Ball valve leaving factory qualified but on-site leakage often due to installation stress leads to valve body deformation >0.3mm, actuator torque amplified 20% damages seal or medium contains particles >50μm scratches sealing face, suggest re-check coaxiality ≤0.5mm, re-set torque and flush pipeline after then put into use.
misalignment
Geometric deviation
A unit DN100’s carbon steel ball valve top, support bracket base and above motor between cracked open a path extremely tiny’s gap. According to industrial assembly requirements, this piece flange plate’s hole distance error cannot exceed 0.15 millimeters. Assembly workers used two roots lengthened socket wrenches, take M8 level’s high strength bolts dead dead twisted to bottom.
Bolt bit metal’s instant, 5 millimeters thick’s Q235 steel plate occurred naked eye cannot see’s distortion. Top’s cylinder heavy reaches 12 kilograms, overall center of gravity forcefully toward outer side moved 2 millimeters. Originally should straight downward’s drive shaft, carrying 0.2 degrees’ inclination angle, slantingly inserted into below valve’s square hole inside.
Even if machine not yet powered on, inside’s parts actually already located in a kind extremely awkward’s force-bearing state:
- Above motor shaft toward left deviated 0.4 millimeters
- Below’s valve rotating shaft is hard dragged toward right side
- Sealing ring all around received’s pressing tight force one side big one side small
- V shape plastic ring single side is pressed flat exceeding 15%
Passed into 0.5 MPa’s compressed air after, equipment begins rotate. Internal gears bite erupted out 80 Newton·meters’ rotation force, attempts to take below’s ball body rotate 90 degrees. Up down not aligned lets originally smooth’s spinning turn into a kind similar to drawing ellipse’s hard pulling. Valve rotating shaft surface’s 316 stainless steel, with surrounding’s metal ring occurred one side stiff’s squeezing.
Computer on’s operation record shows, switch runs to 150th time when, rotate needed’s strength from initial’s 45 Newton·meters rose to 68 Newton·meters. Smooth’s rotating shaft surface originally roughness only has 0.4 microns, forcefully is ground out a strip deep 0.02 millimeters’ scratch. Inside mixed 25% glass fiber’s white sealing ring, being repeatedly dead life squeezed’s that one side no longer springs back.
Other side not being squeezed’s place, plastic and metal between just quietly let open a strip 0.08 millimeters’ tiny gap. Pipe inside exactly flowing pressure up to 1.6 MPa’s thermal oil, temperature fully has 180 degrees Celsius. Liquid always sees gap just drills, along this strip naked eye hard to distinguish’s small path all the way upward climbs.
Pipeline inside’s oil temperature continues upward burns, soars to 220 degrees Celsius when, different’s metal materials begin thermal expansion cold contraction. Long reaches 150 millimeters’ iron frame meets heat elongated roughly 0.18 millimeters. Originally at room temperature under relying on bolt friction force barely maintained’s skewed state, received heat after again secretly occurred 0.05 millimeters’ transverse sliding.
Ordinary punch machine punched out again bent’s U shape iron frame, dimension up down floating often at 0.5 millimeters around. Two ends flat not flat, middle’s hole round not round, all looks at that one whole piece iron sheet original’s state. Some workshops in order to save down 20 bucks money’s processing fee, simply take send into milling machine re-cut flat surface’s process cut off.
Used to take up down two roots shafts connect up’s small square block, inside’s gap similarly hides deviation. Broaching machine made out’s square hole slightly big out 0.2 millimeters, every time start all will carry a burst metal knocking’s impact force.
- Fit gap too big leads to machine reaction slow 0.5 seconds
- Square hole skewed lets every time turn 1 degree all will produce transverse thrust
- No. 45 steel’s inner hole wall used two weeks just shriveled in
At assembly table front, worker master holding pneumatic wind cannon one time just takes single side’s bolts all hit dead. According to rules should diagonal line alternately twist, every piece M10 bolt first pass on 15 Newton·meters’ force, second pass again add to 35 Newton·meters. Single side dead life twist only will let base tilt up, position skewed’s problem at boxing shipping before just already is forever fixed dead.
Leave factory before’s pressurization table on, pipe inside filled into 0.6 MPa’s nitrogen gas, held 15 seconds, water tank inside even a bubble did not pop. Short short dozen seconds’ static test, fundamentally no way imitate pipeline inside 2.4 MPa water pressure one hit hit impact’s oscillation, also tests not out hundreds times friction after sealing ring’s breakage. Surface bright beautiful’s machine, carrying inside 0.35 millimeters’ eccentric distance is packed into wooden box.
