A kind of production method of plastics coated tube
Technical field:
The present invention relates to pipe technology field, a kind of production method of plastics coated tube is specifically related to.
Background technology:
The coating pipe of steel pipe has the steel pipe of galvanized pipe, plating aluminum pipe, chromium-plated tube, aluminizing pipe and other alloy-layers.Coated pipe
There are external coating pipe, undercoating pipe, inside and outside coating pipe.The coating generally used have plastics, epoxy resin, coal tar epoxy with
And the corrosion-inhibiting coating material of various glass moulds.Coating steel pipes are through powder melts spraying technology in inwall(Outer wall also may be used when needing)Coating
Plastics are formed, its excellent performance.Compared with galvanized pipe, with anticorrosive, non-corrosive, not incrustation, it is smooth it is smooth, clean it is nontoxic,
The advantages of service life is long.According to test, the service life of steel-plastics composite pipe is more than the three times of galvanized pipe.Compared with plastic tube,
With high mechanical strength, the advantages of pressure-resistant, heat-resist.Because matrix is steel pipe, so in the absence of brittle, problem of aging.Can
It is widely used in the conveying of the fluids such as running water, coal gas, chemical products and heating engineering.
Plastic-coated steel is to apply plastics on the basis of large-caliber spiral welded tube and ratio-frequency welded tube to form, can be according to different need
Want application of polyvinyl(PVC), polyethylene(PE), epoxy resin(EPOZY)Etc. the plastic coating of various different performances, adhesive force
Good, corrosion resistance is strong, is resistant to strong acid, highly basic and other chemical attacks, and nontoxic, not corrosion, wear-resisting, impact resistance, osmotic-pressure-tolerant are strong,
Pipe surface is smooth, and any material is not adhered to, can reduce resistance during conveying, improves flow and transfer efficiency, reduces delivery pressure
Power is lost, and by updating the Recipe of powdery paints, makes the respective coatings performance to be formed is more prominent to have become certainty.
It is solvent-free in coating, material can not be oozed out, thus conveyed medium will not be polluted, so as to ensure the clarity and health of fluid
Property, -40 DEG C to+80 DEG C scopes can cold cycling be used alternatingly, not aging, be not cracked, thus can be severe in cold zone etc.
Used in the environment of quarter.
Existing technique, such as Chinese patent application CN101823044A disclose a kind of steel pipe inside and outside wall powder spraying, curing
The method of film forming integration, using movable type spraying and heating apparatus, makes powder spray and heating cure carry out simultaneously, using leading
Leading-in device, makes the heating and spraying of steel pipe at the uniform velocity advance, steel pipe sets up in orbit along orbital direction, and railcar is across steel pipe
On, interior spray gun is erected on travel(l)ing rest and is placed in steel pipe, and railcar and travel(l)ing rest are connected to draw-gear by steel wire rope
On, Motionless electromagnetic cartridge heater and outer spray gun in railcar, air pump are connected on electrostatic spraying apparatus by ventilation duct, electrostatic spraying
Device is connected in railcar and interior spray gun by powder delivery hose.Synchronously spraying, Synchronous Heating are solid for this mode inside and outside wall
Change, simplify processing procedure.Moreover, the mode of this synchronous spraying has become the main flow in market.But, defect is as follows:
1st, steel pipe is fixed, cause it is outer spray it is uneven, i.e. bottommost sprayed coating is thin, 2, inside and outside spray gun move to opposite side from side,
Reset again;Then the spraying of next steel pipe could be carried out, it is inefficient, and also Powder Recovery is under-utilized, plastic-coated powder wave
Take serious.3rd, travel(l)ing rest is by steel wire traction, and existing defects are as follows, and support is located in pipeline, easily produces spraying position
Cut, 4, rope traction makes travel(l)ing rest when pipe end takes out, or be placed into not easy to operate during other end original position.
There are problems in the 5th, Synchronous Heating solidification, because electromagnetic heating device can not cover pipeline entirety, and electromagnetic heating device is constantly transported
It is dynamic, cause heating uneven, solidification effect is bad.So, abandon the mode of Synchronous Heating solidification substantially at present, and use system
One case that is heating and curing, can accommodate whole steel pipe and carry out overall heating.
