Chromalox Big Red Book

Technical

Technical Information Heater Selection - Oil Heating

Oil Heating Watt Density Guide

Watt Density & Oil Viscosity The viscosity of oils and hydrocarbons varies widely with type and temperature. Since highly viscous liquids transfer heat poorly, sheath watt densities and operating temperatures are critical in oil heating applications. As a general rule, regular oil heaters rated 20-23 W/in 2 are recommended for heating light weight oils (SAE 10 to SAE 30). For medium weight oils (gear oils, etc.), 12-15 W/in 2 are suggested. Bunker C, tar, asphalt and other highly viscous oils may require 6-8 W/in 2 or less to prevent carbonization, particularly if not under flowing conditions. Some oils may have additives that will boil off or carbonize at very low watt densities. When oils of this type are encoun- tered, a watt density test is recommended to determine a satisfactory watt density. The fol- lowing charts provide guidance and suggested watt densities for various oils. Viscosity SAE 10 90-120 SSU at 130°F SAE 20 120-185 SSU at 130°F SAE 30 185-255 SSU at 130°F SAE 40 255 SSU-up (Drops to 80 at 210°F) SAE 50 80-105 SSU at 210°F #2 Fuel Oil 40 SSU at 100°F (Kerosene) #4 Fuel Oil 45-120 SSU at 100°F #5 Fuel Oil 150-400 SSU at 100°F Bunker C 500-2,000 SSU at 100°F #6 Fuel Oil 3,000 SSU at 122°F (Very Viscous) Typical Viscosities of Various Oils Weight

Viscosity Equivalents

Heavy

Heavy 1500

10000 9000 8000

ASTM

SAE No. Gear Oil

235 265 300

7000

AGMA No. Lubricant

1000

250

7000

4650

8A

185 205

6000

680

3150

8

Medium

5000

95 105 115 125 145 165

460

7

2150

SAE No. Engine Oil

140

4000

320

6

Viscosity at 100°F (SSU)

3000

1500

Viscosity at 210°F (SSU)

50

90

2000

5

220

1000

6.5 W/In 2

42 44 46 48 50 55 60 65 70 75 85

1000 900 800

4

40

150

Light

700

15 W/In 2

3

600 500 700 400

30

100

465

80

68

2

315

20

23 W/In 2

46

215

1

300

75

32

10W

200

150

22

100

105 40

5W

Viscosity Can be Related Horizontally Only. Viscosities Base on 95 VI Single Grade Oils.

Graph G-122S — Surface Temperatures of Oil Immersion Blade Heater for Various Oil Temperatures & Watt Densities

Notes — 1. Curves based on

Viscosity Conversion

25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10

Maximum Safe Watt Density

natural convection of machine oil or its equivalent having an SAE viscosity rating of 30 (5 centipoises at 200°F).

Seconds Saybolt Universal (SSU)

Kinematic Viscosity Centistokes (Cst)

Seconds Saybolt

Furol (SSF)

31 35 40 50 60 70 80 90

1 2.56 4.30 7.4

— — — — —

2. Effective Length of Immersion Heater = “B” Dimension. 3. Area Per Linear Inch of 1-1/2' Wide Immersion Blades = 3.75 Sq. In. 4. Area Per Linear Inch of 1' Wide Immersion Blades = 2.63 Sq. In. 5. In No Case, Exceed 27 Watts Per Sq. In.

10.3 13.1 15.7 18.2 20.6 32.1 43.2 54

1 4 0 ° F — O i l T e m p .

12.95 13.7 14.44 15.24 19.3

9 8 7 6 5 4 3 2 1 0 W/In 2 of Effective Length 100

2 0 0 ° F — O i l T e m p .

3 0 0 ° F — O i l T e m p .

100 150

4 0 0 ° F — O i l T e m p .

5 0 0 ° F — O i l T e m p .

200 250 500 1,000 5,000 10,000 20,000

23.5 28 51.6 100.7

110 220

1,100 2,200 4,400 500 1,000 2,000 Centistokes = Centipoise/specific gravity Centipoise x 2.42 = Lbs/ft/hr

200

300

400

500

600

TECHNICAL

Sheath Surface Temperature (°F)

INFORMATION

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