Change into carrying motor’s electric control valve, inside prevent burn down’s gear group turns exceptionally strenuous. Set well maximum current is 2.5 amperes, when rotor stuck to 45 degrees half open’s position time, ammeter pointer fiercely jumped to 3.8 amperes. Machine shell inside transmits out “clatter” one sound slight noise, deviation produced’s huge friction resistance missed a bit just triggered motor’s forced stop protection.
Change on precision mold cast out, integrated molding’s support bracket, up down two faces’ flatness is suppressed at 0.05 millimeters inside. Assembly table on frames up a carrying probe’s instrument, small probe tops against valve rotating shaft’s circular arc face. Worker uses hand rotates one whole circle, dial face on pointer’s shaking amplitude, is dead dead stuck at 0.08 millimeters‘s that strip scale line behind.
Lateral load
Just now measured’s 0.35 millimeters deviation distance, at equipment power on operate’s that one second, immediately turned into a burst barbarous’s thrust. Motor erupted out 80 Newton·meters’ rotation force, originally should all be used to let below’s metal shaft in place spin. Force-bearing point deviated after, among roughly 400 Newtons’ force turned into bulldozer same’s lateral collision. Thick reaching 16 millimeters’ solid steel shaft is forcefully toward left side pushed.
Metal rotating shaft just like a root being forcefully bent’s crowbar, top end bears motor’s dead life hard push, bottom again is by valve body internal dead dead stuck. 316 stainless steel material’s shaft core, at naked eye completely cannot see’s place occurred 0.12 millimeters‘s slight bending. A root bent’s metal stick in narrow’s hole inside forcefully rotates, every one time open and close, all is using edge go scrape rub surrounding’s parts.
First carry not live is used to block water’s PTFE plastic ring. Normal thickness 2 millimeters’ soft ring, at side face 400 Newtons’ hard top under, is single side squeezed flat to 1.4 millimeters. Pipeline inside 5 MPa’s high pressure water flow originally is blocked tightly completely, due to plastic ring occurred one side thin one side thick’s deformation, water molecules begin desperately toward gap inside drill.
In order to see clear lateral thrust in the end has how much make destruction, laboratory specially did a group destructive comparison test. Engineer at a unit DN50’s valve on, respectively hang on absolute vertical and intentionally made skewed 0.5 millimeters’ motor. Machine continuously ran 1000 pieces switch rounds, recorder captured four groups extremely disparate’s physical parameters:
| Test item | Perfect alignment state | Carrying lateral thrust state |
|---|---|---|
| Metal surface friction coefficient | 0.04 | 0.18 |
| Plastic ring wear depth | 0.01 millimeters | 0.15 millimeters |
| Rotate needs consume’s strength | 45 Newton·meters | 78 Newton·meters |
| 1000 times operation after seepage water amount | 0 milliliters/minute | 3.5 milliliters/minute |
Originally polished to like mirror same’s metal shaft, surface’s friction coefficient forcefully from 0.04 soared to 0.18. Dry’s friction lets 304 stainless steel inner wall begins downward drop extremely tiny’s metal fragments. Powder clamped at plastic sealing ring and rotating shaft between, just like toward precision gear inside sprinkled a handful 0.05 millimeters thickness’s sand, every time rotate all accompanies with rustling’s dark sound.
Friction inevitably brought local abnormal high temperature. Pipeline inside’s cold water obviously only has 15 degrees Celsius, motor with per minute 120 revolutions’ speed forced pulling time, metal contact face’s temperature probe measured 65 degrees Celsius‘s heating. Heat lets bearing pressure deformed’s plastic ring accelerate aging become hard, material internal’s structure at high temperature pulling under begins gradually embrittlement.
Destructive force along metal shaft spread to every corner, lateral thrust just like a at machine internal all around randomly hitting’s iron hammer. Disassemble that unit full is water stains’ equipment, can clearly see several extremely terrible’s physical scars:
- Rotating shaft surface is forcefully scraped out a strip 0.05 millimeters deep’s groove, use hand touch up obviously feel cutting hand.
- Pressed at most bottom layer’s graphite ring lost 30%’s elasticity, pinch up like a piece thoroughly air-dried’s hard mud.
- Above motor internal’s operation current from stable’s 2 amperes, all the way rose soared to 3.5 amperes.
Deformed’s plastic ring catches not live 1.6 MPa’s water pressure. Every minute has roughly 3 milliliters’ liquid along that strip being hard squeezed out’s gap outward climbs. 24 hours after, equipment directly below’s concrete ground on, accumulated a puddle diameter almost 40 centimeters’ water stain. Endured to 72nd hour, occasionally dripping’s water beads already turned into a root continuous not broken’s tiny water line.
Quality inspection sheet on obviously stamped with seal, writing 5 seconds static pressure test dripping water not leaks. Hundreds Newtons’ lateral thrust at initial’s dozens times switch inside, still not enough to thoroughly tear that layer 2 millimeters thick’s sealing ring. Factory inside’s shipping test often only does 3 times open close, fundamentally endures not to plastic ring elasticity exhausted, tiny gap thoroughly cracks open’s that one moment.
