10 kinds of common pipe connection technology

Pipeline connection is a very important link in engineering construction, which is directly related to the quality of the project. With the rapid development of the pipeline industry, there are more and more methods to connect pipelines. However, different pipelines have their own advantages and disadvantages, and also have different uses. The correct selection of connection methods is a skill that engineering personnel must have. The process of this paper summarizes the characteristics of 10 pipe connection methods, and provides relevant pictures and texts for you to learn and exchange.

Threaded connection

It is called screw connection, which connects pipes and valves through internal and external threads. This kind of connection is mainly used for the connection of steel pipe, copper pipe and high pressure pipe.

20210303120949 12375 - 10 kinds of common pipe connection technology

Type selection of threaded fasteners

Type

Characteristics and Application

Bolted connection

Used to connect two thinner parts. The connecting piece is provided with a through hole. There is a gap between the rod and the hole of the common bolt, the processing requirement of the through hole is low, the structure is simple, the assembly and disassembly is convenient, and it is widely used. Transition fit is often used between reamed bolt (GB / T 27) hole and screw, such as H7 / M6, H7 / N6. The connection can fix the relative position of the connected parts accurately. It is suitable for bearing transverse load, but the machining accuracy of the hole is required to be high, so drilling and reaming are often used.

Stud connection

It is used in the situation where one of the connected parts is thick, not suitable for bolt connection, and the thick connected parts have poor strength and need to be removed frequently. Thread holes are machined on thick parts, smooth holes are machined on thin parts, bolts are screwed into thread holes, and nuts are used to compress thin parts. When removing, just screw off the nut without removing the stud. It can avoid the damage of threaded holes on large connected parts.

Screw connection

The bolt (or screw) is directly screwed into the threaded hole of the connected part without nut. The structure is simpler and more compact than stud bolt. It is used for one of the two connected parts is thicker, but it does not need to be removed frequently to avoid damage to the threaded hole.

Set screw connection

To fix the relative position of the two parts, the end of the thread screwed into the threaded hole of the part is pressed against the surface of the other part or into the pit of the other part. The structure of this connection mode is simple, and some parts can be arbitrarily changed in the circumferential or axial position for adjustment, such as the fixing of electrical switch knob.

Countersunk screw

It is used in the situation where the strength requirement is not high and the thread diameter is less than 10 mm. The screw head or part of it is sunk into the connected part. This kind of structure is mostly used in the occasions where the external surface is required to be flat, such as the instrument panel.

Self tapping screw

It is used in the occasion where the connection strength is not required to be high. But the bottom hole should be made in advance. If the self drilling and self tapping screw with drill bit is used, it does not need to prefabricate the bottom hole. It is used for nonferrous metals, wood, etc.

Wood screw connection

Generally used for connection of wood structure. Depending on the hardness of the material and the length of the wood screw, the wood parts can not be prefabricated or made into a certain size and depth of prefabricated holes.

Self tapping locking screw connection

The screw thread is an arc triangle interface, and the screw can be screwed into the preformed hole of metal material after surface hardening to form internal thread. The strength of the internal thread formed by extrusion is increased by more than 30% than that by cutting. The tensile strength of the screw is 800 MPa. With low tightening torque and high locking performance, self tapping locking screw has been widely used in household appliances, electricians and automobile industry.

Fastener assembly connection

The washer and external thread fastener are produced by the standard professional factory and then assembled and supplied in a complete set. In 1988, 23 fastener assembly production standards were issued in China. This kind of connector is easy to use, time-saving, safe and reliable. It is often used in tight connection with fasteners, such as the terminal of electrical cabinet.

Advantages: easy to manufacture and use, reliable connection, easy to use, good versatility, removable and reusable, etc.
Disadvantages: low pressure, easy to rot and leak at the thread.

