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Pharmaceutical Engineering | September-October 2016 | 1

Defects Produced in Orbital Welding for Pharmaceutical Process Piping: Case Study and SimulationJorge Domingo and Margarita Morquillas

Bonding or welding processes used in the construction of distribution systems for utilities are some of the most critical activities on projects with high sanitary requirements in the life sciences and similar industries.

Project implementation experience, both domestically and internationally, indicates that activities requiring high levels of quality monitoring are relat-ed to the installation of critical fluids distribution systems, most specifically those constructed from stainless steel alloy tubes jointed by gas tungsten arc welding (GTAW), also known as tungsten inert gas (TIG), using orbital welding techniques.

Difficulties are more likely to occur when working on-site, where the welding conditions are not as favorable as those in specialized workshops, which pro-vide better opportunities for control. Another challenge is the need in many cases to use resources that are unfamiliar, due to the project requirements of the, the client, or locally applicable regulations. It is also worth noting that lo-cal welding companies contracted to perform work often don’t have enough experience in large welding projects. This increases the risk of noncompliance and may require additional resources for performance monitoring.

This article evaluates the causes of defects in welds. The approach taken was to simulate conditions that can affect the quality of welds by changing the parameters used to diagnose defects. Weld quality was verified visually, since this is the most common method in pharmaceutical facilities, as recommended in American Society of Mechanical Engineers Bioprocess Equipment (ASME BPE) group regulations.

This article also presents a case study performed after extensive experience in installation of international projects, during which various types of nonconformities were identified in a variety of welds (Figure 1).

Orbital WeldingOver the years, the pharmaceutical industry has become increasingly aware that the welding process used to join components of process piping systems that will be in contact with the product must be controlled and consistent to reduce the likelihood of defects in individual welds.

The pharmaceutical industry currently uses orbital GTAW/TIG welding almost exclusively. This produces welds of high quality with very low rejection percentages; these joints possess high strength, high purity meta, and good surface finish.

Orbital welding is the controlled rotation of components within a fixed support, while an adjustable, nonconsumable tungsten electrode attached to a guide moves (or “orbits”) the joint. The electrode, the arc, the area surrounding the weld, and tube interior are protected by a shield of inert gas—usually argon—with a purity of 99.995/99.999% (Figure 2).

Although orbital welding is an automated process, weld quality depends on a number of parameters, in addition to the operator’s training and skill. Changes in any of these parameters can result in weld defects, which can lead to nonconformities. As a result, each weld must be verified individually.

Nondestructive Weld VerificationNondestructive weld verification inspects the surface and subsurface of the weld and surrounding base material to verify weld quality. Commonly used nondestructive verification methods include:

¡ X-ray¡ Penetrant liquid¡ Ultrasound¡ Magnetic particle

Within the world of critical facilities, however, visual verification by video endoscopy has wider acceptance. The main advantage of this method over those listed above is that provides visual verification of the weld surface

Figure 1: Weld rejection due to scratches (a and b)


2 | Pharmaceutical Engineering | September-October 2016

fi nish on the pipeline interior—the main concern in health care facilities. This technique can also be used to verify other weld characteristics, such as homogeneity and absence of surface pores (Figure 3).

Another advantage of this method is its ability to verify the profi le of color over the heat-aff ected zone (HAZ) in the weld bead and surrounding area. This provides valuable information in assessing the quality of the weld, which is not possible using other methods. (See chapter ASME BPE-2014 weld acceptance criteria.)

It is important to note that weld inspection is traditionally carried out by experienced staff with suffi cient knowledge for verifi cation and compliance reporting. Inspectors are currently recommended to have certifi cation proving they are trained according to ASME BPE-2014, GR-4 and ASME B31.3, paragraph 342.2:

¡ Quality Inspector Delegate 1¡ Quality Inspector Delegate 2¡ Quality Inspector Delegate 3

European standards are certifi ed by the Europe-an Welding Federation:

¡ European Welding Engineer ¡ European Welding Technician ¡ Master in Welding

The percentage of welds that will undergo ver-ifi cation must be agreed in advance between the involved parties (customer, engineering, installer, validation and qualifi cation company) so that installation can be planned to accom-modate inspection frequency (ASME BPE-2014: MJ-7.3.3 tubing).

Figure 3: Boroscope probe (a) boroscope machine (b)

Figure 4: Acceptable and unacceptable weld profi les for tube welds

Source: Reprinted from ASME BPE-2014, by permission of The American Soceity of Mechanical Engineers. All rights reserved. No further copies can be made without written permission.

Figure 2: Tungsten and piece preparation (a) and weld head (b)



Figure 5: Discoloration acceptance criteria for weld HAZs on electropolished 316L tubing


We recommend following ASME BPE-2014: MJ-7.3.2 piping and checking 20% of orbital welds. However, such verification should be performed daily and not only at the end of the installation. Daily verification allows nonconformances to be corrected immediately, prevents an accumulation of defects, and reduces dismantling costs. A representative sample of each welder’s or welding operator’s work must be included.

