2.

Overview of the Risk Assessment

for Chiller

JRAIA Chiller Risk Assessment SWG Chief investigator

Kenji Ueda （Mitsubishi Heavy Industries, Ltd.）
Members
Mikio Ito, Tomokazu Tashimo, Isao Iba, Hiroichi Yamaguchi
Mamoru Senda, Masayuki Aiyama, Shuji Fukano, Takuho Hirahara
Tetsuji Saikusa, Yoshihiro Sumida, Koji Yamashita,
Yosuke Mukai, Naoki Kobayashi
© 2013 MITSUBISHI HEAVY INDUSTRIES, LTD. All Rights Reserved.
Today’s Outlines

Schedule

Regal system in Japan

Risk assessment detail
Countermeasure
GL

Conclusions

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1．Risk assessment process chart of chiller SWG

 The working group , which consists of professional chiller engineers, in Japan Refrigeration
and Air Conditioning Industry Assosication (JRAIA) started in 2011.
 Risk assessments(RAs) were executed until last year and the guideline(GL) draft was
created at the end of 2014, which is now being deliberated to be issued as the guideline
during this fiscal year.

2011Fy 2012Fy 2013Fy 2014Fy 2015Fy

▼P report※ ▼P report※ ▼P report※ Ｆ report※▼

Task extraction Risk assessment Risk assessment review

※P reort : Progress report・・・ ◆SWG calculation ◆University calculation

The report disclosed in the risk
assessment working group of the
Japan Refrigeration and Air
Conditioning Industry Association GL deliberation
GL draft and review

JRA-GL◆
Kobe symposium◆ Kobe symposium◆ Final report◆

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 2. Risk assessment and legal system
4．リスクアセスメントの構成概要（１）

Industrial Safety
and Health Law
【Order for Enforcement 】
A workplace employing a certain number of workers shall
appoint a Generaｌ Safety and Health Manager.
【Enforcement Regulations】
The Building The General Safety and Health Manager shall perform risk
assessments.
Standards Act EN1127-1(2011)
JRA Explosive atmospheres –
Explosion prevention and protection
High Pressure Gas -GL15
Safety Act
Guideline of
design IEC60079s(2011)
construction for
Explosive atmospheres – Equipment
Refrigeration Safety Regulations ensuring safety
Article 7.14 Electrical Equipment refers to against refrigerant ;General requirement
leakage form
explosion preventive performance ・・ chillers using JIS60079s
mildly-flammable Electric Machinery and Instruments Used in Explosive Atmospheres
refrigerants General Requirements is the 2007 version of IEC.
＞Outdoor natural ventilation＝Zone2
KHK0302-3(2012) ＞forced ventilation with preliminary and warning devices.
Standards of Refrigeration and Air-Conditioning ＋normally, explosive atmospheres are not formed.
Equipment Facilities〔Fasilities with Flammable Gases ＝Zone2NE(not dangerous）
（including mildly-flammable Gases）〕

ISO5149
Refrigeration system and heat pumps – safety
and environmental requirements

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 3．Target products

Water-cooled chillers Air-cooled heat pumps

Modular Chillers Modular Chillers
Type Screw chillers Screw chillers
Centrifugal
Cooling capacity 7.5kW - 17,500kW

Installation location machine room outdoor

Standard specifications for risk assessments

Cooling capacity Approx. 180kW Approx. 90kW

Refrigerant charge amount 23.4kg 11.7kg（per 1 system ）

Dimensions 1.28W×1.28D×1.28H [m] 1.00W×3.00D×2.30H [m]

Water-cooled chillers Air-cooled heat pumps

Ebara
Mitsubishi Refrigeration
Mayekawa Kobe Steel Heavy Equipment
Industries And Systems Mitsubishi Electric Toshiba-Carrier Hitachi Appliacnes

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4
4. Acceptable probability of harm

Table.4 Probability of occurrence of hazards per a chiller a year

Probability of occurrence of harm Industrial-level product adoption

consumer industrial level product
Number of accidents
goods (cases /units per year)

Frequent 10-3 10-1 （1.0X10-1） once a year per 10 units

5
Probable 10-4 10-2 （1.0X10-2） once a year per 100 units

4
Probable 10-5 10-3 （1.1X10-3） 134 times a year

3
Remote 10-6 10-4 （1.1X10-4） 14 times a yea
2
1 Improbable 10-7 10-5 （7.5X10-6） once or twice a year

0
-7 once or twice
Incredible 10-8 10-6 （7.5x10 ） every ten years

© 2015 JRAIA The Japan Refrigeration and Air Conditioning Industry Association. All Rights Reserved. 5
5. Definition of life stages

