RT inspection is radiographic flaw detection, used to discover cast steel valve internal porosity, shrinkage and other defects.
According to standard (such as ASTM E446), defect grades are divided into 1-5 grades, normally requiring ≤ 2 grade; inspection ratio generally is 10%-100%.
Need to control exposure time, film density (2.0-4.0) and retain reports.
Table of Contents
Toggleinternal defect detection
Porosity
Steelmaking furnace inside temperature reaches as high as 1550 degrees Celsius, boiling steel water belly inside hides large amounts of hydrogen gas and nitrogen gas. Every 100 grams of pure iron can forcefully pour into 27 milliliters of free state hydrogen. Steel water exits furnace poured into sand mold, temperature every second drops down ten-plus degrees, gas can dissolve amount instantly shrinks to original one fourth.
Originally staying at metal inside gas desperately outward squeezes. As long as steel water freezing speed compared to bubbles every second floating up several millimeters speed is faster, hydrogen gas and carbon monoxide are deadly stuck at metal deep place. Waiting for casting completely cools through, hard cross-section on leaves behind diameter 0.5 millimeters to 3 millimeters small empty holes.
Furnace worker needs to at exiting steel before throw in aluminum blocks force exhaust gas. If remaining aluminum is less than 0.02%, not exhausted clean oxygen will with carbon produce reaction. Even if only generates 1 gram carbon monoxide gas, at thousands degrees high temperature under can stretch out several hundreds cubic centimeters volume.
External moisture also will come make trouble. Carrying water vapor sand mold meets high temperature steel water, one drop 0.05 milliliters water will instantly expand 1700 plus times. High pressure water vapor at metal outer skin clumping before hard drills in, at outer skin under 1 to 3 millimeters shallow water zone hits out a piece of dense holes.
Workshop checking holes source will directly flip look production running account:
- Mold baking lower than 250 degrees Celsius
- Resin sand curing agent exceeds 1.2%
- Exhaust port cross-section too small
- Steel water static resting less than 3 minutes
Dark room’s high brightness film viewing lamp under, flaw detector tightly stares at film on deep black round dots. X-ray passes through carrying holes steel completely without resistance, film on will leave black spots. According to ASTM E446 atlas comparison, every square inch has 5 pieces 1 millimeter black dots, is fixed dead at 2 grade.
Drawing requires a diameter DN200, pressure 900 pounds cast steel valve, wall thickness must reach 28.5 millimeters. If certain place bunches up grows full of 2 millimeters bubbles, actual can bear pressure thickness even 25 millimeters does not reach. Pipeline inside high speed flowing liquid adding several megapascals vibration, very easy at fine micro pores between tears out cracks.
Third-party inspector looking at film has strict calipers:
- 150 pounds water pipe relaxed to 3 grade
- 600 pounds steam stuck dead at 2 grade
- Hydrogen-adjacent pipeline forcefully requires 1 grade
- Carrying sharp tail holes entirely scrapped
Hiding deep round holes shooting film time might be by overlapping shadows blocked. Waiting arriving at machining link, lathe blade at every minute 80 meters speed cuts flange end face. Hiding at internal 0.8 millimeters holes suddenly expose at smooth machining face on, high price semi-finished product instantly becomes scrap iron.
Holding certificate welder grabs up carbon arc air gouging gun, tunes out 400 amperes strong current aiming at film marked point opens digging. A soybean big small hole, forcefully is dug into diameter 30 millimeters, slope exceeding 60 degrees big pit. Using ER70S-6 welding wire one layer by one layer fills full, still needs to newly shoot film to see inside in the end tight not tight.
Experienced supervisor more loves to flip look factory’s original base receipts. As long as take steel water internal initial hydrogen content suppress at 2ppm below, film on large area exploding out black dots probability just fiercely falls 80% above.
shrinkage cavity & shrinkage porosity
1580℃ liquid carbon steel following along pouring system surges into sand mold, violent volume shrinkage accompanying happens. From liquid state drops temperature to solid state, steel volume out of thin air shrinks drops 3% to 7.2%. Filling full mold cavity’s metal, at cooling forming crust after leaves out large piece gap.
Casting plant at valve body’s highest point adds installs several cylindrical shape iron lumps, jargon calls riser. Riser inside steel water must compared to valve body late freeze at least 15 minutes. Relying on this 15 minutes time difference and gravity, riser continuously towards bottom underneath shrinking valve body wall supplements liquid metal.
Casting engineer according to experience formula measures calculates supplementing shrinkage distance. A outer diameter 300 millimeters, wall thickness 40 millimeters cylindrical shape valve body, riser can govern effective supplying water scope at most only has 120 millimeters. Exceeding distance cannot get supplement, inevitably leaves behind sponge shape loose tissue.
Workshop meets riser neck design too narrow, diameter 60 millimeters riser neck at air in supported 8 minutes early freezing blocks dead. Bottom underneath thickness reaching 80 millimeters valve body flange still is towards inside shrinking, completely sucks not arriving fresh steel water.
Internal metal gets not supplement, following along crystal growing direction tears out big empty holes. Flaw detection film on presents large area continuous, carrying sawtooth edge extremely black images. ASTM E446 standard atlas inside, macroscopic independent empty holes classify as CA grade defect.