Basic dimensions and tolerances of inch sealing pipe threads

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

Thread size code

Number of teeth

n

 

Pitch

P

Tooth height

h

Basic diameter in datum plane

Reference distance

Assembly allowance

The effective thread of external thread is not less than

Limit deviation of internal thread diameter

±T2/2

Major diameter (datum diameter)

dD

Pitch diameter

d2D2

Narrow path

d1D1

Basic

Limit deviation

±T1/2

Max

Min

The reference distances are

Basic

Max

Min

Radial

Axial

mm

mm

mm

mm

mm

mm

mm

Number of turns

mm

mm

mm

Number of turns

mm

mm

mm

mm

Number of turns

1/16

28

0.907

0.581

7.723

7.142

6.561

4

0.9

1

4.9

3.1

2.5

23/4

6.5

7.4

5.6

0.071

11/4

1/8

28

0.907

0.581

9.728

9.147

8.566

4

0.9

1

4.9

3.1

2.5

23/4

6.5

7.4

5.6

0.071

11/4

1/4

19

1.337

0.856

13.157

12.301

11.445

6

1.3

1

7.3

4.7

3.7

23/4

9.7

11

8.4

0.104

11/4

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

3/8

19

1.337

0.856

16.662

15.806

14.950

6.4

1.3

1

7.7

5.1

3.7

23/4

10.1

11.4

8.8

0.104

11/4

1/2

14

1.814

1.162

20.955

19.793

18.631

8.2

1.8

1

10.0

6.4

5.0

23/4

13.2

15

11.4

0.142

11/4

3/4

14

1.814

1.162

26.441

25.279

24.117

9.5

1.8

1

11.3

7.7

5.0

23/4

14.5

16.3

12.7

0.142

11/4

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1

11

2.309

1.479

33.249

31.770

30.291

10.4

2.3

1

12.7

8.1

6.4

23/4

16.8

19.1

14.5

0.180

11/4

11/4

11

2.309

1.479

41.910

40.431

38.952

12.7

2.3

1

15.0

10.4

6.4

23/4

19.1

21.4

16.8

0.180

11/4

11/2

11

2.309

1.479

47.803

46.324

44.845

12.7

2.3

1

15.0

10.4

6.4

23/4

19.1

21.4

16.8

0.180

11/4

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

2

11

2.309

1.479

59.614

58.135

56.656

15.9

2.3

1

18.2

13.6

7.5

31/4

23.4

25.7

21.0

0.180

11/4

21/2

11

2.309

1.479

75.184

73.705

72.226

17.5

3.5

11/2

21.0

14.0

9.2

4

26.7

30.2

23.2

0.216

11/2

3

11

2.309

1.479

87.884

86.405

84.926

20.6

3.5

11/2

24.1

17.1

9.2

4

29.8

33.3

26.3

0.216

11/2

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

4

11

2.309

1.479

113.030

111.551

110.072

25.4

3.5

11/2

28.9

21.9

10.4

41/2

35.8

39.3

32.3

0.216

11/2

5

11

2.309

1.479

138.430

136.951

135.472

28.6

3.5

11/2

32.1

25.1

11.5

5

40.1

43.6

36.6

0.216

11/2

6

11

2.309

1.479

163.830

162.351

160.872

28.6

3.5

11/2

32.1

25.1

11.5

5

40.1

43.6

36.6

0.216

11/2

Note:

1. See columns 9 and 10 of this table for the limit deviation of the axial position of the reference plane of the British sealing tapered external thread;
2. See column 18 of this table for the limit deviation of each diameter of British sealing cylindrical internal thread; see column 19 of this table for the limit deviation of axial position of reference plane of British sealing conical internal thread
Among them: 

  • D2 = D2 = d-0.640 327p;
  • D1=d1=D - 1.280 654P.

Thread assembly

After tightening, exposed 2-3 teeth screw tail, remove excess filler, exposed wire teeth brush red lead antirust. The painting width of red lead is consistent, the coating is uniform, and there is no flowing and missing phenomenon.
➤ examples of frequently asked questions

20210303124347 51192 - 10 kinds of common pipe connection technology

Antirust treatment of exposed thread

Welding connection

As the most traditional way of connection, welding connection is also the most commonly used way of connection in daily life. Its main characteristics are that the interface is firm and durable, the sealing degree of the interface is high, and there is no need for frequent maintenance. There are many commonly used welding methods, which will not be introduced here one by one.
20210303124455 78523 - 10 kinds of common pipe connection technology