It is not necessary that the team that inspects and approves welds reside on-site permanently. The welding team may perform on-site video endoscopy and transmit digital files (videos, photos) at the end of each day, together with other relevant documentation (isometric reports, weld parameters, logs). This practice will produce benefits such as:

¡ Opportunities for real-time communication¡ Cost savings by eliminating the need to bring in specialists¡ Continuous weld quality monitoring throughout the installation process

All parties involved should agree upon inspection procedures, methodology, and logistics in advance.

Weld Acceptance CriteriaSince one of the recommendations in this article is to follow ASME BPE-2014, we have included references to and extracts from the international standard. For further details, please review MJ-8 pages from 122 to 139.

The BPE welding standard for a sterile environment requires that the weld “shall not result in a surface that will contribute to microbiological growth and contamination of the product. The weld shall not have any discontinuities, such as cracks, voids, porosity, or joint misalignment that will promote contamination of the product. All welding procedures shall be qualified to MJ-5.”

As a guideline for inspectors and welders, ASME BPE-2014 includes acceptable and unacceptable weld profiles for tube welds criteria as seen in Table A, Table B, and Figure 4.

The standard also includes a new criteria related to welding discoloration for weld HAZs, as seen in Figure 5 and Figure 6.

Electronic versions or photocopies of these accept-ance criteria should not be used to evaluate sample or production welds, since subtle color differences can influence weld acceptability. ASME BPE-2014 Appendix M explains the technique by which these acceptance criteria were determined. Figure 5 is also available as a stand-alone document: ASME BPE-2014 (Fig MJ-8.4-3).

Figure 6 is also available as a stand-alone document: ASME BPE-2014 (Fig MJ-8.4-2).

Other factors After compiling and reviewing the tests conducted for this article, and based on the experience gained in implementation of critical facilities, we conclude that the factors having the highest impact on the quality of welds are (from higher to lower impact):

¡ Purge gas quality and control¡ Setting parameters for welding equipment ¡ Welding procedure (tungsten, alignment)¡ Quality and dimensional tolerances of the materials to be welded¡ Condition of the premises where welding is performed

Most welding companies have these (and other) parameters under con-trol in workshops. Provided on-site welding is carried out in appropriately controlled environments to correct procedures and uses required pa-rameters, weld quality can be guaranteed outside the workshop. Due to



on-site constraints (time and resources), however, procedures can be compromised, increasing the risk of nonconformities. It is therefore imperative that time and resources be invested to assure appropriate conditions, and ensure the weld quality.

Case Study: TIG Orbital Welding DefectsTo show our customers the importance of orbital welding, train our employees in the verification of such work, and ensure that it is carried out in the right way, we collected these samples to show how several factors can lead to failure.

General conditionsThe tests were conducted under the direction and advice of specialists using the following equipment and parameters:

Welding conditions¡ Welding procedure: TIG orbital fusion¡ Orbital head model: 8-4000 (Arc Machines, Inc.)¡ Orbital current source model: 207-A (Arc Machines, Inc.)¡ Feed: Continuous¡ Shield gas: Argon 100% [99.995%] (Arcal TIG/MIG) EN 439, I1.¡ Support gas: Argon 100% [99.995%] (Arcal TIG/MIG)

EN 439, I1¡ Component dimensions: 38.1 mm diameter, 1.65 mm

thickness¡ Base material: 316L stainless steel, ASME BPE-2014¡ Electrode: Tungsten, ø 1.6 mm esp., 20 sharp, 1.3 mm

distance

Welding parameters¡ Shield gas flow rate: 20 L/min¡ Purge gas flow: 5 L/min (preliminary purge time, min. 15 sec with O2

sensor)¡ Support gas flow: 5 L/min¡ Tungsten diameter: 1.6; sharp angle 20°¡ Tungsten/workpiece distance: 1.3 mm

Pipe and fittings¡ Material: Stainless steel AISI 316L, ASTM A270-03 S2/BPE ASME,

UNSS31603, EN 1.4404¡ Dimensions: According to ASME BPE-2014

Cleaning before weldingWe used an industrial degreasing formed by solvents, dissolving fats, oils, lubricants, tars, and adhesives of the metal parts, applied generously and allowed to drain. We dried with paper towels and repeated the operation.

Gas-related defectsWelding with excessive purge gasWe increase the purge gas flow by 20 L/min.

