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The National Pollutant Release Inventory Toolbox
Guidance for the Reporting of Welding Activities
Purpose
To provide guidance to facilities with welding activities on how to report to the National Pollutant Release Inventory (NPRI).
Background Information
NPRI substances associated with welding activities occurring at a facility need to be considered when performing the threshold calculations. In order to correctly perform threshold calculations for welding activities you will need to understand the terms "article" and "due care".
An "article" is defined as a manufactured item that does not release an NPRI substance, when it undergoes processing or other use. When an article is processed and there are no releases, or the releases are recycled 100% with due care, the NPRI substances in that article need not be included in the threshold calculation. Exercising "due care" in ensuring 100% recycling means that the facility generated less than 1 kg of the NPRI Part 1A substance as waste during the calendar year. Due to the significantly lower thresholds associated with Part 1B substances, there is no due care criteria for Part 1B substances and all manufacture, process or otherwise use (MPO) must be included in the threshold calculation for each substance.
The primary NPRI substances of concern used in the welding process are the Part 1A and 1B metals. However, Part 4 substances - Criteria Air Contaminants (CAC) are also released during the process. The main CAC's of concern are total particulate matter (TPM), particulate matter less than or equal to 10 microns in diameter (PM10), particulate matter less than or equal to 2.5 microns in diameter (PM2.5), carbon monoxide (CO), and oxides of nitrogen (NOx).
Types of Welding in Canada
There are two main welding processes generally found in Canada:
- Consumable Electrode Processes - e.g., shielded metal arc welding (SMAW), flux cored arc welding (FCAW), gas-metal arc welding (GMAW), and submerged arc welding (SAW). SMAW is the most common welding process. Welding rods and wire are similar and are considered consumable electrodes.
- Non-Consumable Electrode Processes - e.g. gas-tungsten arc welding (GTAW), plasma arc welding (PAW), and fusion welding.
Threshold and Release Calculations for Welding Processes
Consumable Welding Electrode Processes
Parts 1 A&B Metals
The following points can be used to determine which sources of NPRI substances need to be considered in the threshold calculations:
- The weight of the NPRI-listed substances found in the consumable welding electrodes must be calculated. The Material Safety Data Sheet (MSDS) can be used to determine the composition of the welding electrode. This combined with the mass of the specific electrode used can determine the amount of the NPRI substances manufactured, processed or otherwise used (MPO).
- For Part 1A metals (ex. Cr3+, Co, Mn and Ni, or any other) facilities need to determine if they MPO greater than or equal to 10 tonnes of each substance based on the amount and composition of the consumable welding electrodes. If these substances are MPO in other processes at the facility, these sources must also be considered in your facility's threshold calculations.
- For Part 1B metals (ex. hexavalent chromium (Cr6+), and lead, or any other) facilities will need to determine if they MPO greater than or equal to the mass threshold of each substance based on the amount and composition of the consumable materials. 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 the facility, these sources must also be considered in the facility's threshold calculations.
- The base metal being welded retains article status and all NPRI listed substances found in it need not be considered in the threshold calculation.
After the threshold calculations have been completed and the total amounts MPO are compared to the reporting threshold, the released, recycled and disposed values must be calculated for those substances that met or exceeded the reporting threshold.
Method 1 - Electric Arc Welding Spreadsheet
The Electric Arc Welding Spreadsheet available on the NPRI Toolbox website considers four different types of consumable electrode welding processes and various welding electrode or rod/wire types. The table below lists the types of welding rods/wire included in the spreadsheet calculations. The spreadsheet is the most preferred method of calculation.