According to original factory’s mechanical design life, this set transmission components originally should smoothly run finish 10000 pieces cycles. Forced added at side face’s hundreds Newtons force, took normal rotation’s life forcefully cut to not enough 800 times. Used to fix motor’s four pieces M8 bolts, at day after day’s lateral pulling under, thread tooth bottom even appeared length 0.1 millimeters’ fatigue micro crack.
Return to normal’s torque transmission, all relies on that root absolute vertical‘s center line. Replace off rough’s connection accessories, newly on machine tool cut flat base, take lateral thrust dead dead suppress at 10 Newtons below. When motor 80 Newton·meters’ force hundred percent turns into in place spinning’s strength time, pipeline pressure hit to 6 MPa, outer shell edge still can maintain one drop not leak’s absolute dry.
assembly stress
What is assembly stress?
Fitter master holding a handle 60 centimeters long’s torque wrench, aimed at M16 high strength bolt use force downward press. Hear “clatter” one sound crisp noise, wrench on’s scale steadily stops at 120 Newton·meters’ position. Quietly staying at workbench on’s carbon steel valve body, top two pieces thick reaches 25 millimeters’ metal flange plates forcefully are bitten together.
Nut rotates’ instant, one root bolt downward applied whole 40,000 Newtons’ pulling force. Take four roots bolts’ force all add up, equivalent to a unit fully loaded’s 16 tons big truck, entirely pressed on a piece only has adult palm size’s 80 square centimeters iron plate on. Looks like hard’s metal, like pinching dough same quietly changed original’s shape.
Steel material surface covered full high low not flat’s fine lines, roughness roughly at Ra 3.2 up down. 160 MPa’s strong pressure covers down, tiny’s metal protrusions instantly are rolled shattered. No place can go’s huge thrust along 12 millimeters thick’s valve body outer wall desperately toward internal structure drill.
- Thread tooth bottom bears 500 MPa shear force
- Bracket base occurs 0.02 millimeters deflection
- Graphite gasket is pressed flat 25% thickness
- Valve stem neck part bears large amount lateral thrust
A piece heavy reaches 5 kilograms’ 316 stainless steel ball body suspended at there, relying on two circles PTFE soft pads supporting, each other left not reach 15 microns’ activity gap. Outside forcefully added in’s brute force, took harmonious’s mechanical position all messed up.
Soft pad’s plastic material can bear’s limit at most at 15 to 25 MPa between. Above passed down’s force exceeded 20 MPa, plastic inside’s molecule chain resists not live, begins toward side occurs slip. That at lathe inside turned perfectly round’s sealing face, is pressed out extremely tiny’s ellipse shape pit.
Assembly table on’s worker holding vernier caliper measured a measure, bracket diagonal line’s four pieces screw holes, position differed 0.15 millimeters. In order to take a unit 80 kilograms heavy’s pneumatic actuator install up, worker picked up iron hammer knocking forcefully align position, drive shaft firmly is bent skewed a little bit radian.
- Center axis line deviates 0.5 degrees
- Gear bite gap lacked 0.08 millimeters
- Packing ring single side extra receives 30% pressure
- Rubber O shape ring is excessively squeezed
Pipeline once ventilates, 4.0 MPa’s high pressure steam rushes in, pipe inside’s temperature at ten minutes inside soars to 250 degrees Celsius. Carbon steel outer shell and internal’s stainless steel pieces receive heat expand’s speed fundamentally not same, barely maintain balance’s skeleton at high temperature inside begins mutually compete strength.
Temperature every toward up walks 100 degrees, 1 meter long’s carbon steel pipe just will elongate 1.2 millimeters. Originally take wrench dead dead twist tight’s bolt dead bites not release, firmly not lets flange plate has a tiny bit stretch’s space. Thermal expansion cold contraction held out’s force rests on before’s mechanical pulling force on, peak’s force-bearing numerical value broke through 345 MPa’s material limit.
High temperature high pressure take turns force, perfectly matched’s metal joint place is torn open a path opening. Evenly distributed on ring on’s sealing specific pressure messed up set, one side loose one side tight. Pipeline inside 40 kilograms pressure’s water molecules like smelled bloody smell’s shark, along 0.01 millimeters’ gap outward drill.
Destroying seal’s way
50 kilograms heavy’s pneumatic head framed rests on two inches’ metal pipeline on. Installation worker holding a handle full is oil stain’s open-end wrench, relying on many years’ hand feel takes right side’s nut dead dead twist to bottom. Left side’s flange plate instantly is tilted up, exposes a path 0.15 millimeters’ tiny gap.