To solve upper part technical problem, occur in that some rigid spray guns, i.e. steel tube end part set up spray gun on the market,
Spray gun is promoted to advance by moving cart, laying track in moving cart bottom still, the other end is moved to from pipeline one end, sprayed
Rifle length is long to cause end to be trembleed, inequality of dusting, moreover, long pipeline necessarily supports the track of the moving cart of spray gun
Distance increase, adds floor space, greatly reduces plant area's utilization rate.But reduce the length of rigid lance but can not solve
Certainly longer pipeline(Such as more than 8 meters)Spraying.In view of this technical problem is, it is necessary to simple, the user that a kind of method occurs
Just, it is possible to increase production efficiency, it is to avoid spray gun vibration, the producer for the uniform and high a kind of plastics coated tube of powder using efficiency that dusts
Method.
The content of the invention:
It is an object of the invention to overcome shortcoming present in prior art there is provided a kind of method is simple, easy to use, energy
Enough improve production efficiency, it is to avoid spray gun trembles, a kind of production method for the uniform and high plastics coated tube of powder using efficiency that dusts.
To achieve these goals, the invention provides a kind of production method of plastics coated tube, wherein, comprise the following steps:
A. steel pipe is put into pickling tube, carries out acid pickling and rust removing operation,
B. the steel pipe after pickling is rinsed well and dried with clear water, standby,
C. to the steel pipe heating in medium frequency obtained by step B,
D. electrostatic spray is to the inside and outside synchronous plastic-coated of steel pipe,
E. it is heating and curing,
F. Temperature fall.
Step D carries out plastic-coated operation using electrostatic spraying line, and electrostatic spraying line includes steel pipe conveyer, trypsin method dress
Put, inner spray coating device and powder recovering device.
Steel pipe conveyer includes being provided with two moving carts, the bottom of moving cart on process track, process track
Road wheel is provided with, road wheel matches with process track, the top of each moving cart is integrally formed to be provided with slide rail, often
Two motor cabinets are slidably connected on slide rail in individual moving cart, the side of motor cabinet is provided with frame plate, and frame plate and movement are small
It is fixedly connected between car, steel pipe rotary electric machine and shaft coupling, the output shaft and shaft coupling of steel pipe rotary electric machine is fixed with motor cabinet
One end of device is fixedly connected, and the other end of shaft coupling is provided with power transmission shaft, and power transmission shaft is connected with the countershaft of frame plate, in power transmission shaft
Portion is fixed with rotating wheel, and the integrally formed groove for being provided with L shapes in the edge of rotating wheel, steel pipe rotary electric machine passes through shaft coupling band
Dynamic rotating wheel is rotated, and being set up at the groove on rotating wheel in two moving carts has steel pipe, and rotating wheel rotates in place steel pipe,
Two moving carts, to adapt to the steel pipe of different length, are fixed motor cabinet by bolt in the upper distance change of process track
On to slide rail so adjust two motor cabinets distance, that is, the spacing of two rotating wheels is have adjusted to adapt to the steel of different tube diameters
Pipe.
Outer spray coating device includes two work boxs and two groups of work box tracks, and work box track is located at the two of process track
Side, the side of each work box is provided with the outer powder case of spray, and opposite side is provided with collection box, and work box is in n shape, the one of work box
Side wall is fixed with how exclusive spray gun, and adjacent two exclusive spray gun is intersected with each other, and intersecting angle is 30-60 degree, the opposite side of work box
Axle, which is connected with above brush axle, brush axle, is provided with brush spindle motor, and brush spindle motor is located in work box, the output shaft and brush of brush spindle motor
Axle is fixedly connected, and is socketed with suction plastering roller on brush axle, suction plastering roller be provided with superfine fibre textile, collection box blower fan and
Powder falling storehouse, the side wall of collection box is integrally formed to be provided with suction powder mouthful, inhales plastering roller and is located at the side for inhaling powder mouthful, sprays in outer powder case
Pump box is provided with, pump box drives powder in outer lance ejection to outer wall of steel pipe, and the bottom of work box is hooked with backplate backplates
Bottom it is integrally formed be provided with half slot, half slot is the top with steel pipe, sprays outer powder case, the bottom of collection box and is provided with
Road wheel and road wheel matches with work box track.