Big empty holes can use carbon arc air gouging dig away, like sponge same micro small pores very headache. Carbon steel at 1530℃ to 1490℃ between places at viscous solid liquid mixed state. Tree branch shape crystals interlace overlap, taking steel water cuts into several thousands closed micro small melting pools.
Micro melting pool cooling formed pores diameter only has 0.1 to 0.5 millimeters. Several tens of thousands micro pores connect into one piece, at X ray film on like a lump blurry black clouds fog. Flaw detector takes ten times magnifying glass finds details, takes this kind divergent shape black shadow classifies into CB or CC grade classification.
Valve flow channel wall thickness only has 25 millimeters, connecting pipeline flange thickness fiercely increases to 65 millimeters. Thickness violently sudden changing area cooling speed disconnects, neighboring two pieces metal’s temperature difference can exceed 150℃.
Inspector at here catches out extremely nasty CD grade network shape shrinkage porosity. Carrying connectivity shrinkage porosity cast steel valve moved onto pressure test bench, hits in 15 megapascals high pressure water. Less than 5 minutes, valve body outer surface like sweating same towards outside seeps water beads, entire batch goods directly scraps.
| Defect code | Film image feature description | Common latent position | Destructive power manifestation |
|---|---|---|---|
| CA class | Outline clear, edge carrying sawtooth big piece black spots | Riser root part, flange thick big cross-section center | Cuts down bearing pressure effective wall thickness |
| CB class | Like tree branch or vein same divergent black stripes | Pouring system handover place, valve body turning corner | Triggers local area receiving force cracking |
| CC class | Like sponge same dense black tiny pockmarks | Valve middle cavity flow channel area, wall thickness transition section | Causes high pressure fluid penetrating leaking |
| CD class | Blurry not clear network shape or thread shape dark black cloud lumps | Structure extremely complex, cold hot uneven dead corner | Metal tensile strength presents cliff drop |
Handling these film not reaching standard areas, front line workshop has rigid modifying actions:
- Sand mold outside sticks on thickness not lower than 20 millimeters specially made cold iron forcefully locally drops temperature
- All right angle turnings use grinding wheel machine grinds into radius R15 above smooth round corner
- Wall thickness exceeding 50 millimeters flange area at wooden mold stage implements forced local hollowing out
- Riser’s external heat preservation sleeve thickness increases to 15 millimeters to try best extends liquid state time
Reworking personnel facing large area sponge shape shrinkage porosity very tricky. Air gouging gun sprays out 0.6 megapascals high pressure air flow, takes melted iron water forcefully blows away. Meeting area exceeding 100 square centimeters CC grade defect, operator has to continuously gouge cut 40 minutes, until exposes glowing metallic luster dense mother material.
Industrial ray penetrates 60 millimeters thick steel plate needs high strong energy. Flaw detection room takes Iridium-192 radioactive source’s focal length pushes to limit, exposure time stretches long to 15 minutes. Washed out industrial film blackness value strictly controls at 2.0 to 3.0 between, prevents missing hair strand thickness shrinkage porosity dark shadows.
Changes local metal cooling environment, takes dropping temperature speed pulls high to every second 5℃ above. Steel water at becoming tree branch shape crystal before instantly freezes into dense block shape. Film on possibly connecting into one piece black cloud fog is strongly pressed down, cast steel material’s actual measured yield strength deadly bites drawing bottom line.
Slag inclusions & sand inclusions
1600℃ electric arc furnace inside scrap steel mixing iron alloy violently melts, liquid surface on floats a layer thick thick oxide furnace slag. Silicon, manganese, aluminum’s oxides mix into lump, density roughly only has every cubic centimeter 3 grams. Liquid state carbon steel density as high as 7.8 grams, normally speaking furnace slag should float at liquid surface on.
Steel water from steel ladle bottom pours down, pouring flow speed breaks through every second 50 kilograms. Huge impulse takes surface layer’s furnace slag hard rawly rolls into steel water deep place. Steel water temperature falls breaks 1500℃, viscosity presents exponential grade rising, diameter less than 2 millimeters slag blocks fundamentally do not have time to float up.
Resin sand pressed into mold needs at few seconds inside bears extremely high heat impact. 1550℃ liquid metal following along pouring channel violently washes sand mold inner wall. Curing agent at high temperature under instantly burns damages, originally tightly bonded 40 to 70 mesh quartz sand particles instantly loosen detach.
Detached quartz sand particles rolled into high flow speed metal liquid inside four places wander, eventually are frozen at valve body’s various cross-sections inside, accompanying steel completely solidifying.
Flaw detection room washed out industrial film on, non-metal impurities density extremely low, X-ray penetrating them easy and effortless. Film background presents large piece dark gray color, mixed in impurities then show as shape extremely irregular deep black spot blocks. ASTM E446 standard atlas takes them classifies at B class defect category.
Film appraiser hand inside holding blackness meter, carefully measures film on carrying edges corners dark shadows. 150 pounds low pressure valve tolerates B class 3 grade slag inclusion, switching to requirements extremely strict API 600 standard gate valve, drawing takes acceptance threshold deadly stuck at 1 grade red line.
