Under high temperature (≥450℃) or strong wash working conditions, sphere choose Ni60 (hardness about HRC58-62), valve seat choose Ni55 (HRC52-56) can form hard-tough pair.
Suggest spray coating thickness 0.3-0.5mm, grind to Ra≤0.4μm, guarantee sealing wear-resistant and anti-biting performance.
hardness matching
Prevent bite dead phenomenon
In 10 inch Class 600 metal ball valve inside, pipeline pressure all year round tops at 10.3 MPa. Heavy steel ball is pushed by water flow, deadly pressed on width only having 3 to 5 millimeters ring-shaped valve seat. Local extrusion pressure instantly soars break 80 MPa, ordinary stainless steel put inside will like soft mud same be pressed flat.
Factory uses supersonic flame spray gun, takes Ni60 powder with 3000°C high temperature hit on sphere surface, paves on a layer 0.3 millimeters thick armor. Powder inside mixed 3.5% boron and 4.5% silicon, forcefully takes surface hardness propped to HRC 60.
Beside one circle valve seat uses is Ni55 powder, less put a little boron and silicon, hardness drops to HRC 54. Under high pressure forcefully twist open valve, steel ball sticking valve seat uses force friction. Two pieces metal if hardness exactly same, atoms between will mutually “recognize relatives” deadly stick together.
Sphere surface even if polished to Ra 0.2 microns, touching up like glass same slippery, put under microscope magnify 1000 times, surface all is continuous unbroken small mountain peaks. 80 MPa heavy pressure under, metal surface layer anti-rust oxide film 0.1 seconds just is thoroughly crushed.
- Bare metal atoms violently collide
- Exactly same material instantly fuses lock dead
- Relatively soft one side metal block is vividly torn down
- Debris deadly jams into 0.05 millimeters gap inside
Scratched out 0.5 millimeters deep groove sealing surface counts as thoroughly scrapped, high pressure gas carrying reach up to 120 decibels noise towards outside madly sprays. To sphere spray Ni60, valve seat spray Ni55, out of thin air pulled open 5 to 6 HRC hardness difference, forcefully pinched off cold weld sticking process.
HRC 60 hard surface just like a plow rake, hard sweeps across HRC 54 surface. Ni55 material brings a tiny bit small elasticity, encountering hard object friction towards down gives way two three microns pit, absolutely not fracture peel off.
- Hard surface bulge place presses into soft surface 0.01 millimeters deep
- Soft surface bend deform absorbs drop 90% friction heat energy
- Surface presses out a layer extremely thin hardened skin carries secondary friction
- Two pieces metals next to together real area magnifies 1.5 times
Tiny hardness difference takes two pieces metals internal lattice arrangement thoroughly messed up. Atoms between arrangement dislocation exceeds 15%, mutually fundamentally not recognize, two pieces iron plates grow together drama then also sing not down.
Hardness same ball valve opens up ten times, instrument panel reading from calibrated 200 Nm all the way madly soars to 800 Nm, can take a root diameter 40 millimeters thick 17-4PH steel rod on the spot twist break. Change to bring hardness difference accessories, with pressure continuously open close 5000 times, reading all the time steadily stops at 220 Nm up down.
Pipeline inside runs not only is clean water, often wraps Mohs hardness 7 level quartz sand blocks. Big sand grains with per second 15 meters speed rush into valve cavity, be two pieces closing metal surfaces ruthlessly clamped. Ni60 surface distributed full tiny chromium carbide hard points, micro hardness reaches up to HV 1200.
Chromium carbide hard points on the spot take quartz sand crush into 5 microns below powder, following water flow wash away. Occasionally encounter several extremely stubborn 2 millimeters big block iron skin, relatively soft Ni55 valve seat actively towards down indents zero point several millimeters, takes iron skin tolerate inside.
Factory sprays out coating is not absolutely uniform. Inside distributed full 0.8% to 1.5% tiny air pores, every furnace powder melt state all has extremely tiny difference. Forcibly fix out 5 HRC hardness difference, gives workshop workers left enough operation room.