Inner spray coating device includes spray gun traveling box in two interior spray gun traveling boxes, interior spray gun and the interior powder case of spray and is located at corresponding shifting
The outside of dynamic dolly, the bottom of interior spray gun traveling box is provided with road wheel and road wheel matches with process track, interior spray gun row
Walk and fixing pipe is provided with the middle part of case, extension tube is socketed with fixing pipe, one end end of extension tube is fixed with interior spray gun, extend
One end of pipe is connected by connecting tube with powder case in spray, and both sides are fixed with two groups of regulating bolts above and below the tube wall of fixing pipe, interior
The bottom of spray gun traveling box is fixed with bottom plate, and regulating bolt is threadedly coupled with the top of bottom plate, interior spray gun traveling box, regulating bolt
Precession or back-out so adjust fixing pipe apart from the height of bottom plate, that is, have adjusted interior spray gun apart from the height on ground so that interior spray
Rifle adapts to the steel pipe of different tube diameters and ensures that interior spray gun is suspended from the circle centre position of this steel pipe, sprays in interior powder case and is provided with pump box, pump box
Powder is driven to be sprayed along extension tube, interior spray gun, extension tube is steel part.
Powder recovering device include connect powder groove, connect powder groove and be fixed between process track, connect powder groove positioned at steel pipe just under
Side, work box is across the top for connecing powder groove, and the powder part that outer spray gun sprays, which is fallen within, to be connect in powder groove, connects middle part, the two ends of powder groove
It is integrally formed respectively and is provided with Ji Fenkou, the section for connecing powder groove is semicircle shape, and the bottom for connecing powder groove is plugged and connected with mozzle, many
Individual mozzle is connected by recovery tube, and recovery tube is connected with collection box, and the both sides of the half slot of backplate are integrally formed to be set
Have and rubber flap is hooked with link, link, rubber flap is in semicircle shape, and rubber flap is as two work boxs are moved and then will
The powder connect in powder groove is pushed near Ji Fenkou, and the suction of the blower fan in collection box will inhale plastering roller, the powder connect on powder groove
Suction collection box is simultaneously dropped into powder falling storehouse.
Step D job step is:
First, the spacing of two moving carts is adjusted according to length of steel pipe, and moving cart is fixed to work by fixture block
On sequence track;Spray gun walking in the distance between motor cabinet of each moving cart, regulation is adjusted according to the thickness of steel pipe caliber
Regulating bolt on case, makes the steel pipe that interior spray gun is located at after the circle centre position of such a steel pipe, heating in medium frequency hang in shifting by overhead traveling crane
At the groove of the rotating wheel of dynamic dolly, steel pipe rotary electric machine is synchronous, motion in the same direction, and steel pipe revolves with the rotation original place of rotating wheel
Turn;
Secondly, two work boxs are made to be located at the two ends of steel pipe, interior spray gun is located at the two ends of steel pipe, two interior spray gun traveling boxes
To entering and being 5-10s to the time difference entered, two work boxs are to entering and being 5-10s, two interior spray gun walkings to the time difference entered
Case, the travel distance of work box are set as the 1/2+15cm of length of steel pipe, i.e., interior spray gun traveling box, work box move to steel
+ 15cm locates in the middle part of pipe, then return;Because traveling existence time is poor, after one of them interior spray gun traveling box, work box return, separately
One interior spray gun traveling box, work box have been advanced to close at the 1/2 of length of steel pipe, and seam crossing is repeated to spray.
Stepper motor (i.e. movable motor) is provided with work box, on interior spray gun traveling box, for drive its move or
Retreat.
The present invention carries out powder spray using electrostatic hot spray process, i.e., using high-pressure electrostatic corona field principle, will be applied
Steel pipe ground connection is covered as positive pole, inside and outside spray gun spray nozzle connects high pressure negative electrode, make to form a powerful electricity between spray gun and steel pipe
, steel pipe is after Medium frequency induction coil heats, and pump box produces compressed air and powder is sent into spray gun from powder case, the outer powder case of spray in spray
Spray, the aciculiform electroplax on shower nozzle produces corona discharge, the powder flowed through carries negative electrical charge, in electrostatic field and delivery gas
Double action under, orientation flies to steel pipe internal-surface, with becoming molten condition;Pipeline is sent into baking in curing oven again solid
Change, temperature control is at 225-260 DEG C;Temperature fall, strengthens the adhesive force of powder.Become plastics coated tube.During spraying, spray gun with
There is the inclination angle of 15-45 degree in tube wall.