Figure 6: Discoloration acceptance criteria for weld HAZs on mechanically polished 316L tubing


¡ Purge gas flow: 40 L/min¡ Preliminary purge gas flow: 5 L/min (minimum preliminary purge time =

15 sec.)¡ Shielding gas flow: 5 L/min¡ Tungsten diameter: 1.6; sharp angle 20°¡ Distance tungsten piece: 1.3 mm

Observations: The weld bead is sunken in the central part as shown in the exterior weld coupon as seen in Figure 7. The effective thickness of the tube decreases. On the interior, the appearance is good and there is penetration in all weld beads, but there are some zones that have higher penetration than the rest. Externally, the adjacent zone to the weld bead is slightly less dark than in weld coupon with reference to sample P34 E31.

Welding without internal purge gasWe duplicate weld coupons caused by neglect, carelessness, ignorance, etc., not by internal purge gas or shielding gas.

¡ Purge gas flow: 20 L/min¡ Preliminary purge gas flow: 0 L/min (It eliminates the pre-purge flow

for welding)¡ Shielding gas flow: 0 L/min¡ Tungsten diameter: 1.6; sharp angle 20°¡ Distance tungsten piece: 1.3 mm



Observations: The stainless steel needs internal gas protection in the weld bead to avoid the oxidation that we observe in both images, especially in the interior weld coupon. A crack also appears along the entire weld root. Externally, the weld bead is sunken in the central zone, as we can see in Figure 8. Weld without internal purge decreases the effective thickness of the tube.

Welding without shielding gasWe eliminate the shielding gas in the weld head.

¡ Purge gas flow: 0 L/min¡ Preliminary purge gas flow: 5 L/min (preliminary purge time, min. 15 sec.)¡ Shielding gas flow: 0 L/min (eliminates shielding gas flow)¡ Tungsten diameter: 1.6; sharp angle 20°¡ Distance tungsten piece: 1.3 mm

Observations: Although we make the weld with the pieces cleaned, in the external weld coupon image the oxidation also occurs when you do not protect the weld pool with gas. On the other hand, the TIG welding process also needs the protection gas to preserve the tungsten and avoid contamination. We have difficulty maintaining the electric arc. Externally the weld bead is very dark and very rusty (Figure 9).

Figure 9: Weld coupon exterior (a) and interior (b)

Figure 8 (a and b). Weld coupon exterior and interior; welding without internal purge gas


Figure 7 (a and b): Weld coupon exterior and interior; welding with excessive purge gas

Low-purity purge gasWe maintain the purge gas, but to simulate an inert gas with 99.995% purity we use an active gas to represent contaminants in the purge gas. Argon (98%) + CO2 (2%); Arcal 12 (M12; EN 439)

¡ Purge gas flow: 20 L/h¡ Preliminary purge gas flow: 5 L/min (preliminary purge time, min. 15 sec.)¡ Shielding gas flow: 5 L/min¡ Tungsten diameter: 1.6; sharp angle 20°¡ Distance tungsten piece: 1.3 mm

Cleaning before welding: This uses an industrial degreasing formed by solvents, dissolving fats, oils, lubricants, tars, and adhesives of the metal parts. Apply generously and let it drain. We dry with paper towels and repeat the operation.

Observations: The external and internal weld beads are rusted (practically black). The gas used was 98% argon and 2% CO2 (Figure 10).

We also obtain lack of fusion zones, and zones in which the external weld bead is sunken. A composition change in the purge gas implies a change in the welding parameters.

Purge gas with humidityWe maintain flows and welding parameters correctly but simulate a very high relative humidity (80%) through a humidifier and vaporizer.








Observations: Externally, the weld bead is sunken in the central part, but this kind of failure appears by sectors and decreases the effective thickness of the tube (Figure 13).

Installation component defectsDimensional tolerance failure in componentsWelding parameters are correct, but one component is mechanically deformed and dished. This type of failure may occur when tubes and accessories have been stored improperly.

¡ Purge gas flow: 20 L/min¡ Preliminary purge gas flow: 5 L/min (preliminary purge time, min. 15 sec.)¡ Shielding gas flow: 5 L/min¡ Tungsten diameter: 1.6; sharp angle 20°¡ Distance tungsten piece: 1.3 mm

Observations: Externally, we observe misalignment. Internally there also is no lack of penetration. The welding is not uniform and symmetric (Figure 14).

Different component thicknesses Welding parameters are correct, but we use same-diameter components with thicknesses from 1.65 mm to 1.85 mm.

Figure 14: Weld coupon exterior (a), interior (b), and preparation (c)

Observations: Externally, the weld bead is irregular, “nosing,” and appears almost completely sunken. The weld bead has a rusty aspect and the thermal zone was affected. Internally, the weld bead is very irregular, with rouge oxide layers and lack of fusion in some zones.

With one weld coupon we used the humidifier exclusively, and obtained rusted zones in some parts of the weld bead. We used pulverized water in the two other weld coupons; these weld beads were very rusted (Figure 11).

Purge gas overpressureWe increase the shielding gas flow 20 L/min more than the correct gas flow.


