Pipe Flange Protectors protect flange face, studs, and gaskets on the raised face, full face, and ring joint flanges from atmospheric corrosion encountered in chemical plants, onshore oil fields, metering stations, refineries, gas plants, offshore platforms, water and wastewater plants, pump stations, and underground pipelines. Controlling corrosion and awareness of its ever-damaging effects is paramount in piping and pipeline maintenance.
By using the Flange Protectors and Corrosion Inhibitor Grease, flanges are ensured to be safe from hazardous and unsightly corrosion that has huge potential to cause leakage, failure, or even shutdown of equipment. The downtime, coupled with the cost of cutting and welding a new flange, and replacing flange bolts, nuts, and seals, becomes very expensive.
Fig. 1: Typical Flange Protectors
Flange Protectors can even be used on cathodically isolated flanges to prevent foreign matter from shorting out or bridging over an isolating gasket. To ensure complete loading of flange cavities, All Flange Protectors are equipped with an exclusive positive loading relief vent and plug. The extruded, clear, flexible poly band allows visual inspection without removal of the protector and ensures complete filling of the flange cavity. Additionally, it is non-corroding provides many years of service life, and is reusable.
Benefits of Flange Protectors
Benefits of Flange Protectors include:
Envelopes flange and flange internals to prevent corrosion.
Maintains integrity of gasket and seal.
Keeps out moisture, chemicals, saltwater, debris, etc.
Ensures cathodic isolation protection by keeping the foreign matter out of the flange gap.
Quickly installed with a screwdriver.
Available for all size flanges.
Custom-engineered designs available per application
Highly Cost-effective
Can be removed and reused easily.
Materials for Flange Protectors
Flange Protectors can be made of various materials like:
Metallic Flange Protectors are made of Carbon Steel, Aluminum, Stainless Steel, Galvanized Steel, etc.
Non-metallic flange protectors are made of Polyethylene, LDPE, HDPE, Plywood, Sponge Rubber, etc.
Applications of Flange Protectors
The annular gap around the Flange Outer Diameter is highly vulnerable to debris and moisture ingression. These can result in gasket degradation and can cause corrosive damage to the flange, sealing faces, and studs. Excessive corrosion in such areas is hazardous, and replacement could lead to unscheduled downtime. To solve such problems, inexpensive and easy-to-fit range flange protectors are widely used.
Such flange protectors are tightened around a flange and packed with corrosion inhibitor grease. A build-up of pollutants from corrosive and salt-laden environments around the flange, gaskets, and studs is protected using these products. Because of these reasons, flange protectors are used in flanges of pressure vessels, heat exchangers, pipelines, and other process plants, where the ingress of moisture and debris is likely to degrade the mechanical efficiency or sealing integrity of the joint.
Material handling systems mean the control of materials and products for project use in various stages starting from manufacturing, storage, distribution, consumption, and finally disposal. The system must ensure the safe handling of all project materials. In this process, the material handling system uses various manual, automatic, or semi-automatic equipment known as material handling equipment. So, the material handling system basically deals with the safety of material handling equipment & their operations.
Material Handling Systems are very important mechanisms in supply chain management as they efficiently manage material movement in a controlled way. The material handling operation varies between manufacturing, storage, construction, and transportation based on industry types.
The main objective of the material handling system is to ensure proper handling, lifting & offloading of equipment in order to ensure a safe workplace. It ensures the operations are in line with the required guidelines & project specifications. Debating with these standards and guidelines means tolerating the life of self and stakeholders. Basically, standard guidelines are followed in the construction of refineries, chemical & petrochemicals, pharmaceutical companies, and power plants.
Fig. 1: Typical Material Handling Equipment
Advantages of Material Handling Systems
A properly designed material handling system helps a project in many ways like:
Proper resource allocation
Shorten delivery time
Forecasting
Proper Inventory control and management
Improved Production planning
Improved customer service and after-sales support and finally
Reduce overall material handling costs
That is the reason proper material handling systems are widely popular in all industries like chemical, aerospace, construction, automotive, pharmaceutical, manufacturing, oil and gas, petrochemical, paper, material processing, warehousing, distribution, etc.