Brute force along 15 millimeters thick’s cast steel bracket downward transmits, all presses on valve extremely fragile’s neck part flange on. Valve body internal originally absolute symmetrical’s cylindrical empty cavity suffers violent pulling, hard’s metal outer shell occurred micron level’s physical distortion.
Coated tungsten carbide coating’s hard seal ball body, leaving factory time with metal valve seat maintaining 99.9%’s curvature fit degree. External force added’s offset load force broke original’s balance, forcefully took right side’s valve seat toward outer side pushed 8 microns.
8 microns’ dislocation distance, even a root ordinary hair strand’s one third all not reach. Pipeline inside pressure up to 2.5 MPa‘s natural gas immediately captured gap, high pressure gas crazily penetrates defense line, per hour’s leakage amount instantly soars to 300 milliliters.
- Right side single side applied 150 N·m locking force, left side only bears force 60 N·m
- Joint face flange plate inclination angle irreversibly reaches 0.2 degrees
- Hard seal contact band appears length reaches 12 millimeters’ crescent moon shape gap
- Pipeline gas leakage rate exceeds standard, crosses ISO 5208’s Level D upper limit
Factory building top’s traveling crane takes a unit self weight 120 kilograms’ electric actuator hoist over. Tooling base’s hole position processing differed half a millimeter, four pieces connection bolts are by worker use big iron hammer hard knock in. Top’s motor output shaft and base below’s valve stem, at brute force under dislocated 0.3 millimeters.
Motor connected 380V power supply begins operate, instantly erupts out 800 Newton·meters’ strong torque. Two roots dislocated’s metal shafts like a root holding strength’s crowbar, at every time switch rotate time, facing valve stem applies up to 4000 Newtons’ lateral thrust.
PTFE material’s packing ring first suffers disaster. Being pushed skewed’s valve stem dead dead presses packing’s left half side, local contact face’s pressure breaks through 30 MPa. Soft’s white plastic at several seconds inside is squeezed into flat shape.
Right half side’s packing same time lost original’s squeezing support force, exposes a section long roughly 0.05 millimeters’ vacuum zone. Carrying strong corrosive’s liquid chlorine along tiny opening upward climbs, at valve stem stainless steel surface bites out deep green’s corrosion spots.
Huge’s lateral force along 30 centimeters long’s valve stem all the way downward transmits, straightly attacks bottom’s core area. Heavy’s ball body is roughly pushed away from theory on’s rotation center, left side’s soft sealing pad bears normal times two times above’s mechanical oppression force.
| Measurement part | Normal operation parameters | Forceful assembly after parameters | Physical damage performance |
|---|---|---|---|
| Packing bearing pressure side | 15 MPa | 38 MPa | PTFE material severely squeezed out, edge broken |
| Packing losing pressure side | 15 MPa | 2 MPa | Appears 0.05mm liquid fluid escape channel |
| Valve stem friction force | 45 N·m | 180 N·m | Surface coating is scraped out 0.2mm depth scratch |
| Ball body offset amount | 0.01 mm | 0.12 mm | Rubber sealing ring occurs irregular permanent depression |
Many old chemical plants’ main pipeline distance ground has seven eight meters high. Hundreds kilograms heavy’s pneumatic execution mechanism entirely without support suspended lies horizontally at pipeline side face. Huge’s gravity became every day all nibbling internal sealing pieces’ invisible heavy hammer.
300 kilograms’ pig iron lump, toward outside suspends out a half meter more long’s lever. Joint place’s several roots bolts every minute every second all are resisting up to 1500 Newton·meters’ static bending moment. Wind blows sun shines adding on pipeline’s daily tremble, base nut’s biting force gradually decays.
Per minute 120 times’ pipeline high frequency vibration, took static’s gravity amplified several times, turned into terrifying’s alternating load. Graphite wound gasket at day after day’s pulling and squeezing inside, internal’s flexible graphite powder bit by bit shatters and drops into pipeline inside.
Gasket’s overall thickness from nominal’s 4.5 millimeters severely shrank to 3.8 millimeters. Used to maintain sealing specific pressure‘s disc shape spring completely lost original’s tension, bottom’s valve seat begins following every one time fluid’s impact back and forth shaking.
- Suspended’s mechanical center of gravity deviates pipeline center fully 450 millimeters
- Alternating vibration frequency lets connection nut every month retreat thread 0.1 circle
- Metal gasket’s rebound rate from qualified’s 45% plummets to 12%
- Sealing face soft material is repeatedly cut off 0.3 grams fragments
Pipeline inside rushes past 150 degrees Celsius’ boiling hot oil, plastic sealing ring at high temperature under becomes like a piece about to melt’s cheese. Always eccentric pressing at above’s heavy ball body takes opportunity sinks into softened’s washer inside, left a deep reaching 0.5 millimeters’ permanent pressing pit.