- Coating thickness stuck at 0.25 to 0.35 millimeters
- Grinding machine cuts off surface layer 0.05 millimeters loose waste material
- Smear on 1200 mesh boron carbide grinding paste back forth to grind
Assembly table on master takes ball and valve seat piece together, drops several drops machine oil, connects air motor back forth idle turns 30 minutes. Soft side Ni55 in this half hour inside, is forcefully ground off last two three microns unevenness. Take flashlight facing 0.01 millimeters thick feeler gauge gap shine over, a thread light all penetrates not out.
Protect core components
A diameter 250 millimeters solid stainless steel sphere, from casting blank to final finish needs in workshop circulate whole 45 days. Five-axis linkage CNC machine tool needs continuous milling 72 hours, just can take surface roundness tolerance picked to 0.015 millimeters within. Compare under, beside that outer diameter same size ring shape valve seat, on ordinary lathe only needs 3 more hours just can turn shape.
Weight reach 120 kilograms sphere manufacture price easily breaks through 25,000 yuan, occupies whole valve inner parts total cost 70% above. Take tens of bucks one kilogram Ni60 wear-resistant powder priority spray coat on sphere, is most naturally right doing method. Two several kilograms heavy Ni55 valve seats add up no more than 3000 bucks, broken conveniently throw into scrap iron basket also will not too heartache.
Pipeline inside heavy oil mixes with catalyst powder, with per hour 800 cubic meters huge flow madly washes valve cavity. Fully open state under, fluid in sphere internal channel inside straightly passes through, almost no resistance. Arrived closing that few seconds, gap becomes small, local flow speed instantly from per second 3 meters soars to per second 25 meters.
Those 0.2 millimeters size aluminum oxide hard particles, like bullets same smash on sealing surface edge. HRC 60 Ni60 coating hardness extremely high, receiving impact time absolutely still, takes particles on the spot bounce open. Particles rebound after change trajectory, all smash towards opposite slightly softer a little, hardness HRC 54 Ni55 valve seat surface.
Ni55 inside contains about 60% nickel-based solid solution, this kind material in receiving violent impact time, allows surface produce several microns tiny indentation. It just like a micro buffer pad, forcefully takes particles carrying kinetic energy unloaded a big half. Valve seat surface will be smashed out naked eye visible 0.1 millimeters deep small pockmarks.
- 150 thousand times with pressure open close test after, sphere surface wear amount only is 0.002 millimeters
- Ni55 valve seat surface wear depth usually will reach 0.08 millimeters
- Valve seat back part disc shape spring towards front elongates 0.1 millimeters fills wear gap
- Two pieces fit whole sealing life is forcefully dragged long 3 times above
Chemical factory every year stop production overhaul time often only has precious 15 days. Three workers holding 50 kilogram level hydraulic wrench, spend 2 hours dismantle open rusted flange bolts, take valve inner parts all drag out. If is sphere is scratched flowered, send to outside professional repair factory re-spray coat grind, fastest also needs toss whole 7 days.
Rely on hardness match offset consumption, workers only need spend 10 minutes take old sphere take high pressure water gun wash clean, use micrometer measure a bit roundness, confirm error still at 0.02 millimeters within. Turn head go warehouse claim two brand new Ni55 valve seats change on, whole assembly line valve repair process even half day all uses not.
Below this piece certain oil refinery coking device area last year replacement accessories real consumption report, very intuitively recorded this kind directional wear actual effect.
| Accessories Name | Surface Material | Hardness(HRC) | Single Piece Weight(kg) | Purchase Cost(yuan) | Year Replace Frequency |
|---|---|---|---|---|---|
| 10 inch main sphere | Ni60 coating | 60 | 123.5 | 26,500 | 0.2 times |
| Front side valve seat | Ni55 coating | 54 | 4.2 | 1,450 | 2.5 times |
| Back side valve seat | Ni55 coating | 54 | 4.2 | 1,450 | 2.5 times |
Besides hard bump hard physical wash, 350°C high temperature heat conduction oil still at continuously testing internal parts expansion limit. Solid steel ball volume big absorb heat slow, thickness only has 20 millimeters ring shape valve seat heats extremely fast, two’s thermal expansion difference can reach 0.15 millimeters.