Fig. 2: Material Handling using an Overhead Crane
Components of a Material Handling System
There are various components that constitute a material handling system. It may vary significantly from project to project. Some of the widely used components are added below as a reference.
Cranes-
Cranes as material handling equipment are widely used for lifting and shifting equipment and materials. There are a variety of cranes (Fig. 2) available in the market. Some of those are from 5 MT TO 8000 MT. In the construction industry, basically, two types of cranes are being used nowadays.
tyre-mounted cranes and
crawler-mounted cranes.
Both can be used for lifting and shifting. The crawler-mounted cranes are used for high strength and they can move over Mud or difficult places. On the other hand, tyre-mounted cranes are used for clear surfaces, roads, or properly compacted places.
Slings & belt-
Sling and belt both are used to tie a piece of equipment. The number of slings and belts for a particular operation is decided based on load calculation. The formulae for load calculation are mentioned below for reference.
Fig. 3: Load Calculation formula for slings and belts
Here, V1 is the load at point 1, V2 is the load at point 2 & W is the overall load.
D rings-
D rings are used to tie belts or slings with equipment or material to be lifted with cranes, prior to placing color code, specification & TPI (Third party inspection report needs to be ensured).
Eyebolts-
These are the mechanical Bolts that are being used to fix and ensure that D rings and slings or belts have tied properly and are ready to lift. Lifting operations could be performed only after conforming to the inspector. The inspector or safety in charge shall ensure SWL (safe working loads), TPI reports, visual checking of color and threads, and SOPs.
Guiding rope-
After assembly, this one is vital to guide the load/ equipment to place at the foundation or workplace. Because of the presence of air, the material can move here and there so a guiding rope shall be used to guide it under formal instruction. Traditionally 2 guiding ropes shall be used for proper erection, loading, or offloading. The first rope will guide and the 2nd rope will resist the movement.
The other components that can form the material handling system are
In recent times, automation has been used in material handling systems which makes the material handling systems more efficient to perform their job.
Types of Material Handling Systems
Normally four types of material handling systems are used widely.
Storage Systems
Engineered Systems
Industrial Material Handling Trucks and
Bulk Material Handling Equipment
For maximum efficiency and safety, standardization of material handling methods, equipment, controls, and software should be used.
Pre-operation material handling system checklist
Fig. 4: Use the material handling system checklist to avoid mishaps
As the operation is big and is being used by some of the biggest industries such as refineries, power plants, and aviation industries, a checklist should be followed to ensure safe operation. The following points must be ensured:
Crane operators, trailer operators, and rigging foremen should be competent with experience in using specified equipment.
A Job Safety Analysis is a process to integrate health and safety principles into a particular job operation. In a job safety analysis (JSA), potential hazards for a specific job are identified before they occur and the safest way to perform the job is recommended. Such procedures reduce the risk of injury to working professionals and ensure that the workplace is compliant with safety regulations. Job safety analysis is also known as job hazard analysis (JHA) or job hazard breakdown and is an important step toward employee safety.
Advantages of Job Safety Analysis
The main purpose behind job safety analysis are:
Job-oriented risk assessment.
Identification and evaluation of hazards beforehand help in controlling the risk.
Control of incidents and thus minimization of loss.
Standardization through creating procedures and work instructions.
Ensuring safe working methods consistently.
Compliance with regulatory requirements (OSHA requirements)
Getting organized for doing the job right and efficiently.
Improving the work safety culture of the company.
Documentation of Job safety analysis fulfills audit requirements.
Increased productivity in absence of major hazards.
Improved quality of work.
Better planning in job execution and overall increased morale and profit.
Jobs requiring Job Safety Analysis
Job safety analysis is very important for all industries that face safety issues frequently. Typical industries that must include job safety analysis in their work culture are Oil and gas, construction, mining, power industries, electrical, etc. Working professionals from such industries should be constantly vigilant of potential hazard scenarios in the workplace. Even though all kinds of jobs irrespective of their type should be included in job safety analysis, companies can prepare a priority list as follows:
All jobs with the potential to cause fatality.
All jobs with the highest injury rates/ Fire and explosion incidents.
All jobs where human error can lead to severe accidents, fires, or explosions.
Jobs for which no prior work experience is present.
Jobs of complex nature.
