# TECHNICAL SUPPORT DOCUMENT FOR EMISSIONS FROM ELECTRIC EQUIPMENT

MANUFACTURE OR RE FURBISHMENT AND

MANUFACTURING OF ELECTRICAL

COMPONENTS

PROPOSED RULE FOR MANDATORY

REPORTING OF GREENHOUSE GASES

Office of Air and Radiation U.S. Environmental Protection Agency

March 22, 2010

1Contents

1. Source Description

............................................................................................................................... ................3

a. Total U.S. Emissions

............................................................................................................................... ........3

b. Emissions to be Reported

............................................................................................................................... .3

2. Options for Reporting Threshold .........................................................................................................................4

a. Data Analysis Supporting Proposal.................................................................................................................4

3. Options for Monitoring Methods .........................................................................................................................5

a. IPCC Tier 1 Approach

............................................................................................................................... ......5

b. IPCC Tier 2 Approach

............................................................................................................................... ......5

c. IPCC Tier 3 Approach

............................................................................................................................... ......5

4. Issues Related to the Transfer of Equipment from Equipment Manufacturers to Equipment Users ....................9

5. Review of Existing Relevant Reporting Programs/Methodologies ....................................................................10

6. Procedures for Estimating Missing Data ............................................................................................................10

7. QA/QC Requirements

............................................................................................................................... .........10

8. Reporting Procedures

............................................................................................................................... ..........11

9. References

............................................................................................................................... ...........................11

21. 

### Source Description

Sulfur hexafluoride (SF 6 ) is most commonly used in the electrical powe r industry where it acts as an insulator and interrupter in equipment that transmits and distributes elect ricity (RAND 2004). The electric power industry in the

United States has used SF 6 gas since the 1950s because of its superi or dielectric strength and arc-quenching

characteristics. SF 6 has replaced flammable insulating oils in many applications and allows for more compact substations in dense urban areas. Currently, there are no available or foreseen substitutes for SF 6

.

High-voltage circuit breakers account for the majority of SF 6 use in the United States. Other types of electrical equipment that use SF 6 include gas-insulated substations, switches (other than circuit breakers), high-voltage transmission lines, and high-voltage bushings.

Original equipment manufacturers (OEMs) purchase bulk SF 6 gas to:

 install a shipping charge in high-voltage closed-pressure equipment; 1

 ship alongside closed-pressure equipment for topping off at installation site;

 fill sealed-pressure equipment with its intended lifetime supply of SF 6 ; 2 and

 test equipment.

SF 6 emissions from OEMs typically occur during the testing manufacturing, and installation or commissioning of equipment but can also occur when equipment is decommissioned at a manufacturing facility.

Perfluorocarbons (PFCs) are sometimes used as dielectrics and heat transfer flui ds in power transformers. PFCs are also used for retrofitting CFC-113 cooled transformers. One PFC used in this application is perfluorohexane (C 6 F 14 ). In terms of both absolute and carbon-weighted emissions, PFC emissions fro m electrical equipment are generally believed to be much smaller than SF 6 emissions from electrical equipment; however, there may be some exceptions to this pattern (IPCC, 2006). Thro ughout this Technical Support Document, “SF 6 ” will be used to denote

SF 6 and/or PFCs.

a. Total U.S. Emissions

Emissions of SF 6 from OEMs in the United States were estimated to be 0.8 Tg CO 2 Eq. in 2006 (EPA 2008).

The 1990 to 2006 emission estimates for OEMs were derived by assuming that manufacturing emissions equal 10 percent of the quantity of SF 6 charged into new equipment. The quantity of SF 6 charged into new equipment from 1990 to 2000 was estimated based on statistics comp iled by the National Electrical Manufacturers Association (NEMA). The quantities of SF 6 charged into new equipment for 2001 to 2006 were estimated using data reported by participants in EPA’s SF 6 Emission Reduction Partnership for Electric Power Systems along with EPA’s estimate of the total industry SF 6 nameplate capacity (128.4 Tg CO 2 Eq. in 2006). Specifically, EPA calculated the ratio of new nameplate capacity to total nameplate capacity of a subset of Partners for which new nameplate capacity data was available from 1999 to 2006. EPA then multiplied this ratio by the total industry nameplate capacity estimate to

derive the amount of SF 6 charged into new equipment for the entire industry. The 10 percent emission rate is the average of the “ideal” and “realistic” manufacturing emission rates (4 percent and 17 percent, respectively) identified in a paper prepared under the auspices of the International Council on Large Electric Systems (CIGRE) in February 2002 (O’Connell et al. 2002). This method for estimating OEM emissions is the same method used in

EPA’s Inventory of Greenhouse Gas Emissions and Sinks:1990-2006 (EPA 2008).

b. Emissions to be Reported

1 Closed-pressure equipment requires refilling (topping up) gas during its lifetime and generally contains between five and several hundred kilograms of SF 6 per unit (IPCC 2006).

