Quality & Safety

Making the right connections

Ensuring weld quality in structural steel construction

The Northridge, California, earthquake brought to light the shortcomings of several areas in the design, construction, and inspection of connections in steel-framed buildings. Numerous accounts of problems with welding procedures and technique, the quality of completed welds, and the inadequacy of the inspection performed on welds were reported.

Tests conducted on structures previously considered undamaged by the earthquake revealed weld defects and have raised doubts about the ability of existing inspection techniques to identify and classify these problems accurately.

Project specifications for steel building inspection often are stated in general terms such as "inspect in accordance with the Code," usually citing the American Welding Society (AWS) D1.1 Structural Welding Code---Steel, the American Institute of Steel Construction (AISC) Specification for Structural Steel Buildings, and the applicable building code.

Expanded knowledge about design, materials, and workmanship problems lead to a need for more specific instruction to define and delineate the inspection tasks assigned under quality control (QC) and quality assurance (QA), which are the responsibilities of the fabricator or erector and the owner or the owner's representative, who is often the engineer.

The AWS D1.1 specification is not specific about who performs inspections, but simply states that such inspections shall be performed. The reliance upon the fabricator's and erector's quality control program for such inspections, and the reliance on outside quality assurance inspectors to perform such functions, must be clearly defined in the contract. Using hold or witness points at specific stages and/or joints may be a part of the project specifications.

Structures may not perform as intended if they are not constructed to the applicable codes and standards.  Welding filler metal controls, base metal controls, prewelding requirements and inspection, welding procedure verification, and nondestructive testing are all essential elements of the quality assurance process for welded connections.

Inspection items include preheat, interpass, and postheat checks; joint fit-up; base metal conditions; welding personnel requirements; and adherence to welding procedures. Ultrasonic testing, while an extremely important part of the process, is limited in what it can accomplish.

 
Prewelding Inspection

Before the contractor fabricates and fits up parts for welding, an evaluation of the contractor's (fabricator's or erector's) welding personnel is necessary. The AWS D1.1 specification, as well as the building codes, clearly outline the required qualifications for welding personnel.

Welders (who manipulate the electrode by hand), welding operators (who set up automatic welding equipment), and tack welders all must perform specific tests of welding skill to prove their ability to weld using a given process, in a given position, in a given thickness range, and, in some cases, using a given class of electrodes [for shielded metal arc welding (SMAW)].

Written documentation of the tests given to each and every person welding on a project must be available to the inspector. It should be verified that the contractor has properly qualified welding personnel to make the welds required for the project.

An adequate welding procedure specification (WPS) written for each weld on the project is required under both AWS D1.1 and the building codes. A checklist of the weld joints, positions, thicknesses, and planned processes for the welds is a useful tool to facilitate this review.

Although the contractor is responsible for the quality of his/her own welds, it is important to review procedures to determine if they are rational and fall within prequalification limits. If the WPS is prequalified, the procedure does not have to be finally tested in accordance with AWS D1.1 Section 4, but still must produce a quality weld.

If the WPS is not prequalified, it must be supported with a procedure qualification record (PQR) that documents the weld joint and welding parameters used to prepare the WPS. Prequalified WPSs should be reviewed for adequate heat input, reasonable travel speeds, and a rational relationship between electrode size and weld size. Experience and training are needed to perform such a review.

Welding equipment must be in working condition and capable of providing the voltage, current, travel speed, polarity, and other conditions of the WPS. Gauges and controls must be checked to ensure their accuracy within a reasonable tolerance for the selected process and procedure.

The frequency of equipment checks is not mandated by AWS D1.1, but they should be performed on at least an annual basis for building work.  The AWS D1.5---Bridge Welding Code requires welding equipment checks every three months.

An inspector also must verify that the fabricator has an adequate system in place to identify and control materials. Standard fabrication practice requires the fabricator to identify a piece of steel by steel grade only; tracing a piece of steel to a specific heat of steel is not required.

