油系统，所以必须对机械密封进行检修。Low pressure cy
13、linder side of the east, and west into the oil and gas separator of oil return pipeline sealing oil flow increases suddenly, on August 3, 2009 about 10 barrels of oil loss and temperature rise in the oil return line is about 70 , the west side of high pressure cylinder seal oil return pipeline flow
14、from July 28, suddenly become larger, the temperature suddenly increases, in order to achieve the separation of oil and gas to expand the oil return hole. Initially set on both sides of low pressure cylinder and high pressure cylinder on the west side release the seal face mechanical seal failure or
15、 severe eccentric wear. Due to the change of process operating conditions occur surge, the vibration is big, can induce the hydraulic mechanical seal face film thickness changes, when the static ring (spring in a static ring seat) compensating variation, two seal face are disengaged or tilt, may cau
16、se a large sealing leakage and seal failure. On August 2, 2009 by external steam pressure fluctuations 10:05 10:10 surge at a time, on August 3, night shift 0:16 0:1:18 to 36 http:/ http:/ 1:39 units speed fluctuations were (80 r/min), from the recent surge, each time after surging oil seal leakage,
17、 reflected in the oil and gas separator liquid level, processing power is not enough. Finally in order to decrease the loss of lubricating oil to take off the high pressure cylinder of two oil and gas separator float, but it is difficult to maintain a certain level, in order to achieve the separatio
18、n of oil and gas to avoid cracking gas into the lubricating oil system and must maintain a certain level, but as the working condition of the volatility of the leakage in constant change, inevitably make the cracking gas through oil return hole into the lubricating oil system, so you have to repair
19、the mechanical seal. 机械密封损坏现象和原因分析2 mechanical seal damage phenomenon and the cause analysis http:/ http:/ to the unit operation condition and fault analysis of condition monitoring data, think machine seal leakage in high pressure cylinder is stable, preliminary determination of dynamic and static
20、ring sealing is lax eccentric wear or aging sealing ring, jamming. Mechanical seal as compressor surge, resulting in a large number of low pressure cylinder seal oil leakage, due to the leakage has been unable to control, can speculate that the mechanical seal failure: completely static ring damaged
21、 or due to spring binding cost static ring compensation ability. 8 月 5 日 机组解体，发现低压缸西侧机械密封损坏较严重，静环防转销一个从安装位置脱落，一个被切断，造成静环座转动， http:/ http:/ 个压紧弹簧被切断（见图 1a ） ，浮环密封被弹簧碎屑拉伤，动环座、静环座和密封腔体多处被碎了的弹簧磨出沟槽，动环（硬质合金）的端面和外侧有较多的焦油粘附（见图 1b 、 c ） ，静环 ( 石墨 ) 密封端面有严重的摩擦痕迹，内侧边缘有龟裂现象（见图 1d ） 。分析认为由于某种原因上次装配时其中一个静环防转销由于过盈
22、量较小，在某次压缩机喘振时脱落，另外一个防转销限制着静环的转动。由于压缩的喘振，转速的大幅度波动，密封端面的液压膜的厚度在改变，静环在弹簧的作用下开始调节液压膜的厚度，静环在防转销的导向下在轴向开始运动，由于只有一个固定点（防转销） ，静环在动环的带动下发生周向运转，造成动环和静环的不同心，密封端面泄漏量加大，之后密封端面又达到了一个新的平衡点，但是随后的压缩机喘振又破坏了这个平衡点，另一个静环防转销被切断，静环随动环旋转造成压紧弹簧破碎进入密封面导致机封失效，这时进入密封腔的密封油几乎全部泄漏到油气分离器中。经测量分析认为机封静环座防转销固定孔深度太浅，过盈量不够（由于拆开后销孔和销钉均磨损
23、变形，原始尺寸无法测量） ，机组运行中静环座的振动导致一个销钉脱落，另一个由于剪切力加大被切断。对低压缸机封采取了加深销钉固定孔，增加配合过盈量，防转销长度增加到 33mm ( 原 23mm ) ，销钉材质由原来的 18-8 改为强度更高、抗剪切能力更好的 0Cr17Ni4Cu4Nb ，按照新的配合尺寸由厂家重新加工防转销，彻底解决销钉脱落的问题。同时对浮环防转销进行了改造，防止其脱离。此外还和设计厂家共同对密封端面受力进行http:/ http:/ 5 units, found that the west side of low pressure cylinder mechanical se
