2.4

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

1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.
2011Fy2012Fy2013Fy▼P report※

Task extraction

Risk assessment※P reort : Progress report・・・
The report disclosed in the risk
assessment working group of theJapan Refrigeration and Air
Conditioning Industry Association

2014Fy▼P report※

2015Fy▼P report※

Ｆ report※▼

Risk assessment review◆SWG calculation ◆University calculation

GL draftGL deliberation
and review

JRA-GL◆
Kobe symposium◆

Kobe symposium◆© 2015 JRAIA The Japan Refrigeration and Air Conditioning Industry Association. All Rights Reserved.

Final report◆

24．リスクアセスメントの構成概要（１）2. Risk assessment and legal system
Industrial Safety
and Health Law【Order for Enforcement 】
A workplace employing a certain number of workers shallappoint a Generaｌ Safety and Health Manager.
【Enforcement Regulations】
The General Safety and Health Manager shall perform risk
assessments.

The BuildingStandards Act
High Pressure Gas
Safety Act
Refrigeration Safety Regulations
Article 7.14 Electrical Equipment refers to
explosion preventive performance ・・

KHK0302-3(2012)
Standards of Refrigeration and Air-Conditioning
Equipment Facilities〔Fasilities with Flammable Gases（including mildly-flammable Gases）〕

JRA
-GL15
Guideline ofdesignconstruction for
ensuring safety
against refrigerantleakage form
chillers using
mildly-flammable
refrigerants

EN1127-1(2011)
Explosive atmospheres –Explosion prevention and protection

IEC60079s(2011)
Explosive atmospheres – Equipment;General requirement
JIS60079s
Electric Machinery and Instruments Used in Explosive Atmospheres
General Requirements is the 2007 version of IEC.

＞Outdoor natural ventilation＝Zone2＞forced ventilation with preliminary and warning devices.
＋normally, explosive atmospheres are not formed.
＝Zone2NE(not dangerous）

ISO5149
Refrigeration system and heat pumps – safety
and environmental requirements© 2015 JRAIA The Japan Refrigeration and Air Conditioning Industry Association. All Rights Reserved.

3

3．Target products
Water-cooled chillers

Air-cooled heat pumps

Modular Chillers
Screw chillers
Centrifugal

Modular Chillers
Screw chillers

Type

7.5kW - 17,500kW

Cooling capacity

machine room

Installation location

outdoorStandard specifications for risk assessments

Approx. 180kW

Approx. 90kW

23.4kg11.7kg（per 1 system ）1.28W×1.28D×1.28H [m]1.00W×3.00D×2.30H [m]Cooling capacity
Refrigerant charge amount
Dimensions

Air-cooled heat pumps

Water-cooled chillers

Mayekawa

Kobe Steel

Mitsubishi
Heavy
Industries

Ebara
Refrigeration
Equipment
And Systems

Mitsubishi Electric

Toshiba-Carrier© 2015 JRAIA The Japan Refrigeration and Air Conditioning Industry Association. All Rights Reserved.

Hitachi Appliacnes
44. Acceptable probability of harm
Table.4 Probability of occurrence of hazards per a chiller a year

Probability of occurrence of harmIndustrial-level product adoption

consumer industrial level productgoods(cases /units per year)

5

4

Number of accidents

Frequent

10-3

10-1

（1.0X10-1）

once a year per 10 units

Probable

10-4

10-2

（1.0X10-2）

once a year per 100 units

Probable

10-5

10-3

（1.1X10-3）

134 times a year

Remote10-6

10-4（1.1X10-4）

14 times a yea

10-7

10-5

（7.5X10-6）

once or twice a year

10-8

10-6

-7

once or twice
every ten years

3
2
1 Improbable
0

Incredible（7.5x10 ）© 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
Life
Stage

Logistics

TargetWork content

Ratio of
NumberAC
Transpotation and storage in

Supplier warehouse

WC

Number ofsale

LS ratio

9,687

0.0517

Total

Installation

Carrying in・Installation・Storage・
Trial operation

7

3

9,687

0.0517

Usage

During use and halt

73

134,000

0.7145

Total

22,6370.1207

OverhaulDuring disassembly, refrigerant
recoveryAfter recovery container is stored,
during assembly

Total

1,838

0.0098

DisposalDuring refrigerant recovery,after
Supplier recovery container is stored,disassembly, carrying out

Total

9,687

0.0517

RepairDuring pipe connection, pipe
disconnection, refrigerant discharge,
Operator leak detection
During refrigerant recovery, refrigerant
charge, and inspection and repair© 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 ofexistence of ignition sources in 6 Life Stages (LS)（Figure.5）.
Probability of ignition during life stages

Evaluated for each life
stage. The probabilityof accidents isderived from the total

Probability of ignition at・・・

the time of distribution

Probability of ignition (#3)

Presence of aniginiton source(#1)

Probability of ignitionat the time of disposal

Probability ofthe presenceof life stages

Presence offlammable space

Probability ofoccurrence

Important asmeasuresCalculated by
Probability of existence ofignition sources
×
Probability of leakge

Probability ofrefrigerant leak (#2)

Lack ofventilation

No-operation of the detector
and the shut-off device

Figure. 6 Basic FTA at each life stage© 2015 JRAIA The Japan Refrigeration and Air Conditioning Industry Association. All Rights Reserved.

7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）

Other than smoking

Smoking

workers

Chiller

Field equipment

Other construction

Other thanworkers

compressor

pump

Welder

Butt throw-in

Controlpanel

boilerDirect flame・・・Start-up
panel

power
equipment・・・Internal
wiringequipment
wiringelectricalcomponent

Electricalcomponent

・
・
・

・
・
・

Figure 7 Common FTA for probability of the existence of igniton sources© 2015 JRAIA The Japan Refrigeration and Air Conditioning Industry Association. All Rights Reserved.