Impurity blocks edges often grow full of sharp barbs, with surrounding steel entirely bite not arrive at one piece. Tensile testing machine to carrying slag inclusion test bar conducts tearing test, nominal tensile strength 485 megapascals WCB carbon steel, at bearing pressure less than 300 megapascals time extremely easily from impurity tip point crisply fractures.
Experienced foundry workshop will at pouring system front end sets up multiple physical checkpoints to intercept impurities:
- Pouring cup bottom places 10 holes/inch silicon carbide foam ceramic filtering net, sticks dead diameter larger than 1.5 millimeters foreign objects.
- Mold horizontal pouring channel designed into trapezoid cross-section, uses iron water and impurity’s specific gravity difference conducts centrifugal separation.
- Pouring before uses long handle slag pulling board cleans ladle head, tilting steel ladle pouring water angle strictly controlled at 15 degrees inside.
- Casting mold surface sprays coats thickness 0.5 millimeters zircon powder coating, hard resists 1550℃ steel water’s strong force washing.
Quality inspector uses white marker pen at valve body surface circles out film corresponding impurity coordinates. Pneumatic grinding machine installs on hard alloy rotary file, at every minute 20000 revolutions high speed towards down deep digs. Sand inclusion area often compared to film displaying area bigger one circle, worker must towards outside expands digging at least 10 millimeters.
Cleaning work consumes time extremely long, a DN300 valve flange place’s B class 3 grade slag inclusion, frequently needs to grind away 5 pieces outer diameter 125 millimeters resin grinding wheel pieces. Confirming dug arriving silver white pure mother material after, operator has to use high pressure air gun blows clean dust powder, for subsequent argon arc repair welding clears out clean groove.
Dug clean groove surface if leaves behind even if 0.2 millimeters black sand dots, repair welding’s high temperature electric arc immediately explodes out dense continuous string pores.
Furnace slag inside carrying large amounts sulfur, phosphorus elements towards weld seam has extremely strong killing power. Welding wire melting instant, remaining iron sulfide will at crystal boundary form low melting point eutectic crystal. Local temperature drops to 800℃ around, huge shrinkage pulling force easily tears open fragile crystal boundary, triggers micro thermal cracks.
Carrying sharp sand inclusion cast steel valve mixes into natural gas long distance transportation pipeline, needs to face as high as 10 megapascals alternating pressure. Pipeline every time pumping starting stopping bringing physical vibration, all at extremely micro level on pulling tearing impurity irregular edges.
Originally only has 3 millimeters long slag inclusion tip point starts to produce fatigue crack, following along metal crystal boundary at every year several micrometers speed slowly pushes forward. Crack penetrates 40 millimeters thick valve body bearing pressure boundary, pipeline internal high pressure fluid will following along gap towards outside madly sprays.
inspection cost increase
High testing costs
A 3.5 tons heavy carbon steel gate valve lies at workshop, waiting worker takes it transports into anti-radiation room. Moving this machine needs to use a 10 tons grade crane, three people busy whole 45 minutes. That room only four walls’ barite concrete just fully has 1.2 meters thick. Building price as high as 3.5 millions protection room, every day all at account on consuming depreciation fee.
Flaw detection machine inside installed Iridium-192 radioactive source buying one needs to spend 40 thousands to 60 thousands yuan. It only can manage 73.8 days, time arrives penetrating power just not enough, factory only can repeatedly hits report buys new. Old source has no way casually throw, pulls away handles one time’s hazardous waste cleaning fee marks price 5500 yuan.
Shooting film buying film is a calculable clear running account. Factory inside often buys Belgium Agfa D7 industrial film, one box 100 pieces, specification 8×10 inches, entering price 850 yuan. Meeting a 24 inches big caliber valve, only shooting one circle film just has to tears open uses drops 35 to 40 pieces.
Shot finished film needs to be taken into dark room washes out, flushing pool has to 24 hours maintains 20℃ constant temperature. Every washes 250 pieces film, value 300 yuan developing fixing chemical water just has to changes new. Every month only taking washed finished waste liquid gives to environmental protection company transports away, settling bill on at least also needs to write 2200 yuan.
Workshop inside every day all at consuming testing scattered items:
- Washing film wastes dropping chemical water, according to environmental protection regulation gives money pulls away
- Sticking at steel plate on lead letters and image quality indicator, easy to drop, every day supplements
- Clamping film lead foil intensifying screen, surface extra one folding mark just has to throws
- Worker carries on body radiation alarm instrument, every year gives money does annual check calibration
At Yangtze River Delta belt, holding ASNT level 3 flaw detection certificate inspector, works one day starting price 1500 yuan. Normal times at workshop responsible for moving things, sticking film level 2 technician, every month issues salary slip also needs 12000 yuan hitting bottom.
Facing steel wall thickness 85 millimeters valve, skilled worker finds accurate focal length just needs 30 minutes. Retreats to safety line outside opens machine, waits ray completely passes through thick steel plate, exposure time long reaching 45 minutes. Even if one whole day continuous rotating, three people at most also just shoot finishes 7 pieces big caliber valves.