Hot works inside the battery limit of operating plants.
The major modification works.
Jobs that include health and ergonomic issues.
Job safety analysis can be excluded only for routine non-critical jobs without the potential to hazard development. Normally, the Sectional Head / Area in-charge/ Plant Engineers/ or Managers will be responsible to carry out Job Safety Analysis of all activities in respective units. The management of any organization must demonstrate its commitment to safety and health for a job hazard analysis to be effective and should take necessary steps to correct identified hazards.
Job Safety Analysis team composition
The Job Hazard Analysis is normally carried out by forming a team comprising of;
Person/Team who does the work
A person supervising the job
A person with safety knowledge
Person (Specialist/Consultant) with technical knowledge
Area in-charge
Area maintenance and operation engineer
Depending on the complexity of the job, the number of team members can vary.
Job Safety Analysis Procedure
The Job Safety Analysis Procedure for any job consists of the following 7 steps:
Step 1: Select the job for job safety analysis and survey the job based on the site condition.
Step 2: Break down and describe the sequence of job steps
Step 3: Identification and assessment of the potential hazards and risks of each step
Step 4: Description of the recommended safe job procedure against each step.
Step 5: Identification of what might go wrong and backup controls.
Step 6: Review of the Job safety analysis documentation, approval, and checking compliance at the working site.
How to Assess Hazards for Job Safety Analysis
To identify hazards for job safety analysis, brainstorming is required for each step of the job. The previous history of similar jobs, employee complaints, etc must be studied. The following questions can be asked for hazard finding:
What can go wrong?
What could be the possible consequences?
How it could happen?
What are the contributing factors?
What is the probability of the hazard occurring?
What safety measures are in place right now?
Probable Steps for Hazard Elimination in Job Safety Analysis
The following steps are normally followed in job safety analysis for hazard elimination
Eliminate the hazard where possible
Substitute the hazard
Isolate the hazard
Use of Engineering Controls to prevent the hazard
Use of administrative controls
Use of personal protective equipment.
Sample Job Safety Analysis Format
The image in Fig. 1 presents a sample job safety analysis format for reference purposes.
Fig. 1: Job Safety Analysis Sample Format
Improvements in Job Safety Analysis
The manual method of job safety analysis costs time from ongoing projects. So a balance for safety with less time must be achieved by improving the efficiency of the job safety analysis process. A number of steps as mentioned below can be considered for improvement:
Standardization of the process by organizing the required steps.
Digitization of the job safety analysis process. In recent times various software applications are available for performing job safety analysis.
Online Safety Courses
To explore more about safety, the following online courses will help you. Kindly click on the subject, review the course and then enroll for it if interested:
Various equipment is required for any chemical, petrochemical, oil & gas projects. So, this equipment must be procured. In any process industry, Equipment procurement is a long process. So proper equipment procurement planning is required. The process, in general, involves the following steps:
The Demand for the Equipment Purchase is raised by the Technical Department (Mostly Process Department)
MR i.e, Material Requisition Preparation by the Purchase Department with the help of the technical department (It includes all terms and conditions, design standards and specifications, delivery terms, Warranty, etc.)
Thorough Supplier Research and Shortlisting by the Procurement Department.
Value Analysis (Technical Bid Evaluation and Technical Query Resolution) by Process and Mechanical Department.
Price Negotiation and Financing by the Purchase Department
Selecting the Final Vendor by Purchase Department
Proceeding for the Purchase
Inspection and Testing of the Equipment
Administration of Supply Contract terms
Receiving the Equipment at the Construction Site
Regarding the equipment procurement process, one important thing to consider is that this activity is different based on the geographical location of the processing unit. Depending on whether this is being done in North America, the Middle East, Africa, the European Union, Asia-Pacific, or South Asia, the equipment procurement has its own individual characteristics. This article will provide below listed 8 important ideas related to the technical aspects of equipment procurement.
Approved Vendor List for Equipment Procurement
It is always preferable to make an “Approved Vendor List” by the Client or the EPC contractor. This list will reduce the time required for supplier research completely. While floating an inquiry, the procurement personnel is bound by this list without the need to look further beyond this list. Having an approved vendor list makes the procurement activity simpler.