2 Sealed-pressure equipment should not require any refilling (topping up) with gas during its lifetime and generally contains less than 5 kilograms of SF 6 per unit (IPCC 2006).

3EPA is requiring facilities to report all SF 6 and PFC emissions from testing and manufacturing of new equipment, from refurbishing and decommissioning of previously manufactured equipment, and in certain circumstances from installation of new equipment.

2. 

### Options for Reporting Threshold

EPA evaluated a range of emission and consumption-based thresholds for electrical equipment manufacturing. The emission-based thresholds considered were 1,000; 10,000; 25,000; and 100,000 mt CO 2 Eq. These thresholds translate to consumption-based thresholds of 922; 9,220; 23,061, and 92,244 lbs of SF 6 , respectively, assuming an average manufacture emission rate of 10%.

As shown in Table 1 below, EPA estimates that all ten domestic facilities iden tified as consumers of SF 6 will fall above the 1,000; 10,000; and 25,000 mt CO 2 Eq. thresholds and above the 922; 9,220; 23,061 lbs. of SF 6 thresholds, while only the largest five facilities would be captured by the 100,000 mt CO 2 Eq./92,244 lbs SF 6 threshold. However, while EPA attempted to accurately estimate SF 6 consumption per facility, it is conceivable that OEMs specializing in the production of relatively low-voltage switchgear for the distribution market will fall below the consumption threshold.

Additional details on the number of facilities and total emissions that woul d be captured by each threshold are

shown below in Table 1.

Table 1. Emission Threshold Summary

Emission Threshold (Mt CO 2 Eq) 1,000 10,000 25,000 100,000
Consumption Threshold (lbs. of SF 6 ) 922 9,220 23,061 92,244

Number of Facilities Above 10 10 10 5

Percent of Facilities Above 100% 100% 100% 50%
Total Emissions of Facilities Above (Mt CO 2 Eq) 814,128 814,128 814,128 569,890

Percent of Emissions Above 100% 100% 100% 70%

a. Data Analysis Supporting Proposal

The consumption-based threshold offers an important advantage relative to the emission-based threshold because it permits OEMs to quickly determine whether they are covered. It also avoids the scenario in which sources drop in and out of the program based on fluctuating emissions.

EPA performed a threshold analysis to determine how many OEMs would fall above and below the four different consumption thresholds considered. The analysis was performed by:

 Using the Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2006 (EPA 2008) to determine the

estimated amount of SF 6 gas purchased by all OEMs, which was estimated as 750,981 lbs in 2006.

 Converting the 750,981 lbs of SF 6 to metric tons of CO 2 equivalent, which is 8,141,281 Mt CO 2 Eq.

 Estimating total U.S. emissions by multiplying total purchases by the 10% emission rate, which is 814,128

Mt CO 2 Eq.

 Identifying the ten OEMs in the U.S. th at are responsible for most of the SF 6 consumption in the manufacturing sector.

 Dispersing the total amount of U.S. OEM emissions of SF 6 among each of the ten OEMs based on the

estimated market-share of each OEM.

43. 