88. Frequency of refrigerant leakage accidents
We estimated the record with the actual accident data RA members submitted①The total shipment volume of water-cooled (W/C) chillers, air-cooled (A/C) chillers, and turbo chillers arederived 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, andturbo 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.
20042011

Frequency of leakage （cases/units・year）
W/C chiller

A/C HP

Centrifugal

Totalburst leak

5.83×10-6

1.35×10-50

1.07×10-5

rapid leak

1.07×10-4

1.87×10-40

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 andchilled water generator, starter panels, power panels, and electrical components （breakers and solenoid switches) in theoperation 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 throughindependent 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）
Surfacetemperature

Ventilation
for burner

Absorption chiller
by direct boiling(Equipment・
Exhaust air)※Any open flame is strictly
Ventilation(Intake air）

BurnerBurning
appliancesLargecapacity
Electricalequipment

Starterpanel 1

Operation panel

Auxiliary
machine(Pump)P
Chiller No1

Starterpanel 2

P

Operation panel

Small capacity
Air vent（Exhaust）

prohibited
Heaters, gas cooking
appliances, smoking, lighters※Limitation of fire ignition
tools during construction
Welders, burners, cutting tools

Chiller No2

Electricalequipment

P
P

Auxiliary
power
panel

Large
capacity
Electricalequipment

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
SparksIgnition soruce

IgnitionHome appliance and a small-sized
electrical productNo

5kVA or below

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 distanceNo

Metal sparks（fork of a forklift）

Yes

－

No

Electrical power tool

No

Small capacity

No

Refrigerant recovery apparatus

No

Small capacity

No

Smoking
supplies

Match

No

No

Oil lighter

No

No

Human
body

Static electricity emitted from ahuman bodyNo

Minimum ignition energy or lessSmoking
supplies

Match

Yes

Ignition=open fire

4.72x10-9

Oil lighter

Yes

Open fire once ignited

1.18x10-6

Electric lighter

No

Lighter not ignited

Electric radiant heater

Yes

Prohibited to use

3.30x10-6

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 belowNo

Gas cooking appliance

Yes

Prohibited to use

NoBurner for brazing

No

High in gas velocity

NoElectricalparts

Work tools

Open
flame

Burning
appliance

Work tool

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

Usage
No

No

11

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, inwhich 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 wasassumed.
 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 m0.88 m1.245 mThe target 1.01 m
machine0.88 m5.0 m

1.28 m

0.88 mThe target
machine（Side of Control panel）

3.3 m

1.01 m1.21 m3.3m

1.28 m6.6 m

 Standard specifications for risk assessment

6.6 m
Exhaust port
Leakage point

0.1 m

The specification for the volume zone of eachmanufacture was considered as the standard
specifications.
Water-cooled chiller
cooling capacity ：Approx. 180kW

0.15 m（floor surface）

Figure 11 Machine room layout

Refrigerant charge amount ：23.4kg
Chiller dimension ：1.28W×1.28D×1.28H [m]© 2015 JRAIA The Japan Refrigeration and Air Conditioning Industry Association. All Rights Reserved.

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

Air changes [1/h]Machine room
Refrigerant
volume [m3]4

Leakage rate[kg/h]

Burst leak

75

0.011

0.008

0.006

Rapid leak

10

2481

0.00040.0007

R1234ze Burst leak(E)
Rapid leak

54

0.027

0.017

0.015

7.3

3129 0.001 0.0009

Figure 12.1 Analysis result of concentration and time dependent volume

R1234ze(E)wet, air change:0 times, rapid leak）（

2

Case of leak

R32

109

0

Time dependent volume [m3min]

Figure 12.2 Analysis result of concentration and time dependent volume（

R1234ze(E)wet, air changes:4 times, rapid leak)© 2015 JRAIA The Japan Refrigeration and Air Conditioning Industry Association. All Rights Reserved.

13

12．空冷HPモデルの特定
13. Air-cooled Heat Pump Model for CFD
An air-cooled HP installed outdoors and lacking walls on all four sides has low chance of forming a flammable space compared to watercooled 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 therefrigerant 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 heatexchanger of outdoor unit

Leakage from the unit inside thedecorative 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
power [Hp]30

Leakage velocity

Time dependent[kg/h]

volume [m3min]

Rapid leak10

0.0002

Rapid leak

7.3

0.0003

Rapid leak

10

3.732

Burst leak

75

4.242

Rapid leak

7.3

3.989

Burst leak

54

5.685

Leakage point

Refrigerant

Case of leak

Air heatR32

exchanger

R1234ze(E)Unit decorative

R32

panel lower part
R1234ze(E)（a）rapid leak（b）burst leakFigure 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
Life stage

Probability of ignition（times/year・units）

Without ventilation※

Ignition during
logistics

4.28×10-6

Ignition during
installation andcommissioning

4.67×10-6

Ignition during usage

6.19×10-5

Ignition during repair

6.52×10-5

Ignition during
disposal

1.72×10-5

With ventilation

Probabilityofoccurrence－

1.51×10-13

－

1.32
×10-4

2.40×10-12

3.90
×10-12－

9.23×10-12

4.97×10-13
1.00×10-12－※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 thebottom.
Controllable from outside the machine room
2. Installation of refrigerant leakage detection andwarning device
Operation with independent power sourcesuch 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 atappropriate 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 requiredon 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