Table ５ Work content and sales of chiller in each life stage

Ratio of
Life Number Number of
Target Work content LS ratio
Stage sale
AC WC
Transpotation and storage in
Logistics Supplier warehouse Total 9,687 0.0517
Carrying in・Installation・Storage・
Installation Trial operation 7 3 9,687 0.0517

Usage During use and halt 7 3 134,000 0.7145

During pipe connection, pipe
disconnection, refrigerant discharge,
Operator leak detection
Repair Total 22,637 0.1207
During refrigerant recovery, refrigerant
charge, and inspection and repair

During disassembly, refrigerant

recovery
Overhaul After recovery container is stored, Total 1,838 0.0098
during assembly

During refrigerant recovery,after

Disposal Supplier recovery container is stored, Total 9,687 0.0517
disassembly, carrying out

© 2015 JRAIA The Japan Refrigeration and Air Conditioning Industry Association. All Rights Reserved. 6
 6. FTA and calculation method of probability (1)
 Basic FTA was configured to align the probability of refrigerant leakage and probability of
existence of ignition sources in 6 Life Stages (LS)（Figure.5）.
Probability of ignition during life stages

Evaluated for each life Probability of ignition at Probability of ignition

stage. The probability ・・・ at the time of disposal
of accidents is the time of distribution
derived from the total

Probability of ignition (#3) Probability of

the presence
of life stages

Presence of an Presence of
Important as
iginiton source(#1) flammable space Probability of measures
occurrence

Calculated by
Probability of existence of
ignition sources Probability of Lack of No-operation of the detector
× refrigerant leak (#2) ventilation and the shut-off device
Probability of leakge

Figure. 6 Basic FTA at each life stage

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 7. FTA and calculation method of probability (2)
 In order to detect all the probable ignition sources, FTA common to all life stages was configured for
calculating the probability of the existence of ignition sources and prbability of leakage.
Probability of the existence of an ignition source （common to each life stage）

Smoking Other than smoking

workers Chiller Field equipment Other construction

Other than pump

compressor Welder
workers

Control
Butt throw-in panel
boiler Direct flame

・ power ・
・ Start-up
equipment ・
・ panel ・

Internal equipment
wiring wiring

electrical Electrical
component component
・ ・
・ ・
・ ・

Figure 7 Common FTA for probability of the existence of igniton sources

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 8. Frequency of refrigerant leakage accidents
We estimated the record with the actual accident data RA members submitted
①The total shipment volume of water-cooled (W/C) chillers, air-cooled (A/C) chillers, and turbo chillers are
derived from the annual shipment volume of chiller SWG companies.
②Annual proportional rates against the summarized data of this study were derived from annual shipment
volume provided by JRAIA.
③Total numbers of leakage cases were determined by adding each company’s number of WC, AC, and
turbo chiller leakage cases .
④Total number of leakage cases was estimated by the proportional rate of each chiller SWG company.
⑤Frequency of leakage was determined by deviding estimated total number by the volume of METI stock
units （130 K units）. （The ratio of WC/AC chillers was assumed to be 3：7.）

Table 8 Frequency of leakage occurrence for each leakage rate from fiscal 2004 to 2011.

Frequency of leakage （cases/units・year）

2004-
2011
W/C chiller A/C HP Centrifugal Total

burst leak 5.83×10-6 1.35×10-5 0 1.07×10-5

rapid leak 1.07×10-4 1.87×10-4 0 1.56×10-4
slow leak 1.64×10-3 2.21×10-3 7.09×10-3 2.27×10-3

© 2015 JRAIA The Japan Refrigeration and Air Conditioning Industry Association. All Rights Reserved. 9
 9. Machine room model （Image）
 Overview of the chiller machine room
(1) Probable Ignition sources are a boiler with a burner (only the surface temperature should be considered) , a hot and
chilled water generator, starter panels, power panels, and electrical components （breakers and solenoid switches) in the
operation panels of chillers and pumps
(2) Building Standard Act indicates the values of （oxygen consumption, heat removal, oxygen concentration）corresponding
to ventilation and actual circumstances.
(3)Exhaust from the burning appliances such as the boiler and the absorption chiller by direct boiling is discharged outside through
independent duct.
(4)Exhaust air is not discharged to other rooms and does not affect outdoor air exhaust and air intake into other buildings.
(5)Ventilation is 2 air-changes /h ×2 lines , totaling 4 air-changes /h（ISO5149）

