How to process the inner thread of the stainless steel pipe fittings by

Whether it is stainless steel welded pipe fittings or stainless steel seamless pipe fittings have internal thread, this kind of internal thread is how to process? In fact, the method is relatively simple, tap tapping can be done. Although the process is not complicated, but there are still a lot of places to pay attention to.
Stainless steel pipe material has high viscosity, off chip characteristics, so in the tapping process will inevitably appear chip scraping injury thread of the work piece or the tap blade and other undesirable phenomena collapse, thus the machining efficiency and thread quality will be affected. So from design to manufacture, have to careful careful operation.
The first step is to choose the high quality tap material, such as in order to improve the abrasion resistance and toughness tap, you can in ordinary high-speed tool steel special alloy elements added, or can be in thread surface is coated with titanium nitride coating, such performance will be improved.
In the process, you can increase the tap before the angle and shovel back. But also pay attention to, if too large, in the back of the knife when it is easy to cause some bad phenomenon. For example, tap tap thread edge collapse more edges, tap into after cutting angle and thread finish.
And we in tapping on the stainless steel pipe fittings, tapping processing volume as small as the principle, which can effectively avoid the emergence of some adverse consequences. But before the start of the best customized reamer, ensure the grinding thread grinding angle, and the edge of the anterior horn taps straight face.
If you can be very good to comply with the above requirements, the processing of stainless steel pipe fittings will be more ideal, can meet the needs of consumers.
Source: Zhejiang Yaang Pipe Industry Co., Limited (

How to easily find the welding defects in the welded steel pipe by

Spiral welded steel pipe is a kind of welding pipe, which can be welded in the manufacturing process, and there are many defects in the welding area. This is certainly detrimental to the quality and performance of the welded tube, so if we can make it clear that the causes of these defects can be resolved in a timely manner.
1, bubbles
This situation generally occurs in the weld center position, is mainly due to the presence of hydrogen bubbles form. To eliminate such defects, it is necessary to remove the impurities in the wire and weld, including rust, oil, water and moisture, such as material. Then the moisture removal, plus appropriate current increase and decrease of welding speed and slow down the melting metal solidification rate, there will be significantly improved.
2, sulfur crack
This is because the sulfide in the sulfur segregation band is brought into the weld metal in the welding process, which produces a number of cracks. In order to prevent this, as long as the use of sulfur segregation with a small semi killed or killed steel can be, but do not forget the weld surface and flux cleaning and drying is also very necessary.
3, thermal crack
To eliminate the crack is relatively simple, as long as the arc and the arc extinguishing installation of a pad, also in volume of at the end of the weld, the spiral welded steel pipe is reversed and the welding stitch welding. And this crack in the welding seam stress is very large, it is particularly easy to appear, so be sure to control the stress of the welding seam.

Easily identify the defects in the weld zone, we can promptly put the crisis to kill, to ensure that our spiral welded steel pipe is not defective.

Source: Zhejiang Yaang Pipe Industry Co., Limited (

Stainless steel flange stud tip section creep variable by

With neck butt welding of stainless steel flange connection within the flange surface temperature of 573 k load. Stainless steel flange and stainless steel pipe outside surface without applying thermal insulation layer, considering the air layer between the flange and bolt hole air layer, fluctuation on the surface of the stainless steel flange surface heat transfer effect the temperature distribution of the system. External surface of the stainless steel flange, bolt and nut and air contact parts, applying equivalent convective heat transfer coefficient, air layer and the upper and lower flange bolt hole air layer between the exert their equivalent coefficient of thermal conductivity.
Along the gasket by radial temperature gradually reduce outside introversion, temperature difference between inside and outside about 16 k.
On both ends of the bolt temperature from the intermediate section to reduce gradually, and along the outer diameter of flange cover to gradually reduce from the inside-out. Nut and flange interface in the highest temperature, this is because the temperature of the bolt and nut first is passed by the flanges here, in addition, flange material coefficient of thermal conductivity is bigger than bolt hole equivalent coefficient of thermal conductivity of air layer. Gasket stress along the radial distribution of the comparison operation conditions, the gasket seal pressure should not be below mP = 9 for gasket coefficient, take 3; P for the internal pressure, take 3 MPa).
After gasket stress is more than 9 mpa, will not leak. But because the gasket will occur under high temperature creep, compression is more and more big, the amount of springback ability worse and worse. When creep variable is small, but if the gasket stress is greater than the mP, gaskets should not leak, the hydraulic flange without hot tight; But when the worm variables is larger, the gasket stress may be less than mP, gasket leakage will happen at this time, need to consider the hot tight. Operating conditions of bolt stress distribution along the length direction of the inner stress distribution, stress distribution along the length direction plate flange lateral. In length to 0, and 100 mm respectively stud two points, the inside of the cross section at the top and bottom section length of 0 and 100 mm respectively stud section at the top and bottom section of the lateral of the two points. Blind flange on the maximum stress occurs in the nut and the upper and lower flange near the contact position, less stress on both ends.