Control room issues switch command, cylinder push rod carrying damaged’s components forcefully operates. Scar-riddled’s valve seat surface and rough’s metal fragments violently rub, emit extremely ear-piercing’s metal scream sound. Finish degree reaches Ra 0.4‘s ball body surface, is by hard object scratched out dozen paths depth not same’s gullies.
Every one path 0.02 millimeters deep’s metal scratch, all became high pressure fluid excellent’s flood discharge channel. Controller at screen front takes actuator’s output torque opens to maximum, two pieces damaged’s metal dead dead top together, still blocks not live per second 50 milliliters’ continuous internal leak.
Three pieces prevention standards
Test workshop inside, a unit hanging 80 kilograms pneumatic head’s stainless steel ball valve is hoisted on pressure test table. Worker uses four roots two inches thick’s high pressure hoses connect valve body two ends flanges. Water pump crazily operates, dial face pointer at 120 seconds inside climbs to 6.0 MPa.
“Bare valve hits water pressure completely not leak, hangs on pneumatic head must newly hit one time high pressure, many invisible tiny cracks all hide in assembly action inside.”
Tester presses down operation table’s green button, cylinder sucks in 0.6 MPa‘s compressed air. Valve at bearing 60 kilograms strong pressure’s water flow inside, continuously completed three times complete’s open and close. Bottom white’s paving paper on, even one drop 0.05 milliliters’ water stain all not have.
High strength carrying load test can force out metal assembly after’s real mechanics state. Installation worker took bolt twisted skewed even if 0.2 millimeters, high pressure water flow immediately will break through internal damaged’s soft washer. Dashboard on’s pressure holding curve at 15 minutes inside must maintain a strip absolute straight’s horizontal line.
Water pressure maintained whole 900 seconds. Operator holding strong light flashlight, lies at leaving valve body not reach 10 centimeters’ place, along sealing joint line inch by inch ground checks. Electronic pressure sensor’s numerical value display from 6.002 MPa slightly drops to 6.001 MPa. Extremely small pressure drop conforms to ISO 5208’s Level A inspection standard.
Line of sight turns to parts processing area. Several pieces iron sheet pieced together, electric welder wearing face shield casually welded out’s rough bracket is thrown into scrap iron basket. Weld seam cooling after brought’s 3 millimeters thermal deformation, ruined countless high-end pipelines. Factory purchased rotate speed up to 12000 revolutions/minute’s four axis CNC machine tool.
A piece heavy reaches 15 kilograms’ Q345B solid carbon steel blank is fixed on machine tool on. Hard alloy milling cutter spraying milky white’s cooling liquid, layer by layer cuts away extra’s iron scraps. Metal originally having’s cold stern luster slowly appears.
- Up down joint face parallelism controlled at 0.02 millimeters inside
- Four holes diagonal line error absolutely not exceeds 0.05 millimeters
- Overall cutting prevents 200 MPa residual internal stress
- Base flatness reaches 0.01 millimeters processing level
“Machine tool cut out’s solid bracket, flat till like a piece glass, toward valve flange on one buckle, perfectly matched even sheet paper all stuff not in.”
Worker takes pass through 12 hours blackening anti-rust treatment’s bracket sticks on valve flange on. Base hole position and valve top’s four pieces M12 threaded holes perfectly coincide. Up down components’ coaxiality is by pure physical means locked dead, motor main shaft toward down probes out 150 millimeters, whole process no one thread axial deviation.
Thick solid’s steel material will not at 300 kilograms’ lateral thrust under produce a tiny bit bending. Assembly table front, two handles passed through national metrology bureau certified’s digital display torque wrenches placed on tool cart on. Wrench tail part’s metal nameplate writes “error range ±3%”. Shift leader dead dead stares at every one fitter hand inside’s actions.
Thick reaches 30 pages’ assembly operation instruction book spread open on desktop on. White paper black words written extremely clear: targeting 8.8 level’s M16 fasteners, first time preload force must be set at 45 N·m. Fitter picks up one bottle copper base anti-seize agent, uses small brush at thread place smeared thin thin one layer.
- Bolt smears lubricating grease lowers metal dry friction
- According to 1-3-4-2 cross diagonal line alternately tighten
- Numerical value dial face finally locks at 115 N·m
- Thread friction coefficient forced fixed at 0.11 around
“Twist screws absolutely not is competing strength, four roots bolts bearing force differed 10 Newtons, inside’s PTFE washer just will be forcefully pressed into big small head.”
Fitter according to diagonal line sequence, like drawing cross same alternately downward presses wrench. Electronic screen on’s numbers from 40 jump to 80, reading steadily stops at 115. Four directions pressed down’s 7000 Newtons clamping force, extremely evenly distributed on 120 square centimeters’ flange contact face on.