If such a condition is required by the project's engineer, the fabricator must have and implement a system for maintaining the required level of traceability and documentation. In addition to controls being in place for the main structural steel materials, they must also be in place for bolting and welding materials.

 
Filler Metals, Fluxes

For filler metals and fluxes to perform properly, they must be stored properly. Low-hydrogen SMAW electrodes must be supplied in an undamaged, hermetically sealed container, or else baked dry at a very high temperature prior to use. They also must be stored continuously in rod ovens maintained at or above 120 degrees Celsius (C) [250 degrees Fahrenheit (F)].

After the electrodes have been removed from the rod storage ovens, their exposure to the untreated atmosphere must be limited to relatively short periods, depending on the electrode type and strength level and, in some cases, ambient temperature and humidity.

Similarly, submerged arc welding (SAW) fluxes must be received in undamaged bags or dried prior to use. Flux in opened bags must be maintained by removing the top 25 millimeters (1 inch) of exposed flux on a daily basis.

Electrode wires, such as those used for flux colored arc welding (FCAW), gas metal arc welding (GMAW), and SAW must be protected to prevent rust and dirt from fouling the wire feeders and adding impurities to the weld.

FCAW wires may absorb a limited amount of moisture over time but usually not enough to affect performance adversely. When the wires will not be used in production for an extended period, they can be stored in a closed plastic bag to reduce moisture absorption. Rod ovens are not required to store FCAW wire.

It is imperative for the inspector to verify that the contractor has the equipment and systems in place to store and control filler metals and fluxes properly.

 
Inspection Prior to Welding

After it has been verified that the contractor has the necessary material controls and welding personnel and procedures in place, fabricating can begin. First, however, several items must be inspected before any arc strikes the steel.

The steel must be clean and free of moisture, loose or thick mill scale, rust, coatings, oil, grease, and any other material that would be detrimental to weld quality. Some welding processes, such as GMAW, require higher levels of cleanliness than others. Many of these contaminants contribute hydrogen to the heat-affected zone (HAZ), increasing the risk of HAZ cracking.

Groove welds must be configured properly within specified tolerances. A proper root opening is necessary to provide adequate access to the root. A root opening that is too narrow may lead to incomplete penetration, while a root opening that is too wide may lead to root throat shrinkage cracking or base metal cracking.

The proper groove angle also is needed.   A groove that is too narrow may lead to root access problems and a lack of fusion along the groove face.

A groove angle that is too wide contributes to excess shrinkage and distortion, an increased risk of lamellar tearing, as well as increased time and welding expense. Fillet welds also must meet fit-up tolerances, or the root quality may be compromised and the effective leg size of the fillet weld will be reduced.

Tack welds must be of adequate quality to permit quality welding over them, and the welds must not be so large that they interfere with the deposit of the root pass. However, tack welds also must be of adequate size to resist weld shrinkage stresses and member distortion during welding, or cracking of unwelded tacks may occur.

Preheat must be applied to the steel joint prior to welding thicker steels and highly restrained joints. The minimum amount of preheat on a prequalified basis is provided in AWS D1.1. However, additional preheat may be advisable with high restraint conditions, poor weldability steels, or to further reduce the risk of lamellar tearing. Using AWS D1.1 Annex XI may assist in this determination.

Preheat must be measured 75 millimeters (3 inches) away from the joint unless the steel exceeds 75 millimeters (3 inches) in thickness, in which case the preheat is measured a distance equal to the thickness away from the joint.

Preheat is typically measured with temperature-indicating crayons, surface temperature thermometers, or infrared devices. After adequate preheat has been supplied and verified, the first pass must be promptly placed before excessive cooling takes place.

 
Inspection During Welding

It is imperative to follow the welding procedures that have been selected. Welding personnel must have a copy of the WPS readily available, follow procedures as given, and have equipment capable of accurately providing the required welding parameters. It is unnecessary to measure voltage and current during welding, but this is required by some project specifications to serve as a WPS reminder and as documentation that the WPS has been followed.

