Technical library

1. OHM'S LAW
2. General Conversion Chart:
FLOW
  • 1 cc/min = .001 Liters/min
  • 1 cc/min = .000264 Gallons/min
  • 1 Liter/min = 1000 cc/min (ml/min)
  • 1 Liter/min = .264 Gallons/min
  • 1 Gallon/min = 3.785 Liters/min
  • 1 Gallon/min = 3785.41178 cc/min (ml/min)
Conversion factors

To Convert To...

Multiply...

By...

Atmospheres
Atmospheres
Atmospheres
Atmospheres

(atm)
(atm)
(atm)
(atm)

Bar
Inches Mercury
Pounds/square inch
Torr

--
(in Hg)
(psi)
--

0.9869
0.03342
0.06805
0.001316

Bar
Bar

Atmospheres
Pounds/square inch

(atm)
(psi)

1.0133
0.06895

British Thermal Units
British Thermal Units
British Thermal Units
British Thermal Units/hour
British Thermal Units/hour
British Thermal Units---inches
hour-square foot---ºF
British Thermal Units/pound
British Thermal
Units/pound---ºF

(Btu)
(Btu)
(Btu)
(Btu/h)
(Btu/h)
(Btu---in)
(h-ft2---ºF)
(Btu/lb)
(Btu/lb---ºF)

Joules
Kilowatt-hours
Watt-hours
Kilocalories/hour
Watts
Watts/meter---ºC

Kilojoules/kilogram
Kilojoules/kilogram---ºC

(J)
(KWh)
(Wh)
(kcal/h)
(W)
(W/m---ºC)

(kJ/kg)
(kJ/kg---ºC)

0.000948
3412
3.412
3.969
3.412
6.933

0.4299
0.2388

Calories

(cal)

Joules

(J)

0.2388

Centimeters
Centimeters
Centimeters/second
Cubic centimeters
Cubic centimeters
Cubic centimeters

(cm)
(cm)
(cm/s)
(cm3 or cc)
(cm3 or cc)
(cm3 or cc)

Feet
Inches
Feet/minute
Cubic feet
Cubic inches
Milliliters

(ft)
(in)
(fpm)
(ft3)
(in3)
(ml)

30.48
2.54
0.508
28,320
16.39
1.0

Cubic feet
Cubic feet
Cubic feet
Cubic feet/minute
Cubic feet/minute
Cubic feet/minute

(ft3)
(ft3)
(ft3)
(cfm)
(cfm)
(cfm)

Cubic meters
Gallons, U.S.
Liters
Cubic meters/hour
Cubic meters/second
Liters/second

(m3)
(gal)
(l)
(m3/h)
(m3/s)
(l/s)

35.32
0.1337
0.03532
0.5885
2119
2.119

Cubic inches
Cubic meters

(in3)
(m3)

Cubic centimeters
Gallons, U.S.

(cm3 or cc)
(gal)

0.061
0.003785

Cubic meters
Cubic meters
Cubic meters/hour
Cubic meters/hour
Cubic meters/second

(m3)
(m3)
(m3/h)
(m3/h)
(m3/s)

Liters
Cubic feet
Cubic feet/minute
Gallons/minute
Cubic feet/minute

(l)
(ft3)
(cfm)
(gpm)
(cfm)

0.001
0.02832
1.699
0.2271
0.000472

Feet
Feet
Feet/minute
Feet/minute

(ft)
(ft)
(fpm)
(fpm)

Centimeters
Meters
Centimeters/second
Meters/second

(cm)
(m)
(cm/s)
(m/s)

0.03281
3.281
1.969
196.9



To Convert To...

Multiply...

By...

