Arc welding, cutting and spraying activities: guide to reporting

This document outlines the steps that facilities with welding, cutting and spraying activities should follow to report to the National Pollutant Release Inventory (NPRI).

Download the Arc welding, cutting and spraying calculator to help you estimate the releases of National Pollutant Release Inventory (NPRI) substances.

Background information

The main NPRI substances used in the arc welding, cutting and spraying processes are Part 1A metals (for example, chromium, cobalt, manganese, nickel) and Part 1B metals (for example, hexavalent chromium, lead). Part 4 substances – Criteria Air Contaminants (CACs) – are also released during the welding, cutting and spraying processes. The main CACs of concern are total particulate matter (TPM), particulate matter less than or equal to 10 microns in diameter (PM₁₀) and particulate matter less than or equal to 2.5 microns in diameter (PM_2.5).

Categories of arc welding, cutting and spraying processes in Canada

One of the categories of arc welding processes found in Canada is consumable electrode arc welding processes. Examples of this type of process include:

• shielded metal arc welding (SMAW) (the most common)
• flux cored arc welding (FCAW)
• gas-metal arc welding (GMAW)
• submerged arc welding (SAW)

Welding rods and wire are similar and are considered consumable electrodes.

The other category of arc welding processes in Canada is non-consumable electrode arc welding processes. This category includes:

• gas-tungsten arc welding (GTAW)
• plasma arc welding (PAW)

Examples of cutting processes include:

• oxyacetylene and oxy-mapp cutting
• air carbon arc cutting (CAC-A)
• plasma arc cutting (PAC)
• laser cutting
• arc saw cutting
• grinder
• reciprocating saw

Examples of spraying processes include:

• plasma spray
• flame spray (both single wire and other)
• electric arc spray
• high velocity oxy-fuel spray (HVOF)

The remainder of this guidance document will be focused on the reporting requirements related to arc welding, cutting and spraying processes.

Please note that soldering activities are not considered to be a welding operation, although NPRI reporting still applies to them.

Reporting on arc welding, cutting and spraying processes

Threshold calculations

You need to consider the NPRI substances associated with arc welding, cutting and spraying activities occurring at your facility when you perform threshold calculations.

In order to correctly perform threshold calculations for arc welding, cutting and spraying activities, you need to understand the term "article".

An "article" is defined as a manufactured item that does not release an NPRI substance when it undergoes processing or any other use. When an article is processed and there are no releases, or the releases are recycled with due care, the NPRI substances in that article need not be included in the threshold calculation. Exercising due care means that the facility generated less than one kilogram of a Part 1A substance as waste during the year. There is no quantitative measure of due care in recycling Part 1B substances, because even minimal releases of these substances can cause significant adverse effects and can reasonably be expected to contribute to exceeding their low thresholds. Therefore, if an article containing a Part 1B substance is processed or otherwise used and there are releases, the Part 1B substance in the article must be included in the threshold calculation.

Parts 1 A and B metals

You can use these points to determine which sources of NPRI substances need to be considered in your threshold calculations.

• The weight of the NPRI-listed substances found in the arc welding electrodes, filler rods, sprayed materials and cut materials must be calculated (refer to notes 1 and 2 below). The safety data sheet (SDS) can be used to determine the composition of these materials. This, combined with the mass of the materials used, can determine the amount of the NPRI substance(s) manufactured, processed or otherwise used (MPO).
• For Part 1A metals, you need to determine if your facility MPO greater than or equal to 10 tonnes of each substance based on the amount and composition of the arc welding electrodes, filler rods, sprayed materials and cut materials (refer to notes 1 and 2 below). If these substances are MPO in other processes at your facility, these sources must also be considered in your threshold calculations.
• For Part 1B metals, you will need to determine if your facility MPO greater than or equal to the mass threshold of each substance based on the amount and composition of the welding electrodes, filler rods, sprayed materials and cut materials (refer to notes 1 and 2 below). The mass threshold can be found in the Guide for Reporting to the National Pollutant Release Inventory. If these substances are MPO in other processes at your facility, these sources must also be considered in your threshold calculations.