Interpass temperature maintenance as the weld is completed is vital to joint performance. The welding heat may be adequate to maintain the interpass temperature as the joint is welded, provided the cleaning and visual inspection of each pass are rapid enough. However, it is often necessary to add heat from an outside source to maintain the required temperature.

A completed joint's toughness may be adversely affected by excessive preheat and interpass temperatures. The combination of welding heat and the slower cooling rate caused by excessive preheat/interpass temperatures may lead to excessive grain size. Verifying the interpass temperature is as important as verifying the preheat temperature.

AWS D1.1 requires each pass to be inspected visually by the welder. Failure to maintain good pass quality, such as good bead profile, can lead to access problems and a lack of fusion. Failure to clean each pass properly leads to slag inclusions and a subsequent lack of fusion.

However, a visual check of each groove weld or fillet weld pass by an inspector is rarely required or done. To waive such visual inspection and rely solely on the welder, one must be assured that the welder has the proper skills, procedures, and materials for welding. This is a key reason for prewelding inspection.

 
Inspection After Welding

After the weld is complete, a final visual inspection is necessary to confirm that the weld size, location, and quality conform to the project specifications. For certain joints and welds, nondestructive (NDT) testing may be required.

Beyond visual inspection, the common NDT methods of dye penetrant testing (PT), magnetic particle testing (MT), ultrasonic testing (UT), and radiographic testing (RT) may be specified. The building codes require specific levels of NDT, particularly UT, for certain joints in seismic moment-resisting systems if they are located in high seismic regions or are used in designated critical structures.

 
Ultrasonic Testing

Ultrasonic testing has been the method of choice for groove weld inspection for many years. Recent evaluations of existing projects have identified that existing UT practices may be inadequate for the complete inspection of older-style beam-to-column moment connections.

Interpretation of UT has been inconsistent and difficult when used to examine the root area of the beam flange groove welds when backing bars are present. Although techniques have been used to improve examination accuracy in this area, these techniques rarely are used effectively in the field.

Other problems in the UT of beam-to-column moment connections include interference of the beam web at the bottom flange, interference of the groove face when using first-leg scans, and the rare use of second-leg and Face B or Face C scans to overcome such interferences.

Current seismic practice calls for removing the backing bar at the bottom flange and placing a reinforcing fillet, in part to improve the quality of the UT evaluation. These issues must be incorporated into standard inspection practice.

 
Conclusion
The need for high-quality welds in steel structures is obvious, especially in seismic-region structures and in critical joints. Outside quality assurance is needed to supplement the contractor's internal quality control efforts. The engineer must provide specific inspection criteria defining the roles of QA and QC, as well as the structural and quality demands for the project.
 
QA/QC Comments

 Review of Method Statement for Underground (Carbon Steel) Piping Construction and Installation.Note: The following comments are guidelines only and are not instructions from TECHNIP.  Descon’s “Method statement for Underground (Carbon Steel) Piping Construction and Installation” is their full responsibility. Material Handling

· Will the large diameter pipe be fabricated “in situ”? Suggest:-

· For the general large diameter of spools and fittings no shop prefabrication will be attempted to minimize handling. All spools will be delivered to place of erection and prepared. Any of pipe elements or branch connections will be done either next to the trench in moveable temporary shelters or inside the trench “in situ” conditions. Care will be taken to avoid fitting branches to spiral weld seams and spools will be turned to offer maximum interference. Where compensation pads fit over spiral seams same will be ground flush and inspected for any cracks or other defects prior to fitting pad. T weld connections will be subject to X-ray inspection to prove compliance.

· Note: Clarification is required on where the medium and small bore pipe will be fabricated / stored.

 
RECEIPT & STORAGE OF PIPE RAW MATERIAL

» The piping raw material received from Technip shall be offloaded in designated lay down yard or Near the Site where piping will be installed. Specify the transport.