Gallons, Imperial
Gallons, U.S.
Gallons, U.S.
Gallons, U.S.
Gallons, U.S.
Gallons/minute
Gallons/minute

--
(gal)
(gal)
(gal)
(gal)
(gpm)
(gpm)

Gallons, U.S.
Cubic feet
Cubic meters
Gallons, Imperial
Liters
Cubic meters/hour
Liters/second

(gal)
(ft3)
(m3)
--
(l)
(m3/h)
(l/s)

0.8327
7.481
264.2
1.201
0.2642
4.403
15.85

Grams
Grams
Grams/cubic centimeter
Grams/cubic centimeter
Grams/cubic centimeter

(g)
(g)
(g/cm3)
(g/cm3)
(g/cm3)

Ounces
Pounds
Kilograms/cubic meter
Pounds/cubic foot
Pounds/cubic inch

(oz)
(lb)
(kg/m3)
(lb/ft3)
(lb/in3)

28.35
453.6
0.001
0.01602
27.68

Inches
Inches
Inches Mercury
Inches Mercury

(in)
(in)
(in Hg)
(in Hg)

Centimeters
Millimeters
Atmospheres
Torr

(cm)
(mm)
(atm)
--

0.3937
0.03937
29.92
25.4

Joules
Joules
Joules
Joules/second
Joules/second

(J)
(J)
(J)
(J/s)
(J/s)

British Thermal Units
Calories
Watt-hours
British Thermal Units/hour
Watts

(Btu)
(cal)
(Wh)
(Btu/h)
(W)

1055
4.187
3600
0.2931
1

Kilocalories/hour

(kcal/h)

Btu/hour

(Btu/h)

0.252

Kilograms
Kilograms/cubic meter
Kilograms/cubic meter
Kilograms/square centimeter

(kg)
(kg/m3)
(kg/m3)
(kg/cm2)

Pounds
Grams/cubic centimeter
Pounds/cubic foot
Pounds/square inch

(lb)
(g/cm3)
(lb/ft3)
(psi)

0.4536
1000
16.02
0.07031

Kilojoules
Kilojoules/kilogram
Kilojoules/kilogram---ºC

(kJ)
(kJ/kg)
(kJ/kg---ºC)

Watt-hours
British Thermal Units/pound
British Thermal Units/pound---ºF

(Wh)
(Btu/lb)
(Btu/lb---ºF)

3.6
2.326
4.187

Kilometers/hour

(km/h)

Miles/hour

(mph)

1.609

Kilopascals

(kPa)

Pounds/square inch

(psi)

6.895

Kilowatts
Kilowatts
Kilowatt-hours
Kilowatt-hours

(KW)
(KW)
(KWh)
(KWh)

British Thermal Units/hour
Watts
British Thermal Units
Watt-hours

(Btu/h)
(W)
(Btu)
(Wh)

0.0002931
0.001
0.0002931
0.001

Liters
Liters
Liters
Liters/second
Liters/second

(l)
(l)
(l)
(l/s)
(l/s)

Cubic Feet
Cubic Meters
Gallons, U.S.
Cubic feet/minute
Gallons/minute

(ft3)
(m3)
(gal)
(cfm)
(gpm)

28.32
1000
3.785
0.4719
0.06309



To Convert To...

Multiply...

By...

Meters
Meters/second

(m)
(m/s)

Feet
Feet/minute

(ft)
(fpm)

0.3048
0.00508

Miles/hour

(mph)

Kilometers/hour

(km/h)

0.6215

Millimeters

(mm)

Inches

(in)

25.4

Newtons/square meter

(N/m2)

Pounds/square inch

(psi)

6,895

Ounces

(oz)

Grams

(g)

0.035274

Pounds
Pounds

(lb)
(lb)

Grams
Kilograms

(g)
(kg)

0.002205
2.205

Pounds/cubic foot
Pounds/cubic foot

(lb/ft3)
(lb/ft3)

Grams/cubic centimeter Kilograms/cubic meter

(g/cm3)
(kg/m3)

62.43
0.06243

Pounds/cubic inch

(lb/in3)

Grams/cubic centimeter

(g/cm3)

0.03613

Pounds/square inch
Pounds/square inch
Pounds/square inch
Pounds/square inch

(psi)
(psi)
(psi)
(psi)

Bar
Kilograms/square centimeter
Kilopascals
Newtons/square meter

--
(kg/cm2)
(kPa)
(N/m2)

14.504
14.22
0.145
0.000145

Square centimeters
Square centimeters

(cm2)
(cm2)

Square feet
Square inches

(ft2)
(in2)

929
6.452

Square feet
Square feet

(ft2)
(ft2)

Square centimeters
Square meters

(cm2)
(m2)