Observations: Gas overpressure in the weld root produced blacking holes along all the weld bead; some zones even appeared to have perforations (also due to the welding position). We observed a generalized lack of fusion. Projections around the perforations are due to the forced expulsion of material due to excessive internal pressure. Where no perforations are detected, the weld could appear to be proper externally, but internally the weld root or the weld bead could be sunken (Figure 12). In that case, if there are no black holes in the weld we cannot detected an overpressure checking the weld externally.

Flow/pressure purge gas failureWe maintain adequate flow and welding parameters, but simulate a lack of shielding gas flow by sectors to represent a random failure that can occur with the leaks in the conduit gas tubes.



¡ Purge gas fl ow: 20 L/min¡ Preliminary purge gas fl ow: 5 L/min (preliminary purge time, min. 15 sec.)¡ Shielding gas fl ow: 5 L/min¡ Tungsten diameter: 1.6; sharp angle 20°¡ Distance tungsten piece: 1.3 mm

Observations: Externally, the weld bead is sunken, which implies a decrease of eff ective thickness. Internally, the weld bead is irregular and is slightly oxidized. There is penetration along the entire weld bead, but irregular form (Figure 15).

Base material cut failureWelding parameters are correct, but we create a small bevel on the edge of one component to simulate a failure in the cut of the pipes.


Observations: In the zone where incorrect cutting is located, the material breaks in and the weld bead is perforated and sunken. In the other half tube, the welding was correct. Internally, the weld bead is correct except for the perforation that measures about 25 mm (Figure 16).

Figure 15. Weld coupon exterior (a) and interior (b)




Edge facing failure Welding parameters equal to those of the reference sample P 34 E31. We make a defective edge facing (small notch) in one zone of the tube.


Observations: Externally, the weld bead is sunken, implying a decrease of eff ective thickness. Internally, the weld bead is correct, but there is a lack of fusion in the facing zone where the notches are visible (Figure 17).

Defective facing (fi ling)Welding parameters are correct; we fi le the internal edge of one component.


Observations: Externally, the weld bead is sunken; this implies a decrease of eff ective thickness. Internally, the weld bead is correct, but there is a lack of fusion in the defective facing zone where the notches are (Figure 18).

Oil or grease in the welding componentsWelding parameters are correct.




Observations: Externally, the weld bead is very irregular, breaking in, and very rusty. We can see the diff erence of diameter between both compo-nents. The joint is misaligned. Internally, the weld bead is very irregular and it is partially rusted. Color diff erence in base materials is due to the diff erence between the two polished materials (Figure 21).

Weld preparation defects Excessive track welding with penetration and without shielding gasWelding parameters are correct; we make several track welds between both pieces and with 60A of intensity and without shielding gas.


Observations: Externally, we can observe that the track welding is too large in comparison to the rest of the weld bead. The track welding should be invisible, and should be covered with the welding bead. Also there are blacking holes in the crater point. In the internal part of the weld coupon and around the track welding, there is rust and it is completely black and cracked: Figure 22.






Observations: Externally, we can see a mild oxidation, but no other imper-fection. Internally, the weld bead looks dirty, irregular, and in some zones there is a lack of fusion; visually, however, the pores are indistinguishable (Figure 19).

Metallic contaminants in the componentsWelding parameters are correct, iron fi lings are placed inside.


Observations: Internally, we can see metallic inclusions. Externally, the weld bead is sunken and rusty in some zones (Figure 20).

Different base material componentsWelding parameters are correct, but we used a piece made of 316L ASME BPE stainless steel and another piece of the same material for alimentary industry.



Excessive track welding with penetration and with shielding gasWelding parameters are correct; several track welds were made between both pieces with 60A of intensity and with shielding gas.


Observations: Externally, the track welding is too large in comparison to the rest of the weld bead. Track welding should not be visible, and should be





covered with the welding bead. Unlike the previous weld coupon, there are no rusted parts (Figure 23).

Alignment failure of the components in the track weldingWelding parameters are correct, several track welding was done between both pieces with a 30A of intensity.


Observations: Welding is not uniform. Penetration is excessive in some zones and limited/insuffi cient in others. Excessive rust in one external zone of the welding bead. There are “get downs” without even cause perfora-tions (Figure 24).

Excessive distance between componentsWelding parameters are correct, but we separated the pieces to be welded.


Observations: This produces weld bead breakage. Weld thickness is weak due to excessive separation of the pieces, hence its resistance is not enough to support the residual stresses due to heating and subsequent cooling and it breaks, almost after welding, and before removing component holding jaws (Figure 25).

Equipment and welding parameter defects Overlap failureWelding parameters are correct, but we separated the components at 0.22 mm to simulate this failure.


Observations: Overlap failure. Externally, the weld bead is breaking in the overlap. Internally, the weld root has good aspect and penetration, except the overlap zone where, we can observe an excessive penetration and an irregular weld bead (Figure 26).

Component misalignment Welding parameters are correct. To simulate this failure, we leave one of the orbital weld head jaws open (clamp inserts looseness).