Advantages of the present invention is:Method is simple, easy to use, it is possible to increase production efficiency, it is to avoid spray gun trembles, and dusts
It is even and powder using efficiency is high.Specially:
1st, it is of the invention by the way of to entering and poor to entering existence time, spray gun in every group, object for appreciation spray gun is reached steel pipe
At 1/2+15cm distances, that is, exist at 15cm repetition spraying, both saved general spray time, improved operating efficiency
Seam crossing perfection docking can be made again simultaneously.
2nd, the present invention is by the way of to entering, i.e., rigid interior spray gun can be the half length of conventional lance, with 12 meters
Exemplified by steel tube inner spray is applied, if 12 meters of extension tube fixes interior spray gun, with motion, extension tube end vibration is serious, largely effects on
Coating quality in pipe.And use to entering mode, reducing the distance of extension tube half, i.e. 6 meters of extension tube can be achieved, vibration
Significantly reduce, coating quality is good in pipe.
3rd, reclaimed while the present invention is sprayed outside by inhaling plastering roller, being returned by Ji Fenkou in powder groove is connect for dropping into
Receive, greatly reduce the waste situation of powder.(Excessive powder in pipe is collected well, only blows to opposite side with from side, and
And be not in the situation of pollution in pipe, and the powder outside pipe becomes easily infected by dust, iron filings etc., so focusing on pipe
The recycling of outer powder.)
Brief description of the drawings:
Fig. 1 is the structural representation of the electrostatic spraying line of the present invention.
Fig. 2 is the structural representation of the steel pipe conveyer of the present invention.
Fig. 3 is Fig. 2 side view.
Structural representation when Fig. 4 is outer spray coating device operation of the present invention.
Fig. 5 is the structural representation of spray gun traveling box in the present invention.
Fig. 6 is the schematic top plan view for connecing powder groove of the invention.
Fig. 7 is the view for reclaiming powder for connecing powder groove of the invention
Embodiment:
Below in conjunction with the accompanying drawings, the present invention will be described.As shown in Fig. 1-Fig. 7, Fig. 1 is the electrostatic spraying line of the present invention
Structural representation.Fig. 2 is the structural representation of the steel pipe conveyer of the present invention.Fig. 3 is Fig. 2 side view.Fig. 4 is the present invention
Structural representation during outer spray coating device operation.Fig. 5 is the structural representation of spray gun traveling box in the present invention.Fig. 6 is the present invention
The schematic top plan view for connecing powder groove.Fig. 7 is the view for reclaiming powder for connecing powder groove of the invention
A kind of production method of plastics coated tube of the present invention, wherein, comprise the following steps:
A. steel pipe is put into pickling tube, carries out acid pickling and rust removing operation,
B. the steel pipe after pickling is rinsed well and dried with clear water, standby,
C. to the steel pipe heating in medium frequency obtained by step B,
D. electrostatic spray is to the inside and outside synchronous plastic-coated of steel pipe,
E. it is heating and curing,
F. Temperature fall.
Step D carries out plastic-coated operation using electrostatic spraying line, and electrostatic spraying line includes steel pipe conveyer, trypsin method dress
Put, inner spray coating device and powder recovering device.
Steel pipe conveyer includes being provided with two moving carts 9, moving cart 9 on process track 11, process track 11
Bottom be provided with road wheel 10, road wheel 10 matches with process track 11, and the top of each moving cart 9 is integrally formed
Two motor cabinets 8 are slidably connected on the slide rail being provided with slide rail, each moving cart 9, the side of motor cabinet 8 is provided with frame
Plate 2, is fixedly connected between frame plate 2 and moving cart 9, and steel pipe rotary electric machine 7 and shaft coupling 1 are fixed with motor cabinet 8, and steel pipe turns
The output shaft of dynamic motor 7 is fixedly connected with one end of shaft coupling 1, and the other end of shaft coupling 1 is provided with power transmission shaft, power transmission shaft and frame
The countershaft connection of plate 2, power transmission shaft is fixedly arranged in the middle of rotating wheel 2, the integrally formed slope for being provided with L shapes in the edge of rotating wheel
Mouthful, steel pipe rotary electric machine 7 drives rotating wheel 6 to rotate by shaft coupling 1, the groove 3 on rotating wheel 6 in two moving carts 9
Place's erection has steel pipe 4, and rotating wheel 6 rotates in place steel pipe 4, upper distance change of two moving carts 9 in process track 11
To adapt to the steel pipe 4 of different length, motor cabinet 8 is fixed on slide rail by bolt and then the distance of two motor cabinets 8 is adjusted,
The spacing of two rotating wheels 6 is have adjusted to adapt to the steel pipe 4 of different tube diameters.