Surface Absorption chiller Ventilation

temperature by direct boiling for burner
(Equipment・
Exhaust air) ※Any open flame is strictly
prohibited
Ventilation Heaters, gas cooking
Burner
Burning (Intake air） appliances, smoking, lighters
appliances Auxiliary  ※Limitation of fire ignition
Large Operation panel machine tools during construction
capacity Starter  (Pump)
panel 1 Welders, burners, cutting tools
Electrical P
equipment
Chiller No1
Starter  P
panel 2 Operation panel
Small capacity
P
Air vent Electrical
equipment Large
（Exhaust） Chiller No2 P Auxiliary  capacity
power  Electrical
panel equipment

Figure.9 Machine room image

© 2015 JRAIA The Japan Refrigeration and Air Conditioning Industry Association. All Rights Reserved. 10
 10. Ignition sources（igniton assessment）
Table 10 Ignition sources in the machine room
Category Ignition soruce Ignition Remarks Usage
Sparks Electrical Home appliance and a small-sized No 5kVA or below No
parts electrical product
Electrical part inside equipment Yes Solenoid switch with 5ｋVA or above 1.61x01-3
AC power source No Equivalent to quenching distance No
Lightening switch No Equivalent to quenching distance No
Work tools Metal sparks（fork of a forklift） Yes － No
Electrical power tool No Small capacity No
Refrigerant recovery apparatus No Small capacity No

Smoking Match No No
supplies Oil lighter No No
Human Static electricity emitted from a No Minimum ignition energy or less No
body human body
Open Smoking Match Yes Ignition=open fire 4.72x10-9
flame supplies
Oil lighter Yes Open fire once ignited 1.18x10-6
Electric lighter No Lighter not ignited
Burning Electric radiant heater Yes Prohibited to use 3.30x10-6
appliance
Electric fan heater No Prohibited to use No
Gas water heater Yes Prohibited to use No
Gas boiler（burner ） No No timing of ignition No
Ventilation duct, boiler surface No 140℃ or below No
Gas cooking appliance Yes Prohibited to use No
Work tool Burner for brazing No High in gas velocity No

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 11. Machine room model（installation layout）
 A room with the height of 5m and the floor area with the horizontal and longitudinal length ratio of 1:2 was assumed, in
which a chiller was installed on one half of the floor area and auxiliaries were installed on the other half.
 As the maintenance space, the clearance of at least 1.2m in front of the control panel and 1.0m from other surface was
assumed.
 The leakage point was assumed to be located at the height of 0.15m from the floor and the shape of the leakage point was
cylindrical nozzle of 0.10m length.
Suction port Exhaust port
1.245 m 1.245 m
0.88 m
The target 1.01 m
machine
0.88 m 5.0 m （Side of Control panel）

0.88 m 1.28 m
3.3 m
The target 1.01 m
machine 1.21 m
1.28 m

6.6 m
3.3m

6.6 m  Standard specifications for risk assessment

Exhaust port
The specification for the volume zone of each
Leakage point
manufacture was considered as the standard
specifications.
0.1 m Water-cooled chiller
cooling capacity ：Approx. 180kW
0.15 m
Refrigerant charge amount ：23.4kg
（floor surface）
Chiller dimension ：1.28W×1.28D×1.28H [m]
Figure 11 Machine room layout

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12. CFD Analysis result of machine room
Table 12 Unsteady state analysis result(machine room）

Air changes [1/h] 0 2 4

Machine room Leakage rate
Refrigerant Case of leak Time dependent volume [m3min]
volume [m3] [kg/h]
Burst leak 75 0.011 0.008 0.006
R32
Rapid leak 10 2481 0.0004 0.0007
109
R1234ze Burst leak 54 0.027 0.017 0.015
(E) Rapid leak 7.3 3129 0.001 0.0009

Figure 12.1 Analysis result of concentration and time dependent volume Figure 12.2 Analysis result of concentration and time dependent volume

（R1234ze(E)wet, air change:0 times, rapid leak） （ R1234ze(E)wet, air changes:4 times, rapid leak)
© 2015 JRAIA The Japan Refrigeration and Air Conditioning Industry Association. All Rights Reserved. 13
 13. Air-cooled Heat Pump Model for CFD
12．空冷HPモデルの特定
 An air-cooled HP installed outdoors and lacking walls on all four sides has low chance of forming a flammable space compared to water-
cooled chiller installed in the machine room. Based on the soundproofing installation procedure described by the manufacturer, the analysis
model including four walls, two plain walls and two with an aperture of 25%, where flammable space is most possibly formed, are assumed.
 The following two refrigerant leakage points were assumed. （Figure.13.2）
Leakage point ①Leakage from the air heat exchanger of the outdoor unit
・In the center of the front surface of the unit and at the height of 0.15m from the heat exchanger on the floor.
・Slow leak：I.D of 1mm Rapid leak：I. D. of 4mm Burst leak：I.D. Of 8mm（The diameter of the nozzle shall be the length at which the
refrigerant leaks at the velocity of sound）・Leakage direction：horizontal
Leakage point ②Leakage from the unit inside the bottom panel of the outdoor unit
・The apertures of 2m×10mm in the middle of the both side bottom panels with the longitudinal length of 3m were assumed.
・The bottom panel other than those regions were assumed hermetic. ・Leakage direction：horizontal