### Options for Monitoring Methods

For electrical equipment manufacturers, emissions can occur during equipment testing, manufacturing, installation, and decommissioning and refurbishing. EPA evaluated a range of options for estimating emissions that result from these activities. The three primary options reviewed were the Tier 1, Tier 2, and Tier 3 IPCC methods presented in

the 2006 IPCC Guidelines for National Greenhouse Gas Inventories (IPCC 2006). Each of these options is

described below.

a. IPCC Tier 1 Approach

The Tier 1 method, referred to as the default emission factor method, estimates emissions by multiplying the appropriate default regional emission factor by the amount of SF 6 consumed by each equipment manufacturer. Tier 1 emission factors are usually developed through industr y research. However, due to a lack of data availability, IPCC does not provide a default emission factor for the United States. The default em ission factors for emissions

associated with the manufacture of cl osed-pressure electrical equipment in Europe and Japan are 8.5% and 29%, respectively.

b. IPCC Tier 2 Approach

The Tier 2 method, referred to as the country-specific emission factor method, also uses emission factors. But these

emission factors are more accurate than the Tier 1 factors because they are developed us ing criteria specific to the country where the manuf acturer is located and are usually developed by analyzing actual pure-mass balance emissions that were calculated at the life-cycle level.

While the Tier 1 and Tier 2 approaches are relatively simple , they are likely to result in inaccurate facility emissions estimates because they do not take into account the variation in SF 6 handling and management practices among OEMs as well as variation in production methods associated with the different types of electrical equipment produced. Furthermore, due to lack of data availability, IPCC does not provide emission factors for electrical equipment manufacturing in the United States.

c. IPCC Tier 3 Approach

The Tier 3 method measures SF 6 emissions using mass-balance equations for each life-cycle stage of the SF 6 use. The equations below are based on the Tier 3 mass-balance equations for equipment manufacturing emissions and equipment installation emissions.

The Tier 3 equation for estimating emissions from equipment manufacturing emissions, which includes equipment testing, equipment manufacturing, and equipment decommissioning and refurbishing is the following:

Equipment Manufacturing Em issions = Decrease in SF 6 Inventory + Acquisitions of SF 6 – Disbursements of SF 6

Where:

Decrease in SF 6 Inventory = SF 6 stored in containers at the beginning of the year – SF 6 stored in containers at the end of the year

Acquisitions of SF 6 = SF 6 purchased from chemical producers or distributors in bulk + SF 6 returned by equipment users or distributors with or inside equipment + SF 6 returned to site after off-site recycling

5Disbursements of SF 6 = SF 6 contained in new equipment delivered to customers + SF 6 delivered to equipment users in containers + SF 6 returned to suppliers + SF 6 sent off-site for recycling + SF 6 destroyed

In addition, emissions may occur when the manufacturer f ills the equipment offsite from the manufacturing facility, before transferring custody to the equipment user. These emissions, along with other issues related to the transfer of equipment from manufacturers to users, are discussed further below.

To quantitatively determine disbursements of SF 6 to customers in new equipment (or cylinders), four options were

considered:

 Option 1: Disbursements could be estimated by weighing containers before and after gas from the containers was used to fill equipment or cylinders.

 Option 2: Disbursements could be estimated by using flow meters to measure the amount of gas used to fill equipment or cylinders.

 Option 3: Disbursements could be estimated by assuming that the mass of SF 6 or PFCs disbursed to customers in equipment is equal to the nameplate cap acity of the equipment or, where the equipment is shipped with a partial charge, equal to the nameplate capacity of the equipment times the ratio of the densities of the partial charge and the full charge.

 Option 4: Disbursements could be estimated by weighing the equipment filled with SF 6 or the PFC from the container before and after filling. The tare weight of the equipment would then be subtracted from the weight of the filled equipment to determine the weight of the gas in the equipment, and therefore, the weight of the actual disbursement.

These options and their advant ages and disadvantages are discussed, in turn, below.

 Option 1 appears to be a practice currently employed at some manufacturing facilities. A digital scale is used to weigh the containers storing the gas before an d after the equipment is filled (MEPPI 2010). In this regard, this option does not present new costs or chan ges to current procedures. However, EPA recognizes that emissions can occur downstream of the container to the equipment being filled. These emissions can occur through leaks in the hose or line connecting the container to the equipment, during coupling and decoupling activities, as we ll as through general mishandling (e.g., a faulty connection). To accurately estimate disbursements, these emissions should be estimated separately and subtracted from the disbursement total. These emissions could be estimated using measurements and/or engineering assessments or calculations based on chemical engineer ing principles or physical or chemical laws or properties. Such assessments or calculations could be based on, as applicable, the internal volume of the hose or line that is open to the atmosphere during coupling and decoupling activities, the internal pressure of the hose or line, the time the hose or line is open to the atmosphere during coupling and decoupling activities, the frequency with which the hose or line is purged and the flow rate during purges. Such methods could also include the use of leak detection methods (e.g., EPA Method 21 and the Protocol for Equipment Leak Emission Estimates) to determine a loss factor appropriate to calculate emissions. Unexpected or accidental emissions fr om the filling lines or hoses should be included in the total. EPA’s understanding is that electrical equipment is at a vacuum and is sealed prior to being filled with SF 6 or PFCs (MEPPI, 2010). However, if any air or nitrogen is in the equipment and is purged during the filling process, then the method should also account for SF 6 and PFC emissions that occur during such purging.