¡ Shielding gas flow: 5 L/min¡ Tungsten diameter: 1.6; sharp angle 20°¡ Distance tungsten piece: 1.3 mm

Observations: Unfocused electric arc, thermic support is not directed to the weld coupon joint properly. In one weld coupon, the weld bead takes down and generates perforations. In the other weld coupon externally there is no fusion on one side of the weld bead. Finally, in the third weld coupon, the joint was welded, and externally we couldn´t see lack of fusion, but inter-nally there is no fusion in one side of the joint. Internally, this failure occurs in the three weld coupons (Figure 29).

Punctual high tension in the main electrical feedWe divided the tube into 30 sectors of 2 seconds’ duration. In two of these mini-sectors we introduce one high tension to simulate a punctual high ten-sion of the electrical main that generates high random intensity.


Observations: During high-tension sectors, the external aspect of the weld-ing changes, the weld bead is wide, and internally there is more penetra-tion. In the tungsten, the electrode formed into a ball due to overheating during periods of high tension (Figure 30).

Punctual low tension in the main electrical feed We divided the tube into 30 sectors of 2 seconds’ duration. In two of those sectors we simulated a punctual low tension of the general electricity net-work by lowering tension in the welding machine that generates low ran-dom intensity.


Observations: During sectors with insufficient intensity, the external aspect of the welding changes, the weld bead is narrower, and internally, there are zones with a lack of fusion. Externally, there is a part of the weld bead that is slight, punctured, and smaller in width (Figure 31).

Excessive welding intensityWe turn up the intensity about 46A.

¡ Purge gas flow: 20 L/min ¡ Preliminary purge gas flow: 5 L/min (preliminary purge time, min. 15 sec.)¡ Shielding gas flow: 5 L/min¡ Tungsten diameter: 1.6; sharp angle 20°¡ Distance tungsten piece: 1.3 mm




Observations: Misalignment. Internally, the weld bead is irregular, and ex-ternally, it is very rusted in some parts (Figure 27).

Misaligned tungsten related to the jointWelding parameters are correct; tungsten is loose.


Observations: Externally, one weld coupon broke through the side of the cord soldier. In the other, two weld coupons do not appear to have external imperfections, but internally we can observe a lack of fusion and penetra-tion on one side of the joint to be welded (Figure 28).

Tungsten not sharpenedWelding parameters are correct; we do not sharpen the tungsten.

¡ Purge gas flow: 20 L/min¡ Preliminary purge gas flow: 5 L/min (preliminary purge time, min. 15 sec.)



Observations: The weld bead is breaking in with an excessive penetration. In one weld coupon, the joint is perforated. The weld bead is a little wider than in the correct weld coupon example (Figure 32).

Insuffi cient welding intensityWe decreased the welding intensity.

¡ Purge gas fl ow: 20 L/min¡ Preliminary purge gas fl ow: 5 L/min (preliminary purge time, min. 15 sec.)¡ Shielding gas fl ow: 5 L/min¡ Tungsten diameter: 1.6; sharp angle 20º¡ Distance tungsten piece: 1.3 mm

Observations: Visually the weld bead is very narrow. There is a lack of pen-etration along the weld bead. One weld coupon not even get melt reaches a part of the piece (Figure 33).

Insuffi cient angular rate of weldingWe reduce angular speed (welding velocity) in 80 mm/min.








Observations: The weld bead is bulky in the overlap. In the overlap zone, we see an excessively wide root (Figure 34).

Excessive angular rate of weldingWe increase angular speed (welding velocity) in 25 mm/min.


Observations: The weld bead is slightly sunken and narrow. There is a lack of penetration in several zones (Figure 35).



three weld coupons there is an overall lack of fusion in the entire internal weld bead (Figure 36).

Insuffi cient distance between tungsten and pieceDistance between the tungsten and the piece to be welded is 0.5 mm.


Observations: In the weld coupon interior, we can observe that the weld bead is sunken. Fault generated in the three weld coupons and the tungsten gets stuck in the weld pool (Figure 37).

Excessive distance between tungsten and pieceDistance between the tungsten and the piece to be welded is 3 mm.

¡ Purge gas fl ow: 20 L/min¡ Preliminary purge gas fl ow: 5 L/min (preliminary purge time, min. 15 sec.)¡ Shielding gas fl ow: 5 L/min¡ Tungsten diameter: 1.6; sharp angle 20º¡ Distance tungsten piece: 3 mm

Observations: There is a lack of penetration and the root of the weld bead is very narrow (Figure 38).

Correct Welding SampleCorrect welding sample of the weld coupon:


Observations: This weld coupon is without imperfections or fails. The weld bead is plain, regular, and continuous, without breaking in. There is pene-tration in all weld beads without internal and external oxidation (Figure 39).