Just washed good film needs to hang at rack on airs 24 to 48 hours, not issuing report valve only can pile at empty ground on, rawly occupies goes 200 square meters factory space. A price marked 60 thousands yuan cast steel valve at factory inside extra presses 15 days, factory accounts on just extra comes out 150 yuan funds bridge interest.
Hanging on high brightness film viewing lamp, internal larger than 2 millimeters pores fundamentally hide not stopping. According to strict standard sticks down, first time flaw detection not qualified proportion can occupy reaching 25%.
Rework repairing time extra constructs in material fee:
- Digging pit using carbon rods and big tank industrial high pressure oxygen gas
- Grinding wheel machine grinds wastes dropping several tens pieces resin grinding wheels
- Placed at heat preservation bucket inside maintains constant temperature special steel welding rods
- Repairs finished again newly shoots one time film all labor materials
Fills flat that deep pit at least needs to tears 3 packages E7018 special welding rods, total weight reaching 15 kilograms. Just repaired finished parts carrying extremely strong receiving heat shrinking force, immediately has to pushes into natural gas annealing furnace. 650℃ constant temperature bakes 4 hours, gas meter one turns just is 850 yuan single furnace starting price.
If meets no way repairing large area internal pores, entire piece 1.5 tons heavy casting only can according to scrap iron handles. Every ton sells 2400 yuan transports goes backyard melts dropping, in vain loses dropping 4500 yuan casting fee, all calculated at next batch qualified finished product’s bill inside.
Wall thickness exceeding 150 millimeters high pressure big valve, ordinary radioactive source shoots not through. Factory only can goes rents uses a piece building price 8 millions linear accelerator to inspects. Uses 13 meters long semi-trailer runs 50 kilometers sends goes testing institute, single trip freight fee needs to spends 1200 yuan.
Testing institute opens one time accelerator, every hour receives 650 yuan. Escorting car person often still needs to spends 200 bucks money gives operator buys several portions midnight snacks, begging person helps inserts a queue. Waits taking back one piece stamped red seal inspection sheet, this piece valve budget table on early just extra paid out 3200 yuan.
Defect Repair & Heat Treatment
Film viewing lamp under film on, a merely 3 millimeters black dot, will lets entire workshop originally production plan stagnates. Factory inside holding certificate film appraiser taking carrying scale magnifying glass looked three seconds, at marks price 80 thousands yuan 10 inches high pressure gate valve film on drew a red circle. Valve body side face that judged as 3 grade sand inclusion micro small flaw, immediately needs to face a field hurting muscles moving bones renovation.
Worker picks up thick big marker pen, at valve body surface according to film coordinates draws out a long 15 centimeters, wide 8 centimeters ellipse. Repairing absolutely not taking welding gun pastes on a layer iron water that easily, must first takes carrying disease focus whole piece meat thoroughly cuts away. Electric welding clamp clamps holding a piece diameter 8 millimeters copper plated carbon rod, connects 600 amperes strong current, carbon arc air gouging operation immediately starts.
Exceeding 8000℃ high temperature electric arc instantly takes cast steel melts, beside accompanying 0.6 megapascals pressure compressed air, takes glowing red iron water entirely blows flying. Sparks flying four places in, originally only hiding 3 millimeters impurity place, hard rawly is scooped out a depth reaching 45 millimeters big funnel. Dug out scrap iron slag crosses scale one weighing fully has 2.5 kilograms heavy.
Grinding worker follows entering field, hand inside that piece power 2000 watts angle grinder changes on brand new resin flap disc. He needs to lays at valve on works whole 40 minutes, takes just now air gouging leaving behind black gray color oxide skin entirely grinds away. Until pit bottom completely exposes silver white metallic base color, ground on scatters 3 pieces completely ground bald grinding wheel pieces.
Starting welding before needs taking infrared measuring temperature gun pointing at pit bottom measures. Winter workshop air temperature only has 8℃, immediately using welding rod extremely easily lets ice cold steel wall explodes cracks. Worker carrying two pieces baking guns, opens full liquefied gas pointing at repairing area surroundings fiercely burns 15 minutes, forcefully takes local steel plate temperature burns to 150℃ above.
Real filling pit work only can gives to appearance fee extremely high special welder. He hand inside holding is just from 150℃ heat preservation tube inside pulled out E7018 special low hydrogen welding rod. A piece long 350 millimeters welding rod, at hand inside burns less than two minutes just leaves a welding handle head.
Every burns finished one layer weld seam, worker needs to takes sharp head pneumatic knocking slag hammer takes surface welding slag shakes breaks cleans clean. This deep reaching 45 millimeters pit, divides 8 layers just slowly fills flat, fully consumes 22 pieces thick welding rods. Repaired finished place bulges up a small bag, surroundings all are by high temperature baking changing color dark red traces.
Just repaired finished area, internal steel just is by hot expanding cold shrinking force mutually pulling tearing. This piece 2 tons heavy cast steel valve immediately is by forklift sent to factory area back’s heat treatment workshop. Annealing furnace furnace door heavy reaching 800 kilograms, by winch slowly pulled up, valve is pushing iron rail small car sent into deep reaching 4 meters furnace chamber deep place.
