Centrifugal compressor does hermetic seal principle and typical breakdown analysis
In recent years, as consciousness of people safety, environmental protection rise, the production that waits for energy industry to the petro-chemical chemical industry that reach coal moves raised taller requirement. According to not complete count, in the manufacturing unit that waits for an industry in oil refining chemical industry, coal chemical industry, pharmacy, because rotate,accident of the safety that mechanical axis seals leak to cause, environmental protection held very large proportion, serious effect produces device to grow periodic, stable, safe production to move. Accordingly, solve axis of instrument of a favourable turn coming back to seal leak problem, especially Feng Xiangshi of axis of group of large scale computer does not have small progress of leak, free from contamination, macrobian life and carry dimension charge now, already became the important consensus inside course of study and the issue that are badly in need of solving.
As 20 centuries gas of 60 time end lubricates the development of bearing technology, a kind new-style, reliable, the axis seals technical —— to do hermetic seal arise at the historic moment, it is film of a kind of gas lubricant fluid is moved, static press union blame contact machinery is sealed, have without medium leak, on the safe side, service life long, power comsumption is low advantage, the key such as the centrifugal compressor that waits for industrial industry in chemical industry of petro-chemical, coal receives wide application on equipment.
Move in production however in, because do hermetic seal to control exercise of systematic design, type selecting and carry to use,be less than, the breakdown common occurance such as the leak of dry hermetic seal that cause, invalidation. The moving situation that because this basis produces the craft of device to operate operating mode,reachs unit, the design gives a reliable, appropriate dry gas sealed control system, having decisive effect to ensuring the long cycle of aircrew, stability, safe production moves.
1, dry hermetic seal is basic structure and working principle
1.1 dry gas are sealed and basic structure
Dry hermetic seal is film of a kind of gas lubricant fluid is moved, static press union blame contact machinery is sealed. If graph 1-1 place is shown, the bag contains the static annulus, component that move link (move link) , circle of form of deputy sealed O, static sealed, bedspring and bedspring (housing) wait for component. The structure of dry hermetic seal designs a characteristic to open dynamic pressure shallow slot to be on seal face, the gas film that its roll forms is deep all belong to micron class greatly with launder chamfer, use radial and lubrication groove, sealed dam and Zhou Xiangmi to seal lasher composition is sealed and bear the weight of part. Can saying is a face sealed the union with bearing opening slot.
Chamfer of dynamic pressure of dry hermetic seal has odd Xiang Heshuang coming back to come back to, general Chan Xuan to for helix chamfer, shuang Xuan to common have T chamfer, fir chamfer and U chamfer. If graph 1-2 place is shown, chan Xuan does hermetic seal to cannot invert to helix chamfer, invert to produce film of do sth in a fit of pique to return power, bring about seal face impaction, send sealed attaint be no longer in force. And Shuang Xuan is not had to fir chamfer come back to the requirement, it is OK that positive and negative turns. One-way chamfer is opposite at two-way chamfer, have greater fluid dynamic pressure can, the gas film with larger generation returns power amiable film stiffness, produce better stability.
Principle of job of 1.2 dry hermetic seal
Be like graph 1-3, sealed to helix chamfer dry gas, its job principle is to rely on the balance between force of fluid quiet pressure, bedspring and force of fluid dynamic pressure. When seal unit of sealed gas infuse, make move, static annulus gets the action of fluid quiet pressure. And the ability when the dynamic pressure force of the fluid just is turning arises. If graph 1-2 place is shown, when moving annulus to turn along with the axis, the gas in helix chamfer is cut from outside the predestined relationship flows to a center, generation uses pressure, and sealed lasher is right of gas pour out of have inhibition, make aeriform flow suffocate suffocate, aeriform pressure is elevatory, the static annulus that the pressure that this lifts installs flexibility and conjugate move annulus departure, after aeriform pressure and bedspring force restore a balance, keep one the least gap, form gas film, film is deep it is 3-5μm commonly, make rotating ring and stationary ring break away from a contact, thereby end panel is not had almost wear away, at the same time sealed craft gas.
The type with 1.3 sealed dry gas
Basic structure type has dry hermetic seal sheet carries type of sealed, series connection type of labyrinthian series connection is sealed, sealed among the belt He Shuangduan face is sealed.
(1) odd end panel is sealed
Apply to make without harm, allow the craft of minim enrages leak to arrive atmospheric operating mode. The compressor that be like N2, CO2 compressor, air compressor.
(2) series connection type is sealed
Apply to allow a few craft to enrage leak to arrive atmospheric operating mode. Use two class series connection to decorate means commonly, one class is given priority to sealed, 2 class are reserve sealed. Below normal operating mode, all or major negative charge by advocate sealed assume, and 2 class reserve sealed do not bear or bear the bear of fraction and pressure fall. Of leak advocate sealed craft enrages combustion of system of torch be introducinged, the technology vital energy of the thimbleful of leak adopts 2 form sealed put by 2 class introduce refuge to discharge for nothing. When advocate when sealed invalidation, 2 class reserve sealed rise to assist safe and sealed action, ensure craft enrages the leakage outside be being measured not quite.