Welding Track SampleWelding track sample of the weld coupon:


Observations: The welding tracks have been realized at 30A, the weld bead and the welding tracks have been completely melted. The welding tracks have been realized with shielding gas and purge gas in order to avoid permanent oxidations (Figure 40).





Tainted tungstenWe place tainted/contaminated tungsten with stainless steel fi ller rod. Sharp electrode disappears.

¡ Purge gas fl ow: 20 L/min¡ Preliminary purge gas fl ow: 5 L/min (preliminary purge time, min. 15 sec.)¡ Shielding gas fl ow: 5 L/min¡ Tungsten diameter: 1.6; Not sharpened.¡ Distance tungsten piece: 1.3 mm

Observations: Weld bead irregular and rusty. In one of the three weld coupons, we can observe an external lack of fusion in the joint zone. In the



ConclusionIn these studies, the GTAW/TIG orbital welding process is robust and reliable. In many cases, it was very laborious to reproduce weld failures, even when conditions and parameters were quite extreme. In some instances, it was not possible to produce anticipated faults.

There are numerous factors that can affect weld quality, so systematic quality control of the entire welding process—from preparing materials and setting conditions to inspection of the welds obtained—is necessary. In this regard, the importance of using visual systems like video endoscopy demonstrated that in certain cases welds that appeared to be correct externally were found to be nonconforming after inspection. For this reason, tests based on inspection by noninvasive methods that do not provide information on the inside finish should be considered as complementary, but not as a substitute for internal visual inspection.

These studies also demonstrate the importance of purging with an appropriate gas under correct conditions. Variations in gas characteristics (quality, flow, and pressure) produce significant variations in weld quality. We therefore recommend that this is one of the first points checked early in the process. ¢ AcknowledgementsThe authors acknowledge and greatly appreciate the effort and dedication of Oerlikon (Spain) in carrying out the tests and trials, without whom this study would not have been possible.

References1. US Code of Federal Regulations. Title 21, Part 210. “Current Good Manufacturing Practice in

Manufacturing, Processing, Packing, or Holding of Drugs; General.” http://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfcfr/CFRSearch.cfm?CFRPart=210.

2. US Code of Federal Regulations. Title 21, Part 211. “Current Good Manufacturing Practice for Finished Pharmaceuticals.” https://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfCFR/CFRSearch.cfm?CFRPart=211.

3. American Society of Mechanical Engineers. ASME Bioprocessing Equipment Standard: BPE-2014.4. International Society for Pharmaceutical Engineering. Water and Steam Systems, 2nd ed.

ISPE Baseline® Guide, Volume 4. ISPE, December 2011.5. 3A Sanitary Standards. “P3-A Pharmaceutical Standards.”6. American Society of Mechanical Engineers. ASME B31.3-2002. “Process Piping.” Revision of

ASME B31.3-1999. 30 April 2002. http://www.iu.hio.no/~pererikt/Konstr/Konstr-design-II/standarder/ASMEB31.3-1.pdf.

7. 2015 ASME Boiler and Pressure Vessel Code. Section IX: “Qualification Standard for Welding and Brazing Procedures, Welders, Brazers, and Welding and Brazing Operators.” 07 July 2015

8. American Welding Society. D 18.1/D18.1M: 2.009. “Specification for Welding of Austenitic Stainless Steel Tube and Pipe Systems in Sanitary (Hygienic) Applications.”

9. ———. AWS B2.1/B2.1M_BMG: 2009-ADD1. “Base Metal for Welding Procedure and Performance Qualification.” March 2012. https://app.aws.org/technical/B2.1-B2.1M-BMG-2009-ADD1.pdf.

10. ———. AWS B4.0:2007. “Standard Methods for Mechanical Testing of Welds.” 2007. http://bjchaozhan.com/admin/uploadpic/201292386223002249.pdf.

11. ———. AWS D18.2: 2009. Guías Para la Decoloración de la Soldadura en Tubos de Aceros austeníticos.

12. American Society for Nondestructive Testing. Recommended Practice No. SNT-TC-1A 2011. “Personnel Qualification and Certification in Nondestructive Testing.”

13. British Standards Institution. BS EN 287-1:2004. Cualificación de Soldadores. Soldeo por Fusión. Parte 1 Aceros.

14. Riesco, Gemán Hernández. Manual del Soldador. 16º edición. Cesol. 15. Gómez, Manuel Reina. Soldadura de los Aceros. 4ª edición.16. Arc Machines, Inc. Seminario Soldadura Orbital. 17. Barbara K. Henon articles: Henon, Barbara K, and Y.K. Tan. “Autogenous Orbital GTAW of Large, High-Purity Tubes.”

The Fabricator, 15 July 2010. http://www.thefabricator.com/article/arcwelding/autogenous-orbital-gtaw-of-large-high-purity-tubes.

Henon, Barbara K. “Documenting Welds from an Orbital Welding Power Supply.” Practical Welding Today, 12 February 2004. http://www.thefabricator.com/article/tubepipefabrication/documenting-welds-from-an-orbital-welding-power-supply.