| Welding Process | Electrode Type | Last 2 Digits of SCC |
|---|---|---|
| SMAW(SCC 309051xx) | 14Mn-4Cr | (-04) |
| E11018 (includes E11018-M) | (-08) | |
| E308 (includes E308-16 and E308L-15) | (-12) | |
| E310 (includes E310-16) | (-16) | |
| E316 (includes E316-15, E316-16, and E316L-16) | (-20) | |
| E410 (includes E410-16) | (-24) | |
| E6010 | (-28) | |
| E6011 | (-32) | |
| E6012 | (-36) | |
| E6013 | (-40) | |
| E7018 | (-44) | |
| E7024 | (-48) | |
| E7028 | (-52) | |
| E8018 (includes E8018C3) | (-56) | |
| E9015 (includes E9015B3) | (-60) | |
| E9018 (includes E9018B3 and E9018G) | (-64) | |
| ECoCr (includes ECoCr-A) | (-68) | |
| ENi-Cl | (-72) | |
| ENiCrMo (includes ENiCrMo-4) | (-76) | |
| ENi-Cu (includes ENi-Cu-2) | (-80) | |
| GMAW(SCC 309052xx) | E308L (ncludes E308LSi) | (-12) |
| E70S (includes E70S-3, E70S-5, and E70S-6) | (-54) | |
| ER1260 | (-10) | |
| ER5154 | (-26) | |
| ER316 (includes ER316I-Si and ER316L-Si) | (-20) | |
| ERNiCrMo (includes ENiCrMo-3 and ENi-CrMo-4) | (-76) | |
| ERNiCu (includes ERNiCu-7) | (-80) | |
| FCAW(SCC 309053xx) | E110 (includes E110TS-K3) | (-06) |
| E11018 | (-08) | |
| E308LT (includes E308LT-3) | (-12) | |
| E316LT (includes E316LT-3) | (-20) | |
| E70T (includes E70T-1, E70T-2, E70T-4, E70T-5, E70T-7, and E70T-G) | (-54) | |
| E71T (includes E71T-1 and E71T-11) | (-55) | |
| SAW(SCC 309054xx) | EM12K (includes EM12K1 and F72-EM12K2) | (-10) |
If the specific consumable welding electrode process and standard welding rods/wire used is not available in the spreadsheet, and no other site specific estimation method is available for your facilities activities, then the following generic emission factors can be used.
Method 2 - Generic Emission Factors
The following general emission factors can be used to determine the amount of Parts 1A and 1B substance releases to air.
| Substance | Emission Factor* (kg substance/kg total rods used) |
|---|---|
| Cr3+ | 0.0002 |
| Co | 0.0002 |
| Mn | 0.0002 |
| Ni | 0.0002 |
| Cr6+ | 0.0002 |
| Pb | 0.0002 |
Example: Consumable Electrode
Determine the amount of manganese manufactured, processed, or otherwise
used 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.
Parameters:
- Process: SMAW
- Amount of Base Metal Welded: 14 000 tonnes during the reporting year
- Amount of Welding Wire Used: 1 000 tonnes of E310-15 welding wire during the reporting year. The wire contains 1.3% manganese by weight, obtained from the MSDS.
- Additional information: The fume releases are uncontrolled and vented through a roof stack which is 25 m above grade.
Remember: When using a consumable welding electrode process the base metal being welded retains its article status and therefore does not need to be considered in the threshold or release calculations.
Threshold Calculations:
The amount of manganese manufactured, processed, or otherwise used 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, the facility's manganese release must be determined.
Release Estimate
The general emission factor for consumable welding electrode processes of 0.0002 kg manganese/kg weld rod will be used.
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)
=0.2 tonnes manganese released
The amount of 0.2 tonnes of manganese would be reported to the NPRI for the reporting year. In this case it would be reported as a release to air.
Repeat the process above for any other NPRI substance found in the welding rod used at the facility.
Part 4 Criteria Air Contaminants Threshold Calculations
Criteria air contaminants (CAC) have a mass release reporting threshold, therefore release calculations need to be made before it can be determined if a report is required for the substance. The best method of estimation for CAC released from welding processes is to use emission factors. Once the CAC released from welding have been calculated they must be added to the CAC releases from other sources at the facility. For example, the PM10 released from welding needs to be added to the PM10 released from the combustion of natural gas. Once the facility-wide total for each CAC has been calculated it is compared to the reporting threshold.
Example: Criteria Air Contaminants Emissions from Consumable Electrode Welding
Determine the amount of PM10 released from the SMAW welding process described below. Remember this is only one source of PM10 at the facility, all other PM10 releases must be calculated and combined before determining if the reporting threshold has been met.
Parameters:
Process: SMAW
Amount welded: 14 000 tonnes during the reporting year
Amount of Welding Rod Used: 1 000 tonnes of E310-15 welding
rod during the reporting year. The wire contains 1.3% manganese by weight,
obtained from the MSDS.
==> Additional information: The fume releases are uncontrolled and vented through a roof stack which is 25 m above grade.
PM10 emission factor from the US EPA's WebFIRE database of emission factors for E310-15:
0.0151 [ kg PM10 released / kg E310-15 used ]
Threshold Calculations:
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 (1 tonne/1 000 kg)
= 1 000 000 kg welding rod used x 0.0151 (kg PM10 released/kg
welding rod used)x(1 tonne/1 000 kg)
= 15.1 tonnes PM10 released
The reporting threshold for PM10 is 0.5 tonnes released to air, since the release value here is 15.1 tonnes, a report will be required for PM10 . However, all other PM10 releases at the facility must be added to the 15.1 tonnes and the resultant value reported to the NPRI.