Notes:

1. The base metal being welded or sprayed retains article status. As such, all NPRI-listed substances found in the base metal do not have to be considered in your threshold calculation for arc welding and spraying activities.
2. With the exception of the reciprocating saw process, the base metals being cut by any of other the cutting processes (included in the arc welding, cutting and spraying calculator) lose their article status.

Using the arc welding, cutting and spraying calculator

After you have completed your threshold calculations and compared the total amounts MPO to the reporting threshold, you must then calculate the released, recycled and disposed values for those substances that meet or exceed the reporting threshold.

The arc welding, cutting and spraying calculator considers six different types of  arc welding processes and various welding electrode or rod/wire types; five types of spraying processes; and seven types of cutting processes. The spreadsheet calculator is the preferred method of calculation.

The table below lists the arc welding, cutting, and spraying processes in the spreadsheet calculations.

Calculating emissions for “Other” types of processes/electrodes

There are limited or no data available on emission factors for some processes/electrodes. To address this, emission factors and alternative methods have been suggested in arc welding, cutting and spraying calculator for “Other” types of processes/electrodes.

The suggested emission factors for “Other” types of processes/electrodes should only be used if there are no site-specific estimation method available for activities at your facility. Contact the NPRI HelpDesk if you have questions.

“Other” types of arc welding processes/electrodes

If the arc welding type is listed in the calculator but the specific electrode/filler material is unknown or not listed, you can use the following according to the welding type:

• Other SMAW
• Other GMAW
• Other FCAW
• Other SAW
• Other GTAW (only if filler materials are used)
• Other PAW (only if filler materials are used)

If the specific type of arc welding is unknown or is different than SMAW, GMAW, FCAW, SAW, GTAW, or PAW, the calculator provides two methods to determine emissions.

The two methods that are available in the calculator for “Other” types of arc welding processes/electrodes are: Method 1, which is based on average emission factors, and Method 2 which is based on a modified San Diego mass fraction approach (further explanation below).

Method 1 is recommended as the default approach for the calculation of “Other” types of arc welding processes/electrodes. Method 2 can provide an alternative when Method 1 does not provide a reasonable estimation of the emissions. For example, if "Method 1" results in emissions for an element (e.g. Manganese) that does not exist in the electrode, then Method 2 could be used instead. In order to use Method 2, you must have access to a reliable source that specifies mass fraction of elements in the electrode. The safety data sheet (SDS) of an electrode is an example of a reliable source which could be used.

Method 1 - Average Emission Factor Approach

In the absence of supporting data, the emission factors for “Other” types of processes/electrodes have been obtained by averaging the known and non-zero emission factors of the similar category. You can use the input fields for “Other” electrodes (if the welding process is known: SMAW, GMAW, FCAW, SAW, GTAW or PAW) or “Other Arc Welding Methods” to enter the quantities of electrode/filler material used.

For example, the PM₁₀ emission factor for “Other SMAW” electrodes is an arithmetic average of all known PM₁₀ emission factors of SMAW electrodes. This approach ensures that the PM₁₀ emission factor for “Other SMAW” electrodes is in the range of known SMAW PM₁₀ emission factors. The PM₁₀ emission factor for “Other Arc Welding Methods” electrode is an arithmetic average of all known PM₁₀ emission factors of SMAW, GMAW, FCAW, SAW, GTAW and PAW electrodes.

Method 2 - Modified San Diego Mass Fraction Approach

Method 2 is inspired by an emission calculation methodology used by Air Pollution Control District of San Diego County. This method uses composition of substances in the arc welding electrode / filler material along with emission factors to estimate the quantities of emissions. The table below lists the factors and equations used by the Method 2.

“Other” types of cutting or spraying processes

If the specific type of cutting or spraying process is unknown or not listed, you can use the input field for “Other Cutting Methods” or “Other Spraying Methods,” respectively.

Please note: The arc welding, cutting and spraying calculator should not be used for mechanical/cold cutting methods (for example, press cutting) that have not been specified in the calculator.