Flange plate received’s physical downward press error is firmly suppressed at 0.01 millimeters inside. Located at pipeline center position’s stainless steel ball body, still can in PTFE soft pad inside preserve original’s 15 microns breathing space. Factory every interval 180 days just takes all torque wrenches send to laboratory newly calibrate.
sealing problems
Misalignment
A heavy reaches 20 kilograms’ black metal cylinder, installed at a unit 4 inches’ flange ball valve top. Connecting two units equipment’s part is a root edge length 22 millimeters’ square shape metal drive shaft, pairing a with groove’s connection iron block.
On-site two names assembly workers respectively holding a handle 300 millimeters long’s adjustable wrench, aimed at four pieces M10 specifications’ carbon steel bolts use force twist tight. Naked eye looks past, two units equipment up down pencil-straight. Take out a handle precision 0.02 millimeters‘s digital display vernier caliper go stick position measure, above cylinder rotating shaft’s center point, deviated below valve center point 0.15 millimeters.
This 0.15 millimeters’ deviation has specific’s physical source:
- Bracket base bolt hole’s punching error skewed big 0.2 millimeters
- Valve flange face sprayed’s blue anti-rust paint thickness completely not even
- Left side half circle paint film thick 75 microns, right side half circle thick reaches 150 microns
- Cast iron cylinder outer shell hard rubs carbon steel bracket produced dozens microns’ interference
Instrument air pipe connects 0.6 MPa’s compressed air, cylinder internal’s two pieces metal pistons violently toward two sides push open. Rack and pinion’s mechanical structure takes piston’s straight line movement, forcefully turned into up to 400 Newton meters’ huge rotation force. Up down shaft core not aligned, this burst rotation force fundamentally draws not out a perfect’s circle.
A root diameter 30 millimeters’ 316 stainless steel metal rod, is by this burst lateral’s destructive force dead dead toward side push. Tightly wrapped at this root metal rod periphery’s, is a group 4 millimeters thick’s V shape white PTFE plastic ring.
Sealing packing ring‘s left half side is by hundreds Newtons’ force heavily squeezed. Plastic material bearing pressure’s limit at 14 MPa up down, slantingly thrust at 0.5 seconds inside lets material surface depressed dozens microns. Relative’s right half side, plastic ring left metal rod, middle cracked open a path 0.05 millimeters’ tiny gap.
Metal pipeline inside flowing 5 MPa’s high pressure natural gas. Gas molecules all-pervasive, escaping only needs 0.01 millimeters’ channel.
Two units equipment back and forth open close 200 times, polymer plastic bearing force excessively lost spring same’s memory. High pressure gas along that path being hard squeezed out’s 0.05 millimeters gap, emits tiny’s hiss sound outward pops.
With pressure plugging leak’s technical personnel at on-site disassemble equipment, can clearly see quite a few places damage traces:
- Stainless steel rod left side appeared a long strip polishing shining’s friction trace
- Pressing tight plastic ring’s flange plate below accumulated a pile black’s graphite powder
- Cylinder rotates to 45 degree angle’s position emits one sound metal dry grinding’s scream
- Top’s thread naked eye visible produced three four degrees’ severe skewing
Used to connect two units equipment’s metal bracket thickness, took slanting thrust amplified several times. A piece 5 millimeters thick’s ordinary Q235 steel plate, adult uses hand go bend absolutely still. Bearing 400 Newton meters’ torque time, steel plate at 0.1 seconds inside occurred 0.5 degrees’ inclination bending.
Tiny’s 0.5 degrees inclination, took cylinder’s rotating shaft at rotating to half time, ruthlessly dragged away from original’s position. Bolt applied 25 Newton meters locking force’s gland, completely pulls not live a root exactly inclining spinning’s metal rod.
Two pieces metal dead knocking’s friction resistance instantly becomes big. Original 0.04’s extremely low friction coefficient, at single side receiving force friction under soars to 0.25. Cylinder begins strenuously stuck, originally planned give 0.5 MPa air pressure just can smoothly complete’s 90 degrees rotation, dashboard pointer hit to 0.7 MPa just barely turned over.
Pipeline inside’s fluid temperature intensified destruction progress. 80 degrees Celsius’ industrial thermal oil flows into valve inner cavity, 316 stainless steel metal rod receives heat expands, diameter became thick 0.03 millimeters. Single side stuck dead’s metal rod dead life rubbing plastic ring, produces extremely high’s heat takes cross section grounds out naked eye visible’s burrs.
Over-torquing
A unit heavy reaches 45 kilograms’ rack and pinion style pneumatic motor, installed on a unit 6 inches’ carbon steel pipeline valve on. Motor internal connects 0.5 MPa’s compressed air, instantly erupts out up to 800 Newton meters’ torque. A adult man gripping one meter long’s extended iron stick exhausting whole body strength go press, at most produces 100 Newton meters’ force.