0.001076
10.76

Square inches

(in2)

Square centimeters

(cm2)

0.155

Square meters

(m2)

Square feet

(ft2)

0.0929

Torr
Torr

Inches Mercury
Pounds/square inch

(in. Hg)
(psi)

0.03937
51.71

Watts
Watts
Watt-hours
Watt-hours
Watt-hours
Watts/meter---ºC
--
Watts/square centimeter
Watts/square inch

(W)
(W)
(Wh)
(Wh)
(Wh)
(W/m---ºC)
--
(W/cm2)
(W/in2)

British_Thermal_Units/hour
Joules/second
British_Thermal_Units
Joules
Kilojoules

Watts/square inch
Watts/square centimeter

(Btu/h)
(J/s)
(Btu)
(J)
(kJ)

(W/in2)
(W/cm2)

0.2931
1
0.2931
0.0002778
0.2778
0.1442
--
0.155
6.452

3. THERMOCOUPLE TYPES AND WIRE SPECIFICATIONS AND TOLERANCE:
THERMOCOUPLE TYPES

Thermocouple
Type

Useful/General
Application Range

Notes

B

1370-1700°C
(2500-3100°F)

Easily contaminated, require protection.

C*

1650-2315°C
(3000-4200°F)

No oxidation resistance. Vacuum, hydrogen or inert atmospheres.

E**

95-900°C
(200-1650°F)

Highest output of base metal thermocouples. Not subject to corrosion at cryogenic temperatures.

J

95-760°C
(200-1400°F)

Reducing atmosphere recommended. Iron leg subject to oxidation at elevated temperatures--use larger gauge to compensate.

K**

95-1260°C
(200-2300°F)

Well suited for oxidizing atmospheres.

N

650-1260°C
(1200-2300°F)

For general use, better resistance to oxidation and sulfur than Type K.

R

870-1450°C
(1600-2640°F)

Oxidizing atmosphere recommended. Easily contaminated, require protection.

S

980-1450°C
(1800-2640°F)

Laboratory standard, highly reproducible. Easily contaminated, require protection.

T**

-200-350°C
(-330-660°F)

Most stable at cryogenic temperatures ranges. Excellent in oxidizing and reducing atmospheres within temperature range.

Type E
The Type E thermocouple is suitable for use at temperatures up to 900°C (1650°F) in a vacuum, inert, mildly oxidizing or reducing atmosphere. At cryogenic temperatures, the thermocouple is not subject to corrosion. This thermocouple has the highest EMF output per degree of all the commonly used thermocouples.
Type J
The Type J may be used, exposed or unexposed, where there is a deficiency of free oxygen. For cleanliness and longer life, a protecting tube is recommended. Since JP (iron) wire will oxidize rapidly at temperatures over 540°C (1000°F), it is recommended that larger gauge wires be used to compensate. Maximum recommended operating temperature is 760°C (1400°F).
Type K
Due to its reliability and accuracy, Type K is used extensively at temperatures up to 1260°C (2300°F). It's good practice to protect this type of thermocouple with a suitable metal or ceramic protecting tube, especially in reducing atmospheres. In oxidizing atmospheres, such as electric furnaces, tube protection is not always necessary when other conditions are suitable; however, it is recommended for cleanliness and general mechanical protection. Type K will generally outlast Type J because the JP (iron) wire rapidly oxidizes, especially at higher temperatures.
Type N
This nickel-based thermocouple alloy is used primarily at high temperatures up to 1260°C (2300°F). While not a direct replacement for Type K, Type N provides better resistance to oxidation at high temperatures and longer life in applications where sulfur is present.
Type T
This thermocouple can be used in either oxidizing or reducing atmospheres, though for longer life a protecting tube is recommended. Because of its stability at lower temperatures, this is a superior thermocouple for a wide variety of applications in low and cryogenic temperatures. It's recommended operating range is— -200° to 350°C (-330° to 660°F), but it can be used to -269°C (-452°F) (boiling helium).
Type S,R and B
Maximum recommended operating temperature for Type S or R is 1450°C (2640°F); Type B is recommended for use at as high as 1700°C (3100°F). These thermocouples are easily contaminated. Reducing atmospheres are particularly damaging to the calibration. Noble metal thermocouples should always be protected with a gas-tight ceramic tube, a secondary tube of alumina and a silicon carbide or metal outer tube as conditions require.
W-5 Percent Re/W-26 Percent Re (Type C*)
This refractory metal thermocouple may be used at temperatures up to 2315°C (4200°F). Because it has no resistance to oxidation, its use is restricted to vacuum, hydrogen or inert atmospheres.
Initial Calibration Tolerances for Wire and Cable Reference Junction 0°C (32°F)