Advantages: the interface is firm and durable, not easy to leak, high joint strength and tightness, and does not need frequent management after use. Welding has the advantages of saving metal materials, high production efficiency and good joint sealing.
Disadvantages: the welded joint is easy to produce large welding deformation and welding residual stress, which affects the bearing capacity, processing accuracy and dimensional stability of the joint. At the same time, the production stress concentration at the junction of the weld and the pipe (heat affected zone) has a great impact on the fatigue fracture of the joint. Welding defects (crack, air hole, slag inclusion, incomplete fusion, incomplete penetration) are easy to occur in welded joints. The existence of these defects will reduce the strength of the welded joint, cause stress concentration and damage the weld compactness.
➤ weld groove
According to the specification requirements, the groove is generally V-shaped, the groove angle is 60-75 ° and the assembly clearance is 2-3mm.
➤ weld assembly
The misalignment of the inner wall should not exceed 10% of the wall thickness and should not be more than 2mm; the misalignment of the outer wall should not be more than 3mm.
20210303124922 16040 - 10 kinds of common pipe connection technology

Weld groove and assembly dimension

20210303124941 43346 - 10 kinds of common pipe connection technology

Weld assembly method

20210303124952 55212 - 10 kinds of common pipe connection technology

Correction of weld alignment misalignment

20210303125003 99818 - 10 kinds of common pipe connection technology

Pipe weld misalignment

➤ welding

  • 1) After welding, the weld and heat affected zone are pickled and passivated;
  • 2) The brazing of copper pipe shall not be overheated (650-750 ℃), and the residual slag and other impurities at the welding joint shall be removed after welding;
  • 3) No defects such as undercut, slag inclusion, crack and spatter are found in the weld appearance inspection.

20210303125147 84407 - 10 kinds of common pipe connection technology

Brazed connection of copper tube

20210303125157 39307 - 10 kinds of common pipe connection technology

Good appearance of weld

➤ examples of frequently asked questions

20210303125353 98460 - 10 kinds of common pipe connection technology

After the copper pipe is welded, when the solder is fully solidified but not completely cooled, wipe the flux left at the weld with return wire and clean water, and dry it with dry return wire. Then clean paint shall be applied on the weld for one time to prevent corrosion.
After the stainless steel pipe is welded, use stainless steel brush dipped in acid paste to brush the weld until it is white and bright, and then rinse it with clean water; then wipe it with passivation solution, scrub it with cold water, and finally rinse it with hot water and dry it.

Socket connection

In the chemical pipeline, the cast iron pipe used for water conveyance mostly adopts socket connection. Socket connection is suitable for cast iron pipe, ceramic pipe, plastic pipe, etc. It is mainly used in the upper and lower pipes with little pressure.
20210303125724 33930 - 10 kinds of common pipe connection technology

  • 1. Green lead joint: green lead joint is the earliest used joint form of socket cast iron pipe, which has good elasticity, rigidity and seismic resistance, and does not need maintenance after construction. However, lead is a relatively precious metal, which consumes a lot and the project cost is too high. It is mainly used in places with large vibration, such as crossing railway, highway, river bed and emergency repair.
  • Advantages: good interface quality, high strength, good shock resistance, water or pressure test can be conducted immediately after operation, without maintenance. If a small amount of water leakage is found after water supply, it can be repaired by twisting chisel.
  • Disadvantages: large consumption of non-ferrous metals, high cost, so it can only be used in engineering repair or pipeline seismic requirements.
  • 2. Asbestos cement interface: advantages: high strength and good seismic resistance, good water tightness and adhesion. Disadvantages: high labor intensity.
  • 3. Self stress cement interface: advantages: low labor intensity and high efficiency. Disadvantages: only suitable for socket pipe with working pressure less than 1.2MPa, poor seismic performance, not suitable for soft soil and weak foundation.
  • 4. Socket connection of non-metallic pipe: unplasticized polyvinyl chloride pipe: unplasticized polyvinyl chloride pipe: the socket connection of unplasticized polyvinyl chloride is to connect pipes or pipe fittings by means of socket bonding, and it is not necessary to weld the pipe orifice. The FRP pipe adopts socket type connection, which generally requires that the inner diameter of the pipe is relatively large, and the minimum inner diameter that can be seen in the market is not less than 300 mm. If the inner diameter is too small, it is difficult to meet the design of the rubber ring groove on the plug due to the thin wall thickness of the FRP pipe. Most of the glass fiber reinforced plastic sand pipe used in municipal engineering water supply and drainage engineering adopts socket connection, which has the advantages of simple, fast, time-saving, labor-saving and low installation cost. Disadvantages: in some muddy areas with poor geological conditions, because the FRP pipe is flexible connection, it is easy to cause floating pipe and pipe connection separation when the adjacent two pipes have uneven settlement.