Heat treatment absolutely not fierce fire blindly burns, instrument panel on heating curve sets clear clear. 6 pieces big caliber natural gas burners together ignites fire, furnace temperature according to every hour 50℃ speed slowly climbs upwards. Only is rising to 620℃ regulated temperature, just hard rawly burns roughly 12 hours.
Arriving 620℃ needs according to regulation heat preservation, dial quota according to valve body maximum thickness to calculate, every 25 millimeters thickness corresponds 1 hour. This casting heat preservation time sets as 3.5 hours. Heat preservation period once passes, needs to turn off fire lets valve body at furnace inside stuffs, according to every hour 30℃ progress slowly drops temperature.
Waiting until furnace temperature drops to 300℃ below, winch just will newly pulls open furnace door puts valve exits furnace. One enters one exits, whole 24 hours passed. That piece leading to heat treatment furnace natural gas pipeline on flow meter, solidly extra ran 280 cubic meters. According to industrial using gas 4.2 yuan one cubic price calculates, bill extra comes out 1176 yuan.
Valve exits furnace cools to room temperature, worker needs to uses grinding wheel machine takes surface that bulge newly grinds flat. Mover pushing small cart, takes radioactive source and film newly pulls over. At just now repair welded same one position, again sticks on 3 pieces 8×10 inches film, originally without moving takes flaw detection process again walks one time.
Workshop normally prepares repairing auxiliary materials consuming list:
- Diameter 8mm air gouging carbon rod, single box 50 pieces, consumes wears extremely fast
- E7018 special grade welding rod, every package 5 kilograms, opens seal receiving damp immediately wastes
- 125mm resin grinding wheel piece, consuming amount according to hundred pieces starting calculates
- Industrial liquefied gas tank, single tank 50 kilograms, supplies baking gun preheating using
Industry inside has a not written rule, same one place at most only allows digging open repairing two times. Supposing second time shot out film on, repair welding area inside carries on new pores or not welded through cracks, this expensive casting declares scrapping.
Common repairing operations corresponding fee detailed table:
| Operation item | Time length estimate | Consumables and energy bill reference |
|---|---|---|
| Carbon arc air gouging digging groove | 45 minutes | Carbon rod, 600A electricity fee approx 85 yuan |
| Angle grinder cleaning root grinding | 40 minutes | Grinding wheel piece, labor fee approx 120 yuan |
| Preheating and multi-layer repair welding | 1.5 hours | Special welding rod, liquefied gas approx 180 yuan |
| Enters furnace annealing eliminates stress | 24 hours | Natural gas burning 280 cubic approx 1176 yuan |
| Original position film re-inspection | 3 hours | Film chemical water, flaw detection labor approx 350 yuan |
Above entire set process walked finished, a valve delivery period towards back drags whole 3 days. Originally only calculated one time flaw detection money budget table, rawly by this set digging meat repairing sore continuous actions pulls out several thousands bucks deficit.
Production delivery time extension
Workshop south side open air empty ground on, densely densely piles placing 150 plus pieces waiting flaw detection cast steel valve bodies. This piece occupying ground 300 square meters turnover area, originally was used to park stop delivering goods trucks. Now, a single heavy 2.8 tons 14 inches gate valve only can quietly lie at wooden pallet on, waiting queuing enters anti-radiation room.
Moving this pile heavy iron lumps, all relies on workshop top on that 15 tons grade bridge crane. Whole factory totally has 6 work sections at grabbing this crane’s control right, flaw detection group needs to early half day at drawing board on writes down crane scheduling table. Even if only takes a piece big valve towards front parallel moves 50 meters, worker often also needs to at original place dryly waits 3 hours.
“Front still has 8 pieces high pressure valves not shot finished film, today night shift calculating on overtime fee also turns not to you this batch goods enters field.” Flaw detection room door mouth dispatcher often takes this sentence hangs at mouth edge.
Factory inside only one room barite concrete flaw detection room, 24 hours three shifts continuous rotating. Meeting wall thickness 60 millimeters alloy steel casting, ray machine every time exposure long reaching 40 minutes. Gives a piece big caliber valve body shoots on one circle, changing 6 times position, fastest also needs to consumes dropping 4 hours. Full hit full calculate, this room one day at most swallows spits 12 pieces big items.
Shot finished film cannot see light, immediately is sent into 20 square meters constant temperature dark room. Developing and fixing chemical water pool beside, hangs full of wet dripping black film. Film only can relies on room temperature slowly airs dry, absolutely cannot uses hot air blower goes blow, surface even if slightly raised a bit wrinkling folds, entire piece film voids newly shoots.
Natural wind drying this process, hard rawly ate dropping 24 to 48 hours time. Waits film completely dries thorough bright, just will be sent into film appraising room. Two holding certificate film appraisers desk face on, every day piles exceeding 300 pieces waiting looking film, beside placing two cups early just cooled thorough strong tea.
Delivery period delay at workshop various processes consuming time bill:
- Crane queuing and placing finding focal length, single machine consumes 4.5 hours
- Waiting front batches big items exposure, average queuing 2 to 3 days
- Dark room film fixing and natural wind drying, fixedly locks dead 36 hours
- Flaw detection report typesetting printing finding person signing, walking process consumes 1 day
Meeting this factory machine shoots not through 150 millimeters super thick item, needs to hires a 9.6 meters flatbed truck pulls goes outside. From factory area drives to 80 kilometers outside third-party testing institution, road on just needs to run two hours. Unloaded car’s valve piles at testing institute yard inside, queuing waiting accelerator opens machine at least again needs to wait on 3 days.