Calibration Type

Temperature Range

Tolerances
(whichever is greater)

°C

°F

Standard

Special

Thermocouple Wire Type

B
E
J
K
N
R or S
T

870 to 1700
0 to 900
0 to 750
0 to 1250
0 to 1250
0 to 1450
0 to 350

1598 to 3092
32 to 1652
32 to 1382
32 to 2282
32 to 2282
32 to 2642
32 to 662

±0.5%
±1.7ºC or ±0.5%
±2.2ºC or ±0.75%
±2.2ºC or ±0.75%
±2.2ºC or ±0.75%
±1.5ºC or ±0.25%
±1.0ºC or ±0.75%


±1.0ºC or ±0.4%
±1.1ºC or ±0.4%
±1.1ºC or ±0.4%
±1.1ºC or ±0.4%
±0.6ºC or ±0.1%
±0.5ºC or ±0.4%

Extension Wire Type

EX
JX
KX
NX
TX

0 to 200
0 to 200
0 to 200
0 to 200
0 to 100

32 to 392
32 to 392
32 to 392
32 to 392
32 to 212

±1.7ºC
±2.2ºC
±2.2ºC
±2.2ºC
±1.0ºC

±1.0ºC
±1.1ºC
±1.1ºC
±1.1ºC
±0.5ºC

Compensating Extension Wire Type

BX
CX
RX, SX

0 to 200
0 to 870
0 to 200

32 to 392 5
32 to 1600 5
32 to 392 5

±3.7ºC
±6.8ºC
±5ºC

 

Cryogenic Range Wire Type

E
K
T

-200 to 0
-200 to 0
-200 to 0

-328 to 32
-328 to 32
-328 to 32

±1.7ºC or ±1%
±2.2ºC or ±2%
±1.0ºC or ±1.5%

7

1. Where tolerances are given in percent, the percentage applies to the temperature being measured in degrees Celsius. For example, the standard tolerance of Type J over the temperature range 277 to 750ºC is ± 0.75 percent. If the temperature being measured is 538ºC, the tolerance is ± 0.75 percent of 538ºC, or ± 4.0ºC. To determine the tolerance in degrees Fahrenheit, multiply the tolerance in degrees Celsius times 1.8.

2. Copper versus copper compensating extension wire, usable to 100ºC (212ºF) with maximum deviations as indicated, but with no significant deviation over 32 to 0 to 50ºC (122ºF) range. Matched proprietary alloy compensating wire is available for use over the range 0 to 200ºC (32 to 392ºF) with tolerances of ±0.033 mV (±3.7ºC5).

3. Not an ANSI symbol.

4. Copper (+) versus copper nickel alloy (-).

5. Due to the non-linearity of the Types B, C R and S temperature-EMF curves, the error introduced into a thermocouple system by the compensating wire will be variable when expressed in degrees. The degree C tolerances given are based on the following measuring junction temperatures:

Type Wire Measuring Junction Temperature
  • BX Greater than 1000ºC (1832ºF)
  • SX Greater than 870ºC (1598ºF)

6. Thermocouples and thermocouple material are normally supplied to meet the tolerances specified in the table for the normal specified range. The same materials, however, may not fall within the cryogenic tolerances in the second section of the table. If materials are required to meet the cryogenic tolerances, the purchase order must so state. Selection of materials usually will be required. Tolerances indicated in this table are not necessarily an indication of the accuracy of temperature measurements in use after initial heating of the materials.