Trimming/Shortlisting the Approved Vendor List
Now it could so happen that for a piece of particular equipment, there are many vendors in the approved vendor list. Normally, most of the client companies have a registration process for being an approved vendor for the company. And it is quite natural that all the manufacturers will try to include their names in the “Approved Vendor List” list which causes the list to be too big with numerous vendors.
Hence, Floating an inquiry for a piece of particular equipment to all the listed for that equipment is not a practical thing to do. In such a situation, An experienced purchase professional should trim the list of these vendors based on his knowledge of the vendor’s capabilities and restrict his inquiry to a top few vendors. It is preferable to restrict floating an inquiry to 4 to 5 vendors.
Fast-Tracking of Long-Lead Items
Long lead items can be referred to as equipment, products, or systems that have a delivery time long enough to directly influence the overall lead time of the project during the EPC phase.
An experienced equipment procurement engineer must identify all such equipment at the earliest stage of a project and ensure that the inquiries are fast-tracked. Generally, various organizations have their own terms to decide long-lead items depending on the type of plant being installed. As a rule of thumb, any item with a lead time of more than 8 calendar months can be considered a long lead in today’s perspective of fast-tracked plants.
Raising Technical Query (TQ) and Resolution for the equipment
In terms of the submission of offers as per the inquiry, efficient procurement personnel should continuously keep track of the responses provided by each vendor. He or she must be familiar with the process of raising “Technical Queries”, popularly known as “TQ” on the offers provided by the vendors. Most companies have a standard TQ format for various types of standard equipment.
Most of the time, individual engineering disciplines raise the TQs in their own TQ formats. The procurement engineer must collate all this information in one document for the sake of clarity and final documentation.
Across the table, Clarification Meetings to Resolve issues
Equipment Information normally flows via e-mails with attachments and occasional telephonic conversation and video conferencing. However, it is always preferable to arrange face-to-face (across-the-table) communication (discussion) with vendors. The unanswered questions and issues are resolved best when you are sitting across the table and discussing them.
Some good procurement engineers prefer to follow this very principle. Obviously, an advance discussion agenda must be provided to the party with whom you want the discussion to happen to make the meeting more fruitful.
Based on TQ resolution, when the offers from the vendors are streamlined to match the project requirements the “Technical Bid Analysis (/Evaluation)” abbreviated as “TBA (/or TBE)” is conducted by the engineering design disciplines with active support and follow-up from the procurement engineer.
Most of the reputed/established engineering companies have their standard TBA formats for standard process plant equipment. The purpose of the TBA is to compare the offers of the vendors in the race for bagging the equipment order strictly from a technical viewpoint. The standard TBA worksheet has the benchmarking parameters of the particular equipment in the first column of the worksheet and the subsequent columns are information provided by the vendors against those benchmarked parameters.
For example, if you have 4 vendors for the same equipment there will be 4 columns in the worksheet for filling in the data provided by the vendors against the selected pre-decided parameters. A summary section provided in the worksheet will rate each vendor’s overall technical capabilities and provide rankings and in some cases, even reject one or more of the vendors.
Commercial Negotiation of the Equipment Order
Commercial negotiations for the equipment order will be the next step of the procurement cycle. For example, if four vendors have submitted offers and the TBE concludes that all four are equal in their technical capabilities then by simple logic, the vendor offering the lowest cost of the equipment will be selected. Note that this may not always be true as a few other factors like market reputation, past association with the company, and other extraneous factors may take precedence in the selection of the vendor.
Purchase Order Specification
The last step from a technical viewpoint in the procurement cycle is to place the order of the equipment to the selected vendor in the form of a proper “Purchase Order” (PO) specification or requisition along with the commercial terms and conditions of purchase. The PO specification would generally include some technical data and information specific to the selected vendor’s evaluated and accepted offer.
However, The aforementioned steps do not end the procurement cycle or the responsibility of the procurement engineer. The logistics of equipment procurement now come into the forefront including items such as stage-wise inspection, factory acceptance test, test certification, packing, shipping, warehouse storage, insurance, and demurrage.
Hot Rolled vs Cold Rolled Steel: What are the differences?