Ni55 less added boron element, material’s plastic reserve compared to Ni60 high out about 12%. Meet heat expand time, it can silently bear this 0.15 millimeters extrusion deformation amount, absolutely will not take tens of thousands sphere jam dead in narrow valve cavity inside. Wait pipeline temperature drops back to room temperature 25°C, it again can follow spring thrust slowly reset.
Factory assembly workshop very hard guarantee valve seat and sphere do to 100% absolute center, often will exist 0.05 millimeters eccentric error. Bringing weak give way ability Ni55 surface, in pipeline 5 MPa fluid pressure push under, will automatically produce extremely slight biased wear.
sealing pair friction behavior
Create hardness difference
Pipeline pressure often soars to 15 MPa. Two pieces metals are deadly pressed together, local received extrusion pressure breaks through 120 MPa. Take polished metals put in magnify 800 times microscope under look, surface not flat. Above distributed full height in 0.5 to 1.5 microns small bulges.
Manufacture sphere Ni60 alloy powder mixed 2.5% to 3.5% boron and 0.8% carbon. Metal in high temperature melts, crystallizes out extremely hard chromium carbide particles. Take Rockwell hardness tester towards sphere surface hit a bit, value steadily stops at HRC 58.
Beside next to valve seat uses Ni55 alloy. Recipe made change, iron element added to 4%, carbon content dropped to 0.4%. Composition fine tune makes valve seat hardness drop to HRC 52, compared to sphere soft 6 degrees.
Pipe inside medium temperature burns to 500 Celsius, valve starts turn. Sphere with per second 15 millimeters speed sticking valve seat wipe pass. Two pieces metal surfaces micron level small bulges head on collide.
Two pieces HRC 60 hard metals collide, instantly wipe out 800 Celsius high temperature. Metal atoms are forcefully extruded, break through 0.2 nanometers safe distance. Metal blocks are forcefully torn down, surface leaves exceed 50 microns deep pit holes.
Hardness low a bit Ni55 bulges in 120 MPa heavy pressure under first happen retreat. Relatively soft tip is pressed flat, two metal surfaces contact area instantly more out 18%. Receiving force area becomes big, 120 MPa local pressure slides drop to 95 MPa.
- Local receive pressure reduces 15%
- Friction instant temperature drops to 450 degrees
- Microscopic crystal dislocation slides 0.8 microns
- 75% friction energy becomes heat amount
Two pieces dry metals dry rub friction coefficient from extremely high 0.85 dropped to 0.35. Ni55 surface extremely tiny deformation, absorbed tear metal destructive force.
Pipe inside water flow carries 0.1 to 0.5 millimeters thick quartz sand grains. Mixture with per second 25 meters speed madly rushes sphere surface. HRC 58 hard particles like iron armor same bounce open sand stone. Wash 8 months after, sphere surface roughness maintains in 0.2 microns below.
Usually not how moving valve seat slightly soft, receive force time produces a strip micron level retreat belt. Chemical factory bottom pipeline temperature all year round stuck at 480 Celsius. Heat expand cold shrink makes sphere outer diameter fat 0.15 millimeters.
Relatively soft Ni55 valve seat conveniently absorbs metal expansion brought extrusion force. Two sides all use Ni60 hard metal, expansion produced force will top to 500 MPa, few seconds inside press crush sealing surface.
- Open close 500 times: contact gap 0.2 millimeters
- Open close 2000 times: grind out 0.6 millimeters contact belt
- Turn 10000 rounds: 1.2 millimeters fit surface
- Friction 50000 times: polish out 2.5 millimeters mirror surface
Motor gives valve stem applies 800 Newton meters torque. Ni55 inside more added iron makes metal possess 1.5% tiny ductility. Valve seat in huge twist force under, obediently hugs tight round rolling sphere.
