# EPA – CRP1234 Meeting



# Presentation Outline  

## Overview of CRP Fault Tree Analysis  

## Sensitivity Analysis  

### New thoughts from CRP members since 11/20/09 meeting  

### Risk Comparison R134a – HFO - 1234yf  

## Stakeholders arguments regarding the proposed rule  

## Status of new SAE standards  

## Comments on UBA report
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# Fault Tree Analysis

Overview

2 Tom Lewandowski, Ph.D., DABT

Gradient LLC Seattle, WA

### Tables 2 -4 (1234yf) and 5-4 (R-744) in Phase III 

### Report explain scenarios that were evaluated via FTA

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### Table 2 -5 in Phase III Report explains how

CRP1234 considered key fault tree scenario

conditions

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## Attachment S contains detailed collision data that support the FTA assumptions  Based on OEM interpretation of GIDAS and Delphi collision data

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## Attachments A (1234yf) and B (744) contain the basis and values for all FTA inputs...

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# As well as the fault trees themselves  Trees for HFO - 1234yf – 45 pages  Trees for R - 744 – 12 pages NOTE: The first page of each set of trees shows the various subtrees being added. This is an artifact of the software but should be disregarded. Some subtrees have different denominators (per year, per operating hour, per hour vehicle service) and should not be added.
7Risk driver trees both involve operating vehicles, have the same denominator, and can be added

8 Results of some, but not all, branches can be added

All trees involve operating vehicles, have the same denominator, and can be added Adding not possible but also not necessary because risk is dominated by single scenariosFault Tree Structure: Example

9 Speed independent event

Speed dependent branchesPage 15, High Speed Branch Common factors for all high speed collisions

Inputs for all high speed frontal collisions Inputs for all high speed side collisions Transfer to preceding slide

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## Non - Collision related trees are generally 

## simpler in structure (i.e., single sheet)

11 Inverse gate (1 -X): This tree requires the probability occupants stay in vehicle, the inverse (occupants leave vehicle) is used elsewhere

# FTA Additional Comments  

### Some collision trees share very similar but not identical inputs  Thus some of the fault tree pages will look similar but have important differences  Example - HF4.2 and HF5  

### EV and Hybrid vehicle types are not addressed in this Risk Assessment  Technology is still evolving  OEMs will perform risk assessments of their specific designs  No new general use conditions are needed
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# 2. Sensitivity Analysis  Evaluated several parameters where OEMs were uncertain  Changed parameters to the alternative value and looked at overall impact on predicted top event frequency  Looked at:  Removal of secondary fires as a source of HF generation  Change in hot surface temperature likely to ignite refrigerant  Less conservative assumptions regarding collisions and engine surface temperatures  Reduced “scrubbing” by rain/fog of air drawn into the cabin  Increasing evaporator failure rate

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# Results of Sensitivity Analysis  

### Most of the alternative values/scenarios had a minimal impact on the resulting top event 

### probabilities  

### Adopting less conservative assumptions regarding collisions, hot surfaces, and possible ignition sources reduced top event probabilities for refrigerant ignition by four orders of magnitude  

### The sensitivity analysis demonstrates that the risk assessment is robust against changes in the input values
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## 3. Risk Assessment Changes in 

## Response to November 20 Meeting  

### Changed references to “professional service worker/repair worker” to “certified service 

### technicians”  CRP recommends training according to J2845 and certification according to J2911  CRP1234 Risk Assessment assumed this level of certification will occur  

### Added comparison of risks to R - 134a and R - 12  

### Improved documentation on fault tree 

### development process

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### HFO- 1234yf and R -744 are compared to 

### R- 12 and R- 134a

LCCP not included because this was not a part of the risk assessment but EPA has results 17

# Conclusions of CRP1234 risk assessment  

## FTA expanded relative to Phase I and II 

## risk assessments  

### More detailed consideration of possible risk scenarios – greater confidence in results of the analysis  

### Sensitivity analysis demonstrates that uncertainties in some input parameters have little impact on risk assessment conclusions  

### Comparison of HFO - 1234yf to R - 12 and R - 134a demonstrates an improved risk profile.

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# CRP1234 

# Risk Comparison R - 134a and HFO - 1234yf

Dr. Chris Seeton Honeywell20 

# HFO - 1234yf Risk of HF Exposure

There are two primary risk scenarios associated with the production of HF from a fluorinated refrigerant. The other risk scenarios are relatively insignificant for the basic comparison between R- 134a and HFO- 1234yf. Exposure to HF above HBL due to vehicle fire caused by non -AC component failure in the engine compartment (former occupant, non collision)
Exposure to HF above HBL due to aspiration of HF from engine compartment (occupant, collision)21 