As per the World Steel Association, there are over 3,500 different steel grades with unique properties available. The manufacturing processes of steel contribute significantly towards the properties of the final product. Hot rolling and cold rolling are two such processes of steel that affect the overall performance and application. In this article, we will discuss, the main differences between hot-rolled and cold-rolled steel.
What is Hot Rolled Steel?
Hot-rolled steel is produced by rolling the steel at temperatures above the steel’s recrystallization temperature (>1700° F.). Heating the steel above the recrystallization temperature makes the steel easier to shape and form, and the steel can be produced in much larger sizes. For products where tight tolerances are not required, hot-rolled steel is ideal.
The manufacturing of hot rolled steel starts with heating a large billet. Next, it is sent for pre-processing and the billet turns into a large roll. The final dimension is achieved by running it through a series of rollers at high temperatures. For sheet metal, hot rolled steel is spun into coils and left to cool. For other forms like bars or plates, materials are sectioned and packaged for despatch.
What is Cold Rolled Steel?
Cold-rolled steel is produced in cold reduction mills by processing the hot-rolled steel after cooling it to room temperature. Cold-rolled steels can be produced with tighter dimensional tolerances and a wide range of surface finishes.
Differences between Hot Rolled and Cold Rolled Steel
Let’s find out the main differences between hot-rolled and cold-rolled steel.
Differences between hot-rolled and cold-rolled steel
Hot Rolled vs Cold Rolled Steel: Mechanical Properties
Cold-rolled steel members normally have around a 20% increase in mechanical strength because of strain hardening. The hardness value also increases while making cold-rolled steel from hot-rolled steel due to cold forming. So cold-rolled steel members are stronger and harder than hot-rolled steel members. As the metal is shaped at lower temperatures, due to the work hardening effect, the cold rolled steel’s hardness, resistance against tension breaking, and deformation are all increased.
Depending on the grade of the steel the mechanical properties vary. In the following table, a comparison of common mechanical properties for hot-rolled and cold-rolled steel grade 1018 is provided to get a feel of the mechanical property changes.
Mechanical Properties
Hot Rolled
Cold Rolled
% change
Tensile Strength
67,000 psi
85,000 psi
26.9
Yield Strength
45,000 psi
70,000 psi
55.6
Reduction of Area
58
55
-5.2
Elongation in 2″
36
28
-22.2
Brinell Hardness
137
167
18.0
Table 1: Hot Rolled vs Cold Rolled Steel – Mechanical Properties
Hot Rolled vs Cold Rolled Steel: Manufacturing, Cost
Hot-rolled steel manufacturing is done above recrystallization temperature whereas cold-rolled steel involves much lower temperatures, generally room temperature.
As the metal is hot in hot rolled steel, it needs less force and energy to shape it. But the force and energy required to shape a cold rolled product is more.
Hot-rolled steel is easier to make. Cold-rolled steel involves further processing steps that increase the manufacturing steps as well as time requirements. So, overall the cost of cold-rolled steel is much higher than hot-rolled steel of the same grade.
Hot Rolled vs Cold Rolled Steel: Surface characteristics
Hot rolled steel is characterized by a scaly surface, slightly rounded corners, and edges and the surface is not smooth and non-oily. On the contrary, cold rolled steel comes with an oily or greasy finish, a very smooth surface, and very sharp edges. The concentricity and straightness of cold-rolled steel are better when compared to hot-rolled.
Hot Rolled vs Cold Rolled Steel: Dimensional Tolerances
Cold-rolled steel can produce tighter tolerances for products as compared to hot-rolled steel. A more consistent and accurate shape is the feature of cold-rolled steel. For bars, they produce true and square sections. Pipes and tubes of uniform concentricity and straightness are produced using cold-rolled steel.
On the other hand, due to shrinkage during cooling dimensional imperfections exist in hot-rolled steel.
Hot Rolled vs Cold Rolled Steel: Applications
Most popular commercially available shapes are made from hot-rolled steel. All structural members like UC, UB, RSA, PFC, etc, and blooms, billets, sheets, slabs, tubes, bars, etc are hot rolled. On the contrary, only fewer specific shapes like Sheets, box section shapes (CHS, SHS, RHS), and round shapes are made from cold rolled steel.