Pipe internal that diameter 150 millimeters’ smooth stainless steel round ball, must accurately rotate to perfect’s 90 degree angle. Early turn one degree or late turn one degree, pipeline inside’s liquid leaks out pipe cavity. Responsible for blocking round ball over head randomly turning’s, is motor outer shell side two roots diameter 16 millimeters’ iron bolts.
Debugging worker holding a handle big size inner hexagon wrench go twist tight those two roots bolts. Industrial bolts’ thread spacing mostly is 1.5 millimeters. Worker twists bolt time wrist extra used a little force, wrench extra turned half circle, bolt toward inside extra walked 0.75 millimeters’ distance.
Stainless steel round ball early just completely blocked dead on pipeline mouth on, top huge’s motor not has any stopping action’s mechanical command. 800 Newton meters’ terrifying rotation force, dead life downward pushing that heavy reaches 12 kilograms’ iron ball.
Round ball is by all around’s iron walls trapped no place can go, only can take back on pressed down’s hundreds catties weight, all smash toward tightly pasting its belly’s two pieces white plastic rings. Industry on calls these two pieces plastic rings call soft seal valve seat, material mostly is PTFE.
PTFE’s texture extremely soft, take thumb’s fingernail use force pinch one bit its surface, all will leave a half millimeter deep’s half moon shape fingernail print. Its bearing pressure’s limit data, at most at 14 MPa to 15 MPa up down.
800 Newton meters’ brute force transforms into squeezing stress, instantly broke through 20 MPa’s plastic bearing pressure bottom line. At continuous 3 seconds’ barbarous rolling pressing under, thickness originally being 8.5 millimeters’ white plastic ring, is forcefully stepped flat to 7.8 millimeters.
Imagine a bit kitchen inside a fermented well’s round soft dough, is by a piece thick heavy’s iron plate ruthlessly downward pressed collapsed a small half. Plastic ring’s inner edge occurred irreversible’s plastic deformation, edge place is hard squeezed out a strip thin long’s white burr.
Naked eye lies over look, originally should perfectly matched’s circular arc fit face on, tore open a strip long roughly 4 centimeters, wide roughly 0.2 millimeters’ thin long gap. Pipeline inside rushes in pressure up to 4 MPa’s liquid chemical propylene, liquid molecules along that strip 0.2 millimeters wide’s tiny channel crazily outward run.
Stop machine take whole set equipment from pipe on disassemble down throw on cement ground on, take high light flashlight illuminate into pipe cavity internal, being over big torque rolled pressed past’s parts left clear traceable’s traces:
- White plastic ring surface depresses out a strip deep reaches 0.8 millimeters’ stainless steel spherical face pressing mark
- Padded at plastic outer ring back face’s one circle metal wave shape spring, is thoroughly pressed flat lost 2 millimeters’ rebound leeway
- Being squeezed shattered falling off’s hard plastic particles, at bright silver color’s ball body surface scraped out dozen paths 0.1 millimeters deep’s scratches
Different material’s plastic components, at encountering same size’s barbarous torque rolling pressing time, thoroughly destroyed’s data performance completely not same:
| Sealing ring material | Material hardness measurement value (Shore D) | Crushing deformation bearing limit | Being 800Nm torque extra squeezed 3 degrees after’s ending |
|---|---|---|---|
| Pure PTFE (common white plastic) | 55 | 14 MPa | Edge is pressed collapsed 0.5 millimeters, liquid continuously leaks out |
| RPTFE (mixed in 15% glass fiber) | 65 | 20 MPa | Surface pops out tiny cracks, pressure resisting ability instantly dropped a half |
| PEEK (light coffee color hard polymer) | 85 | 90 MPa | Plastic not shatter, metal ball body surface’s coating knocked off a piece |
A strip conveying 120 degrees Celsius saturated steam’s thick pipeline, high temperature takes pipe cavity inside’s that circle plastic roasted till like a piece about to melt’s soft candy.
Room temperature under hard carrying 800 Newton meters just will press collapse’s material, at 120 degrees’ steam roasting under, only needs 250 Newton meters’ force takes it squeezes into a pile irregular’s fragments. Top on assemble a unit carrying 3 kilowatts industrial motor’s electric actuator, destructive force multiplied toward up flips.
Motor pulled out power supply cut power’s that zero point several seconds, rotor carrying dozens catties heavy’s gears produces huge’s inertia, not receiving control ground again toward front fiercely rushes roughly 1 to 2 degrees’ distance.
Weak Bracket Flexing
A unit heavy reaches 30 kilograms’ pneumatic actuator, suspended framed at a unit 8 inches’ metal ball valve directly above. Taking this one up one down two iron lumps connected together’s, is a piece height 150 millimeters, bent into U shape’s silver metal bracket.