Henon, Barbara K. “Specifying the Sulfur Content of 316L Stainless Steel for Orbital Welding.” TPJ: The Tube & Pipe Journal, 27 March 2003. http://www.thefabricator.com/article/tubepipefabrication/specifying-the-sulfur-content-of-316l-stainless-steel-for-orbital-welding.



About the authorsJorge Domingo has a BSc in industrial engineering from Polytechnical University of Madrid (UPM) and a Masters in sales and marketing management from ESDEN Business School. He has more than 10 years of experience in process, high purity water, CIP and biowaste technologies, acting as engineer and product manager in the pharmaceutical industry sector. Until August 2015, as a Technology Unit Manager at Telstar he was responsible for pharmaceutical and biotechnology process and high purity water systems. Presently he combines the role as an Engineer Expert in Pharmaceutical Water Systems with this position as the Asia Pacific Regional Office Manager at Telstar. He can be contacted by email at [email protected], and by post at Telstar, Av, Font i Sagué, 55 Terrassa Barcelona 08227, Spain.

Margarita Morquillas started her career as a draftsman designer and has developed extensive experience in the design of pharmaceutical process installations. She has been working in the biopharmaceutical industry for more than 19 years with more than 16 years in the performance of welding works, welding documentation and welding inspection. She is currently the TIG Welding Senior Expert, responsible for commissioning and start-up at Telstar. She conducts welding inspections and performs commissioning plans for Telstar’s project facilities. She can be contacted by email at [email protected], and by post at: Telstar, Av, Font i Sagué, 55 Terrassa Barcelona 08227, Spain.



Table A: Acceptance criteria for pipe welds

Welds on process contact surfaces Welds on nonprocess contact surfaces

Discontinuity Welds left in the as-welded condition

Prior to finishing(as welded)

After postweld finishing

Welds left in the as-welded condition

After postweld finishing

Cracks None None None None None

Lack of fusion None None None None None

Incomplete penetration None None on product contact side; otherwise, see note 1

None on product contact side; otherwise, see note 1

See notes 1 and 2 See notes 1 and 2

Porosity None open to the surface; otherwise see note 1

See note 1 None open to the surface; otherwise see note 1

None open to the surface; otherwise see note 1


Inclusions: metallic (e.g., tungsten) or nonmetallic


See note 1 None open to the surface; otherwise see note 1



Undercut None See note 1 None See note 1 See note 1

Concavity See note 1 See note 1 See note 1 See note 1 See note 1

Fillet weld convexity 1/16 inch (1.5 mm) max. See note 1 1/32 inch (0.8 mm) max. See note 1 See note 1

Discoloration: heat-affected zone

HAZ may be permitted to have light straw to light blue color (see Figs. MJ-8.4.2 and MJ-8.4.3). Any discoloration present must be tightly adhering to the surface such that normal operations will not remove it. In any case, the HAZ shall have no evidence of rust, free iron, or sugaring. See note 3.

N/A, see note 3 HAZ may be permitted to have light straw to light blue color (see Figs. MJ-8.4.2 and MJ-8.4.3). Any discoloration present must be tightly adhering to the surface such that normal operations will not remove it. In any case, the HAZ shall have no evidence of rust, free iron, or sugaring. See note 3.

Per customer specification Per customer specification

Discoloration: weld bead None allowed. For welds in nickel alloys, and for welds in superaustenitic alloys made with nickel alloy inserts or filler metals, slag is permitted as long as it is silver to light gray in color and adherent to the surface. See note 3.

N/A, see note 3 None allowed. For welds in nickel alloys, and for welds in superaustenitic alloys made with nickel alloy inserts or filler metals, slag is permitted as long as it is silver to light gray in color and adherent to the surface. See note 3.


Reinforcement See note 1 See note 1 1/32 inch (0.8 mm) max. See note 1 See note 1

Tack welds Must be fully consumed by final weld bead

Must be fully consumed by final weld bead

Must be fully consumed by final weld bead


Arc strikes None None None None None

Overlap None None None None None

Weld bend width N/A N/A N/A N/A N/A

Minimum fillet weld size See note 1 See note 1 See note 1 See note 1 See note 1

Misalignment (mismatch) See note 1 See note 1 See note 1 See note 1 See note 1

NOTES1. The limits of ASME B31.3 shall apply2. Does not apply to insulation sheathing and similar welds3. Special surface preparation may be needed to meet criteria. Welds on piping that has been in service may require unique criteria.

Source: Reprinted from ASME BPE-2014 (Table MJ-8.3-1), by permission of the American Society of Mechanical Engineers. All Rights Reserved. No further copies can be made without written permission.

One of the most critical activities on projects with high sanitary requirements in the life sciences and other industries is related to the bonding or welding processes used in the construction of distribution systems for utilities.