Hot rolled steels are widely used as structural beams, railroad tracks, sheet metal, automotive frames, agricultural equipment, etc. Cold-rolled steel finds its application in bars, rods, strips, pipes, metal furniture, aerospace structures, hole appliances, roof, and wall systems.
Hot Rolled vs Cold Rolled Steel: Disadvantages
Poor surface finish, lower hardness, and strength are the only concerns for hot rolled steel. Cold work treatments in cold rolled steel can create internal stresses and unpredictable warping.
How to Weld Galvanized Steel? Risks Associated with Galvanized Steel Welding
Galvanizing, a coating of zinc has been used to protect iron and steel from rusting or corrosion. Galvanized steel, due to its high durability is used widely worldwide. Even though it is always suggested to avoid welding on galvanized steel due to the generation of hazardous fumes, they can be welded like normal steel using similar welding techniques. But, proper care must be exercised to protect the welding personnel during the galvanized steel welding process. Common welding techniques for galvanized steel are gas metal arc, carbon arc, gas tungsten arc, manual metal arc, and torch welding. In this article, we will find out more details about the welding of galvanized steel.
Personal Protection for Welding Galvanized Steel
The zinc coating of the galvanized steel easily vaporizes at a high temperature during the welding process. This creates zinc oxide fumes that can cause a short-term health effect known as metal fume fever or galvanized poisoning. Galvanized poisoning is characterized by flu-like symptoms including nausea, headaches, high fever, shivers, and thirst. Also, a small amount of lead that may be present on galvanized coating can lead to the generation of lead oxide fumes. These fumes have long-term health hazards like lung or brain cancer and complications in the nervous system.
It is, therefore, first and foremost to use proper welding protective equipment when welding galvanized steel. The welder must wear high-quality welding helmets, gloves, leather jackets, steel toe boots, and respirators. The respirator during welding galvanized steel ensures that the zinc and lead oxide fumes are not inhaled. The welder must be well-trained for welding galvanized steel and the welding must be performed in a well-ventilated area to maximize clean airflow.
Preparing to Weld Galvanized Steel
The first step in welding galvanized steel is to adequately prepare it for welding. The galvanizing layer near the weld region (at least 2 to 4 inches from either side) must be removed first by grinding or other methods. Other methods of removing zinc coating are by burning with a carbon arc or an acetylene torch while using an oxidizing flame, or by shot blasting with portable equipment. So, the welding can easily be performed now like uncoated carbon steel. Once the welding operation is complete, the protective coating must be restored to get proper corrosion resistance. ASTM A780 or similar other standards can be used for restoring the zinc protective layer after welding galvanized steel.
When the galvanized coating is not removed, the weld should be made using the galvanized base metal with the thickest coating anticipated and qualified by test following AWS D1.1 or AWS D1.4. These Welding Procedure Specifications (WPS) will permit welding over surfaces with zinc coatings equal to or less than the coating used in qualification testing. In general, to avoid zinc penetration of the welds, the procedure should involve greater root openings in joints, electrodes with low silicon content, and slower welding speeds.
Galvanized Steel Welding by Gas Metal Arc Welding
Gas metal arc (GMA) welding, or Metal-Inert Gas (MIG) welding, is a versatile semi-automatic welding process that is easily and conveniently used for welding galvanized steel of thinner materials. Fig. 1 below shows a typical illustration of the GMA welding process. In the GMA welding of galvanized steel, the zinc coating does not affect weld mechanical properties, other than some appearance changes due to weld spatter. Excellent Arc stability is achieved which is generally unaffected by the galvanized coating. However, Some reduction in welding speed is required.
A protective gas shield is used. Carbon dioxide is the cheapest and most widely used shielding gas for welding uncoated galvanized steel. However, due to its superior surface appearance, weld bead shape, and reduced spatter, a more expensive shielding gas, comprising 75% argon and 25% CO2, is sometimes preferred for welding uncoated mild steel. For welding galvanized steel, less expensive CO2 may be satisfactorily used. However, most welding shops normally use an argon-CO2 mixture for galvanized material.
Fig. 1: Gas metal arc welding process with CO2 shielding gas
To allow time for the galvanized coating to burn off at the front of the weld pool GMA welding speeds should be slower. The welding speed reduction relates to the zinc coating thickness, the joint type, and the welding position. By increasing the current, steels with thicker galvanized coatings may be fillet welded more readily. The increased heat input is required to burn away the extra zinc at the front of the weld pool.