» During offloading, pipes shall not be dropped off the transport. A crane & nylon slings shall be used to handle CS pipes & fittings. More details required for the handling. How to remove the slings, will pipe be on sandbags for easy removal?

» The pipes shall be placed with suitable material in place to ensure that no damage to pipe or paint occurs. They shall be adequately supported to minimize sagging.

» The piping end covers shall be kept in place to prevent foreign particle entry into the pipes.

» All material shall come with color-coding as per size, material & schedule.

» The piping material shall be segregated accordingly to facilitate location of items.

» Small-bore pipe fittings, less than 2”, shall be stacked on racks in warehouses. They will be segregated accordingly to material, size, and rating & by tag number.

»  Suggest: A maximum of one week spool requirement will be stockpiled on site to avoid congestion

 
SPOOL BREAKDOWN

»  The piping isometrics shall be marked into number of spools to facilitate the fabrication & erection works.

»  Each spool shall be marked with a unique number.

»   Each joint on the isometric will be given a unique number preparing a welding map for traceability. Separate numbering system will be followed for butt welds & fillet welds.

»  The details of piping isometric breakdown into spools and joints will be recorded for reference.

 
PIPING FABRICATION

»  As per the relevant isometric drawings material will be shifted from lay down area to fabrication shop or to the place of erection.

»  The carbon steel & low temperature carbon steel pipe fabrication work will be done in separate areas.

»  The cutting and beveling of pipes shall be done by mechanical means like flame cutting machine.

»   Pipes for socket weld joints shall be cut square.

»  Reinforcement pads shall be installed only if required in the isometric. The material for reinforcement pad shall be same as that for the pipes unless otherwise authorized by Technip. The pad size & thickness of the pad will be specified in the isometric. It is preferable that the pad shape is circular, however the pad size may be altered provided equivalent cross-sectioned area is maintained as per ASME requirement. The pad shall have a 1/8” NPT vent hole, drilled & tapped to NPT prior to installation of reinforcement pad.

 
IDENTIFICATION OF SPOOLS

»  Heat No of Pipe shall be transferred on each cut length of Pipe spools by Permanent Paint Marker.

»  Spool identification shall be done by marking spool no, Isometric No/Line No of Pipe spools with Permanent Paint marker.

 
FIT UP BUT WELDS

§  The fit up of pipe ends, fittings & weld neck flanges shall be done to obtain uniform root opening. The criterion given in related WPS shall be followed.

§  The primer paint coat on pipes & fitting ends required to be welded shall be removed. What distances from the end of the pipe will the paint is removed?

§  The pipes shall be tack welded by qualified welder with approved wire /Electrode. Where bridge tacks are deemed to be required it will be in the form of tack welded wedge clamps (strong backs) in area requiring adjusting. After fit up strong backs will be removed, area ground smooth and MPI carried out to verify integrity of pipe. It will require conformation from TECHNIP QA/QC to apply bridge tack method.

§  If the pipes are of different thickness, the larger thickness will be tapered in compliance with the standard to match the smaller thickness.

§  The adjacent section of longitudinally welded pipes that are to be joined by butt-welds shall have longitudinal welds seam positioned such that they are at least 30˚ apart from horizontal center line Ref Fig NoX. The fabricator will also not locate longitudinal weld seams on top or bottom of the pipes so that branch connection is not located on the seam.

§  Tack weld for fit up joint shall be done by using a bridge Clit of same material in such a way that it will not disturb the root face of the weld joint Ref Fig No2X:

 
SOCKET WELDS
The pipe for welded sockets joints shall be ground to remove burrs due to cutting. A gap of approximately 1.6 mm between ends of the pipe & bottom of socket will be provided Ref Fig N o: 3X how will this be achieved and what inspection will be undertaken to verify?
 
WELDING

· All welding work will be according to approved WPS, B31.3 and Technip piping welding specification. Only qualified welders shall be employed.