 Option 2 presents the same issue as in option 1 in that emissions downstream of the containers would be required to be estimated separately and subtracted fr om the disbursement total. One disadvantage in this approach is that flow meters may not be used by the OEM, in which case, the OEM would need to purchase these devices. OEMs commonly rely only on the pressu re rise to monitor the transfer of the gas from a container to a breaker or other pi ece of equipment (MEPPI 2010).

 Option 3 equates the mass of SF 6 or PFCs disbursed to customers in equipment to the nameplate capacity of the equipment or, where the equipment is shipped w ith a partial charge, equal to the nameplate capacity

6of the equipment times the ratio of the densities of the partial charge and the full charge. The nameplate capacity could be based on the manufact urer’s current estimate (i.e., the one that appears on the nameplate) or it could be measured. One disadvantage of assuming that the mass of SF 6 or PFCs disbursed to customers in equipment is equal to the current estim ate of the nameplate capacity is that the current estimate may never have been measur ed with good precision and accuracy. Even if the nameplate capacity has previously been carefully meas ured, the internal volume of the equipment or density to which the equipment is charged might have changed since the original measurement. Because the mass-balance approach requires precise inputs, inaccuracies of even two or three percent could lead to very large inaccuracies in the facility’s emissions estimate.

One way of developing a more precise estimate of the nameplate capacity of equipment would be to fill the equipment with a fluid and then to carefully recover the fluid, measuring what was recovered. This fluid

could be SF 6 , another gas, or a liquid. If SF 6 was used, the equipment would be charged to its operational or shipping SF 6 density using the facility’s usual methods and then emptied. The mass of the SF 6 recovered, adjusted slightly for the residual pressure of the SF 6 that would remain in the equipment even at a deep vacuum, could be equated to the full or shipping charge, as applicable. One advantage of this approach is that it would reflect the actual SF 6 charging practices of the facility; one disadvantage is that it

could result in small SF 6 emissions during the charging and recovery steps.

If a liquid was used, the equipment would be filled carefully, ensuring that the full volume was filled, and then emptied. The volume of the liquid recovered would be equated to the internal volume of the equipment. The temperature of the liquid would need to be kept constant throughout this exercise to obtain

an accurate measurement of the volume. This volume multiplied by the SF 6 density at the full charge would yield the nameplate capacity of the equipment.

To account for variability, a certain number of these measurements would need to be performed to develop a robust and representative average nameplate capacity (or shipping charge) for each make and model. Equipment samples should be selected so as to re flect predictable variability in the fac ility’s filling practices and conditions. 3 In addition, within a particular set of conditions, equipment should be selected at random. The specific number of samples would depend on the variability of the nameplate capacity within each make and model and on the desired level of precision of the estimated mean nameplate capacity of each make and model. As discussed below, the desired level of precision of the mean would depend on the level of precision of the emissions estimate as a whole.

A Student T distribution calculation is the appropriate statistical procedure for determining when additional samples should be taken to achieve a tolerable error for the average nameplate capacity of a certain make

and model of SF 6 -containing electrical equipment. 4 The calculation presumes an approximately normal, bell-shaped distribution of the underlying parameter, which implies that the distribution of the average is the Student’s t distribution. In principle, the mean of the samples taken approaches the true mean as more samples are taken; this procedure determines how many samples are needed as a function of the relative standard deviation of the sample measurements. The following matrix demonstrates this concept using a 95 percent confidence level and an assumed initial sample size of ten. On the left is the relative standard
deviation of the sample population; an initial sample size of ten was chosen for this computation. 5 For example, an equipment manufacturer conducts a minimu m of ten tests to determine the nominal nameplate capacity of ten samples from a given make and model of a high voltage circuit breaker. In this hypothetical example, the resulting standard deviation of those samples is 1.5 percent. If the tolerable error is one

3 For example, if equipment is filled to a particular pressu re, and the temperature of the facility varies during the day or seasonally, then the density to which the equipment is filled will vary as well (with higher densities at lower temperatures). In this case, samples should be taken to reflect the typical range of temperatures at which equipment

is filled.