Active cutting hours

For cutting processes, annual active cutting hours (hours/year) are required as an input for the calculator. Active cutting refers to the time that the material is being cut. You also have to calculate the time-averaged mass fraction (See Example four: cutting calculation) for each of the following elements for all materials that went through cutting:

• chromium
• cobalt
• nickel
• manganese
• lead
• zinc
• copper
• silver
• antimony

The time-averaged mass fraction should be calculated separately for each cutting process.

For spraying processes, the annual amount (kg/year) of material sprayed is required as an input for the calculator. The base metal being sprayed retains article status. You have to calculate the weight-averaged mass fraction (see Example three: spraying calculation) for the following elements over all sprayed materials:

• chromium
• cobalt
• nickel
• manganese
• lead
• zinc
• copper
• silver
• antimony

The weight-averaged mass fraction should be calculated separately for each spraying process.

Conservativeness in estimation of chromium emissions

In the NPRI substance list, chromium emission is defined as: “Total of pure chromium and the equivalent weight of chromium contained in any compound, alloy or mixture. Excludes hexavalent chromium (and its compounds).”

The emission factors used in the arc welding, cutting and spraying calculator for “chromium and its compounds” include hexavalent chromium. This results in a conservative estimation of emissions of “chromium and its compounds”. The ratio of Cr(VI) to total Cr varies for different processes and electrodes. The table below lists the typical Cr(VI) to total Cr ratios for some processes:

It should be noted that Cr(VI) is also calculated separately in the arc welding, cutting and spraying calculator for the processes and electrodes. Therefore, users that would like to avoid the conservative estimation of emissions of “chromium and its compounds” can deduct the total Cr(VI) emission from emissions of “chromium and its compounds” to obtain emissions that exclude hexavalent chromium.

Example one: arc welding calculation

Let’s assume the following for our example:

• process: SMAW
• amount of base metal welded: 14,000 tonnes during the reporting year
• amount of welding wire used: 1,000 tonnes of E310-16 welding wire during the reporting year; the wire contains 1.3% manganese by weight, obtained from the SDS

Step One: Determine the amount of manganese (a Part 1A substance) MPO and compare it to the 10-tonne reporting threshold. If it is greater than the 10-tonne threshold, calculate the amount of manganese released due to the welding process.

Remember: When using an arc welding process, the base metal being welded retains its article status. Therefore, it does not need to be considered in either the threshold or release calculations.

The amount of MPO can be calculated using the following equation:

Amount of manganese = Amount of welding rod used [tonnes] x (weight percent manganese in welding/100%)
= 1,000 tonnes x (1.3%/100%)
= 13 tonnes of manganese

Since the amount of manganese is greater than the 10-tonne reporting threshold, your facility must submit a manganese substance report. In this example, we assumed that no manganese is recycled or disposed, but that some manganese is released as a result of the welding activity. As a result, the release estimate must be completed.

The arc welding, cutting and spraying calculator will automatically calculate the releases for all relevant substances once you enter the rod usage amount.

The amount of manganese released can be calculated using the following equation:

Manganese released [tonnes] = Amount of welding rod used [kg] x emission factor [kg Mn released/kg welding rod used] x [1 tonne/1,000 kg]
= 1,000 [tonnes] welding rod used x 1,000 [kg/tonne] x 0.0022 [kg Mn released/kg welding rod used] x 0.001 [tonnes/kg]
= 2.2 tonnes manganese released

Based on the above, you would report 2.2 tonnes of manganese to the NPRI for the reporting year as a result of the welding activities occurring onsite. In this case, it would be reported as a release to air. Note that since the reporting threshold was satisfied for manganese, you must now report for all manganese that was released, recycled or disposed.

Step Two: Determine the amount of PM₁₀ released from the welding process. As mentioned above, the arc welding, cutting and spraying calculator will automatically calculate the releases for all applicable substances once you enter the rod usage amount.

The amount of PM₁₀ released can be calculated using the following equation:

PM₁₀ released [tonnes] = Amount of welding rod used [kg] x emission factor [kg PM₁₀ released/kg welding rod used] x 0.001 [tonne/kg]
= 1,000 [tonnes] welding rod used x 1,000 [kg/tonne] x 0.0151 [kg PM₁₀ released/kg welding rod used] x 0.001 [tonne/kg]
= 15.1 tonnes PM₁₀ released

The reporting threshold for PM₁₀ is 0.5 tonnes released to air. Since the release value for this example is 15.1 tonnes, a substance report is required for PM₁₀. As well, you must add all other PM₁₀ releases at the facility to the 15.1 tonnes. You must report the resulting value to the NPRI.