7. Little information is available to justify establishing special tolerances for cryogenic temperatures. Limited experience suggests the following tolerances for Types E and T thermocouples:

  • Type E -200 to 0ºC ±1.0ºC or ±0.5% (whichever is greater)
  • Type T -200 to 0ºC ±0.5ºC or ±0.8% (whichever is greater)
4. HEATER POWER ESTIMATING EQUATIONS
Equation 1
Heat Required To Raise The Temperature of A Material

Where:
  • Q1 = Heat required to raise temperature
  • W = Pounds of material
  • CP = Specific heat of material (Btu/lb-ºF)
  • T = Temperature rise of material
  • (TFinal - TInitial) ºF
Equation 2
Heat Required To Vaporize A Material (To Melt a Substance, Substitute Latent Heat of Fusion ---Hf---for Latent Heat of Vaporization)

Where:
  • Q2 = Heat required to vaporize
  • W = Pounds of material
  • Hv = Latent heat of vaporization (Btu/lb)
Equation 3
Heat Losses From Surfaces

Where:
  • Q3 = Surface heat losses
  • A = Surface area (ft2)
  • FSL = Surface loss factors (W/ft2) evaluated at surface temperature
  • t = Exposure time (hours)
Equation 4
Heat Losses By Conduction Through Materials

Where:
  • Q4 = Conduction heat losses
  • K = Thermal Conductivity (Btu · in/ft2 · ºF · hour)
  • A = Heat transfer surface area (ft2)
  • X = Thickness of material (inches)
  • T = Temperature difference across material (T2 - T1)ºF
  • t = Conduction time (hours)
5. DELTA AND WYE CIRCUIT EQUATION
Typical 3-Phase Wiring Diagrams and Equations for Resistive Heaters
Definitions

For Both Wye and Delta (Balanced Loads)

Wye and Delta Equivalent

VP = Phase Voltage
VL = Line Voltage
IP = Phase Current
IL = Line Current
R = R1 = R2 = R3 = Resistance of each branch
W = Wattage

WDELTA = 3 WWYE
WODELTA = ¾ WDELTA
WOWYE = ½ WWYE

Equations

3-Phase Wye (Balanced Load)

3-Phase Open Wye (No Neutral)

IP = I L
VP = VL/1.73
WWYE = VL2/R = 3 (VP2)/R
WWYE = 1.73VLIL

IPO = I LO
VPO = VL/2
WOWYE = 1/2 ( VL /R)
WOWYE = 2 (VPO2/R)

3-Phase Delta (Balanced Load)

3-Phase Open Delta

IP = I L/1.73
VP = VL
WDELTA = 3(VL2)/R
WDELTA = 1.73VLIL

VP = VL
IPO1 = I PO3 = I LO2
ILO3 = 1.73 I PO1
WODELTA = 2(VL2/R)

Calculations for Required Heat Energy
The total heat energy (kWh or Btu) required to satisfy the system needs will be either of the two values shown below depending on which calculated result is larger.

A. Heat required for start-up

B. Heat required to maintain the desired temperature


The power required (kW) will be the heat energy value (kWh) divided by the required start-up or working cycle time. The kW rating of the heater will be the greater of these values plus a safety factor.

The calculation of start-up and operating requirements consist of several distinct parts that are best handled separately. However, a short method can also be used for a quick estimate of heat energy required.

Short Method
Start-up watts = A + C + 2/3L + Safety Factor
Operating watts = B + D + L + Safety Factor
Safety Factor is normally 10% to 35% based on application.
A = Watts required to raise the temperature of material and equipment to the operating point, within the time desired.
B = Watts required to raise temperature of the material during the working cycle.
Equation for A and B (Absorbed watts-raising temperature)
C = Watts required to melt or vaporize material during start-up period.
D = Watts required to melt or vaporize material during working cycle.
Equation for C and D (Absorbed watts-raising temperature)
Weight of Material (lbs) · Heat of Fusion or Vaporization (Btu/lb)
Start-up or Cycle Time (hrs) · 3.412
L = Watts lost from surfaces by:
  • Conduction — use equation below
  • Radiation — use heat loss curves
  • Convection — use heat loss curves
Equation for C and D (Absorbed watts-raising temperature)
SAFETY FACTOR CALCULATION

You should always include a safety factor of varying size to allow for unknown or unexpected conditions. The size of the safety factor is dependent on the accuracy of the wattage calculation. Heaters should always be sized for a higher value than the calculated figure. A factor of 10% is adequate for small systems that are closely calculated; 20% additional wattage is more common. Safety factors of 20% and 35% are not uncommon, and should be considered for large systems, such as those containing doorsthat open or are large radiant heat applications. You'll also want to predict how long your system will operate without failure, so examine the amount of heater life you'll be needing. And because electricity costs money, take efficiency factors into account so your system will cost as little as possible to operate.