· All welders will carry an approved weld identification badge when welding.

· Before welding of joint following information shall be provided at adjacent of pipe joint.

a) Piping Class

b) WPS NO.

c) Pipe material (CS)

d) Welding Process (GTAW/SMAW)

e) Tig wire for Root (ER70S-6)

f) Welder Stamp NO

g) Electrode (E7018-1)

· The welding work piece will be shielded against high winds and rain. The wind speed exceeding 10m/sec and 3 m/sec for SMAW & GTAW respectively.

· The weld surface shall be cleaned with the wire brush or grinding prior to welding operations to give a surface free from rust, scale or mill cutting.

· Between each layer of welding any cracks, pores or welding spatters shall be removed by grinding the surface before application of next layer.

· The appearance of finished welds shall conform to ASME B 31.3 codes & WPS and shall be free from any under cuts, spatters & cracks.

· All branch connections shall be joined to header with full penetration welding. The bore side shall be ground smooth, free from rust.

· For flange to pipe connections if welding shrinkage can lead to misalignment, two similar flanges shall be joined by inserting a temporary gasket and then welded.

· Above Sequence shall be followed for heavy wall thickness for avoiding after or during weld distortion.

· The flange indicated on isometric to be supplied loose shall be tack welded with the pipe. Full welding shall be made after site checking.

· For socket welding the pipe ends shall be cut straight.

 
THREADED JOINTS
· In case of threaded pipes (for Potable Water Line) screw threads shall be concentric with axis of pipes with no burrs or stripping. The Threading dies shall be sharp & properly designated for piping material.
 
GALVENIZED PIPES

· The pipe work up to 2” shall be threaded & galvanized by hot dip process to both inside & outside.

· The pipe work 3”& larger shall be fabricated in flanged spools as per design. The size of spools shall confirm to dimensions of hot dip galvanizing bath. The same shall be galvanized from both inside & outside.

· The threaded joints of galvanized pipes shall not be seal welded. A PTFE tape will be used as a sealant.

 
INSPECTION

· The fabricated pipe spools shall be checked against TECHNIP drawings to verify its compliance.

· The dimensions angle and direction of bent portions and allowances for field welding shall be according to ASME B 31.3 (Chapter V).

· NDE shall be performed as per ASME section V after PWHT if specified on isometric drawings.

· The acceptance criteria for visual inspection shall be done according to ASME B 31.3(Chapter V).

· Visible small transverse cracks & star cracks of limited thickness shall be removed by grinding & repaired by welding. However circumferential cracks shall result in weld rejection. The defective material will be cut out & re welding shall be performed.

· NDE (RT/ UT/MPT) will be requested as per piping specification of welding provided by Technip.

· NDE results shall be interpreted by qualified inspectors (level II) & if resulted in defect, repair of the same joint shall be done & Re inspection shall be offered.

· After NDE clearance in all respect Pipe spool shall be released for Painting/Storage/Erection.

· Branch connection shall be examined by dye penetrate or magnetic particle or ultrasonic methods. Where the header thickness exceeds 16 mm, this type of examination shall be made for every 9 mm thickness of weld built up.

· All welding records for each joint shall be maintained throughout the fabrication work.

· Low temperature carbon steel material traceability shall be maintained through out the fabrication work such that location & heat numbers of all welded pressure retaining pipe component is maintained. Permanent marker will transfer the heat number to all pieces cut from pipe.

 
IDENTIFICATION
Each fabricated spool shall be clearly marked with a number. This number shall include line number & spool number as shown on the piping isometric. For piping up to ¢ 6” it will be hard marked on to a steel plate 2” x 3” x 1/16” which shall be securely wired to the pipe. However for piping greater than ¢ 6”, the number will mark on inside of the pipe using a permanent marker.
 
STORAGE

· The pipe spool complete in all respect shall be stored separately.

· All spools shall have their piece number clearly designated on each spool.