Penetration of the weld in zinc-coated steels is less than for uncoated steels. A slightly wider gap, therefore, must be provided for butt welds. While making butt weld in a flat position, a slight side-to-side movement of the welding torch helps achieve consistent penetration.
Spatter increases when welding galvanized steel using both CO2 and an argon-CO2 mixture shielding gas. Spatter particles that adhere to the workpiece can cause an unsightly appearance. By applying silicone, petroleum, or graphite-based spatter release compounds to the workpiece before welding, this can be avoided. Spatter particles are then removed by brushing. However, a build-up of spatter in the nozzle of the welding gun may be encountered. The application of an anti-spatter compound will reduce the particles trapped by the welding nozzle.
With an increase in the zinc coating thickness, the spatter formation increases and is, therefore, greater on batch-galvanized materials than on continuously coated sheet materials. Spatter particles tend to roll into the corner of the joint when tee joints in batch galvanized steel are welded in the flat position, causing difficulty in welding. While welding in the overhead position, the spatter may fall into the nozzle of the welding gun.
The higher heat input to remove the zinc from the weld pool and slower welding speeds to burn off the zinc coating are what differentiate the GMA welding process between welding zinc-coated steel and uncoated steel. Using a shielding gas of argon and carbon dioxide can give a more stable arc and produce smoother weld deposits with minimum spatter and zinc loss.
Welding Galvanized Steel by SMAW & MMAW
Both Shielded Metal Arc Welding (SMAW) and Manual Metal Arc Welding (MMAW) for welding galvanized steel are manual processes using flux-covered electrodes of 1.6 mm to 12.7 mm in diameter. The welding conditions necessary for galvanized steel welding by SMAW and MMAW are similar to those used on uncoated steel. However, the welding speed needs to be slower because the angle of the electrode is reduced to about 30º and a whipping motion of the electrode back and forth is needed to move the molten zinc pool away from the weld.
The major difference between welding zinc-coated steel (galvanized steel) and welding uncoated steel using the SMAW process is that the root opening must be increased to give full weld penetration. In the SMAW process, the amount of spatter is slightly higher as compared to welding on uncoated steel. The conditions for the root pass in butt-welds on batch galvanized steel by SMAW process are available in AWS D19.0, Tables 6.2 through 6.5.
Fig. 2: Welding Galvanized Steel using the SMAW method
MMAW is used for galvanized steels of 12.7 mm thickness or greater. In general, welders can use the same procedures for welding galvanized steel as for uncoated steel. However, the following points must be kept in mind:
The electrode speed applied should be lower than normal. A whipping action by moving the electrode forward along the seam in the direction of the weld and then back into the molten zinc pool must be provided.
Weaving and multiple weld beads should be avoided, as should excessive heat injection into the joint that may damage the adjacent zinc coating.
To give better control of the weld pool and to prevent either intermittent excessive penetration or undercutting a short arc length is recommended for all positions.
For butt welding, slightly wider gaps are required to have complete penetration.
To achieve better welding quality, grinding off edges before welding is suggested. It also will reduce the fuming from the galvanized coating. Further welding procedures will then be the same as for uncoated steel.
Welding Galvanized Steel with Other Metals
Galvanized steel can be welded to other metals, including stainless steel, using the above-mentioned techniques. To get quality welding in such cases, it’s always preferable to remove the zinc coating from around the weld area. Sometimes, zinc can penetrate other metals and may cause embrittlement problems. Upon completion of dissimilar welding, the weld area should be coated using a zinc touch-up product to avoid corrosion.
Can you weld galvanized steel?
Galvanized steel is a common steel with a coating of zinc layer over it. In general, galvanized steel pipes are suggested not to weld as during welding the coating will be damaged. So, the sole purpose of galvanizing for corrosion prevention is lost. Also, the melting of that zinc coating causes serious health hazards. This is the reason that galvanized steel is usually not welded. However, by removing the zinc coating from the pipe, galvanized steel pipes can safely be welded.
Video Courses in Welding
To learn more about welding the following video courses you can refer to:
