butt welded pipe and fittings

 

 

butt welded pipe:

(1) Items: Seamless Pipes; Welded Pipes; Glavanized Steel Pipes; Round and Square Pipe; Rectangular Pipe

(2) Standard: BS1387/1985;DIN1629/17175/2440/2448/2458;ANSI/ASME/ASTM A234 WPB/ASTM A 106 A53/ASTM A572 GRADE50/API 5LX-52/API5CT J55/API X42 H40

(3)Size:1/2" to 42"

(4)Thickness:>=0.7mm

butt welded pipe fittings:

1. Material: carbon steel,stainless steel,alloy steel

 2. Size range: FROM 1/2" TO 106"

 3.Pressure: Sch5--Sch160,XXS

 4. STANDARDS  ANSI, ISO, JIS, DIN, BS, GB, SH, HG, QOST, ETC.

 

 

Ultrasonic testing of butt weld pipe

 

     For the characteristics of the process pipe butt weld, butt method, location and easy to produce welding defects were analyzed. As the process pipe butt weld thickness range, mostly straight pipe and elbow, straight pipe and elbows, flanges, valves and other fittings butt welding using single-sided double-sided molding process, this particular structure type and welding the ultrasonic detection can only scan single-sided or single-sided unilateral bilateral scanning. In order to improve the detection rate of defects of different specifications, different structural welds in the choice of scanning surface, the number of probes, probe and probe dimensions are not models should be targeted. Determine the root defect scan line regulation accuracy of the instrument put forward higher requirements for typical defects echo offerings were analyzed. Through the above analysis and the measures that can effectively improve the process aerospace industry ultrasonic testing of butt weld quality.

    Petrochemical process pipe butt weld ultrasonic device with a certain degree of difficulty. Earlier analog ultrasonic flaw detector due to positioning accuracy is not high, for the identification and determination of defects root abundance in the larger difficulty, every time you change the angle of the probe after different time baseline must be re-adjusted, very inconvenient, which in the process pipe butt weld seam ultrasonic detection technology by promoting the field has become very difficult. In recent years, ultrasonic testing equipment has undergone tremendous change and update soon, digital flaw detector instead of the analog meter. Digital flaw detector than originally used analog ultrasonic flaw detector has significant advantages. First, the positioning accuracy training, positioning accuracy of 0.1mm, for the pipe weld toe signal to provide a reliable basis for the decision; Second, the probe can be stored in a variety of parameters and their distance - volatility curve for the current sound using a variety of angles probe detection provides a convenient, improve different angles defect detection sensitivity of spirit, but also can be easily changed and did not probe for identification true, false signal provides convenient; Third, you can store dynamic waveform and envelope defects, and as electronic files archived for future reference. Digital ultrasonic flaw detector solves the problem of ultrasonic testing pipe welds.

    I recommend using pipe welding flaw digital ultrasonic flaw detection. Through professional training and rigorous assessment, you can filter out qualified butt weld pipe ultrasonic testing personnel, fully able to ensure the quality of ultrasonic testing of pipe welds.

    Through the ultrasonic detection methods, scanning surface, the number of probes, the probe type and probe size control, and theoretical analysis and experimental verification, table lamps ultrasonic testing can effectively guarantee the pipeline weld inspection quality.

    Ultrasonic testing operational flexibility, thick-walled pipe detection sensitivity and detection efficiency were higher than ray detection, cost less than the radiation detection and harmless to human body, is a scientific, environmental detection methods.

A pipe butt weld and butt weld containers at different points

    Butt weld pipe butt weld than container from the welding process, structure type, the main site of defects, defect signal identification, probe scanning plane, the angle of refraction of the probe selection and coupling surface curvature are quite different. So in ultrasonic testing of butt weld pipe must have a certain understanding.

2 welding process and defect analysis

   Ultrasonic testing of butt weld pipe there are two important aspects of how we can ensure that no one is missed, the second is how to correctly identify and determine the defects. The following form of the pipe joints, welding, welding position and is easy to produce a defect analysis, design testing process, to improve defect detection and signal decision reference.

2.1 Structure and surface scanning

    Petrochemical plant process piping butt welds generally be divided into three forms: straight pipe with straight pipe butt, butt straight pipe and pipe fittings, pipe fittings and pipe fittings butt.

(A) straight pipe with straight pipe butt weld probe scanning both sides of the weld.

(2) straight pipe and pipe fittings butt weld pipe fittings from the surface of the irregular surface (such as elbows, flanges, valves or three-way, etc.), the probe can not be well coupled, therefore, only from one side scanning straight pipe, In order to improve defect detection rate, should choose two different angles probe scanning.