Purchaser in order to take cost pick down 20 bucks money, let contract factory use 3 millimeters thick’s Q235 ordinary carbon steel plate, put on CNC bending machine on pressed out this U shape part. Take finger knuckle knock up, thin iron sheet emits crisp’s clank clank sound.
Underground pipeline inside passed into 6 MPa’s high pressure crude oil, viscous’s liquid dead dead pressing pipe cavity internal that piece heavy reaches 25 kilograms’ stainless steel round ball. Top’s cylinder suddenly connects power supply exerts force, instantly erupts out 600 Newton meters’ rotation torque go hard drag that ball.
Physics’ reaction force at here reveals thoroughly. Cylinder uses 600 Newton meters’ strength go twist below’s round ball, round ball similarly will take 600 Newton meters’ counter thrust, along center that root metal shaft intact ground top back to top cylinder.
Hundreds catties’ huge counter thrust, all smashed on that piece 3 millimeters thick’s U shape carbon steel bracket on. High speed camera recorded down next’s 0.2 seconds: iron sheet bracket emits one sound extremely muffled’s metal neighing, U shape’s two roots side walls toward outside cast open 2.5 millimeters.
3 millimeters thick’s iron plate at 600 Newton meters’ counter thrust front, like a piece being used force pinched bent’s thin crispy cracker, forcefully dragged out 0.8 degrees’ physical inclination angle.
Bracket skewed 0.8 degrees, suspended in mid-air’s 30 kilograms cylinder following together toward left side dumped roughly 4 millimeters. Cylinder below that root dead dead connecting round ball’s metal rotating shaft, was forced at pipe cavity internal occurred one time slight’s mechanics dislocation.
Originally perfectly matched tightly pasting stainless steel round ball surface’s two pieces PTFE sealing pads, left side that piece suddenly was unloaded 300 Newtons’ pressing tight force. Original 0.05 millimeters’ tight fit state, instantly tore open a path 0.15 millimeters’ tiny crack.
6 MPa’s carrying pressure crude oil like found floodgate, along this 0.15 millimeters’ tiny crack crazily outward pops. Pipe outside’s inspector not yet reacted over, hundreds milliliters’ black crude oil along flange bottom’s gap dripped to cement ground on.
Disassemble down bracket take to laboratory go measure rigid stretching data, different thickness and process’s iron plates, at facing same torque time’s performance completely different:
- Use 3 millimeters ordinary steel plate bent’s bracket, bearing torque time occurs 2.5 millimeters’ naked eye visible displacement
- Change into 6 millimeters thick’s 304 stainless steel plate full weld, displacement amount is dead dead suppressed at 0.4 millimeters inside
- Use one whole piece No. 45 steel material at four axis machine tool on hollowed dug out’s solid bracket, displacement amount only is minimal’s 0.02 millimeters
As long as motor every switch one time, that piece 3 millimeters thick’s thin iron sheet just will experience one time “being propped open again rebounds”’s physical torture. One day continuous switch 80 times, iron sheet internal’s metal lattice structure begins appear microscopic fracture.
Continuous high strength worked three months, bending place’s metal surface popped out dozen paths naked eye hard to detect’s tiny cracks. Bracket’s load bearing ability cliff style falls, originally inclined 0.8 degrees, now once ventilates toward outside flips down whole 2 degrees.
Round ball being dragged skewed’s distance multiplied increases. Pipe cavity internal’s fluid no longer is dripping leak, turned into continuous not broken’s high pressure line shape injection. Liquid sweeping along pipeline bottom’s tiny iron rust sand grains, like a handle high pressure water knife same repeatedly cuts plastic sealing pad’s edge.
Plastic washer at continuous one week’s high pressure scouring under, originally flat’s cut face is cut out a strip deep reaches 1.2 millimeters’ groove, whole set sealing components thoroughly scrapped.
Prevent bracket at receiving force instant becoming soft foot shrimp, on-site assembly time needs to increase hard core’s physical reinforcement process:
- At U shape bracket’s four bottom corners on, use argon arc welding dead dead weld on four pieces thickness 8 millimeters’ triangle shape reinforcing ribs
- Abandon original factory’s ordinary bolts, change to use 12.9 level’s high strength alloy steel blackened bolts go lock dead every one connection hole
- Take thickness feeler gauge go stick cylinder and bracket’s joint, has one thread light transmission just pad into 0.1 millimeters’ purple copper foil level fit face
Purchase contract on that string conforming to Europe America standards’ leaving factory air tightness data, measurement environment inside fundamentally not has that piece saved 20 bucks money’s thin iron sheet. Hundreds catties’ machine once suspended framed and connected on high pressure pipeline, mechanical world’s hardness competition tolerates not half a bit jerry-building.