Outer spray coating device includes two work boxs 13 and two groups of work box tracks 19, and work box track 19 is located at process track
11 both sides, the side of each work box 13 is provided with the outer powder case 12 of spray, and opposite side is provided with collection box 18, and work box 13 is in n
Shape, the side wall of work box 13 is fixed with how exclusive spray gun 14, and adjacent two exclusive spray gun 14 is intersected with each other, and intersecting angle is
30-60 degree, another side axle of work box 13 is connected with brush axle 16, and the top of brush axle 16 is provided with brush spindle motor, and brush spindle motor is located at
In work box 13, the output shaft of brush spindle motor is fixedly connected with brush axle 16, and suction plastering roller 17 is socketed with brush axle 16, plastering roller is inhaled
17 be that blower fan and powder falling storehouse are provided with superfine fibre textile, collection box 18, and the side wall of collection box 18 is integrally formed to be set
There is suction powder mouthful, inhale plastering roller 17 and be located at the side for inhaling powder mouthful, spray and pump box is provided with outer powder case 13, pump box drives powder along outer
Spray gun 14 is ejected on the outer wall of steel pipe 4, and the bottom of work box 13 is hooked with the integrally formed setting in bottom of the backplate 15 of backplate 15.
There is half slot, half slot is the top with steel pipe 4, sprays outer powder case 12, the bottom of collection box 18 and is provided with road wheel and road wheel
Match with work box track 19.
Inner spray coating device includes powder case 20, interior spray gun traveling box 22 in two interior spray gun traveling boxes 22, interior spray gun 26 and spray
Positioned at the outside of corresponding moving cart 9, the bottom of interior spray gun traveling box 22 is provided with road wheel and road wheel and process track 11
Match, the middle part of interior spray gun traveling box 22, which is provided with fixing pipe 23, fixing pipe 23, is socketed with extension tube 25, extension tube 25
One end end is fixed with interior spray gun 26, and one end of extension tube 25 is connected by connecting tube with powder case 20 in spray, fixing pipe 23
Both sides are fixed with two groups of regulating bolts 21 above and below tube wall, and the bottom of interior spray gun traveling box 22 is fixed with bottom plate 24, regulating bolt 21
Be threadedly coupled with the top of bottom plate, interior spray gun traveling box 22, the precession or back-out of regulating bolt 21 so that adjust fixing pipe 23 away from
From the height of bottom plate 24, that is, interior spray gun is have adjusted apart from the height on ground so that interior spray gun 26 adapts to the steel pipe of different tube diameters and true
Spray gun 26, which is suspended from the circle centre position of this steel pipe, spray, in protecting is provided with pump box in powder case 20, pump box drive powder along extension tube 25,
Interior spray gun 26 sprays, and extension tube 25 is steel part.
Powder recovering device includes connecing powder groove 5, connects powder groove 5 and is fixed between process track 11, connects powder groove 5 positioned at steel pipe
Underface, work box 13 is across the top for connecing powder groove 5, and the powder part that outer spray gun 14 sprays, which is fallen within, to be connect in powder groove 5, connects powder groove 5
Middle part, two ends be integrally formed be provided with collection powder mouthfuls 29 respectively, the section for connecing powder groove 5 is semicircle shape, and the bottom for connecing powder groove 5 is plugged together
Mozzle 30 is connected with, multiple mozzles 30 are connected by recovery tube 31, and recovery tube 31 is connected with collection box 18, backplate 15
Integrally formed be provided with link 28, link 28 in the both sides of half slot is hooked with rubber flap, and rubber flap is in semicircle shape, rubber
Glue scraper plate is moved with two work boxs and then the powder connect in powder groove is pushed near collection powder mouthful 29, the wind in collection box 18
The powder inhaled plastering roller 17, connect on powder groove 5 is sucked collection box 18 and dropped into powder falling storehouse by the suction of machine.
Stepper motor (i.e. movable motor 27) is provided with work box, on interior spray gun traveling box, for driving it to move
Or retreat.
