Risk Assessment for Chillers
Working Group for Risk Assessment Lower Flammability refrigerant

Conclusion

Introduction• With ventilation, the lower flammable refrigerants can be safety used for chillers[Subject system] water-cooled chillers and air-cooled heat pumps[Refrigerants (A2L)] R32, R1234yf, R1234ze(E)[Risk assessment procedure]
1. Setup of an object product2. Analysis of risks
3. Calculation of accident probability
4. Planning of safety measures
5. Establishment of the guideline

Installation

Table 2 Specification of a typical modelType of chillers
Water-cooledAir-cooled
Cooling capacity [kW]170 kW
90 kW
Refrigerant charge [kg]23.4 kg
11.7 kg *Outer dimensions [m]1.28 X 1.28 X 1.28 1.00 X 3.00 X 2.30
Installation location
Machinery room
Outdoors*single refrigeration circuit

Wall B： back side

(numerical壁B：背面
aperture 0%)

Suction port

(numerical aperture 25%)

Wall壁Ｄ：左側面
D： left side

1.245 m0.88 m1.245 mWall
A： right side
壁Ａ：右側面(numerical aperture 0%)
Wall
C： front side
壁Ｃ：正面

(numerical aperture 25%)0.88 m

5.0 m

The targetmachine

2,300

System[1/(unit year)]
Table 1 Probability of accidental fireWith ventilation
Without ventilation
3.89 X 10-12
1.32 X 10-4

900

3.3m

(3,000)
4,800

6.6 m
Exhaust port090)
00
0,0(180,0290

900

Leakage point

Air空気熱交換器面
heat exchanger

0.1 m

Exhaust port

0.15 mLeakage point①

The target 1.01 m
machine（floor surface）（Side of Control panel）

1.28 m

0.88 m

Bottom panel
下部パネル面
3.3 m

1.01 m1.21 m10mm

1.28 mLeakage point②2m

6.6 m

Water-cooled chillers

Water-cooled chiller model(machinery room)

Air-cooled heat pumps

Air-cooled heat pump model(outdoor)

Occurrence of refrigerant leakage

Flammable region

Table 3 Probability of the occurrence of refrigerant leakage[case/(unit year)]
Water-cooled
Air-cooled
Centrifugal
2004-2011FY
Chillerheat pumpchiller
Burst leakage
5.83 X 10-6
1.35 X 10-50
Rapid leakage
1.07 X 10-4
1.87 X 10-4
0Slow leakage
1.64 X 10-3
2.21 X 10-3
7.09 X 10-3

The probability of existence of a flammable space=the time-dependent volume of the flammable space [m3 min]/(target space [m3] X 8760 [h] X 60 [min])Ignition source[Spark]• Electrical part inside equipment(solenoid switch with 5kVA or above)• Metal spark (by forklift)[Open flame]• Match, Oil lighter (open fire once ignited)• Burning appliance-Electric radiant heater-Gas water heater-Gas cooking appliance

Introductio
nTable 4 Probability of existence of a flammable space[1/year]Life Stage (LS)Burst leakage
Rapid leakage
Slow leakage
Logistics
2.64 X 10-10
5.46 X 10-70
Installation [carry-in]
7.84 X 10-8
8.26 X 10-60
Installation [trial]
7.84 X 10-82.33 X 10-70
Usage [machinery room]
2.64 X 10-10
5.46 X 10-70
Usage [outdoor]
1.12 X 10-7
9.84 X 10-80
Repair / Service
7.84 X 10-8
2.33 X 10-70Overhaul
7.84 X 10-8
2.33 X 10-70
Disposal
7.84 X 10-8
8.26 X 10-60

Probability of accidental fire
TargetLS

Supplier Logistics

UserConclusio
nInstallation [carry-in]
Installation [trial]
Usage [machinery room]
Usage [outdoor]
Repair / Service
Overhaul

Supplier Disposal

Table 5 Probability of accidental fireWithout ventilation
LS ratio
Probability
Probability
under user
0.05174.28 X 10-6
0.0517(0.0023)0.21440.50020.12070.00980.0517

4.66 X 10-6
6.19 X 10-5

2.39 X 10-12
1.32 X 10-4

6.51 X 10-5
1.72 X 10-5

[1/(unit year)]With ventilation
Probability
Probability
under user
1.51 X 10-13-

4.97 X 10-13

3.89 X 10-12

1.00 X 10-12-

9.22 X 10-12-

Technical requirements for safety
1. Ventilation:-Mechanical ventilation is always indispensable-In this risk assessment, it has proved that 4 times/h ventilation is required for the standard machinery room
-In JRA GL-15, the ventilation frequency, n=380/V ,is adopted in accord with RA for other products in the machinery rooms
2. Refrigerant detector and refrigerant leakage alarm(n: ventilation frequency [times/h], V: machinery room volume[m3])3. Open flame prohibition

Documentation
1. Guideline of design construction for ensuring safety against refrigerant leakage from chiller using lower flammability (A2L) refrigerants JRA GL-15：2016