Leakage from the air heat

exchanger of outdoor unit

Leakage from the unit inside the

decorative panel of outdoor unit

Figure 13.1 Air-cooled HP analysis model （wall aperture） Figure13.2 Air-cooled HP analysis model（leakage point）

© 2015 JRAIA The Japan Refrigeration and Air Conditioning Industry Association. All Rights Reserved. 14
14. CFD Analysis result of Air cooled HP
 In case of leakage from air heat exchanger, the flammable space is very small and negligible.
 Meanwhile, in case of leakage from the aperture of the bottom panel , the refrigerant accumulates in
the lower region of the unit forming flammable space.
Table 14 Unsteady state analysis result（Wind velocity 0m/s）
Unit horse Leakage velocity Time dependent
Leakage point Refrigerant Case of leak
power [Hp] [kg/h] volume [m3min]
Air heat R32 Rapid leak 10 0.0002
exchanger R1234ze(E) Rapid leak 7.3 0.0003

Rapid leak 10 3.732

30 R32
Unit decorative Burst leak 75 4.242
panel lower part
Rapid leak 7.3 3.989
R1234ze(E)
Burst leak 54 5.685

（a）rapid leak （b）burst leak

Figure 14 Concentration isosurface in case of leakage from the bottom aperture of the decorative panel （R32, wind velocity:0m/s）

© 2015 JRAIA The Japan Refrigeration and Air Conditioning Industry Association. All Rights Reserved. 15
 15. Probability of accidental fire

 Integrated value of the probability of ignition is calculated both for with and without ventilation.
 With ventilation, the highest probability of ignition is 10-12 . Therefore, it was evaluated as
”Incredible”.
Risk assessment result Probability of ignition（times/year・units）

Life stage Without ventilation※ With ventilation Probability

Ignition during of
4.28×10-6 － 1.51×10-13 －
logistics occurrence
Ignition during
installation and 4.67×10-6 2.40×10-12
commissioning 1.32 3.90
Ignition during usage 6.19×10-5 4.97×10-13
Ignition during repair 6.52×10-5
×10-4 1.00×10-12
×10-12
Ignition during
1.72×10-5 － 9.23×10-12 －
disposal
※On the assumption that the probability of flammable space is 1. （Ignition occurrs when there is an ignition source. ）

Guideline basic policy

・Since mechanical ventilation essentially guarantees safety, it is important to establish
mechanical ventilation standards and mechanical ventilation installation check procedures.

© 2015 JRAIA The Japan Refrigeration and Air Conditioning Industry Association. All Rights Reserved. 16
 16. Measures and guidelne
1. Installation of mechanical ventialtion
:2 air-changes/h×2 lines
with backup to guarantee ventilation effectiveness .
Air intake from the above and exhaust from the
bottom.
Controllable from outside the machine room
2. Installation of refrigerant leakage detection and
warning device
Operation with independent power source
such as UPS, installed in the place where
refrigerant could accumulate.

3. Chiller start interlock

Chiller will not start when mechanical ventilation fails or stops.

4. Inspection
Compulsory inspections of mechanical ventilation and refrigerant leakage detector at
appropriate frequency.

5. Strict prohibition of open flame

Strict prohibition of smoking, open flame （cooking appliance and heaters）, hot water generator.

© 2015 JRAIA The Japan Refrigeration and Air Conditioning Industry Association. All Rights Reserved. 17
 17. Conclusion

The results of Risk assessment for chillers,

・the probability of accidental fire and burn using the flammable

refrigerant is 3.9 x 10-12 with appropriate measures.
It is smaller than once every hundred years.

・2-Independent mechanical ventilation lines will be required

on the GL as most important countermeasure to prevent
accident in the machine room

・We are going to develop JRA-GL and general overview of RA

in 2015fy.

© 2015 JRAIA The Japan Refrigeration and Air Conditioning Industry Association. All Rights Reserved. 18
 Thank you for your attention.

© 2015 JRAIA The Japan Refrigeration and Air Conditioning Industry Association. All Rights Reserved. 19