Meeting continuous falling three days big rain, open air placing casting surface all grows full of a layer yellow brown color floating rust. Pulling back factory inside fundamentally no way puts on paint, still has to pulls goes shot blasting room spends 2 hours newly beats sand.
Meeting finds out pores needs reworking situation, time table on numbers even more exponentially upwards flips. Worker spends half day time air gouging grinding, special welder consumes 3 hours fills repairs deep pit. Following pushes into natural gas heat treatment furnace constant temperature bakes 24 hours, again puts out naturally cools. This set repairing process walks finished, calendar already towards back flipped whole 7 days.
Valve body stuck at flaw detection link comes not out, assembling workshop only can dryly stare eyes. 1.2 meters long valve stem, diameter 400 millimeters hand wheel, still has whole 24 pieces high strength connecting bolts, all lie at assembling area shelf on dropping ash. Several assembling workers counting days, continuous 5 days gets not piece-rate sheet.
Outsourcing wooden box factory custom made plywood packing boxes early just delivered. Long wide each 1.5 meters, high 2 meters big boxes neatly piles placed at big door outside. Originally scheduled this month 15th needs to packs boxes sends away, valve still at queuing waiting re-inspection film. Wooden boxes at outside sun baking rain soaking 10 days, edges corners receiving damp opening cracking, factory inside only can spends money buys 50 meters one roll thick plastic film goes wraps reinforces.
delivery time pressure
Repair time and cost
One piece long 43 centimeters, wide 35 centimeters industrial X ray film on, penetrates out a compared to rice grain slightly big emitting light spot. Film appraiser takes magnifying ruler measured a bit, this is a long 12 millimeters, wide 8 millimeters internal hole. Buyer according to ASME B16.34 standard gives out highest grade 1 grade no defect requirement, this heavy reaching two tons 24 inches carbon steel valve is original road returned back general assembly workshop. Originally already twisted tight several tens pieces bolts needs to entirely tears open, only is transports back several hundreds meters outside sand cleaning area, forklift master just needs to tosses near half hour.
Needs to take hiding at 50 millimeters thick steel plate deep place hole digs out, worker has to takes a piece clamping 8 millimeters thick carbon rod welding gun. Connects on 350 amperes current, adding 0.5 megapascals pressure strong wind, iron water instantly is blown flying. Hand slightly shakes a bit, good steel just is extra dug dropping several taels. Only is scoops out a deep 25 millimeters, long 40 millimeters pit, worker at sparks inside just needs to squats approaching 60 minutes.
- Several tens degrees electricity and one whole box thick carbon rods at this several tens minutes inside burn into black ash
- Heavy reaching several kilograms angle grinder has to changes on flap disc back forth takes iron rust polishes
- Digging slightly deep will let wall thickness lower than 45 millimeters qualified line thoroughly becomes scrap iron
Quality inspector takes comes a can red color penetrating liquid sprays at emitting light metal concave pit inside. Early winter workshop inside only has 15 degrees Celsius, this kind red chemical water must quietly stay enough 15 minutes, just can seeps into possibly not dug clean naked eye looking not seeing fine cracks inside. Wiping dry after sprays on a layer thin thin white developing powder, if pops out hair strand that thin red line, just now that set grinding actions just has to pushes down comes anew.
Pit bottom confirms clean, enters into extremely consuming time repair welding link. Extremely thick carbon steel extremely fears cold, rawly hard doing welding extremely easily opens cracks. Worker finds comes 10 kilowatts ceramic heating blanket takes surroundings wraps solid, connects electricity bakes to 150℃, still has to constant temperature stuffs on 30 minutes just allowed moving weld. Below zero several degrees severe cold day, preheating temperature needs to hard pulls to 200℃. Welder from 350℃ heat preservation tube inside pulls out 3.2 millimeters thick electric welding rod, one piece following one piece towards pit inside fills entering several thousands degrees iron water.
Welding gun moving speed is deadly fixed at every minute 120 millimeters. Every paves finishes thin thin one layer, has to takes pneumatic pick takes surface hard shell knocks breaks blows clean, takes measuring temperature gun measures a bit, drops to 250℃ below just can paves second layer. Fills full this not standing out small concave pit, old welder continuous at piercing eyes strong light under operation exceeding 3 hours, hand side throws down ten-plus pieces abandoned welding rod heads.
- Several tons heavy big guys queuing waiting enters big fire furnace often consumes three four hours
- Six burners simultaneously opens fire at every hour less than 100℃ speed slowly boils
- Steel at 620℃ red hot state under is forcefully required stays enough whole 120 minutes
Several hundreds megapascals internal pulling tearing force leaves at just now repaired passed place, must relies on big fire furnace slowly anneals eliminates. Cuts off power supply after refractory furnace door closes tightly seamlessly, needs to wait iron blocks at inside naturally cool thorough to 300℃ below just can drags out, night shift 8 hours just this dryly consumes passes. Waiting until several hundreds kilograms high pressure steel shot takes baked black surface newly grinds into gray white color, again is small half day passed. Flaw detector again takes several tens kilograms heavy radioactive source instrument moves to front.