Contrast is bolt due to bending moments, the inner tension and the lateral pressure, the pre-tightening force and bending moment under the joint action of the medial tensile stress is larger, the lateral smaller. After add internal pressure butt weldingflange bolt stress distribution in whole with a preloaded consistent, but the stress increase. Flat welding flange on both ends of the stress increased obviously after heating, other position slightly increased.

Source: Zhejiang Yaang Pipe Industry Co., Limited (

What are the general requirements of pipe fittings in petrochemical industry

What are the general requirements of pipe fittings in petrochemical industry
(1) the valve and other static sealing joints should be installed in the vicinity of the satinless steel pipe support point;
(2) in addition to the special requirements of the process, the tower, reactor, vertical vessels and other equipment in the skirt of the pipe shall not be arranged on the flange and threaded joints;
(3) machine pump lubricating oil system of satinless steel pipe, conveying solid deposition and slagging medium satinless steel pipeline shall be divided into sections and is provided with flanges. satinless steel pipe elbow not lubricating oil pump system each section of the satinless steel pipeline on more than 2;
(4) the end of the lubricating oil system of the machine pump lubricating oil system;
(5) the different diameter satinless steel pipes on both sides of the regulating valve should be close to the control valve;
(6) with different diameter flange connection, the transmission medium to large caliber caliber should be brought to.
(7) elbow should be selected curvature radius equal to 1.5 times the nominal diameter of the long radius elbow; gas transportation of solid and liquid solid two phase flow material of satinless steel pipe shall be used in the large curvature radius of elbow;
(8) province corridor level adjustable satinless steel pipe connection, if no special requirements, should use the end flat eccentric different diameter satinless steel pipe, vertical satinless steel pipe should be selected concentric different diametersatinless steel pipe;
(9) for the centrifugal pump suction level, when the entrance satinless steel pipe diameter, should be set in eccentric different diameter satinless steel pipe near the pump at the entrance. When the satinless steel pipeline from the down to the upward progress of the pump, should be used to install flat, when the satinless steel pipe from the pump down into the pump, it is appropriate to use the bottom flat;

(10) flange should not be directly connected with the elbow without straight satinless steel pipe;

Source: Zhejiang Yaang Pipe Industry Co., Limited (

Cause of rust and pollution of stainless steel pipe and notice by

Stainless steel pipe products with excellent corrosion resistance, and not easy to rust, it is as I mentioned earlier, its composition containing chromium elements. Combines with oxygen in air and solid surface and form a tight-knit not state oxide, this does not scale membrane can prevent the steel surface oxidation (rust), and can play a role of protecting surface, in order to prevent the corrosion of various corrosion factors.

As a result, such skin membrane corrosion if for some reason, and damage, and in the chromium and oxygen cannot junction, so will start to rust stainless steel pipe.

1. When the road construction, construction engineering, or walking all kinds of vehicles, by its flying sand soil, dust, iron powder, such as the attachment.

2. By cars, buses and other harmful material such as sulfurous acid content in the exhaust gas pollution.

3. Affected by various industrial and mining waste incineration, building warm and cool gas and dust, elimination of harmful ingredients in exhaust pollution.

4. The hot spring area produce corrosive gas pollution.

5. Polluted by coastal sea breeze contains salt adhesion.

6. The cleaning solution to pollution. Polluted by grain hands dirty.

7. Protected by surface with mucous membrane pollution.

However, as long as eliminate corrosion reason and make chromium can combine with oxygen, so that will produce again not scale membrane, and restore its corrosion resistant function. stainless steel pipe, which is a metal which is not easy to rust, but not absolutely not rusty metal. On the basis of different conditions of use or the use of the environment, will also be contaminated and rust. You don’t think stainless steel pipe is not rust, neglect the daily maintenance, wait for contamination, rust is the most serious, and in a ticket to do clearance, such measures are the most down.