Workers towards above coat silicon carbide grinding paste. Particles thick thin from W40 slowly change to extremely fine W5. Two pieces metals put on eccentric distance 15 millimeters machine tool to grind. Relatively soft Ni55 surface first bites extremely tiny grinding particles.
Tiny particles reversed come towards HRC 58 sphere do slow polish. Machine tool on grind 45 minutes, two pieces metal fit rate exceeds 95%.
Factory inside uses 1100 Celsius oxygen acetylene flame spray roast. Alloy powder melts after on surface form 1.8 millimeters thick dense coating.
- Spray gun move speed: per minute 120 millimeters
- Flame spray speed: per second 450 meters
- Coating dense degree: exceeds 98.5%
- Pull tear fracture limit: 380 MPa
- Surface hardness drop difference: less than HV 50
Main shaft per minute turns 800 circles, every circle knife head eats in 0.05 millimeters. Cut off 0.4 millimeters surface layer after, exposed alloy layer even air pores all find not arrive.
Leave factory before hit in 10 MPa high pressure nitrogen gas. Held 5 minutes, detector on one bubble all pop out not. Two pieces metals between grind out a layer thickness not reach 0.1 microns oxide protect film.
Friction thousands ten thousands times after dismantle open look. Metal on tiny scratches all follow sphere rotation direction go. Deepest groove only 0.08 microns, exactly be intercepted liquid molecules fill full. 5 to 10 degrees hardness drop difference, makes metal in few millimeters space inside finish ten million times micro repair.
Deformation & Tearing
Pipeline inside gas pressure topped to 20 MPa. Weight reach 80 kilograms metal sphere is deadly pressed on ring-shaped valve seat. Contact surface micro stress instantly pulls high to 140 MPa.
Two pieces polished metals stick together. Use electron microscope magnify 1000 times, surface is a piece high low up down metal mountain range. Mountain peaks average height in 0.8 microns about.
Suppose two pieces metals hardness completely same, all are HRC 60. Motor outputs 1200 Newton meters strength forcefully twist sphere. Two seats 0.8 microns metal mountain peaks violently collide.
Collide point in 0.02 seconds inside erupts reach up to 600 Celsius high temperature. Two pieces metal surfaces atom distance is extruded to 0.2 nanometers limit. Metal lattice happened cross-boundary fusion.
Two seats mountain peaks welded dead at together. Valve stem still desperately towards down turns. A strand exceeds 400 MPa shear force tears just welded firm micro points.
Hard bump hard not have any one side willing retreat. A piece wide 40 microns, deep 15 microns metal debris is vividly torn down. Originally flat sealing surface left a huge tear pit.
High pressure gas found breakthrough mouth. Pipeline starts with per minute 50 liters speed towards outside leak gas. Install up not reach 3 days, whole machine only can exhaust pressure stop machine dismantle.
Change recipe fine tuned Ni55 alloy do valve seat. Hardness tester hit out value stops at HRC 52. Opposite sphere still is extremely hard HRC 58.
Same 20 MPa gas pressure, same 0.8 microns mountain peaks collide. HRC 52 relatively soft metal mountain peaks bear not hold 140 MPa stress, surface starts towards down collapse.
Relatively soft tip is pressed flat 0.15 microns. Originally sharp touch point becomes a wide 2 microns small platform. Two pieces metals actual contact area all at once flipped three times.
- Receive force area flips three times: unit stress from 140 MPa violently drops to 85 MPa.
- Friction flash temperature greatly drops: collide produced highest temperature stuck at 320 Celsius.
- Lattice dislocation slides: soft metal crystal produces 1.2 microns plastic move.
- Anti-tear protect layer: surface generates 0.05 microns thick process harden film.