Lets gamma ray penetrates just repaired good steel plate, needs hard boils 15 minutes exposure period. Takes film washes out hangs at developing lamp under one look, supposing even if one piece welding rod received a bit damp, inside just will pop out a diameter 2 millimeters small bubble. Meeting this piece small bubble, from air gouging scooping pit, angle grinder grinding, heating blanket baking hot, repair welding to stuffs into big fire furnace slowly anneals, yesterday walked passed ten-plus hours all has to original appearance again walks one time.
Construction period compression
Purchasing contract on covers bright red official seal, originally needs 45 days just can walks finished carrying RT flaw detection valve order, hard rawly is by buyer pressed to 25 days delivery. If late issues goods one day, finance just needs to from tail payment inside deducts total amount 0.5% default money. Facing a piece single price 120 thousands yuan 24 inches big caliber cast steel valve, late delivers half month factory inside just needs to in vain loses ten thousands yuan profit.
According to process table, yesterday just repair welded finished that batch heavy reaching 1.5 tons valve bodies, this morning must stuffs into bogie hearth furnace conducts removing stress annealing. Furnace director looking at back queuing waiting 20 plus pieces raw iron lumps, if honestly according to rule rises temperature to 620℃ again constant temperature bakes 120 minutes, this batch goods absolutely catches not up day after tomorrow’s shipping schedule.
Just welded finished groove still emits remainder temperature, originally scheduled entering furnace valve body is by forklift secretly transported to workshop outside empty ground on. Early spring night inside air temperature less than 8℃, mixing water vapor cold wind whooshing towards 50 millimeters thick steel plate on blows. Without long slow following furnace dropping temperature process, metal internal crystal lattice is instantly frozen, several hundreds megapascals pulling tearing force is deadly locked at repair welding area surroundings.
- Furnace one opens one closes consuming 12 hours is hard rawly saved down
- Burner needs to consume dropping near thousand degrees industrial using electricity all exempted
- Surface not passed secondary fire baking even grinding oxide skin effort all saved
Outer surface looks this valve body with normal goods has no any difference, even because not entered furnace less a layer black ash, appears even more shiny bright. Naked eye looking not seeing micro world inside, material yield strength already is forced to limit. Waits installs on pipeline passes into 4 megapascals high pressure steam, weld seam edge as long as slightly receives a bit force, extremely fine micro cracks just will like spider web same rapidly crawls full entire inner wall.
Forced to dead corner not only is heat treatment workshop, flaw detection room inside dark room similarly is staging a field thrilling number game. Film appraiser hand inside that piece magnifying ruler stops at one piece film on, high light lamp shines out a diameter 3.2 millimeters round shape black spot. Buyer’s acceptance drawing on writes clear clear, exceeding 3.0 millimeters pores must digs away newly welds.
Newly welds just has to newly walks one time seven eight days process, delivery period red line early just was stepped broken. Film appraiser takes pen at recording table on hesitated three seconds, hard rawly takes 3.2 millimeters altered writes into 2.8 millimeters. Merely differs 0.4 millimeters, this not qualified 2 grade defective product shaking body one changes, gets green light releasing inspection qualified certificate, grandly is pushed towards general assembly assembly line.
Meeting large area shrinkage holes really covering not over time, even more outrageous forging tricks just will at late night office inside stage. Supplier at archive cabinet inside flips out last month same specification same wall thickness one batch qualified valve film. They take out a branch very thin pencil, takes film top right corner using lead letters typesetting furnace batch number 8841, carefully altering into 8845.
- Finds out one piece pipe wall thickness same is 50 millimeters old film serves as substitute
- Cuts away original film edge carrying last month date exposure mark
- Newly prints one copy containing fake film number inspection report sheet hands over task
In order to deal with buyer stationed at factory inside supervisor personnel, workshop even will arrange workers performs a field fake grinding. Angle grinder at without defect metal surface rubs out several strings sparks, pretends is currently working hard repairing. One copy full of loopholes progress table is submitted to purchasing desk face on, above fills full in order to piece enough 30 days delivery period then reverse deducing fabricated out various nodes time.
| Manufacturing link | Rule doing method consuming time | Extreme compression consuming time | Covering technique details |
|---|---|---|---|
| Defect repairing | 5 to 7 days | 1 day | Only digs surface layer not deep investigates bottom end micro small cracks |
| Weld after heat treatment | 12 hours | 0 hours | Puts outdoor cold wind blows, forges furnace temperature curve chart |
| Ray appraising film | 2 days | Half day | Size exceeds standard 0.5 millimeters hard modifies data judges qualified |
| Film archiving | 1 day | 2 hours | Misappropriates last batch qualified item film tampers numbers hands over task |
Time at factory inside is treated as sponge inside water deadly squeezes. A sum amount exceeding million order, as long as late issues ship one voyage, only port demurrage fee just needs to compensates drops several tens thousands bucks money. Purchaser at office inside looking at on time delivered to site wooden boxes, thinks fought won a beautiful progress defense battle.