4 See the Technical Support Document for Fluorinated Gas Production for more discussion of the Student’s t test.

5 Table 2 is provided as an example; a manufacturer would apply the Student T distribution to determine the appropriate number of samples based on the variability of the quantity of gas charged into equipment of a given

make and model.

7percent of the true mean, the manufacturer must increas e its sample size to twelve, i.e., conduct two more tests, according to the chart below. If the standard de viation of the sample popula tion tested was larger, the number of samples that would need to be taken would also increase. 6

Table 2. Example Lookup Table of Total Sample Size required to meet Precisions, given Initial Sample Size of 10

Precision

0.25% 0.50% 1.00% 5.00%

0.5% 18 10 10 10

1.0% 64 18 10 10

1.5% 141 38 12 10

2.0% 249 64 18 10

2.5% 389 99 27 10

3.0% 560 141 38 10

3.5% 763 191 50 10

4.0% 996 249 64 10

4.5% 1260 315 81 10Relative Standard Deviation of Sample

5.0% 1556 389 99 10

The actual precision with which the mean nameplate capacity would need to be measured would depend on (1) the desired level of precision for the emissions estimate for the facility, (2) the precision with which the other quantities in the mass-balance equation were monitored, (3) the share of the facility’s SF 6 disbursements accounted for by a particular make an d model, (4) the number of makes and models whose nameplate capacities were measured, 7 and (5) the level of emissions. Example calculations indicate that a facility that measured gas acquisiti ons with a precision and accuracy of one percent and that had an emission rate of 10 percent might need to estimate th e mean nameplate capacity (or shipping charge) to a precision of two percent to achieve a precision in its emissions estimate of about 20 percent (expressed as a 95-percent confidence interval). A facility that measured gas acquisitions with a precision and accuracy of one percent and that had an emission rate of 5 percent might need to estimate the mean nameplate capacity to a precision of one half of one percent to achieve a precision in its emission estimate of about 25 percent. (The accuracy of the device used for the nameplate capac ity measurement would also need to be one half of one percent or better.)

For other sources (e.g., fluorinated GHG production processes using the mass-balance approach), EPA is proposing a maximum error of 30 percent. However, in general, the tolerable level of error in an estimate depends in part on the size of the emissions. For smaller emission sources, errors larger than 30 percent might be tolerable.

6 It is important to note that the reliability of the mean nameplate capacity estimate depends on the accuracy and precision of the individual measuremen ts as well as on the number of times they are repeated. Accuracy is a measure of the bias (systematic error) of a measurement; precision is a measure of the random error. The precision includes the random errors from the measuring devices such as the scales used and the variation in the nameplate capacity for a single make and model. Repeated measurements using the same measurement device improve the precision of the mean, but they do no t improve accuracy because each measuremen t has the same systematic error. For example, if the scale used to weigh the SF 6 shipping charges is only guaranteed to be accurate within one percent, and it happens to be biased upward by 0.75 percen t, the mean of ev en 2,000 weight measurements of the same device will be biased upward by 0.75 percent.

7 If the nameplate capacities of multiple models were measured independently, using multiple measurement devices, then the “error” (more precisely, the relative standard de viation) of their summed or averaged nameplate capacities would be smaller than the errors of their individual nameplate capacities. However, if the nameplate capacities were measured using the same measuring device (with the same systematic error), then the error of the summed nameplate capacities would not be reduced below the syst ematic error of the individual nameplate capacity

measurements.

8To reflect subtle changes in manufacturing methods and conditions over time, it may be appropriate to require re-measurement of nameplate capacities at so me interval, e.g., every five or ten years.

According to industry, equipment manuf acturers are filling breakers with SF 6 gas to a full charge as part of their testing procedures; the equipment is then evacuat ed and filled to a partial charge for shipment at a later stage in the process (MEPPI 20 10). Therefore, an advantage to this option is that it appears that it could be integrated into normal facility procedures without introducing any significant filling and recovering related activities. However, if the test charge were used to estimate the nameplate capacity, equipment manufacturers would need to account for possible variations between the density to which the equipment was charged during the test and that to which it was charged for shipping.