Contact area becomes big, receive force is seriously dispersed. 320 Celsius temperature far reach not atom fusion threshold. Two pieces metals not weld dead, naturally also will not happen savage metal tear.
| Friction Physical State | Collide Instant Temperature | Surface Micro Damage | Open Close 500 Times After Leak Amount |
|---|---|---|---|
| Two sides equal hardness | 600°C above | 15 microns deep pit | 4500 ml/min |
| 6 degrees hardness drop difference | 320°C about | 0.15 microns indent mark | 0 ml/min |
Collapsed micro pit holes inside filled full be pressed solid tiny debris. In coal chemical transport ash pipeline on, valve every day needs back forth friction 40 times. Soft metal surface plastic deformation area little by little links into a piece.
Experienced 2000 times back forth scratch rub, valve seat on pressed out a strip wide 0.5 millimeters extremely shallow groove. This strip groove arc with sphere outer diameter strictly fits seamless.
Forcefully torn out pit holes edge all is 15 microns high sharp burrs. Burrs in next time turn time will scratch out deeper scars. Scratch marks depth will in short short 10 times open close inside expand to 50 microns.
Pipeline inside runs is brings strong corrosive hydrogen sulfide gas. Tear pits take no anti-corrosion ability base material exposed in air middle. Concentration 150 ppm acid gas will quickly corrode drop below carbon steel.
Micro pit holes inside iron atoms with every day 0.02 millimeters speed be dissolved. Corrosion spots in short short two weeks inside will expand into 2 millimeters wide gap.
Happen benign deformation sealing surface smooth get like a surface mirror. Surface roughness test instrument probe scratches pass, Ra value stable at 0.12 microns. 1.8 millimeters thick alloy coating perfectly complete not damaged.
Be torn jammed valve, start torque will madly soar to 1800 Newton meters. Control room inside motor protect switch immediately overload trips.
Sealing surface produces micro plastic deformation after, turns up very silky smooth. In reach long 18 months heavy load run inside, motor output torque all the time smoothly maintains at 750 Newton meters up down.
Take Ni55 alloy cut open put in high magnification microscope under. Surface layer 2 microns inside metal crystal grains are pulled long 12%. Deform to bottom after, this layer thin thin metal happens physical process harden.
Change wear trajectory
Chemical factory catalytic cracking device continuously ran 8000 hours. Pipeline inside mixed 0.2 millimeters bauxite powder fluid day night washes.
Past two pieces HRC 60 hard metals to grind, wear consume route is a strip rough straight line. Every day has 0.05 microns thick metal is forcefully scraped drop.
Change on HRC 58 sphere match HRC 52 valve seat. 6 degrees drop difference makes destructive plow groove becomes extremely slow polish. Surface roughness probe sweeps pass, Ra value not becomes big, from 0.12 microns slid drop to 0.08 microns.
Two pieces metals in micron level space inside, take hard tear becomes mild self-grind.
Mine powder particles follow fluid squeeze into seal gap. HRC 58 Ni60 sphere completely not damaged. Relatively soft Ni55 valve seat surface tiny pores became natural refuge haven. Extremely tiny 0.01 millimeters powder dust is soft metal surface layer firmly wrapped inside.
Inlaid powder dust Ni55 surface layer becomes a piece extremely fine grinding sand paper. Every time sphere with per second 12 millimeters speed turns, “sand paper” just at gives it do full body polish. Lathe on left 0.3 microns knife lines are little by little wiped flat.
Metal contact area slowly towards outside expands. Valve just on line test time, sealing surface width merely 0.8 millimeters. Experienced 15000 times high temperature open close, contact belt width grew to 2.2 millimeters.
Contact area fully expanded 2.7 times. Distributed on contact surface medium thrust is largely thinned out. Concentrated at one point 120 MPa extrusion force, evenly sprinkled on whole 2.2 millimeters sealing belt on.
Pressure meter on receive force reading steadily stops at 45 MPa. Lower than metal fatigue limit state makes wear damage speed step down brake. First one month grind drop metal thickness has 0.02 millimeters.
- Run 1000th hour: wear amount drops down to 0.008 millimeters
- Run 3000th hour: surface consume only is 0.002 millimeters
- Run 8000th hour: probe very hard measure out obvious size change
- Run 15000th hour: surface generates 0.05 microns ultra dense layer
Grind down metal powder extremely tiny. Lab takes filter paper to catch discharge matter. Put to 800 times microscope under, all are irregular round smooth small particles, diameter not reach 0.005 millimeters.