(3) pipe fittings and pipe fittings butt weld on both sides of the weld are irregular surface (such as elbows, flanges, valves or three-way, etc.), the probe can not be well coupled, therefore, can not be a normal type of ultrasonic weld detection, if the customer has polished weld reinforcement measures (flush with the base material), you can melt the probe through the flat weld testing. The welds polished to flush with the base metal is a very difficult thing, generally do not.

2.2 Welding position

    Welding position helps to understand the nature of defect analysis and judgment. Butt weld pipe welding position is divided into horizontal rotation, horizontal fixed, heavy straight-fixed and fixed 45 degree oblique.

(1) horizontal rotation mouth welding, the welding position 11 always or 1:00 clock position near the most easy to control the welding operation, the most difficult to produce welding defects.

(2) the level of the fixed orifice welding, the upper part is flat welding position, overhead welding position in the lower half of the sides in the vertical welding position.

(3) re-direct fixed orifice welding, its position is horizontal welding.

(4) 45 degree tilt fixed orifice welding, in various parts of the level fixed on the basis of an increase of the tilt angle, and increased welding difficult.

2.3 The welding position is easy to produce defect types

(A) the current petrochemical plant pipe welding procedures are used welding backing butt weld, welder before the end of the primer used to stay a short inspection hole, observe root pass with a flashlight case, if the defective immediately unhealthy site with grinder to remove heavy welding, final inspection of the roots of good will last a short weld. After welding backing, commonly used for thicker manual arc welding or submerged arc welding filling and capping.

(2) melting molten weld position under the action of gravity drip down, so flat welding position to control the welding current is not too large, welding current and welding speed should be appropriate, or easy to weld and burn forming, welding joints and weld parts prone pores.

(3) vertical welding position welding of position due under the drip molten weld ripples resulting weld inside and outside surface roughness and poor, but also prone to incomplete penetration, lack of fusion, weld and undercut, so to control the welding current is not too , welding speed can not be too fast.

(4) Yang Yang welding position welding position is easy to produce concave, incomplete penetration, lack of fusion and weld, overhead welding current is too large prone position concave, burn fat and weld current is too small easy to produce incomplete penetration and lack of fusion, thus saith the most difficult welding position welding. Arc welders often used until a moment solidified molten pool, and then continue melting point arc welding arc off immediately .... so the cycle continues until the hot metal forming achieve controllable far, burning the second layer when the current does not pass weld large, or the first layer of hot metal melt is formed concave fall, the greater the current the deeper concave form.

(5) heavy straight pipe horizontal welding position fixed transverse weld welder welding around, horizontal welding position welding, molten iron by gravity, the upper prone to undercut groove is not easy to produce fusion welded between each layer if the cleanup easy to produce bad slag, poor control of the weld surface horizontal lines will be rough.

3 Probe selection

   Probe selection factors to consider are:

(A) detecting a thin seam thickness measurement should choose a large value of K, the short frontier exploration along the probe, as a wave of cross-sectional scanning more welds; For large thickness of the weld should choose a larger die size, K value appropriate , the probe has sufficient sensitivity.

    According to the actual work experience, I recommend 7mm wall thickness greater than or equal welds and the use of a single oblique probe to detect weld wall thickness less than 7mm clutter detection of serious focus now more choice of probe or double crystal probe. But focusing probe and double crystal probe general width larger diameter tube is coupled with the need to grind, because focusing probe and double crystal probe near the focus are the highest sensitivity, detection range affected, process piping pipe wall thickness less than 7mm diameters are generally smaller, and thus, for the pipe wall thickness less than 7mm ultrasonic testing method is not recommended for testing.

(2) detecting a smaller radius of curvature R of the pipe, to select the small contact surface of the probe, in order to ensure good coupling; large diameter pipe can select a larger size of the probe, in order to improve the detection efficiency. Probe contact with the work surface dimensions W should satisfy the following equation.

R greater than or equal W * W / 4 (1)

    Currently marketed chip size is 6mm * 6mm short forefront small wafer probe, the probe width is generally 12mm. By the formula (1) can be calculated by the pipe diameter should be greater than 72mm, to enhance the coupling effect, the author recommended width of 12mm probe short edge of the small wafer probe test, the pipe diameter lower limit of 100mm.

(3) scanning plane straight pipe with straight pipe butt weld both sides of the scanning probe, you can choose one kind of K value of the probe; straight pipe and pipe fittings butt weld joints can only scan one side when , you should choose one of two off the body angle less than 10 degrees away from scanning probe, the smaller the value of K probe, a wave scanning range of not less than one quarter of the weld cross-section.

(4) Pipeline inspection probe frequency should choose a higher frequency of the probe in order to improve directivity and positioning accuracy. 5MHZ recommended frequency probes for thicker pipes can choose 2.5MHZ probe.

   For roots suspicious signal possible, choose a small value of K probe reinspection. Experience has shown that a small value of K probe positioning accuracy, small error.