Make the stainless steel pipe with pollution, the cause of the rust, have a lot of kinds, but in general, are affected by composition of phytoplankton iron powder or harmful gas in the atmosphere, because of adhesion, accumulation, and the wind caused by salt contained in the attachment. These attachments will gradually gathered, add moisture and fixation, so that damage does not scale membrane on the surface of the stainless steel pipe, and breach of the skin membrane regeneration effect, and stainless steel pipe began to rust.

The rust of the initial state, do clear is more simple, can restore the original state. Even after long placed, as long as the proper cleanup, also can restore the appearance of the slightly different than the original condition. So that the rust of the stainless steel pipe, it’s just the surface, rather than the corrosion of material itself. This and raw steel rust, is fundamentally different. Therefore, stainless steel pipe can sometimes be rusty, but as long as they often do maintenance, you can always keep the stainless steel pipe was beautiful.

Source: Zhejiang Yaang Pipe Industry Co., Limited (

Automatic welding technology and process control of pipeline

Pipeline all position automatic welding refers to the relatively fixed in the pipe, welding pipe car drive the welding torch along the orbit around the tube wall motion, so as to realize the automatic welding. Generally speaking, the whole position automatic welding device is composed of welding pipe trolley, running track, automatic control system and so on. The purpose of developing a fully automatic welding equipment is to improve the welding quality and productivity, to reduce the labor intensity of workers.
Welding pipe trolley
Welding pipe car is to realize automatic welding process of the driving mechanism, which is installed in the welding track, with a torch along the pipe wall of the circular motion, it is one of an important link of the pipe automatic welding. Welding pipe trolley should have the characteristics of beautiful appearance, small size, light weight, convenient operation and so on. The core part of it is walking wire mechanism and welding torch swing mechanism, regulating mechanism of feeding. Walking mechanism is composed of a motor and a gear transmission mechanism and the walking motor execution of the computer control unit sends the position and velocity command, the motor should be with speed feedback mechanism, in order to ensure the motor in pipeline girth seam of each location accurate positioning, but also has better speed tracking function. The wire feeding mechanism must ensure that the wire feeding speed is stable and accurate, with a small moment of inertia, a better dynamic performance, and at the same time, should have sufficient driving torque. And welding torch swing adjusting mechanism should have the torch relative weld left and right swing, left and right end of the stay, up, down, left and right attitude controllable torch angle can be adjusted. Welding pipe of the various parts of the car, the computer can be programmed to achieve automatic control, after the program started, the welding pipeline car parts in accordance with the procedures of the logical sequence of coordination. In the process of welding, the welding parameters can be automatically adjusted according to the amount of the intervention, and the welding parameters can be adjusted according to the amount of the intervention.
Welding track
Rail is clamped in pipe for welding pipeline trolley walking and positioning of a special mechanism, its structure directly affects the welding pipe car walking stability and positional accuracy, also affects the welding quality. The rail shall satisfy the following conditions: convenient installation and disassembly, easy positioning, reasonable structure, light weight, strength and hardness, wear resistance and corrosion resistance. Orbit is divided into two kinds of flexible track and rigid track. The so-called rigid track is that the body of the track is larger, not easy to deformation, and the flexible track is relatively rigid track. Two types of tracks each have their own characteristics. Rigid track positioning accurate and clamping deformation small, can ensure welding pipe car running smoothly, welding torch radial adjustment is small, but the weight of large, demolition is not convenient. The flexible rail is easy to install and remove, the weight is light, and the precision is not high.
Wire feeding mode

The smooth degree of wire feed directly affects the welding quality. Wire feeding method can be divided into two types of wire drawing and wire drawing. Wire drawing welding gun from send silk machine installation location is near, welding wire fittings left to send silk machine after being subjected to the smaller resistance. Therefore, it can guarantee wire feeding process is stable, but sent wire machine and wire set shall be installed in the pipeline welding car above and increases welding pipe car weight, to manual assembly disassembly increases the difficulty, increase the weight but also easy to cause pipeline welding trolley is not smooth. Diameter of 0.8 mm or 1.0 mm small wire (weighing about 5 kg) reduced the welding pipe car weight and load, and the welding process is easy to control, but the welding efficiency has certain influence.