Example two: “Other” types of arc welding processes/electrodes

Let’s assume the following for our example:

• process: GMAW
• amount of base metal welded: 10,000 tonnes during the reporting year
• amount of welding wire used: 1,000 tonnes of an unknown welding electrode during the reporting year; the wire contains 9% copper by weight, obtained from the SDS

Step One: Determine the amount of copper (a Part 1A substance) MPO and compare it to the 10-tonne reporting threshold. If it is greater than the 10-tonne threshold, calculate the amount of copper released due to the welding process.

Remember: When using an arc welding process, the base metal being welded retains its article status. Therefore, it does not need to be considered in either the threshold or release calculations.

The amount of MPO can be calculated using the following equation:

Amount of copper = Amount of welding rod used [tonnes] x (weight percent copper in welding/100%)
= 1,000 tonnes x (9%/100%)
= 90 tonnes of copper

Since the amount of copper is greater than the 10-tonne reporting threshold, your facility must submit a copper substance report. In this example, we assumed that no copper is recycled or disposed, but that some copper is released as a result of the welding activity. As a result, the release estimate must be completed.

Since the electrode type is unknown, you should first attempt to estimate the emissions using Method 1 of “Other” types of arc welding processes/electrodes. However, if Method 1 is used emission estimated for copper will be zero because there is no emission factor for copper under Method 1.

Copper content in the electrode is relatively high and copper emissions is not expected to be zero. Therefore, you should use Method 2 of “Other” types of arc welding processes/electrodes. The arc welding, cutting and spraying calculator will automatically calculate the releases for all relevant substances once you enter the usage amount of the unknown electrode and its mass composition.

The amount of copper released can be calculated based on Method 2 using the following equation:

Emission factor [g Cu released/kg welding rod used] = TPM emission factor for GMAW based on Method 2 [g TPM released/kg welding rod used] x factor for GMAW based on Method 2 x mass fraction of copper in the rod
= 10 [g TPM released/kg welding rod used]  x 0.5464 x (9%/100%)
= 0.492 [g released/kg welding rod used]

Copper released [tonnes] = Amount of welding rod used [kg] x emission factor [kg Cu released/kg welding rod used] x [1 tonne/1,000 kg]
= 1,000 [tonnes] welding rod used x 1,000 [kg/tonne] x 0.000492 [kg Cu released/kg welding rod used] x 0.001 [tonnes/kg]
= 0.492 tonnes copper released

Based on the above, you would report 0.492 tonnes of copper to the NPRI for the reporting year as a result of the welding activities occurring onsite. In this case, it would be reported as a release to air. Note that since the reporting threshold was satisfied for copper, you must now report for all copper that was released, recycled or disposed.

Step Two: Determine the amount of PM₁₀ released from the welding process. As mentioned above, the arc welding, cutting and spraying calculator will automatically calculate the releases for all applicable substances once you enter the rod usage amount.

The amount of PM₁₀ released can be calculated based on Method 2 using the following equation:

PM₁₀ released [tonnes] = Amount of welding rod used [kg] x emission factor [kg PM₁₀ released/kg welding rod used] x 0.001 [tonne/kg]
= 1,000 [tonnes] welding rod used x 1,000 [kg/tonne] x 0.010 [kg PM₁₀ released/kg welding rod used] x 0.001 [tonne/kg]
= 10.0 tonnes PM₁₀ released

The reporting threshold for PM₁₀ is 0.5 tonnes released to air. Since the release value for this example is 10.0 tonnes, a substance report is required for PM₁₀. As well, you must add all other PM₁₀ releases at the facility to the 10.0 tonnes. You must report the resulting value to the NPRI.