Bonding (UPVC, ABS pipe)

Bonding connection is to use adhesive as bonding filler to bond homogeneous pipes and fittings together, so as to play a sealing role. Adhesive connection has the advantages of simple construction and fast curing speed, which is widely used in drainage system.

20210303125936 62095 - 10 kinds of common pipe connection technology

Advantages: bonding interface stress distribution is uniform; prevent metal electrochemical corrosion; ensure the fatigue strength of structural components; bonding process equipment investment is low, easy to use, fast, safe, energy saving; strong adaptability, can meet special needs, such as heat conduction, conductivity, oil resistance, etc.
Disadvantages: the peel strength, uneven pull-off strength and impact strength of the adhesive layer are low. Generally, the heat resistance of adhesives is not high (generally 150 ℃, up to 300 C), the aging resistance is poor, and there is a lack of non-destructive testing methods for bonding quality.

Flange connection

Flange connection is a kind of detachable joint that first fix two pipes, pipe fittings or equipment on one flange, then add flange gasket between the two flanges, and finally tighten the two flanges with bolts to make them closely combined.

20210303130041 66764 - 10 kinds of common pipe connection technology

Advantages: flange connection has good strength and tightness, wide applicable size range, can be applied in equipment and pipeline, so it is the most common application.
Disadvantages: but when the flange is connected, it can not be assembled and disassembled quickly, and the manufacturing cost is high.
pipe flange

  • 1) The specification and model of matching flange are the same; when connecting with equipment flange, it should be matched according to its specification;
  • 2) The flange connection is coaxial and parallel, and the flange surface is perpendicular to the pipe center;
  • 3) The fastening bolts have the same specifications, the same direction, the exposed length of bolts is 1 / 2 of the bolt diameter or flush with the nut;
  • 4) When connecting the valve, put the nut on the valve side;
  • 5) The top two screw holes of horizontal pipe flange shall be kept horizontal, and the two screw holes of vertical pipe flange shall be parallel to the wall.

Flange standard: national standard GB9112-9123, Ministry of machinery standard JB79-86, Ministry of chemical industry standard HG5008-5028 and Ministry of petroleum industry standard syj4, flange bolt hole center is the same, JB standard and Hg standard pipe diameter is “small outer diameter”, GB standard and SYJ standard is “large outer diameter”, when using, it should pay attention to the different number of bolt hole of individual specification flange.
20210303130225 96676 - 10 kinds of common pipe connection technology

Welding profile of flange and pipe

20210303130349 74179 - 10 kinds of common pipe connection technology

Automatic welding of flange and pipe

20210303130411 59988 - 10 kinds of common pipe connection technology
Specification for bolt direction and length
➤ examples of frequently asked questions
20210303130614 35621 - 10 kinds of common pipe connection technology

Flange inner ring not welded

20210303130648 65770 - 10 kinds of common pipe connection technology
The bolts on both sides are not aligned

20210303130710 21584 - 10 kinds of common pipe connection technology
Flange mismatch
➤ angle steel flange of air duct

  • 1) The flange surface shall be flat, the length of diagonal line shall be equal, and the welding seam shall be full;
  • 2) The distance between flange bolt holes and rivets shall be uniform and meet the specification requirements, and screw holes shall be set at the four corners of flange;
  • 3) When flange connection, the bolt direction should be unified and the length should be consistent, and the bolt material should correspond to the air duct;
  • 4) The flange shall be tight without leakage after fastening, the flange surface clearance shall be uniform, and the gasket shall not protrude into the pipe or out of the flange;
  • 5) After flange connection, the bolts are not corroded.