Source: Zhejiang Yaang Pipe Industry Co., Limited (

Chemical piping design and layout By

Chemical piping design and layout of content mainly includes the design and calculation of pipeline and pipeline layout design of the two parts content. Calculation in the design of pipe including pipe diameter, pipe pressure drop calculation, pipe insulation thermal insulation engineering, selection of pipe stress analysis and thermal compensation calculation, pipe fittings, calculating steam-water pipes and other content; Piping layout design of the main content is to design drawing said pipe connection in spatial position. The valve parts, pipe fittings and control instrument installation of pattern. Specific content as follows.
(1) to choose pipe material. According to the chemical nature of the medium, flow, temperature, pressure and other factors. Economic and reasonable to choose pipe material.
(2) to choose medium velocity. According to the state of the nature of the medium, conveying, viscosity, composition, and connected to the equipment, flow, etc. With reference to the table data. Choose reasonable and economical medium velocity.
(3) determine the pipe diameter. According to the medium flow rate and flow velocity. Through calculation, graph or table. Determine appropriate diameter.
(4) determine the wall thickness. According to the pressure of the medium and the selection of pipeline material, wall thickness is determined. In fact, given in the table of pipes. Selection of pipe wall thickness is limited. According to the nominal pressure of the selected wall thickness are generally can meet the requirements of the strength of the pipe. For pipeline design. Often choose some medium pressure. Or wall thinner pipe. Pipe strength check, to check up on the wall thickness of the identified whether meet the requirements.
(5) determine the pipeline connection. Between pipe and pipe, pipe and equipment. Between pipe and valve. There is a connection between equipment and valves method problem. There are connections, such as diameter range also has a diameter connection, according to the pressure of pipes, pipe diameter, medium, properties, USES, the use of the equipment or pipeline maintenance state, determine the connection mode.
6. Valves and pipe fittings. Medium in the process of transportation pipe. There are points, close, turn, variable speed, etc., in order to ensure the safety of the process requirements and. You also need to various types of valves and fittings. According to the situation of equipment layout and process, the safety requirements. Choose the right elbow, tee, reducer, flange pipe fittings and all kinds of valves, etc.
All landowners to choose pipe thermal compensator. Pipelines often there is temperature difference during installation and use, winter and summer use often also has very big difference in temperature, in order to eliminate the thermal stress. The first thing to calculate the heat pipe expansion length. Then the method of eliminating thermal stress is considered: when the low thermal expansion length by the turning of pipe, pipe, fixed compensation nature; When large thermal expansion length. Should from the waveform, square, arc, sleeve type etc. Various kinds of thermal compensation to choose the appropriate thermal compensation form.
Today adiabatic forms, the thickness of the insulation blanket and thermal insulation material selection. According to the characteristics and technical requirements of pipeline medium, selected adiabatic approach: thermal insulation, heat protection, or cold. Then according to the medium temperature and the surrounding environment. By calculation or look-up table to determine the tube wall temperature. Then by calculating, table or graph to determine the thickness of the insulation blanket. According to the pipe environment (vibration, temperature, corrosive), the service life of pipelines, based on convenience and cost factors, choose the appropriate thermal insulation materials and auxiliary materials. Need to mention is. Should calculate the heat pipe heat loss. And other design team to provide information.
Pet-name ruby piping layout. First of all, according to the production process, the nature of the medium and flow, the position of the related equipment, environment, operation, installation and maintenance, and so on and so forth. To determine the pipeline laying way – in Ming or dark set. When second pipeline layout, arrangement in vertical plane and horizontal and configuration. The distance between the tube and tube and distance of the wall, pipe grade. Pipe wall and floor. Connect with situations such as pipeline and equipment, in accordance with the relevant provisions.

