for Injection Molding

May 19, 2022

The Right Type
Most refrigeration is designed for static loads, like in a meat cooler.
In plastics processing, heat is added to and removed from the mold
during every cycle. Select a chiller designed for active heat loads.

Water Flow through the Mold
At a flow of 10 gpm, chilled water must rise 12°F through the mold to
remove 1,000 BTU/minute. At a flow of 3 gpm, the temperature must
rise 40°F to remove 1,000 BTU.
If low flow is due to the mold’s design, the only solution is having
the mold reworked. But if normally occurring water deposits are
clogging the lines, water line cleaner, IMS Lime Buster III, can greatly
boost mold flow and increase heat transfer.

Computing Size for IMS Chillers (2 Methods)
Method 1 (Based on coolant temperature and flow rate)
To determine chiller tonnage required, you must calculate the
delta T between the inlet and outlet water temperatures and the
rate of flow in gallons per minute. Measuring the delta T requires a
thermocouple or thermometer. To perform a load test: 1.) Strap a
thermocouple to the inlet water line of the processing equipment and
wrap it with tape to hold it in place. 2.) Strap a thermocouple on the
outlet water line of the processing equipment to record the amount of
heat the water is picking up in your equipment.
To measure flow rate of the water place a flow meter on the outlet
water line of your equipment. If a flow meter is not available, simply
disconnect the outlet line and let the water pour into a five gallon
bucket while you time it with a watch. This provides you with the
“GPM” (gallons per minute) rate of discharge.
Now you have the necessary information to size a unit properly. Use
the following formula to calculate your equipment’s BTU’s of required
cooling.

BTU = Constant (weight of water) x GPM x Temperature Differential
Multiply the fluid flow (GPM) by 500. Multiply the result by the
temperature differential or rise (return water temperature minus the
input or supply water temperature). Divide the result by 12,000 and
you now have your required rating.

Example: 500 Constant (weight of water)
x 10 GPM (gallons per minute)
5000
x 12° Temperature Differential (or rise)
60,000 Required BTU’s per hour
12,000 EACH 12,000 BTU’s requires 1 Ton of Cooling
= 5 Ton (This equipment would require a 5 Tons capacity)

Method 2 (Based on material use and melt temperature)
You can also calculate the proper tonnage using the following formula:
Tonnage = A × (B – C)
Removal Capacity
where: A = Material use in lbs./hr.
Use actual lbs./hr., not machine’s capacity rating
B = Temperature of melt
C = Temperature of part when it comes out of mold

Removal = 12,000 BTU/hr./ton removal capacity of chiller system set
Capacity at 50°F, which includes estimated radiation losses, etc.
At 40°F, use 8,000. At 30°F, use 6,100. At 20°F, use 5,800.

Example: 100 lbs./hr.
450° F melt temperature
150° F part temperature when mold opens

Tonnage = 100 x (450 – 150)
12,000

= 100 x 300
12,000

30,000
12,000
= 2.5
Use the next size up, in this case a three ton chiller, to avoid problems
caused by using an undersized chiller.

Blow Molding
40#/Hr HDPE = 1 Ton 45#/Hr LDPE = 1 Ton
40#/Hr PET = 1 Ton 45#/Hr PP = 1 Ton
Minimum process flow = 4.8 GPM/ton @ 65 PSI

Extrusion
Coating
40#/Hr LDPE = 1 Ton
Process flow required = 12 GPM/ton for direct roll cooling

Pipe & Profile
80 #/Hr ABS = 1 ton 90#/Hr PVC = 1 Ton

Sheet
40#/Hr UHMWPE = 1 Ton 55#/Hr PP = 1 Ton
80#/Hr PVC = 1 Ton
50#/Hr HDPE = 1 Ton 75#/Hr PS = 1 Ton
55#/Hr LDPE = 1 Ton 75#/Hr ABS = 1 Ton
Process flow = 8 GPM/ton for direct roll cooling

Equipment Cooling
Gearbox cooling = 0.5 Ton/Inch of extruder barrel
Screw cooling = 0.5 Ton/Inch of extruder barrel
Feed throat cooling = 0.33 Ton/ Inch of extruder barrel
Barrel cooling = 1 Ton/Inch of extruder barrel
Eddy current clutch (light load) = 0.2 Ton/HP
Eddy current clutch (normal operation) = 0.05 Ton/HP

Injection Molding
Mold Cooling
30#/Hr HDPE = 1 Ton 40#/Hr Nylon = 1 Ton
65#/Hr PVC = 1 Ton
35#/Hr LDPE = 1 Ton 50#/Hr PS = 1 Ton
40#/Hr PET = 1 Ton
35#/Hr PP = 1 Ton 50#/Hr ABS = 1 ton
Hot runner molds = 1 Ton/10.5 KW hot runner

Machine Cooling
10 HP Hydraulic Motor HP = 1 Ton
Feed throat cooling = 1 Ton (machines under 400 ton use 1/2 ton)

Thermoforming
180#/Hr PE = 1 Ton 250#/Hr HIPS = 1 Ton
240#/Hr PVC = 1 Ton Rail Cooling = 3 Tons
Minimum process flow of 4.8 GPM/Ton

Other
Mold room heating = 25 BTU/FT2 Vacuum pump = 0.1 Ton/HP
Non-mold room heating = 50 BTU/FT2 Water pump = 0.2 Ton/HP
Mold room cooling = 80 BTU/FT2
Air compressor without after cooler = 0.15 Ton/HP
Air compressor with after cooler = 0.20 Ton/HP

Flow Rates vs Temp Difference Per Ton
1.2 GPM = 20°F ΔT 4.8 GPM = 5°F ΔT
2.4 GPM = 10°F ΔT 9.6 GPM = 2.5°F ΔT

Pipe Sizing Guide for Schedule 40 Steel Pipe
(10’HD/100’ Run,10’/Sec Velocity Max)
½” = 3 GPM 1¼” = 25 GPM 2½” = 120 GPM 6″ = 900 GPM
¾” = 6 GPM 1½” = 40 GPM 3″ = 200 GPM 8″ = 1500 GPM
1″ = 12 GPM 2″ = 75 GPM 4″ = 400 GPM 10″ = 2400 GPM

Commonly Used Equivalents & Formulae
1 HP = 2547.16 Btu/Hr 1 Cu Ft = 7.48 gallons (water)
1 Gallon = 8.33 lbs (water) 1 KW = 3414.4 Btu/Hr
1 KW = 1.341 HP Q = 4.5xCFMxDH = Btu (air cooling)

PSI = ft of head
2.31
Pump HP = GPM x P(feet of head)
3960x(0.65 to 0.75) (Pump Eff)

KW = Amps x Volts x 0.85 x 1.73
1,000

Tower water make-up requirements: untreated 2% of flow rate, treated
1.5% of flow rate.

Water cooled requires 3 GPM/Min/Ton

Lose 1.5% capacity per degree lower than rating

For assistance with sizing, contact the IMS Equipment Team at
sales@imscompany.com