The distance between bolts and rivet holes of air duct flange of medium and low pressure system shall not be greater than 150 mm, and that of air duct of high pressure system shall not be greater than 100 mm. The four corners of the rectangular duct flange shall be provided with screw holes.

20210303130906 64129 - 10 kinds of common pipe connection technology
Angle steel flange of rectangular duct

20210303130919 32140 - 10 kinds of common pipe connection technology
Angle steel flange connection

Specification of metal circular duct flange and bolt (mm)

Duct diameter

D

Flange material specification

Bolt specification

Flat steel

Angle steel

D≤140

20×4

 

M6

140<D≤280

25×4

280<D≤630

25×3

630<D≤1250

30×4

M8

1250<D≤2000

40×4

Specification of metal rectangular duct flange and bolt (mm)

Dimension of long side of air duct B

Flange material specification (angle steel)

Bolt specification

b≤630

25×3

M6

630<b≤1500

30×3

M8

1500<b≤2500

40×4

2500<b≤4000

50×5

M10


➤ steel sheet flange of air duct

  • 1) The flange shall be vertical to the air duct and closely connected;
  • 2) Apply sealant on the inside and outside of the four corners of the air duct flange for sealing;
  • 3) The four corners of the flange shall be fixed with bolts, the middle part shall be fixed with spring clip or top screw clip, the spacing shall be no more than 150 mm, and the distance between the outer end and the edge of the air duct shall be no more than 100 mm.

20210303131557 81879 - 10 kinds of common pipe connection technology
The direction and length of connecting bolts of angle steel flange are unified

20210303131626 47328 - 10 kinds of common pipe connection technology
The spring clip (left) is connected with the top screw clip (right), and the fixed spacing is uniform

Pipe connector connection

The pipe connector is a new type of pipe connection device, which breaks through the traditional connection concept. It is made of stainless steel and rubber to achieve the sealing and pressure bearing function. During the construction, there is no need to do any treatment on the pipe end. As long as the connector is set on the two pipe ends to be connected, and the side bolts are tightened, the clamping teeth will bite the surface of the pipe end to achieve the limit fixation, and the sealing sleeve will stick tightly Achieve the locking state of sealing and firm connection on the pipeline.
20210303131806 48686 - 10 kinds of common pipe connection technology

Advantages: flexible connection, fast installation, no need to fire, strong and durable, versatility and other features.

Single groove connection

Groove connection is a sleeve type quick joint which is made up of clamps, rubber sealing rings and fasteners and is processed to form a ring groove at the pipe joint. During installation, after a special-shaped rubber sealing ring is put on the adjacent pipe end, it is connected with a split type clamp. The inner edge of the clamp is located in the groove and is fastened with fasteners to ensure the sealing performance of the pipe. This connection method has the advantages of no damage to the galvanized layer of steel pipe, fast construction, good sealing and easy disassembly. It can be used in building water supply, fire water supply, production water supply and other pipeline projects.
20210303131900 38727 - 10 kinds of common pipe connection technology

Advantages: simple operation, the original characteristics of the pipeline are not affected, which is conducive to construction safety, good system stability, convenient maintenance and good economic benefits.
➤ grooving

  • 1) Check the nozzle size, roundness and manufacturing quality to meet the requirements of groove manufacturing;
  • 2) According to the specified time, the groove is processed by stages, and the depth and other dimensions of the groove are retested;
  • 3) Groove processing shall not damage the galvanized layer and inner coating of the pipe.

20210303132220 82748 - 10 kinds of common pipe connection technology

20210303132359 30720 - 10 kinds of common pipe connection technology

Steel pipe groove processing

➤ groove assembly

  • 1) Clean the pipe end, put on the rubber sealing ring, install the clamp and fasten the bolt;
  • 2) The center line of the pipeline at the two ends of the groove is consistent, and the groove installation direction (fastening bolt position) is consistent;
  • 3) Rigid joint should be used for straight pipe section, and a flexible joint should be set between every 4-5 continuous rigid joints on the pipe section.