Half year after, installing this piece forged valve chemical pipeline started full load trial run. 350℃ high temperature heat transfer oil following pipeline surges in, once by cutting corners saving dropping annealing that piece weld seam, bears not stopping internal stress instantly bursts opens a 15 millimeters long mouth.
Procurement Target Setting
Flips opens large scale petrochemical project purchasing detailed list, marked “ASME B16.34 radiographic flaw detection” words 24 inches cast steel valve delivery period is rigidly filled on 45 days. Not understanding trade purchaser according to conventional 30 days to reverse deduce production nodes, arriving 25th day still is giving supplier madly dialing urging phone calls.
Understands trade buyer drafts contract before, will at calendar on extra draws out 15 days to 20 days preventing risk blank period. A piece heavy reaching two tons WCB carbon steel valve body experiences whole set air gouging, filling repairing weld seam, 620 degrees Celsius big fire furnace annealing, full hit full calculate needs to consumes goes whole 120 hours working hours.
Signs attaching 100% flaw detection requirement order, conventional 35 days manufacturing period outside, must add on at least 10 days repairing standby days.
Sits into casting plant negotiation room, having experience factory inspector fundamentally not asks “fastest several days can deliver goods”. They require flipping reading factory previous 6 months flaw detection film paper register book, specially clearing counting those several stamped blue “return repair” seal numbers occupy how big proportion.
Management qualified casting workshop, 12 inches above big caliber valve body one time shooting film passing rate at least needs to maintain at 65% above. Register book on continuous 10 pieces big valves has 6 pieces all at executing digging repairing actions, even if factory director pats chest guarantees 20 days loads car delivers goods, purchaser absolutely cannot takes words signs down.
- Checks workshop last month flaw detection report verifies returning repairing rate whether breaks through 40%
- Flips finds 50 millimeters wall thickness casting repair welding record book checks annealing heat preservation time length
- Retrieves 3 pieces same type order freight bills looks actual delaying dispatching car true days
Deadly staring delivery period far far not enough, sampling checking factory inside dropping full dust paperwork archives is another line preventing risk defense line. Quality inspection office iron cabinet inside stuffs full various batches bogie hearth furnace heat treatment curve charts. Thin thin printing paper on, temperature climbing slope curve matching high place flat smooth line segments, records several tens hours inside fire heat changes.
Takes scale ruler measures a bit coordinate paper on flat straight line segment, 620℃ constant temperature time in the end enough not enough 120 minutes, one eye clear.
Certain rough processing small workshops will take last month old charts go copying machine on walk one circle deals with inspection. Carefully inspects drawing bottom printing time stamp, quite a few batches originally should differ three five days completed workpieces, curve chart bottom right corner exiting furnace time all squeeze at same one afternoon two ten, forging suspicion extremely big.
Storehouse inside piling placed welding materials consuming ledger, can reveal out returning repairing frequency bottom cards. Single piece 24 inches big valve normal assembling at most receives uses 5 boxes E7018 welding rods. Flips opens last week materials exiting storehouse bill, same batch number 8845 workpiece name under, 3 days inside continuous received walked 18 boxes low hydrogen type welding rods, documents behind casting internal absolutely exists large area micro shrinkage holes.
Prevents factory rushing project period forging, factory inspector will at contract inside sets up several extremely harsh witnessing points holding waiting inspection (Hold Point). Buyer stationed at site supervisor personnel not signs, 50 millimeters thick casting absolutely not allowed sent into grinding room.
Requires factory takes repairing position at drawing on marks out accurate coordinates parameters, connecting with newly shot passed 3 pieces above film originals packaged sends to buyer office reviews. Those merely providing one copy all green releasing report sheet suppliers, compared to providing two three times shooting film repairing records factories even more makes person suspends heart hangs gall.
Takes staring default money numbers energy, divides out two tenths goes checks workshop inside auxiliary materials consuming bills, materials using amounts between huge drop difference will tear drop quality report camouflage.
Takes default money big stick high high lifts up goes frightening person has not much use, blindly urging project period only will urge out one batch saved dropping annealing procedure scrap iron. Purchasing clauses inside paying money nodes completely can follow workshop flaw detection true progress walk.
A sum total price 1 million goods money, three tenths advance payment hits over after, remaining money do not all press at issuing goods loading ship that day. Flaw detection room issues first batch 10 pieces valves true qualified film that day, allocates 20% progress money, forces factory takes human power material power all press at lifting one time shooting film passing rate on.
Buying selling both parties gaming lands at contract clauses white paper black words on. Takes delivery period red line towards back moves 15 days, exchanges comes is flaw detection room inside proper 15 minutes gamma ray exposure, matching bogie hearth furnace inside honest three hours constant temperature slow baking.
Checks previous 6 months not qualified product handling sheets (NCR) accompanying Welding Procedure Specification (WPS) documents, is senior buyer feeling bottom factory family property compulsory course. One copy thick reaching 20 pages, carrying complete 600℃ heat treatment parameters records delaying delivery explanation book, weight far far heavier than one piece hastily signed on time issuing goods guarantee book.