Two pieces equal hardness metals bump out debris, all are bring sharp thorn metal pieces. Length usually exceeds 0.08 millimeters. Sharp thorn debris clip in middle, every time turn all at deep digging base seat.
Extremely tiny round smooth particles follow sphere ball surface roll. Like extremely bearing inside add enter lubricate rolling balls. High pressure dry friction environment inside hard is gathered out a layer micron level solid thin film.
Torque sensor recorded equipment whole life cycle change. Front 300 strokes, metal surface still at looking flat, drive torque in 800 to 850 Newton meters between jumps. Two pieces metals little by little close gather.
5000th time open, torque meter on reading fixed at 680 Newton meters. Arrived 20000th time, numbers fell to smooth 620 Newton meters. Wear trajectory walked out a opening towards down parabola.
More grind more slippery phenomenon violates common machine wear damage common sense. Pipeline inside fluid pressure reaches up to 25 MPa. Valve seat tightly hugs sphere, two pieces metal surfaces between even one water molecule all drill not enter.
Test instrument leak rate all year round shows as 0.00 ml/min. Engineer takes hand touched valve body outer shell. 500 Celsius high temperature medium flows pass, outer side keep warm layer measure temperature gun shows 65 degrees.
repair and manufacturing practicality
Thermal stress & Cracking
Welder stares workshop inside operation screen, temperature numbers jumped to 1050℃. Weld gun sprays out eye piercing strong light, Ni60 metal powder meets extremely high temperature instantly becomes liquid, firmly sticks on stainless steel surface.
Beside that pipe diameter 80 millimeters solid big iron ball fully has 25 kilograms heavy, metal wall thickness exceeds 18 millimeters. It like a super big size absorb heat sponge, weld gun continuously roasted 45 minutes, it also can take 800℃ high temperature slowly resolve drop.
Just welded finish sphere red get shines, workers immediately take it push enter asbestos keep warm box. Drop temperature speed stuck very dead, one hour only can drop 30℃. Metal internal tiny particles taking advantage this period time re-line up, occupies 15% proportion chromium element runs out, becomes hard hard chromium carbide.
Turn head look process valve seat work station, lathe on clamped a outer circle diameter 90 millimeters thin iron ring. Used to do sealing that cut surface, thickness merely only 4.5 millimeters, thin get like a pop can bottom.
If taking weld gun hard gives this thin piece spray 1050℃ Ni60 iron water, not reach 3 seconds thin piece local just will burn get white.
Use microscope look weld seam, destroy marks very scare people:
- Follow metal texture crack open gap has 0.5 millimeters deep
- Temperature drops to 400℃ time bursts out horizontal big crack mouth
- Whole round ring deforms warps up becomes 0.8 millimeters oval
- Just welded on alloy layer like drop paint same pieces peel off
Change medicine recipe becomes workshop only out road, workers take fill full Ni55 powder pot connects machine. New recipe inside took away 2% boron and silicon, towards inside more added a little iron powder.
Boron and silicon originally can make iron water flows get more smooth. Take away them after, Ni55 from liquid becomes solid time, shrink amplitude becomes small. Just at solidify that one instant, metal becomes slightly has a little elasticity, no longer like glass that brittle.
Meet up 4.5 millimeters thick thin wall ring, weld machine sends give Ni55 heat amount lowered 15%, current meter from 180 amperes dialed to 150 amperes. Receive high heat affect area is forcefully squeezed in 2 millimeters wide ground border inside, material itself takes pull tear force give digested.
Quality inspect room inside ultraviolet lamp lit, just made well Ni55 thin ring surface sprayed a layer fluorescent water. Lamp light one shine, one strip emit light fine line all not have, out factory qualified rate hard is from not reach 40% pulled to 98% above.