Example three: spraying calculation

Let’s assume the following for our example:

• process: plasma spray
• amount of base metal: 18,000 tonnes during the reporting year
• amount of spraying material A used: 50 tonnes during the reporting year; the sprayed material contains 35% nickel by weight, obtained from the SDS
• amount of spraying material B used: 50 tonnes during the reporting year; the sprayed material contains 15% nickel by weight, obtained from the SDS

Step One: Determine the amount of nickel (a Part 1A substance) MPO and compare it to the 10-tonne reporting threshold. If it is greater than the 10-tonne threshold, calculate the amount of nickel released due to the spraying process.

Remember: When using a spraying process, the base metal retains its article status. Therefore, it does not need to be considered in either the threshold or release calculations.

The amount of MPO can be calculated using the following equation:

Amount of nickel in spraying material A= Amount of spraying material A used [tonnes] x (weight percent nickel in the spraying material A/100%)
= 50 tonnes x (35%/100%)
= 17.5 tonnes of nickel

Amount of nickel in spraying material B= Amount of spraying material B used [tonnes] x (weight percent nickel in the spraying material B/100%)

= 50 tonnes x (15%/100%)

= 7.5 tonnes of nickel

Total mass of sprayed nickel = Amount of nickel in material A [tonnes] + Amount of nickel in material B [tonnes]

= 17.5 tonnes + 7.5 tonnes

= 25 tonnes

Since the amount of nickel is greater than the 10-tonne reporting threshold, your facility must submit a nickel substance report. In this example, we assumed that no nickel is recycled or disposed, but that some nickel is released as a result of the spray welding activity. As a result, the release estimate must be completed.

 

The weight-averaged mass fraction of nickel for plasma spray can be calculated using the following equations:

Weight-averaged mass fraction of nickel for plasma spray = (mass of material A [tonnes] x (weight percent nickel in material A/100%) + mass of material B [tonnes] x (weight percent nickel in material B/100%)) / (mass of material A [tonnes] + mass of material B [tonnes])

= (50 tonnes x (35.0%/100%) + 50 tonnes x (15.0%/100%)) / (100 tonnes)

= 25% (0.25)

The total mass of sprayed material A and B and weight-averaged mass fraction of nickel should be entered in the calculator for the plasma spray process.

 

The arc welding, cutting and spraying calculator will automatically calculate the releases for all relevant substances once you enter the required input information.

The amount of nickel released can be calculated using the following equation:

Nickel released [tonnes] = Amount of total spraying material used [kg] x (weight-averaged percent nickel in the total spraying material/100%) x emission factor [g nickel released/kg nickel sprayed] x 0.000001 [tonne/g]
= 100 [tonnes] total spraying material used x 1,000 [kg/tonne] x (25%/100%) x 150 [g nickel released/kg nickel sprayed] x 0.000001 [tonne/g]
= 3.75 tonnes nickel released

Based on the above, you would report 3.75 tonnes of nickel to the NPRI for the reporting year as a result of the spraying activities occurring onsite. In this case, it would be reported as a release to air. Note that since the reporting threshold was satisfied for nickel, you must now report for all nickel that was released, recycled or disposed.

Step Two: Determine the amount of PM₁₀ released from the spraying process. As mentioned above, the arc welding, cutting and spraying calculator will automatically calculate the releases for all applicable substances once you enter the required input information.

The amount of PM₁₀ released can be calculated using the following equation:

PM₁₀ released [tonnes] = Amount of total spraying material used [kg] x emission factor [g PM₁₀ released/kg spraying material used] x 0.000001 [tonne/g]
= 100 [tonnes] total spraying material used x 1,000 [kg/tonne] x 60 [g PM₁₀ released/kg spraying material used] x 0.000001 [tonne/kg]
= 6 tonnes PM₁₀ released

The reporting threshold for PM₁₀ is 0.5 tonnes released to air. Since the release value for this example is 6 tonnes, a substance report is required for PM₁₀. As well, you must add all other PM₁₀ releases at the facility to the 6 tonnes. You must report the resulting value to the NPRI.