24、al damage is relatively serious, stop pin a static ring fall off from the installation position, one is cut off, causing static ring rotation, 10 compression spring is cut (see figure 1 a), floating ring seal is a spring elastic strain, ring and static ring and the seal cavity broken at many points
25、along the spring grinding groove, ring (hard alloy) of end face and outside more tar adhesion (see FIG. 1 b, c), static ring (graphite) the seals have serious friction marks, the medial edge crack phenomenon (see FIG. 1 d). Analysis thought for some reason the last assembly is one of the static ring
26、 and written off due to the over surplus quantity is small, falls off when one compressor surge, another stop pin limits the rotation of static ring. Due to compression of the surge, the large fluctuation of rotating speed, hydraulic pressure of the membrane thickness of the seals in the change, und
27、er the action of static ring on the spring began to adjust http:/ http:/ hydraulic pressure of the membrane thickness, static ring under the guide of stop pin in axial movement, since there is only one fixed point (the stop pin), static ring ring leads in the week to operate, causing different heart
28、 ring and static ring, the seals leakage increased, after the seals and reached a new equilibrium, but then the compressor surge and destroyed the balance, the other a static ring stop pin is cut off, the static loop servo loop caused by compression springs are broken into the sealing machine for se
29、aling failure, then into the sealed cavity of almost all the sealing oil leakage in oil and gas separator. Measured analysis machine static sealing ring seat fixed stop pin hole depth is too shallow, interference quantity is not enough (because of the pin hole and pin are wear deformation after apar
30、t, unable to original size measurement), in the operation of the unit vibration causing static ring fall off a pin, another due to the shear stress increases were cut off. Of low pressure cylinder machine adopted to deepen taper pin hole, increase the interference with the amount, length of stop pin
31、 (23 mm) increased to 33 mm, pin material from 8 to 18 - have higher strength and better 0 cr17ni4cu4nb shear resistance, according to new dimension by manufacturer reprocessed stop pin, thoroughly solve the problem of pin fall off. To stop pin floating ring at the same time, to prevent its escape.
32、In addition to common stress distribution on the seal face was analyzed and design manufacturer, checking calculation result, fall off or stop pin was cut out there must be a http:/ http:/ of force, the stop pin in addition to prevent static ring rotation also have static rings in the axial movement
33、 of the guiding role, according to the stop pin axial force of force bearing analysis on the static ring (static friction ring) is very small cant make it fall off, there may be a negative moment on the stop pin, just may make the stop pin fall off from the fixed pin hole. Normally most shear force
34、when the machine is started up, than one moment when surge seal face pressure, seal end is passed to the static ring friction increase, shall be borne by the stop pin of the shear force increases suddenly, stop pin was suddenly cut off. 拆开后观察高压缸两端机械密封没有明显损坏和变形的情况，但动、静环密封面之间有积碳，动环（硬质合金）的端面和外侧有较多的焦油粘附