· The spool will be cleaned in an inclined position by tapping so that all foreign materials are removed.

· The spool shall be placed on wooden baton to avoid direct contact with soil.

· The open ends shall be securely covered by polyethylene sheets or end caps. In case of flanged spools the same shall be covered by securely tied wooden blanks to avoid foreign material entering the pipes.

· The spool shall be handled using nylon lifting slings.

 
PIPING ERECTION

· The fabricated piping spools of random length shall be shifted to site near the Trench.

· After the Trench acceptance related for piping erection piping will be lay down on the sides of the trench on wooden sleepers or sand bags.

· A detailed planning schedule will be prepared to cover the order of work which will include any ‘tie-in’s’ with other contractors. The detail plan will be approved by TECHNIP before any work commences.

· Piping slopes shall be maintained as per isometric.

· The pipe spools requiring field joints shall be welded at site. The pipe ends shall be prepared for welding after site checking the dimensions.

· A procedure similar to that described under fabrication will be followed for welding. Not enough detail for site welding.  Suggest: Sandbags will be used when placing the pipe in the trench. The height of the sandbags will be determined by depth of excavation versus the required BOP elevation. Welding on the bottom of the pipe will be achieved by trenches dug at weld seams coordinates as instructed by TECHNIP.

· The piping shall be erected & supported plumb & level such that there will be no undue strain on corresponding equipment flange. The alignment of flanged joints shall be according to the ASME B.31.3 (chapter V).

· For fit-up of spools, sections will be adjusted by hydraulic jack if minor adjustment is required. Where spools require being brought closer together this will be achieved by moving with crane.

· In case of flanged connections, the surfaces in contact with gaskets shall be checked before assembly and all traces of dirt oxides & grease shall be removed.

· The flanges shall not be joined together without the insertion of gaskets.

· All temporary gaskets shall identify by color-coding on their handles exposed.

· All bolt heads shall be assembled from the same side. A logical sequence of bolt tightening shall be followed to evenly tighten the flanges.

·      The Screwed joints shall be thoroughly cleaned for dirt or any other foreign matter. Teflon tape shall be used for all screwed connections. The tape will be wound in correct direction. All excess Teflon tape shall be removed. Care shall be taken that the tape does not enter inside of pipe.

· Seal welding of screwed joints shall not be performed unless specially permitted.

· Cathodic protection work will be carried out as per Project Specification and approved by other discipline (Electrical) as per schedule and in coordination with piping and civil departments.

· Visual / NDE will be done as per piping class requirement.

· Suggest: The NDE activities shall be carried out in accordance with the relative line class designation and as per the QCP’s for Radiography, Magnetic Particle Inspection and Dye Penetrant Inspection by appointed sub –contractor and monitored by Lehoud.

· Touch up coating and corrosion protection of pipes shall be completed as per manufactures recommendations. This may be accomplished while temporarily supported on sandbags ensuring a sufficient distance is maintained between the pipe and the trench bottom at the area where the inspection and the repairs are to be completed.

· Piping will be inspected for cleanliness and swept clean by means of compressed air or other means if required. Lehoud will ensure that all coupons and debris deposited in the new lines during cutting and grinding shall be removed and the affected area cleaned. Cleaned sections of piping will be closed with a temporary wooden blank to prevent foreign particles entering. The blank will be moved as the next section of pipe is cleaned. Cleanliness records will be kept and updated as work progresses.

· A joint inspection TECHNIP and Lahoud shall be performed prior to backfill, a punch list shall be established and backfilling will only be authorized upon clearance of all punch items

· Sand bedding and backfilling will be carried out as per specification. Sand bedding surrounds and backfilling works will be conducted in a manner that will prevent damage and abrasion to the coating

· Service testing activities will be carried out. This activity will be subject to a deviation request.