Example four: cutting calculation

Let’s assume the following for our example:

• process: oxy cutting
• amount of material A being cut (base metal A): 50 tonnes during the reporting year
• amount of material B being cut (base metal B): 100 tonnes during the reporting year
• active oxy cutting time: 1,000 hours for material A, and 2,000 hours for material B during the reporting year
• mass percent of copper in material A: 20.0%, obtained from the SDS
• mass percent of copper in material B: 40.0%, obtained from the SDS

Step One: Determine the amount of copper (a Part 1A substance) MPO and compare it to the 10-tonne reporting threshold. If it is greater than the 10-tonne threshold, calculate the amount of copper released due to the cutting process.

Remember: When using an oxy cutting process, the base metal being cut revokes its article status. Therefore, it needs to be considered in either the threshold or release calculations.

The amount of MPO can be calculated using the following equation:

Amount of copper in material A = Amount of material A [tonnes] x (weight percent copper in material A /100%)
= 50 tonnes x (20.0%/100%)
= 10 tonnes of copper

Amount of copper in material B = Amount of material B [tonnes] x (weight percent copper in material B /100%)
= 100 tonnes x (40.0%/100%)
= 40 tonnes of copper

Amount of copper = Amount of copper in material A + Amount of copper in material B
= 50 tonnes of copper

Since the total amount of copper is greater than the 10-tonne reporting threshold, your facility must submit a copper substance report. In this example, we assumed that no copper is recycled or disposed, but that some copper is released as a result of the cutting activity. As a result, the release estimate must be completed.

The time-averaged mass fraction of copper for oxy cutting can be calculated using the following equations:

Total active oxy cutting hours = Time spent for material A [hours] + Time spent for material B [hours]
= 1,000 hours + 2,000 hours
= 3,000 hours

Time-averaged mass fraction of copper for oxy cutting = (Time spent for material A [hours] x (weight percent copper in material A/100%) + Time spent for material B [hours] x (weight percent copper in material B/100%)) / (Total active oxy cutting hours [hours])

= (1,000 hours x (20.0%/100%) + 2,000 hours x (40.0%/100%)) / (3,000 hours)
= 0.333

The total active oxy cutting hours and time-averaged mass fraction of copper should be entered in the calculator for the oxy cutting process.

The arc welding, cutting and spraying calculator will automatically calculate the releases for all relevant substances once you enter the required input information.

The amount of copper released can be calculated after determining the amount of TPM released from the oxy cutting process. In the arc welding, cutting and spraying calculator, all PM₁₀ emissions are assumed to be the same as TPM.

The amount of PM₁₀ released can be calculated using the following equation.

PM₁₀ released [tonnes] = Total active oxy cutting hours [hours] x (60 min/1 hour) x emission factor [g PM₁₀ released/min of cutting] x 0.000001 [tonne/g]
= 3,000 [hours] x 60 [min/hour] x 0.38 [g PM₁₀ released/ min of cutting] x 0.000001 [tonne/g]
= 0.068 tonnes PM₁₀ released

The amount of copper released can be calculated using the following equation:

Copper released from oxy cutting process [tonnes] = Amount of TPM released from oxy cutting [tonnes] x Time-averaged mass fraction of copper for oxy cutting
= 0.068 [tonnes] x 0.333
= 0.023 tonnes copper released

Based on the above, you would report 0.023 tonnes of copper to the NPRI for the reporting year as a result of the cutting activities occurring onsite. In this case, it would be reported as a release to air. Note that since the reporting threshold was satisfied for copper, you must now report for all copper that was released, recycled or disposed.

The reporting threshold for PM₁₀ is 0.5 tonnes released to air. The release value for this example is 0.068 tonnes. If the sum of all PM₁₀ releases at the facility is less than 0.5 tonnes, a substance report is not required for PM₁₀.

References

US Environmental Protection Agency (US EPA), 1998. "Section 313 of the Emergency planning and community right-to-know act - EPCRA section 313 questions and answers," Office of Pollution Prevention and Toxics, revised 1998 version, EPA 745-B-98-004, December 1998.

US Environmental Protection Agency (US EPA), 1994. "Development of particulate and hazardous emission factors for electric arc welding," revised final report, EPA contract no. 68-D2-0159, MRI project no. 4601-02, May 20, 1994.

Air Pollution Control District of San Diego County, Welding Operations, October 16, 1998.