# R134a versus HFO - 1234yf

 

### Extremely low risk for both refrigerants (same order of magnitude)  

### HFO - 1234yf is appropriate for use in MAC systems without use restrictions Risk Scenario HFO- 1234yf R- 134a HF 7.2: Exposure to HF above HBL due to vehicle fire caused by non -AC component failure in the engine compartment (former occupant, non collision) 2.3 * 10 - 12 Same HF 4.2: Exposure to HF above HBL due to aspiration of HF from engine compartment (occupant, collision) 2.3 * 10 - 12 Lower Combined Risk 4.6 * 10 - 12 ~ 10 - 1222 

# Major vehicle fires (HF 7.2)
 

### All fluorinated refrigerants, in a major vehicle fire 

### will decompose to produce HF  The amount of HF generated depends on the amount of refrigerant combusted  The amount of HF generated will be smaller for HFO - 1234yf than R - 134a for complete combustion 

## R- 134a and HFO- 1234yf have the same risk

both generate HF23



## Aspiration of HF into Passenger 

## Compartment (HF 4.2)  

## Data indicates ignition of R134a+oil and 

## HFO - 1234yf+oil on hot surfaces  

### Toyota, Hyundai and Honeywell report that R - 134a+oil ignites >800oC on a hot plate  

### INERIS reports that HFO - 1234yf+oil ignites >750 ± 50oC on a hot surface The risk is lower for R- 134a compared to HFO- 1234yf



### for this scenario24 

# R134a versus HFO - 1234yf

 

### Extremely low risk for both refrigerants (same order of magnitude)  

### HFO - 1234yf is appropriate for use in MAC systems without use restrictions Risk Scenario HFO- 1234yf R- 134a HF 7.2: Exposure to HF above HBL due to vehicle fire caused by non -AC component failure in the engine compartment (former occupant, non collision) 2.3 * 10 - 12 Same HF 4.2: Exposure to HF above HBL due to aspiration of HF from engine compartment (occupant, collision) 2.3 * 10 - 12 Lower Combined Risk 4.6 * 10 - 12 ~ 10 - 1225 

## Overall Risk Comparison Conclusions  Use of HFO - 1234yf in MAC systems poses a extremely low level of risk for all affected segments  Use of HFO - 1234yf in MAC systems will have a negligible impact on current risks associated with vehicle operation or service with current design practices  Recommendation for SNAP wording: "HFO - 1234yf MAC systems shall incorporate engineering strategies reasonably necessary to manage risks of injury and/or property damage caused by HFO - 1234yf, similar to R - 134a MAC systems. Such strategies shall be based on risk assessments using SAE J1739 (FMEA) or its equivalent."26 

# Status of SAE Standards



# for HFO - 1234yf

Ward Atkinson Chairperson SAE ICCC28



# SAE CRP1234 

# Response to UBA Docket Comment
Mary Koban DuPont

## Response to UBA Comment  BAM testing found some HFO- 1234yf ternary mixtures had LFL< 6.2 vol %.  Expected result when mixing HC with other refrigerant and/or air  UBA expects HC’s in automotive workplace and/or from oil decomposition on engine and therefore HFO - 1234yf should not be used with A/C.  When oil breaks down, only small levels of HC’s are formed [PPM levels]  LFL of ethane and HFO- 1234yf are given below: Ethane LFL 2.4 vol % HFO- 1234yf LFL 6.2 vol %  Adding HFO- 1234yf to ethane/air increases the LFL of the mixture above that of pure ethane, “quenching” the flammability of ethane

### Results are for ethane/R - 134a/air similar to

ethane/HFO - 1234yf/air 

## Response to UBA Comment

Further Comment will be submitted by DuPont and Honeywell

# UBA test for HF  

### UBA received a report by a German Institute IBExU (Institute for Security Techniques ltd.),  Temperature from 100 ° C to 500 ° C  Qualitative measurements of HF were done with gas test tubes (Draeger).  Report shows HF formation at 300 ° C with a measurement of about 70 ppm HF  

### CRP measured with a real vehicle at 450 ° C and obtained maximum levels of 7.5 PPM  

### Exposure times and test method used by IBExU do not represent real world conditions

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