 
The Basics of Welding Safety

Proper welding safety starts with familiarizing yourself and other operators with the welding equipment and the manufacturer’s recommendations. Take the time to read the operator’s manual thoroughly and follow all of the safety, operation and maintenance instructions it contains. Keep the manual handy so new users can acquaint themselves with the machine. Should the operator’s manual become lost or damaged, request a new one from the manufacturer. Miller Electric and many other manufacturers provide product manuals on-line. Spanish and French language versions are available for some of the most common products.

 
The Well-Dressed Welder
Arc welding produces sparks and emits intense visible and invisible rays that pose several hazards to unprotected skin and eyes. When welding, adequately protect your skin. Shorts, short sleeves, open collars all leave you vulnerable to burns from both flying sparks and the arc rays. Wear only flame-resistant clothing, and button your cuffs and pockets to prevent them from catching sparks. Pants cuffs, too, can catch sparks and should be avoided.
Figure 1: The well-dressed (or safely dressed welder) no longer has to use a clumsy, ill-fitting jacket. Modern welding garments are more functional, flexible and better fitting. Note that once the welder dons the helmet, he will have no skin exposed to sparks or arc burns. A flame resistant jacket is completely buttoned, allowing no pockets or spaces for a spark to catch. A welding bandana protects the top of his head from sparks. Anauto-darkening welding helmet decreases the chance for repetitive stress injury to one’s neck and can adjust to changing arc parameters conditions.
 

With respect to footwear, high top leather shoes offer the best protection. Tennis shoes and other cloth shoes are inadequate; they can catch a spark and smolder unnoticed and their components can melt and stick to your skin.

Always wear proper gloves when welding or handling recently welded material to protect yourself from sparks, arc burns and the heat from the workpiece. Remember, even a quick tack weld requires the use of a welding helmet and appropriate apparel (see Figure 1).

Although the above sounds obvious, a common fault among welders is not wearing the right safety equipment. While expediency is one reason often given, some welders complain that the common, one-size-fits-all apparel is too bulky, heavy and restricting and that gloves, especially in TIG applications, do not provide the necessary sensitivity and flexibility.

While that may have been true in the past, leading manufacturers now offer safety apparel that address the welder’s comfort and specific needs.

"The welding industry is moving beyond the cookie cutter, one-size-fits-all idea of safety products, demanding garments that are safe from a functional standpoint, yet attractive with a better fit,” says John Swartz, welding components & consumables product manager, Miller Electric Mfg. Co.

Lightweight flame resistant cloth, pigskin leather and combinations of the two offer the welder better protection, even when welding overhead, and increased ease of movement than ever before. For additional flexibility, some jacketsfeature snaps for the addition of a leather bib or apron.

Gloves in small to extra-large sizes with ergonomically curved fingers are now available for specific welding processes. Heavy duty MIG/Stick gloves, medium MIG gloves and TIG gloves that provide that added dexterity and touch are just some of the recent additions to the field (see Figure 2)

 
Figure 2: Welding gloves are now available in different styles to meet the demand of different welding applications. The medium duty MIG gloves shown here (left) offer ergonomically curved fingers and padded palm for increased comfort and rugged construction for increased longevity. The TIG gloves (bottom center) are made from goatskin, which provides excellent dexterity, comfort and durability. Metal working gloves (top center) and heavy duty MIG gloves widen the choices available to the welder.
 
Helmets

Even a brief exposure to the arc’s radiation may be damaging to your eyes, causing symptoms from a burning sensation to temporary blindness. Repeated exposure can lead to permanent injury. Always wear proper eye protection when welding or when exposed to a welding arc.

If you use a standard, fixed shade helmet, pick one that has a lens shade appropriate for your welding application. OSHA offers a guide for choosing the correct lens based on welding criteria. If your weld parameters and materials don’t vary, a fixed-shade lens may be right for you. However, if you’ll be switching processes, materials or parameters, an auto-darkening helmet may be your best solution.