Hidden in metal deep place fine small dark wounds, hit 15 MPa water pressure test fundamentally test not out. Not know emotion assembly worker takes bring wound valve twist well, subsequently send towards chemical factory install enter temperature reach up to 200℃ steam pipeline inside.
Factory inside evil bad pipeline environment will make a thread small problem brew into big disaster:
- Pipe sudden cold sudden hot brings pipe wall back forth pull tear
- Valve one open per second 6 meters steam madly washes
- Worker takes big wrench twist screw add go up several hundreds catties dead strength
- Fine small crack gap tip tops per square millimeter 200 Newtons pressure
- Short short three months inside crack mouth just can take 4.5 millimeters iron wall thoroughly gnaw penetrate
Before workshop corner waste product basket inside stuffed full scrap iron rings, good tens of thousands true gold white silver hit water drift. Technician holding measure thickness instrument everywhere measures, on white board newly changed operation rules.
Thin ring on weld Ni55 layer, thickness deadly stuck at 1.5 to 2.0 millimeters middle. Just weld finish absolutely cannot touch cold water blow cold wind, quickly send enter 550℃ roast box inside suffocate on whole 4 hours.
Match grind process
That is use 200 mesh silicon carbide micro powder and machine oil according 3 to 1 weight proportion blend out paste shape matter. Master uses small hair brush picks up 5 grams about paste body, evenly smears on hardness HRC 52 Ni55 valve seat sealing surface on.
Beside Ni60 solid big iron ball early just be travel crane hoisted to operation tool dress on, its surface hardness reached HRC 58.
Ear piercing metal friction sound instantly rings through tens square meters assembly area, sounds like just like holding rough sand paper on not scraped putty cement wall surface on use force wipe pass.
Factory inside before tried let HRC 58 valve seat go forcefully grind HRC 58 sphere, two pieces same hard steel mutually hard top dead knock. Masters fully consumed enter 3 pots expensive import diamond grind paste, open machine tool ground whole 8 half hours.
Machine stops use stained gasoline broken cloth takes oil dirt wipe clean one look, sealing surface on all is irregular white points and scratch marks. In micro world inside, equal high hardness metal surface friction long local heats up bites fit, originally flat surface vividly is torn out 0.1 millimeters deep pock pits.
Take valve seat change to hardness low 6 HRC values Ni55 material after, situation happened dramatic flip turn. Just open machine front 15 minutes, bring edge corner silicon carbide sand grains in two pieces metal tiny gap between madly roll tumble cut shave.
Slightly relatively soft Ni55 valve seat smartly made physical give way, its surface produced several microns depth micro plastic indent. It actively goes tolerate that extremely hard Ni60 sphere natural arc degree, slowly fits into a pick not out problem sphere shape curved surface.
Masters according to process card change use different thick fine sand paste, hand inside moves also have strict time particularity:
- Front 30 minutes use 200 mesh rough sand grind, specially gnaw drop lathe process left high low not flat lathe knife lines.
- Middle 1 hour change to 400 mesh fine sand, takes metal between contact gap deadly compresses to 0.05 millimeters within.
- Last 20 minutes dot on 800 mesh polish liquid, purely rely workers double hands clockwise slow shake turn circles to hand work close tail.
Grind process can not can hand cross, not look wall on hang clock time, all rely one tube Prussian blue print mud dye material. Master uses cotton swab dips erythromycin soft ointment size one tiny bit Prussian blue, on Ni60 sphere on thin thin coats out a strip 2 centimeters wide horizontal color belt.
Take ground well Ni55 valve seat newly buckle back sphere on, double hands use force towards down press hold, same time left right lightly rotate 45 degrees angle. Pull up valve seat one look, that one circle 4.5 millimeters wide metal contact surface on, stained full blue area must reach percent of hundred, even if leave has a needle tip size white point all not okay.