Attending to calculate pipeline resistance loss. According to the actual length of pipe. Pipe connected to the equipment, the relative elevation of the pipe, tube medium. The actual velocity and medium flows through the pipe fittings, valves, etc. To calculate the pipeline resistance power loss. In order to check check the selected pump, to choose equipment, pipeline, etc. The foregoing steps is correct and reasonable. Reporting loss calculation of the pipeline resistance, of course. Not all the pipe are all calculated. Want to choose some typical pipe is calculated. When problems arise, or change the pipe diameter. Or change the pipe fittings, valves, or re-election of transportation equipment or other equipment such as pump capacity.

Source: Zhejiang Yaang Pipe Industry Co., Limited (

Manufacture of stainless steel reducer with different diameters by

Stainless steel reducer is used for pipe diameter changes in a pipe. Usually adopted for reducing the forming process of pressing, expanding to suppress or reducing and expanding, to certain specifications of the stainless steel reducer and stamping can be applied.
A. stainless steel reducer forming/hole enlargement
Stainless steel reducer forming technology is will be equal and reducer big end diameter of tube rounds into the forming mould, through along the axial direction of tube billet, shrink along the cavity movement and metal forming. According to the size of the stainless steel reducer, divided into the one of pressing or more press forming.
Forming hole diameter is less than stainless steel reducer big end diameter of the tube billet, used in die forming along the tube billet diameter hole enlargement. Hole enlargement technology mainly to solve the stainless steel reducer in the variable diameter is larger not easily by reducing forming, sometimes according to the requirements of the materials and products forming, expanding and reducing method of combination.
In the process of reducing or expanding deformation, according to different materials and variable diameter, determination by cold pressing and hot pressing. Under normal circumstances, as far as possible by cold pressing, but the multiple variable diameter and cause serious work hardening of the thick or alloy steel, wall thickness of materials appropriate USES hot pressing.
B. stamping
In addition to the use of steel tube as raw material to produce stainless steel reducer, the part of the specifications of the stainless steel reducer can also be used steel plate stamping forming technology is adopted to improve the production. Drawing die shapes used by reference to reducing tube surface size design, use after blanking punching die, stamping steel stretch forming.
The stress distribution and deformation characteristics:
(1) the inner pressure function similarly hereinafter heart stainless steel reducer an area about the size of the pressure difference between the bending moment caused by big end is relatively open, small end relative shrinkage phenomenon;

(2) the internal pressure under the action of eccentric reducer in central eccentric side inside the big end surface and eccentric side to the outer ring stress is the largest.

Source: Zhejiang Yaang Pipe Industry Co., Limited (

Brief introduction of pipe fittings manufacturing process and analysis of the weak parts

Inspection personnel to implement incoming inspection before should be understanding pipe fittings manufacturing process, clear the weak link in the pipe. The scientific inspection technology and advanced inspection methods, determine the reasonable proportion of sampling and testing focus, effectively play the role of quality control and check.
Elbow for changing the direction of the pipe fittings, seamless elbow and welded elbow, the seamless elbow mostly adopt hot pushingpipe method manufacturing is straight pipe set on the mandrel, mandrel head for bending of the core head (or horn shaped core head), ox horn core head by induction heating, the external forces are applied at the other end of the pipe section, in the induction heating and under the action of external force, straight pipe push made certain curvature radius of elbow. Mainly to the welded elbow plate is pressed into a certain shape and then welded. Can also be used to push and seamless steel pipe.

According to the manufacturing process of the seamless elbow, the outer side of the elbow is in tension stress state, and the wall thickness is easy to be thinned, the inner side is in the stress state, and the wall thickness is easy to be thickened or folded. For weld elbow, the weld seam is a complex part of stress distribution, which is easy to produce crack and weld defects.