All auto-darkening helmets must meet ANSI standards, the most recent being ANSI Z87.1-2003. When an arc triggers the sensors on an auto-darkening helmet, the lens darkens in a fraction of a second. Some fixed-shade auto-darkening helmets darken to a #10 shade with a reaction time of 1/2000 to 1/3,600 of a second and are not adequate for frequent tack welds, TIG welding and other industrial applications.

Industrial grade helmets react at speeds of 1/10,000 of a second or higher to prevent eye fatigue and arc flash symptoms, and have adjustable shades settings of #9-#12 or #13. (Miller Elite auto-darkening helmets react in 1/20,000 of a second, with shade settings of #8 to #13.) Industrial grade helmets, such as the Miller Elite series, will also have adjustable sensitivity and delay controls (see Figure 3).

Adjustable sensitivity is useful when welding at low amperages, especially TIG, when the light isn’t as bright as other processes. Adjustable delay controls how long the lens remains darkened after the arc stops. When tack welding, a short delay may be desired, while a longer delay may be desirable after welding at very high temperatures. Even when not activated, the lens provides UV/IR protection and usually has a light state of a #3 or #4 shade, which is relatively easy to see through.

Auto-darkening helmets provide some other important benefits also. With a fixed-shade helmet, the welder positions the gun, torch or electrode and then jerks his head down to bring the helmet into place. This may lead to neck injury through the repeated motion, especially for welders who perform a series of tack welds. For the novice or person who welds infrequently, the jerking action can cause him to move out of position and lead to a weld defect. An auto-darkening helmet allows the welder to keep the helmet in place while positioning the electrode, leading to better positioning and relieving some of the stress from the welder’s neck.

 
Work Environment

You must also protect others in the welding area. Use a weld screen to ensure passersby will not be subjected to the arc flash.

Keep your work area free from clutter. This promotes safety and helps increase efficiency by making necessary equipment easier to find. Remove rags, paper or anything else that could be a fire hazard. Cables and hoses can create a tripping hazard. Organize the workspace to minimize the number of cables underfoot and position them so they are not in danger of being run over or stepped on (see Figure 4). If possible, suspend hoses off the ground and coil up excess hose to prevent kinks and tangles. MIG welding with a wire feeder that allows remote control of the power source is one way to free up space in the welding cell.

 
Figure 3: Auto-darkening helmets provide many benefits, including increased efficiency, decreased chance for repetitive stress injury and responsiveness to changing arc quality. Attractive graphic designs promote safety while allowing the wearer to express his or her personality 
 

Figure 4: By using the remote control capability of its Miller Delta-Fab welders, Godwin Mfg., keeps the power sources out of the welding cells and hides the hoses and cables underground where they can’t be tripped over or run over by a forklift. The result is a safe and efficient work area.

Examine hoses regularly for leaks, wear and loose connections. To check for leaks, immerse pressured hoses in water (bubbles will indicate leaks.) Repair a leaky or worn hose by cutting out damaged area and splicing. Do NOT use tape.

Avoid working in wet conditions, since water conducts electricity, and insulate yourself from the work and the ground by standing on a dry rubber mat or similar non-flammable material. Connect the workpiece to a proper earth ground and connect the frames of all electrically powered machines to a properly grounded disconnect switch, receptacle or other appropriate ground. Always double-check the installation and verify proper grounding. Never use chains, wire ropes, cranes, hoists and elevators as grounding connectors.

When using gas cylinders, chain them securely to a stationary, upright support or cart at all times. When moving or storing a cylinder, fasten the threaded protector cap to the top of the cylinder. Doing so shields the valve system from impact damage.

Immediately remove a faulty regulator from service for repair by a manufacturer’s designated repair center. Do not attempt to repair it yourself.

Use only recommended ferrules or clamps designed to connect hoses to fittings—never use ordinary wire or other substitutes.

    Photo Gallery
Copyright © 2010 - Gafoorxspeed.com - All about welding and x-ray welding .., All rights reserved..,