Step D job step is:
First, the spacing of two moving carts is adjusted according to length of steel pipe, and moving cart is fixed to work by fixture block
On sequence track;Spray gun walking in the distance between motor cabinet of each moving cart, regulation is adjusted according to the thickness of steel pipe caliber
Regulating bolt on case, makes the steel pipe that interior spray gun is located at after the circle centre position of such a steel pipe, heating in medium frequency hang in shifting by overhead traveling crane
At the groove of the rotating wheel of dynamic dolly, steel pipe rotary electric machine is synchronous, motion in the same direction, and steel pipe revolves with the rotation original place of rotating wheel
Turn;
Secondly, two work boxs are made to be located at the two ends of steel pipe, interior spray gun is located at the two ends of steel pipe, two interior spray gun traveling boxes
To entering and being 5-10s to the time difference entered, two work boxs are to entering and being 5-10s, two interior spray gun walkings to the time difference entered
Case, the travel distance of work box are set as the 1/2+15cm of length of steel pipe, i.e., interior spray gun traveling box, work box move to steel
+ 15cm locates in the middle part of pipe, then return;Because traveling existence time is poor, after one of them interior spray gun traveling box, work box return, separately
One interior spray gun traveling box, work box have been advanced to close at the 1/2 of length of steel pipe, and seam crossing is repeated to spray.
The present invention carries out powder spray using electrostatic hot spray process, i.e., using high-pressure electrostatic corona field principle, will be applied
Steel pipe ground connection is covered as positive pole, inside and outside spray gun spray nozzle connects high pressure negative electrode, make to form a powerful electricity between spray gun and steel pipe
, steel pipe is after Medium frequency induction coil heats, and pump box produces compressed air and powder is sent into spray gun from powder case, the outer powder case of spray in spray
Spray, the aciculiform electroplax on shower nozzle produces corona discharge, the powder flowed through carries negative electrical charge, in electrostatic field and delivery gas
Double action under, orientation flies to steel pipe internal-surface, with becoming molten condition;Pipeline is sent into baking in curing oven again solid
Change, temperature control is at 225-260 DEG C;Temperature fall, strengthens the adhesive force of powder.Become plastics coated tube.
Comparative experiments:
By taking the polyvinyl chloride spraying pipeline for producing 12m as an example, first group is used as using background technology CN101823044A.This
Invention is used as second group.Using an interior spray gun, it is that one group of outer spray coating device advances to the operating type of the other end from one end
Three groups.Every group of processing ten, compares and is listed as follows:
Group |
Single pipe processes average time |
Interior spraying effect |
Trypsin method effect |
Powder consumption |
First group |
15min |
There is tomography, it is uneven |
Bottom is thin or nothing |
40kg |
Second group |
5min |
Uniformly, there is 15cm at repetition spraying centre |
Uniformly, there is 15cm at repetition spraying centre. |
20kg |
3rd group |
10min |
It is uneven after 7m because interior spray gun trembles |
Uniformly |
30kg |
To sum up, the inventive method is simple, easy to use, it is possible to increase production efficiency, it is to avoid spray gun trembles, dust it is uniform and
Powder using efficiency is high.1st, it is of the invention by the way of to entering and poor to entering existence time, spray gun in every group, object for appreciation spray gun is arrived
Up at steel pipe 1/2+15cm distances, that is, exist at 15cm repetition spraying, both saved general spray time, improved work
Seam crossing perfection docking can be made while efficiency again.2nd, the present invention is by the way of to entering, i.e., rigid interior spray gun can be
The half length of conventional lance, so that 12 meters of steel tube inner sprays are applied as an example, if 12 meters of extension tube fixes interior spray gun, with motion, prolongs
Long tube end vibration is serious, largely effects on the coating quality in pipe.And use to entering mode, reduce extension tube half away from
From that is, 6 meters of extension tube be can be achieved, and vibration is significantly reduced, and coating quality is good in pipe.3rd, by inhaling while the present invention is sprayed outside
Plastering roller is reclaimed, and is connect being reclaimed by Ji Fenkou in powder groove for dropping into, is greatly reduced the waste situation of powder.(In pipe
Excessive powder collect well, only blow to opposite side with from side, and be not in the situation of pollution in pipe, and
Powder outside pipe becomes easily infected by dust, iron filings etc., so focusing on the recycling of the outer powder of pipe.)