 Lastly, Option 4 would require the weighing of the equipment filled with SF 6 or the PFC before and after the equipment is charged. The tare weight of the eq uipment would then be subtracted from the weight of the filled equipment to determine the weight of the gas in the equipment, and therefore, the weight of the actual disbursement. Although, in theory this option is advantageous because it shifts the emphasis to the equipment that is being disbursed (rather than weighing the containers at the intermediary step), this option is not practical for two reasons. First, the mass of the SF 6 or PFC charged into the equipment is likely to be low relative to the mass of the equipment; thus, it may be difficult to obtain a precise measurement of the

mass of the SF 6 or PFC using this method (i.e., within 1 percent) even if the scale is precise and accurate to within 1 percent of full scale. Second, it would be very difficult and impractical to weigh the shipping unit, which can be large and difficult to maneuver onto a scale (MEPPI 2010).

4. 

### Issues Related to the Transfer of Equipment from Equipment Manufacturers to Equipment Users

As noted above, emissions may occur when the manufactur er fills the equipment offsite from the manufacturing facility, before transferring custody to the equipment user . Such emissions could be estimated using the following equation:

Equipment Installation Emissions (offsite from OEM facility) = SF 6 used to fill equipment offsite (from the OEM facility) + SF 6 charged into the equipment at the OEM facility – Nameplate capacity of equipment installed offsite (from the OEM facility)

These emissions could be attributed to the equipment manuf acturer. In addition, any emissions from equipment that was filled (partially or completely) at the OEM’s facility bu t whose charge leaked out before being delivered to and

installed for the customer could also be the manufacturer’s responsibility to report.

EPA understands that in some cases, manufacturers may deliberately exceed the name plate capacity of equipment when charging it, e.g., to postpone the re-fill of the equipm ent in the event that the equipment develops a leak. If this is the case, then the actual initial charge of the equipment should be conveyed clearly to the equipment user. If it is not, the user will underestimate emissions. The un derestimate will occur because the user will underestimate the quantity of gas “purchased with or inside of equipment.” Effectively, an extra supply of gas is hidden inside the equipment rather than conveyed alongside it in a container.

For example, suppose that a piece of equipment is charged to 105 percent of its proper charge (nameplate capacity) when it is first installed, but that its initial charge is reco rded as 100 percent of the proper charge. Suppose further that the equipment slowly leaks over its lifetime so that it has 90 percent of its proper charge left upon retirement. When the equipment is retired, only the difference betwee n the proper charge (100 percent) and the actual charge (90 percent) will be noticed. The loss of the extra five pe rcent will not be recorded because the initial gain of that five percent was not recorded. In the event that the equipment never leaks during its lifetime and is retired with 105 percent of its charge, the five-percent overcharge, when recovered along with the rest of the SF 6 inside the equipment, will register as an addition to the SF 6 in storage that is five percent above the retired nameplate capacity. Again, this will result in emissions being underestimated by the quantity of the overcharge.

9To avoid the underestimate, equipment manufacturers should provide equipment users with an accurate estimate of the quantity of SF 6 actually charged into newly commissioned equipment. The user would then record this as additional gas “purchased with or inside of equipment.” Using the standard mass-balance approach, this extra gas would register as an emission during the first year. This is because the extra gas would be recorded as part of the total amount of gas purchased during the year, but would not be canceled out by a corresponding increase to cylinder inventory (since the extra gas is inside the equi pment) or by the increase to nameplate capacity (since the extra gas is by definition the amount of gas remaining once the nameplate capacity of the equipment is subtracted from the amount of gas actually inside the equipment). Since it would not be accounted for as an addition to inventory or as part of the new name plate capacity, it would seem to have been emitted or used to replace emitted gas. However, this apparent loss would be made up for when the equipment was retired, as discussed above.

An alternative approach to tr acking the overcharge would be to record it as stored inside the particular piece(s) of equipment that is (are) overcharged. Effectively, this extra charge would be tracked as if it were stored inside a cylinder that happened to be attached to the equipment. The equipment would be checked annually to see whether and how much of its charge had leaked during the year; if the overcharge had not leaked out, then the overcharge would still be considered to be in storage and would not be recorded as an emission. Although this approach would avoid indicating an emission before any occurred, the need for annual checks of overcharged equipment would make it relatively burdensome to carry out.