(3) labyrinthian series connection type is sealed among the belt
Its structural characteristic adds labyrinthian and sealed texture to be between the two class with series connection sealed type. Among them one class advocate sealed gas is enraged for craft, middling pressure N2 stops to leave machine is auxiliary gas; 2 class are sealed and among labyrinthian, segregation gas uses nitrogen. When one class advocate when sealed invalidation, 2 class are sealed remove auxiliary and safe block to seal with sealed action. Apply to explode combustibly, easily, dangerous sex is big, do not allow leak to arrive in atmosphere, also do not allow block to seal gas to enter the operating mode inside machine. Compressor of compressor of the air that be like hydrogen, CO compressor, ethylene, propylene.
(4) double end panel is sealed
Double end panel is sealed apply to without torch condition, not allow makes craft enrages leak to arrive in atmosphere, but allow makes block seals gas to enter the operating mode inside machine. Its structure is decorated be equivalent to decorating two odd end panel face-to-face sealed, sometimes two sealed and common one moves link. Use nitrogen to regard block as gas commonly, control block is sealed gas (N2) pressure is maintained from beginning to end comparing prep above of craft gas pressure 0.2 ～ 0.3MPa.
2, the composition that centrifugal type compressor does hermetic seal to control a system
If graph 2-1 place is shown, some centrifugal type compressor diagram of flow of sealed system of group dry gas, system of control of this aircrew dry hermetic seal enrages system of system, segregation hermetic seal, incendiary fire and perch to put the empty system that monitor to comprise by craft hermetic seal, among them sealed gas and segregation gas design have gas source to filter pressure of processing unit, gas controls unit with discharge adjustment, platoon deflate setting has torch to discharge put with perch empty, design sealed gas leak is monitored.
This aircrew does hermetic seal to control control flow of the system:
(1) one class advocate sealed gas is enraged by compressor exit and nitrogen of tubal net middling pressure is offerred, pass colander to handle, control valve, flowmeter, throttle controls the pressure of sealed gas and flow; And middling pressure nitrogen serves as tubal net to stay the one course when machine sealed gas reserves gas source.
(2) sealed gas and postposition segregation enrage 2 class to be offerred by nitrogen of low pressure tubal a network, the course is filter processing, pressure regulating regard 2 class as sealed gas and postposition segregation gas with flow control gas source. Purpose of system of hermetic seal of segregation of aircrew design postposition is to prevent bearing box lube is entered, pollute sealing surface.
(3) at the same time the design has sealed gas to put torch and amortize, segregation to enrage system of exalted air defence. Put in leak mouth and torch line or perch namely current limliting orifice plate and flowmeter are installed between empty cop, the leak circumstance that will monitor dry hermetic seal through discharging angry pressure, discharge.
Accordingly, to ensure dry hermetic seal controls a system reliable, macrobian life stabilizes safe production to move, answer to reach the demand that produces operating conditions to sealed medium quality, pressure, discharge, temperature according to the system, design of system of control of aircrew dry hermetic seal has filter unit, adjust control unit and sealed leak monitor unit, the angry to the sealed gas in the system, segregation, discharge that discharges gas, pressure, temperature and clean degree wait for a respect to undertake control and be monitoringed, monitor dry hermetic seal to run a state. Dry hermetic seal controls a system to design type selecting to want to note the following points:
(1) usually, rich to carrying medium to be energy of life or gas are embedded hydrocarbon kind the gas with more material often uses N2 to serve as sealed gas; And use compressor to export craft to enrage to transporting the gas such as CO2, N2, H2, CO and air + nitrogen reserves air program is sealed gas, should supply cleanness and dry sealed gas at the same time, sealed gas must not contain solid grain, dust and liquid, should maintain appropriate pressure, temperature and flow. Of sealed gas filter precision should achieve 3um the following, temperature should at least temperature of prep above dew point 10 ℃ above.
(2) sealed gas, amortize gas, segregation gas has pilot system, mix in order to satisfy sealed amortize, segregation to aeriform pressure, discharge the requirement of temperature. Can use aeriform pressure control, flow control, pressure and discharge combination to control fashion commonly. The demand that controls a design is sealed gas to should maintain what be in charge of with the balance to press difference to be in commonly 0.3 MPa above, speed of the smallest air stream is 5 M/s when labyrinthian gap is the biggest inside machine. Enrage pressure to prevent sealed craft at the same time low, general and sealed gas and balance canal press poor design to have low call the police and low call the police interlocking, enable nitrogen of middling pressure tubal a network to undertake filling enraging, in order to satisfy the requirement of pressure of sealed hermetic seal.
(3) is discharged in torch of dry hermetic seal commonly or perch puts empty pipeline to design sealed leak to monitor. Put in leak mouth and torch line or perch namely orifice plate of setting current limliting and flowmeter are set between empty cop, the leak circumstance that will monitor dry hermetic seal through discharging angry pressure, discharge. Discharge presses poor implementation by around of current limliting orifice plate, the design has flow low call the police, tall call the police and call the police high stop machine is interlocking; Pressure comes true by the change of the pressure before orifice plate, the design has pressure tall call the police and call the police high stop machine is interlocking. Can adopt 3 take the interlocking and logistic kind of 2.