Source: Zhejiang Yaang Pipe Industry Co., Limited (

The strain method of Y type tee by

Y type tee needed feeding strain method, forming manipulation of the most difficult because wall thin, its primary forming difficulty lies in along the axial feeding, under the effect of axial force, if the lack of internal pressure head instability wrinkling is easy to attack, especially the y-shaped tee as fill material than the big, unilateral mending shoes than T tee tube internal high pressure forming, so the wrinkling control more difficult. Progressive forming inner pressure, however, branch item of easy cracking attacks caused excessive thinning, and, if the internal pressure booster has shaken or it is no good opportunity, again after corrugate pipe will attack craze, namely two shortcomings exist together, as shown in figure 3 b. This article through the manipulation of the inductive skills measures such as loading path, and to prevent wrinkling and cracking defects, the end of the ultra-thin y-shaped tee forming. For aerospace tee pipe fittings need all the thin-walled aluminum alloy, choose 5 kneading a03 aluminum alloy pipe, the internal high pressure forming aluminum alloy tee for discussion. Its head diameter D – 40 t, branch pipe axis and head Angle, branch pipe diameter D = 36 t. Its diameter-thick ratio reaches 40, director of wrinkling and branch pipe, high pressure forming crack is still need some processing of key problem. In the 1960 s of hydraulic bulge forming tee skills, forming pressure is less than 30 mpa, forming precision; In the 1990 s, because of the ultrahigh pressure and computer manipulation skills break, the rapid development of internal high pressure forming ability, for the thin-walled tube all the multipass fine supply for more than a new skill path through seminars and use first touch the T tube high pressure forming t-pipe, Y type tee and cross cross pipe, etc., meantime y-shaped tee because of the asymmetry, forming the most difficult.
T type tee in thin-walled tube high pressure forming, the German experts put forward T tee tube high pressure forming mould clamping force, axial feed force, backstepping punch, plastic pressure formula for technology parameters, such as budget, axial instability criterion was deduced. Experts in the United States, when the pressure is not high, friction is satisfied with the coulomb’s law; In contact pressure near the pipe metal at the stress of the event, need to introduce the pure shear stress model, gives the branch pipe pushing force calculation formula of the punch, a beneficial effect to prevent the top of the branch pipe cracking. Japanese expert seminar elongation, hardening exponent and the filling rate of the data on the effects of aluminum alloy T tee branch pipe height. Primary discussion of the wall thickness is larger domestic experts T hydraulic extrusion forming t-pipe, choose low pressure, three-way pipe diameter and thickness ratio (hereinafter referred to as diameter-thick ratio) is less than 3518 ~ 1 ยจ, less, high pressure forming aspects for discussion.
American experts on the internal high pressure forming technology parameters of Y type tees budget to choose stainless steel tube billet diameter thick than 34, developed the branch Angle for 600 Y type tee. Shanghai jiaotong university, this paper introduces a y-shaped tee hydraulic extrusion mold equipment, can make the biggest diameter tee thickness ratio.
The article first introduces Harbin industrial university in Y type tee tube high pressure forming over the years has made some research achievements, especially in diameter-thick ratio of 183 stainless steel Y type tee and diameter of 40 ratio of thick aluminum alloy y-shaped three-way tube internal high pressure forming research results. Pressure forming, because branch and director of the Angle, the branch of obtuse Angle side and acute side, information activity, difficult for shoes also is different. To grasp the tee both sides decided to fill capacity is remind mending shoes in Y type tee forming, the influence of the obtuse Angle to fill recycle ratio and acute side filling capacity is define as the loading ratio, the stainless steel thin wall tee practice feeding ratio 5.0.
Because of lower aluminium alloy material plastic, after adding preform has the tee pipe fittings of internal high pressure forming process, the preform and the end tee pipe fittings as shown in figure 4. Branch pipe maximum height of 0.71 D. The obtuse Angle side filling capacity is a practice of 1.22 D, and acute side filling rate of only 0.06 D, the loading ratio has reached 20, can all the loading along the obtuse Angle lateral side.
Because with thin wall and aluminum alloy pipe and steel mould friction coefficient between data to a district activity comparison difficult, in the process of axial feeding easy corrugate faults, as shown in figure 5 a. Together, because of the aluminum alloy material hardening exponent only 0.23, far below the stainless steel material, the forming process is used for the top branch crack faults, usually along with the wrinkling and cracking, and this shortcoming is similar to that of a thin-walled stainless steel tee forming, as shown in figure 5 b. As long as after forming difficulty preform differentiation, and reasonable control loading paths, the ability to prevent faults, shape and dimension satisfied with the requirements of the parts. For all components in aerospace lightweight piping system to supply a new path.

Internal high pressure forming has a forcing all the forming characteristics of single section components, can use hollow pipe material to make all the variable cross-section components, so in aviation, aerospace and car parts to improve the internal flow field, such as cutting seam, progressive components reliability, progressive fatigue strength, etc.

Source: Zhejiang Yaang Pipe Industry Co., Limited (