35、（见上图的照片） ，静环 ( 石墨 ) 密封端面的内侧边缘有龟裂现象。造成这种现象的原因如下。Apart after observation of high pressure on both ends of the cylinder, there was no significant damage and deformation of mechanical seal, but between dynamic and static ring sealing surface carbon deposition, ring http:/ http:/ alloy) of end face and o
36、utside more tar adhesion (see above picture), the static ring (graphite) seals the inside edge of the crack phenomenon. The cause of this phenomenon as follows. （ 1 ）密封面上无磨痕，说明存在某种障碍，检查弹簧和密封腔体分析认为静环轴套跟随性差，造成动静密封环密封面未完全贴合造成密封油泄漏量较正常增大，可能机械密封静环座加工存在误差，机封静环座与“ O ”型圈接触部分表面粗糙度不够，造成静环轴套运动阻力过大，跟随移动不畅。也可能遇到
37、弹簧被卡住，密封介质很脏而且在密封腔中不能轴向移动会发生弹簧卡住，通过密封端面的泄漏量很大，为了保持静环的跟随补偿性，应正确选择弹簧的刚度和弹簧的个数。 高速离心式压缩机机械密封的动环随轴做轴向运动，压缩机的负荷波动、或其它原因引起的喘振等促使转子发生轴向移动，受止推轴承的限制该移动的距离在 0.30mm 以内。由于负荷波动是无规律的，因此轴向移动也是不定期无规律的，只要轴向位移在弹簧力补偿的范围内，机械密封就不会泄漏。此外动环还要发生轴向振动，由于动环本身的制造精度和安装的误差，动环和轴的垂直度也有一定的误差，动环随轴旋转时动环端面便产生了http:/ http:/ s ）为(1) the
38、sealing surface grinding marks, indicating some obstacles, check the springs and seal cavity is analyzed that the static ring collar with sexual difference, causes of dynamic and static sealing ring sealing surface is not completely joint seal oil leakage caused by the normal increase, may be mechan
39、ical seal static ring processing error, machine static sealing ring seat contact with “O“ type circle part surface roughness is not enough, cause static ring sleeve movement resistance is too large, to follow a moving. Also may encounter spring stuck, sealing medium is dirty and axial moving in the
40、seal chamber cant spring gets stuck, will happen through the end of the seal leakage is large, in order to maintain a static ring with compensatory, should be the right choice of spring stiffness and the number of spring. High-speed centrifugal compressor mechanical seal ring with the shaft axial mo
41、vement, compressor load fluctuations, or other causes of surge and locomotion of the rotor in axial, http:/ http:/ by thrust bearing the moving distance within 0.30 mm. Due to load fluctuations are irregular, so axial movement is not irregular regularly, as long as the axial displacement in spring f
42、orce compensation, within the scope of the mechanical seal will not leak. In addition ring axial vibration will occur, because the manufacturing precision of the ring itself and installation error, ring and shaft of vertical degree also has a certain error, ring rotates with the shaft ring end face,
43、 the swing, oscillation frequency is equal to the axis of rotation speed, oscillation amplitude depends on ring perpendicularity error. When axis at high speed, the ring with the shaft axial displacement and swing, in under the action of spring force and static ring ring close contact, in under the
44、action of swinging ring, every turn a week will be static ring for a very small gap, static ring in time under the action of spring force to fit on the ring end face, if the frequency is not the same mechanical seal face poor compensatory or clearance increases, increases the sealing oil leakage. To
45、 simplify the static ring as a resonant system and its auxiliary component, ignore the damping function according to the principle of resonance its circular frequency (s) 经过计算静环组件在弹簧力的作用下的振动周期约为 3000 次 /min ，而裂解气压缩机的转速为 7600r/min ，即静环组件的补偿频率为动环摆动频率（压缩机转速）的 0.395 倍 2 。因此高http:/ http:/ ic 值或者减小静环组合件的质量。由于受密封腔结构尺寸和材料密度的限制，静环组合件的质量减小是很有限的，增大弹簧刚度受到弹簧比压和弹簧压缩量的限制，如果增大弹簧刚度必将导致弹簧比压增大，通常弹簧比压取 0.20.4MPa ，要使静环组合件的摆动频率与转速相同根据上述公式弹簧的刚度就得增加 67 倍，即弹簧比压要增大 67 倍，导致密封端面比压过大无法使用，此为机械密封在高转速机器上运用的弊端之一。为了使补偿性能