Table B: Visual examination acceptance criteria for groove welds on tube-to-tube butt joints

Includes all products (e.g., tubes, fittings, castings, forgings, and bars) whose final dimensions meet Part DT requirements

Discontinuities Welds on product contact surfaces Welds on nonproduct contact surfaces

Cracks None None

Lack of fusion None None

Incomplete penetration None [see Fig. MJ-8.4-1, illustration (e)] None [see Fig. MJ-8.4-1, illustration (e)]

Porosity None open to the surface; otherwise, see note 1. None open to the surface; otherwise, see note 1.

Inclusions [metallic (e.g., tungsten) or nonmetallic] None open to the surface; otherwise, see note 1. See note 1

Undercut None See note 1

Concavity 10% TW max. [see Fig. MJ-8.4-1. Illustrations (c) and (d). However, O.D. and I.D. concavity shall be such that the wall thickness is not reduced below the minimum thickness required in DT-3 [see note 2]

10% TW max. [see Fig. MJ-8.4-1, illustrations (c) and (d)] over entire circumference with up to 15% of the nominal wall thick-ness permitted over a maximum of 25% of the circumference [see note 2].

Convexity 10% TW max. [see Fig. MJ-8.4-1, illustration (f)] [See note 2] Maximum of 0.015 in. (0.38 mm) [see Fig. MJ-8.4-1, illustration (f)] [See note 2].

Discoloration (heat-affected zone) Heat affected zone (HAZ) may be permitted to have light straw to light blue color (see Figs. MJ-8.4-2 and MJ-8.4-3). Any discoloration present must be tightly adhering to the surface such that normal operations will not remove it. In any case, the HAZ shall have no evidence of rust, free iron, or sugaring. See note 3

Discoloration level will be agreed upon between the owner/user and contractor. Postweld conditioning may be allowed to meet discoloration requirements at the discretion of the owner/user. See note 3.

Discoloration (weld bead) None allowed. For welds in nickel alloys, and for welds in superaustenitic alloys made with nickel alloy inserts or filler metals, slag is permitted as long as it is silver to light gray in color and adherent to the surface. See note 3.

Discoloration level will be agreed upon between the owner/user and contractor. Postweld conditioning may be allowed to meet discoloration requirements at the discretion of the owner/user. See note 3.

Reinforcement See Convexity See Convexity

Tack welds Must be fully consumed by final weld bead [see note 4] Same as product contact side.

Arc strikes None See note 5

Overlap None None

Weld bead width No limit provided that complete joint penetration is achieved. If process contact surface cannot be inspected (such as I.D. of a tube beyond the reach of remote vision equipment), then the nonproccess contact surface weld bead shall be straight and uniform around the entire weld circumference [see Fig. MJ-8.4-1, illustration (g)]. The minimum weld bead with shall not be less than 50% of the maximum weld bead width [see Fig. MJ-8.4-1, illustration (h)]. The maximum weld bead meander shall be 25% of the weld bead width, measured as a deviation from the weld centerline, as define in Fig. MJ-8.4-1, illustration (i).

Minimum throat N/A N/A

Misalignment (mismatch) 15% TW max. [see Fig. MJ-8.4-1, illustration (b)], except that 4 in. tube may have a maximum of 0.015 in. (0.38 mm) misalignment on the O.D and 6 in. tube may have a maximum of 0.030 in. (0.76 mm) misalignment on the O.D. Figure MJ-8.4-1, illustration (b) does not apply to 4 in. and 6 in. tube [see note 2].

Same as process contact surfaces

General note: Includes all product forms (e.g.: tube, fittings, castings, forgings, and bar) whose final dimensions meet Part DT requirements.NOTES1. The limits of ASME B31.3 shall apply2. TW is the nominal wall thickness of the thinner of the two members being joined. Weld metal must blend smoothly into base metal. 3. Welds on tubing that has been in service may require unique criteria.4. Any weld that shows unconsumed tack welds on the nonproduct contact surface must be inspected on the product contact surface; otherwise they are rejected. If the weld cannot be

inspected on the product contact surface, rewelding per MJ-8.4.2 is not allowed. Rewelding per MJ-8.4.2 is allowed if the weld can be inspected on the product contact surface after rewelding.5. Arc strikes on the nonproduct contact surface may be removed by mechanical polishing as long as the minimum design wall thickness is not compromised.6. Note that misalignment is controlled on the O.D. and is based on allowable O.D. dimensions and tolerances of fittings and tubing. The owner/user is cautioned that this can result in

greater ID misalignment because this also takes into consideration that wall thickness dimensions and tolerances of fittings and tubing. However, there are no specified ID misalignment acceptance criteria.

Source: Reprinted from ASME BPE-2014 (Table MJ-8.4-1), by permission of the American Society of Mechanical Engineers. All Rights Reserved. No further copies can be made without written permission.

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