➤ examples of frequently asked questions
20210303132637 59917 - 10 kinds of common pipe connection technology
The direction of groove joint is not uniform
20210303132654 86000 - 10 kinds of common pipe connection technology
The pipes at both ends of the groove are not straight

Ferrule connection (aluminum plastic composite pipe)

It is a connection mode that the pipe is pressed on the pipe fittings with the lock nut and the open compression ring. Features: the sealing surface of ferrule type pipe fittings is short, easy to install, and can be disassembled without special tools. It is generally used in tap water and gas systems with specifications below 2632.
20210303132903 63355 - 10 kinds of common pipe connection technology

Advantages: reliable connection, high pressure resistance, temperature resistance, good sealing and repeatability, convenient installation and maintenance, safe and reliable work, etc.

20210303132928 10040 - 10 kinds of common pipe connection technology

Thin walled stainless steel pipe clamp connection
Clean the insertion port and mark the insertion depth. Insert the pipe according to the specified depth and keep the axis vertical. Use the special clamping tool to clamp the connector. After clamping, use the gauge to check whether the clamping size is in place.

Hot melt connection

20210303133019 88508 - 10 kinds of common pipe connection technology

Clean the hot-melt part and mark the hot-melt depth of socket connection. Use a special hot melting machine to heat the connection part according to the specified heating time. After heating, the joint is fused according to the specified pressure and time, and a uniform fusion ring is formed at the joint.
20210303133225 73724 - 10 kinds of common pipe connection technology
Hot melt socket connection of plastic pipe

Technical parameters of hot melt socket connection

Outer diameter of PE water supply pipe (mm) Melting depth (mm) Heating time (s) Melting time (s) Cooling time (min)
20 14.0 5 4 2
25 15.0 7 4 2
32 16.5 8 4 2
40 18.0 12 6 4
50 20.0 18 6 4
63 24.0 24 8 6

Note: the temperature is generally low in winter in North China, and the heating time should be extended by 50% of the calibrated heating time.

Socket flexible connection

20210303133434 30667 - 10 kinds of common pipe connection technology

Before connecting the cast iron pipe, clean up the sundries that affect the tightness of the socket and spigot, and put the rubber sealing ring correctly. The perpendicularity of the two pipe sections shall be inserted and maintained according to the depth required by the construction standard.

20210303133711 16966 - 10 kinds of common pipe connection technology

Flange connection of flexible cast iron pipe

The above are some of the most common ways of pipe connection, and the specific method depends on the working condition.

Source: Network Arrangement – China Pipe Flange Manufacturer – Yaang Pipe Industry Co., Limited (www.pipelinedubai.com)

(Yaang Pipe Industry is a leading flange manufacturer and supplier of nickel alloy and stainless steel products, including Super Duplex Stainless Steel Flanges, Stainless Steel Flanges, Stainless Steel Pipe Fittings, Stainless Steel Pipe. Yaang products are widely used in Shipbuilding, Nuclear power, Marine engineering, Petroleum, Chemical, Mining, Sewage treatment, Natural gas and Pressure vessels and other industries.)

If you want to have more information about the article or you want to share your opinion with us, contact us at sales@pipelinedubai.com

Please notice that you might be interested in the other technical articles we’ve published:

Summary
10 kinds of common pipe connection technology - 10 kinds of common pipe connection technology
Article Name
10 kinds of common pipe connection technology
Description
The process of this paper summarizes the characteristics of 10 pipe ​connection methods, and provides relevant pictures and texts for you to learn and exchange.
Author
Publisher Name
www.pipelinedubai.com
Publisher Logo

Related News

  • * 暂无相关文章
العربيةБългарски简体中文繁體中文DanskNederlandsEnglishFrançaisDeutschBahasa IndonesiaItaliano日本語한국어LatinPortuguêsРусскийEspañolதமிழ்ไทยTürkçe