Technology section takes half year workshop produce original report forms did sum up, paper surface on numbers take different material combine work work difference calculated clear clear Chu Chu:
| Material Combine Type | Valve Seat and Sphere Hardness Difference | Single Machine DN50 Equipment Match Grind Consume Time | Grind Consume Material Single Time Use Amount | Prussian Blue Test One Time Pass Rate |
|---|---|---|---|---|
| Ni60 Sphere + Ni60 Seat | 0 HRC | 8.5 Hours | 150 Grams | 21% |
| Ni60 Sphere + Ni55 Seat | 6-8 HRC | 1.8 Hours | 45 Grams | 96% |
Table inside that saved down 6 more hours, towards delivery period urgent flow water line speaking is take money all buy not arrive progress. Operation worker not need at machine tool front stand to waist sour back pain, workshop one month can more assemble out whole 400 machines high pressure metal seal ball valves.
Instrument tungsten steel probe at ground well Ni55 valve seat surface slowly glides pass 3 millimeters test distance, palm big screen on jumps out Ra value stable at 0.2 to 0.4 microns between.
Maintenance & Spare Parts
Northwest chemical factory coal chemical pipeline inside, galloping temperature reaches up to 320℃ black coal slurry. This strip inner diameter 100 millimeters steel pipe internal, mixed large amount bring edge corner quartz sand and not completely react catalyst particles. Impurity hardness reached Mohs 6 to 7 level, exactly with per second 12 meters terrifying flow speed madly washing pipe wall.
A machine weight reach 120 kilograms high pressure metal hard seal ball valve installed in pipeline relay pump exit place. Operator at control room presses down close button, sphere slowly rotates cuts off liquid instant, several pieces sharp quartz sand are forcefully squeezed enter sphere and valve seat middle gap inside.
Accompanying heavy dull metal friction sound, thickness only has 4.5 millimeters Ni55 valve seat head bear its brunt received wound. Its slightly soft surface be hard sand grains heartlessly plowed out a strip deep about 0.2 millimeters fine long groove.
Three months after big repair period, maintain team holding heavy pneumatic wrench climbs up pipe frame. 8 roots M20 flange bolts are fast uninstalled drop, bringing oil dirt valve be travel crane hoisted to repair workshop disassemble table on.
Worker uses soaked full acetone broken cloth, takes stained full black mud internal parts wipe get reveals metal original bottom color. That surface hardness reaches up to HRC 58 Ni60 solid big iron ball, still bright clean get like a surface mirror, even most fine slight scratch marks all not left drop.
Beside that hardness stops at HRC 52 Ni55 valve seat round ring miserable not endure look, that strip 0.2 millimeters deep groove thoroughly destroyed dense closed block water ability.
Factory inside old masters often point at dismantled down parts give apprentices mutter: “Machine inside iron pieces always must have soft have hard, soft that one exactly is taken to block gun protect cover. Guarded live middle most worth money iron lump, our this trip rush repair just counts not in vain do.”
Equipment section purchase account book on calculates get very clear. Go factory newly custom make a DN100 caliber Ni60 pure solid sphere, single piece purchase quote price reaches up to 12500 yuan RMB.
High hardness big volume parts manufacture, needs experience lathe rough process, high temperature pile weld, flaw detect remove stress as well as consume time curved surface grind. From place order to receive goods, factory at least needs wait on whole 15 days long long delivery period.
Broken drop Ni55 thin wall valve seat merely is a common consume material. Factory inside spare parts warehouse goods shelf on all year round prepares tens stock, every one enter storage price merely only has 650 bucks, weight still not reach 1 kilogram.
At first drawing paper on if takes valve seat design into same extremely hard Ni60 material, two pieces hard bones under sand stone squeeze will two lose both wounded. Value over ten thousand sphere be scratched wound scrap, whole pipeline just needs accompany stop work half month.
Chemical factory ethylene produce line every stop machine one hour just needs burn drop whole 80000 yuan pure profit. Workshop director fundamentally wait not afford 15 days spare parts purchase time, factory inside wants is immediately install back restore work valve.
Repair table front, master takes that piece scrap valve seat conveniently throws enter waste iron basket, turns body from paper box inside dismantle out a painted anti-rust oil brand new Ni55 valve seat.