Non-consumable Welding Electrode Processes:
The following points can be used to determine which sources of NPRI substances need to be considered in the threshold calculations:
- The base metal being welded loses article status, thus the amount of all NPRI-listed substances found in the base metal being welded must be considered in the threshold calculations.
- NPRI-listed substances found in non-consumable welding electrode processes must also be considered during threshold determination.
- For Part 1A metals (ex. Cr3+ , Co, Mn and Ni, or any other) facilities will need to determine if they MPO greater than or equal to 10 tonnes of each substance based on the amount and composition of the materials being welded (i.e., the base metal and welding rod/wire). If these substances are MPO in other processes at the facility, these sources must also be considered in the facility's threshold calculations.
- For Part 1B metals (ex. hexavalent chromium (Cr6+), lead, or any other) facilities will need to determine if they MPO greater than or equal to the mass threshold of each substance based on the amount and composition of the materials being welded. The mass thresholds can be found in the Guide for Reporting to the National Pollutant release Inventory. If these substances are MPO in other processes at the facility, they must be considered in the facility's threshold calculations.
For each of the Part 1A and 1B substances that met or exceeded the reporting threshold the following emission factors can be used to determine the amount released to air.
| Substance | Emission Factor* (kg substance/m weld length used) |
|---|---|
| Cr3+ | 0.000033 |
| Co | 0.000033 |
| Mn | 0.000033 |
| Ni | 0.000033 |
| Cr6+ | 0.000033 |
| Pb | 0.000033 |
Example: Non-consumable Electrode
Determine the amount of manganese manufactured, processed, or otherwise
used and compare it to the 10-tonne reporting threshold. If it is greater
than the 10-tonne threshold calculate the amount released due to the
welding process.
Parameters:
- Process: resistance spot welding (RSW)
- Number of sheets welded: 60 000 metal sheets during the reporting year
- Sheet weight: 150 kg
- Sheet thickness: 0.079 cm
- Spot welds per sheet: 1 000
- The sheets contain 1.09% manganese by weight, obtained from the MSDS.
- Additional information: The fume releases are uncontrolled and vented through a roof stack which is 25 m above grade.
Remember: When using only a non-consumable welding electrode process the base metal being welded does not retain its article status and therefore must be considered in the threshold or release calculations.
Threshold Calculations:
The amount of manganese MPO can be calculated using the following equation:
Amount of Manganese(tonnes) = Number of Sheets x Sheet weight(kg) x
(Weight percent manganese per sheet/100%)x(1 tonne/1000 kg)
= 60 000 Sheets x 150 kg x (1.09%/100%)x(1 tonne/1000 kg)
=98.1 tonnes of manganese
Since the amount of manganese is greater then the 10-tonne reporting threshold, the facility's manganese releases must be determined.
Release Estimate
The general emission factor for consumable welding electrode processes of 0.000033 kg manganese / m weld length will be used.
To use the emission factor above, first the weld length must be determined. To find the weld length first the weld diameter must be calculated. This can be done using the following general formula:
Weld Diameter (m) = Assembly Thickness (m) x 4
Since two sheets are being welded together the assembly thickness is:
Assembly Thickness (cm) = Thickness of One Sheet (cm) x 2
= (0.079 cm) x 2
= 0.158 cm
Using the assembly thickness to determine the weld diameter is as follows:
Weld Diameter (m) = (0.00158 m) x 4
= 0.00632 m
Now the weld length can be calculated using the following formula:
Weld Length (m) = Weld Diameter (m) x Number of Sheets x Welds per Sheet
= (0.00632 m) x (60 000 sheets) x (1 000 welds/sheet)
= 379 200 m
Now the release may be calculated using the formula shown below:
Manganese Released (kg) = Weld Length (m) x Emission Factor (kg/m)
= (379 200 m) x (0.000033 kg/m)
= 12.514 kg
= 0.012 tonnes
Criteria Air Contaminant Threshold Calculations
Non-consumable welding processes do not release significant amounts of CACs
Other Tools and Sources of Information for Welding
The NPRI Toolbox contains a spreadsheet for calculating Part 1A, 1B and CAC releases from various consumable electrode welding processes. The threshold calculations will still need to be calculated as shown above for Parts 1A and 1B metals, and then the spreadsheet can be used to determine the releases of those substances. The CAC portion of the spreadsheet can be used to calculate the welding contribution to the total particulate matter and PM10 reporting thresholds.
The US EPA's WebFIRE database and AP-42 documents (section 12.19) can be used for more background information on the releases from welding processes.
References
Canadian ORTECH Environmental Inc. (ORTECH), 2001. "NPRI Guidance for Welding Processes for Environment Canada Prairie and Northern Region", Report Prepared for Environment Canada by ORTECH, May 2001.
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, 1004.