(4) to ensure the safety of aircrew moves, prevent aircrew damage, leave in aircrew jockey reach sealed invalidation breakdown is urgent stop car operating mode, system of control of dry hermetic seal can design have the following interlocking:
Discharge of deflate of platoon of class of thick front cover of ① each dry gas switchs on the mobile phone normally interlocking.
Pressure of air of ② postposition segregation is low before switching on the mobile phone, prohibit lube pump is started interlocking, prevent bearing box lube to pollute dry hermetic seal.
One class of ③ discharges baric force to call the police high stop machine is interlocking call the police high with discharge stop machine is interlocking.
3, dry gas of centrifugal type compressor is sealed and common typical breakdown
Centrifugal type compressor does hermetic seal to control a system is the support system with centrifugal type very important compressor, dry hermetic seal is reliable, stable, macrobian the destiny is to ensure aircrew is installed all right, the key that firm, long, full, actor runs. Understand accordingly and master dry gas sealed and common typical breakdown, do hermetic seal trouble to be judged quickly and be being solved, ensure aircrew security stability moves.
(1) postposition keeps apart sealed invalidation, outside side is sealed by pollution
Aircrew designs postposition to keep apart purpose of hermetic seal system to be entered to prevent bearing box lubricating oil, pollute sealing surface. In use process, because design or the account that handle a side bring about lube,may pollute seal face. For example: Bearing antrum platoon is empty not free (breathing cap screen pack jams) , aeriform design velocity of flow is low cause tolerance too small, labyrinthian tine is counted or improper, orifice plate has designed space problem of control of small, system, nitrogen fluctuates or air feed is interrupted, jockey operation order is wrong, operate by accident etc.
Operate by accident to avoid to drive, pressure of air of segregation of general design postposition is low before switching on the mobile phone, prohibit lube pump is started interlocking, prevent bearing box lube to pollute dry hermetic seal.
(2) one-way chamfer inverts
Do hermetic seal to cannot invert to helix chamfer to Chan Xuan, invert to produce film of do sth in a fit of pique to return power, bring about seal face impaction, send sealed attaint be no longer in force. As a result of installation in doing hermetic seal to use a process the mistake brings about drive end and blame drive upright outfit is turned over, aircrew jockeys inevitable existence inverts the existence such as operating mode, cause sealed damage, serious when link is direct disintegrate.
(3) low speed operating mode moves for long
Be in switch on the mobile phone or in process of operating mode of low speed warming-up, because aircrew is long low rotate speed moves, dry hermetic seal did not produce power of enough fluid dynamic pressure, did not form gas film, bring about easily sealed wear away, serious when link is direct disintegrate.
Accordingly, in switch on the mobile phone in the process, should not be long low rotate speed moves, in normal movement, should maintain rotate speed constant, when moving rotate speed as far as possible slow operation, in order to avoid the effect with undesirable generation of pairs of rotate speed wave motion is too big dry hermetic seal.
(4) open park manage is undeserved, sealed pollution
Leaving jockey in the process, sealed throughput assures one class not easily, the gas inside machine opposes change easily, create one class the pollution of seal face, accordingly the likelihood drives in first try in pressure boost process, pressure is inferior, leakage rate slants big. Preparing to drive to aircrew, before undertaking punch, must use sealed gas through controlling systematic infuse to drive first, avoid technology vital energy to turn over change to cause sealed pollution; In jockey in the process, answer to cut source of take a breath in time, avoid to cause craft to enrage the pollution that oppose change sealed; During jockeying, because the reason such as the operation causes sealed pollution,avoid.
(5) when moving normally, filter systematic invalidation, sealed pollution
Sealed gas may appear to take fluid badly in doing hermetic seal spot to move, exceed filter to handle ability; After filter jams not seasonable switch, cause filter core damaged; Many fine pink is contained in gas source, its granuality is less than the precision of filter, exceeded the processing capacity of filter, but gross is big, right sealed reach a system to all can cause the circumstance such as the influence to bring about filter systematic invalidation, pollute thereby sealed bring about invalidation. Accordingly, should be checked regularly and clear filter, ensure filter is in good condition, achieve filter the requirement of precision, of general and sealed gas filter precision should achieve 3um the following.
(6) the sealed be no longer in force that unit account creates
Because of aircrew breakdown, produce intense vibration, vibration is too big, exceeded sealed can susceptive limits, cause sealed damage. Accordingly, should strengthen the moving care and maintenance of aircrew usually, strengthen aircrew to run oscillatory condition to monitor especially, because aircrew vibration brings about dry airtight invalidation greatly too,prevent.
4, epilogue
On put together, design an appropriate, complete, reliable dry gas through type selecting sealed control system, install to centrifugal type compressor, firm, long, full production moves the effect with a very main move. In be the same as opportunity group to move in production, should strengthen unit move safeguard, always monitor the moving circumstance of dry gas sealed system and leak state, seasonable discovery, eliminate and handle aircrew trouble, ensure device is installed, production of firm, long, full, actor moves.
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