5. 

### Review of Existing Relevant Reporting Programs/Methodologies

In addition to the 2006 IPCC Guidelines , EPA also reviewed the protocols and guidance in the Inventory of U.S.

Greenhouse Gas Emissions and Sinks , the Technical Guidelines for the Vo luntary Reporting of Greenhouse Gases (1605(b)) Program, EPA’s Climate L eaders Program, and The Climate Registry. These protocols and guidance coalesce around the IPCC 2006 Tier 3 guidelines.

6. 

### Procedures for Estimating Missing Data

It is expected that equipment manufacturers should be able to obtain 100 percent of the data needed to perform the

mass balance calculations for both SF 6 and PFCs. The use of the mass-balance approach requires correct records for all inputs. However, if needed, repl ace missing data using data from sim ilar manufacturing operations, and from similar equipment testing and decommissioning activities for which data is available.

7. 

### QA/QC Requirements

QA/QC methods for reviewing completeness and accuracy of reporting include the following:

 Review inputs to the mass balance equation to ensure inputs and outputs to the manufacturer’s system are all accounted for in all appropriate sections.

 Ensure no negative inputs are entered and negative emissions are not calculated. However, the change in storage inventory may be calculated as a negative number.

 Ensure that beginning of year inventory matches end of year inventory from previous year.

 Ensure that in addition to SF 6 purchased from bulk gas distributors, SF 6 returned from utilities and received from off-site recycling are properly accounted as additions to inventory.

QA/QC methods should be employed throughout the year. Important checks/procedures include the following:

 Ensure that cylinders returned to the vendor are weighed in a consistent manner.

 Ensure that gas suppliers measure the amount of gas remaining in cylinders/tanks returned (residual gas).

 Adopt practices such as tracking cylinders leaving an d entering storage with ch eck-out sheets and weigh-in procedures.

 Ensure all facilities have provided information to the manager compiling the emissions report (if it is not already handled through an elect ronic inventory system).

108. 

### Reporting Procedures

The following supplemental data would aid in verifying facilities’ emissions estimates:

 SF 6 and PFC sales and purchases;

 SF 6 and PFCs sent off site for destruction;

 SF 6 and PFCs sent off site to be recycled;

 SF 6 and PFCs returned from off site after recycling;

 SF 6 and PFCs returned by equipment users with or inside equipment;

 SF 6 and PFCs stored in containers at the beginning and end of the year;

 SF 6 and PFCs inside equipment delivered to customers;

 SF 6 and PFCs returned to suppliers;

 The nameplate capacity of the equipm ent delivered to customers with SF 6 or PFCs inside, if different from the quantity in delivered to customers inside equipment;

 A description of the engineering methods and calculations used to determine emissions from hoses or other flow lines that connect the container to the equipment that is being filled.

 For any missing data, the reason the data were missing, the length of time the data were missing, the method used to estimate emissions in their absence, and the quantity of emissions thereby estimated.

9. 

### References

EPA (2008) Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2006. U.S. Environmental Protection Agency, Washington, D.C.

IPCC (2006) 2006 IPCC Guidelines for National Greenhouse Gas Inventories . The National Greenhouse Gas Inventories Programme, The Intergovernmental Panel on Climate Change, H.S. Eggleston, L. Buendia, K. Miwa, T Ngara, and K. Tanabe (eds.). Hayama, Kanagawa, Japan.

MEPPI (2010) Personal Communication between Phil Bolin and Dave Giegel of Mitsubishi Electric Power Products, Inc. and Mollie Averyt of ICF International, February 24, 2010.

O’Connell, P., F. Heil, J. Henriot, G. Mauthe, H. Morrison, L. Neimeyer, M. Pittroff, R. Probst, J.P. Tailebois (2002) SF 6 in the Electric Industry, Status 2000, Cigre. February 2002.

RAND (2004) RAND Enviro nmental Science and Policy Center, “Trends in SF 6 Sales and End-Use Applications: 1961-2003,” Katie D. Smythe. International Conference on SF 6 and the Environment: Emission Reduction Strategies . Scottsdale, AZ. December 1-3, 2004.

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