With these considerations in mind, carefully review them all to be sure you do, in fact, have definitive information to decide on a particular solution to your heating problem. Some of this supporting information may not be readily available or apparent to you. You may find it necessary to consult the reference tables and charts in this reference data section, or reference a book that deals with the particular parameter you need to define. At the minimum, the thermal properties of both the material(s) being processed/heated and their containing vessel(s) will be required.

Figuring a safety factor requires some intuition on your part. The list of possible influences can be great. From changing ambient operating temperatures, caused by seasonal changes, to a change in material or material temperature being processed, you must carefully examine all the influences.

Generally speaking, the smaller the system with fewer variables and outside influences---the smaller the safety factor. Conversely, the larger the system and the greater the variables and outside influences — the greater the safety factor.

Here are some general guidelines:
  • 10% safety factor for small systems with closely calculated power requirements
  • 20% safety factor is average
  • 20% to 35% for large systems
The safety factor should be higher for systems that have production operations that contain equipment cycles subjecting them to excessive heat dissipations, e.g.: opening doors on furnaces, introducing new batches of material that can be of varying temperatures, large radiant applications and the like.
6. AMPERAGE CONVERSION

Watts

Volts Single Phase

Volts 3 Phase
Balanced Load

120

240

480

240

480

100
150
200
250
300

0.83
1.25
1.67
2.08
2.50

0.42
0.63
0.83
1.04
1.25

0.21
0.31
0.42
0.52
0.63

0.24
0.36
0.49
0.61
0.73

0.13
0.18
0.25
0.30
0.37

350
400
450
500
600

2.92
3.33
3.75
4.17
5.00

1.46
1.67
1.88
2.08
2.50

0.73
0.84
0.93
1.04
1.25

0.85
0.97
1.10
1.20
1.45

0.43
0.49
0.55
0.60
0.73

700
750
800
900
1000

5.83
6.25
6.67
7.50
8.33

2.92
3.13
3.33
3.75
4.17

1.46
1.56
1.67
1.87
2.10

1.70
1.81
1.93
2.17
2.41

0.85
0.91
0.97
1.09
1.21

1100
1200
1250
1300
1400

9.17
10.0
10.4
10.8
11.7

4.58
5.00
5.21
5.42
5.83

2.30
2.51
2.61
2.71
2.91

2.65
2.90
3.10
3.13
3.38

1.33
1.45
1.55
1.57
1.69

1500
1600
1700
1750
1800

12.5
13.3
14.2
14.6
15.0

6.25
6.67
7.08
7.29
7.50

3.12
3.34
3.54
3.65
3.75

3.62
3.86
4.10
4.22
4.34

1.82
1.93
2.05
2.10
2.17

1900
2000
2200
2500
2750

15.8
16.7
18.3
20.8
23.0

7.92
8.33
9.17
10.4
11.5

3.96
4.17
4.59
5.21
5.73

4.58
4.82
5.30
6.10
6.63

2.29
2.41
2.65
3.05
3.32

3000
3500
4000
4500
5000

25.0
29.2
33.3
37.5
41.7

12.5
14.6
16.7
18.8
20.8

6.25
7.30
8.33
9.38
10.42

7.23
8.45
9.64
10.84
12.1

3.62
4.23
4.82
5.42
6.1

6000
7000
8000
9000
10000

50.0
58.3
66.7
75.0
83.3

25.0
29.2
33.3
37.5
41.7

12.50
14.59
16.67
18.75
20.85

14.50
16.9
19.3
21.7
24.1

7.25
8.5
9.65
10.85
12.1

7. HEAT LOSS FACTORS
Heat Losses from Uninsulated Surfaces
Heat Losses at 70°F Ambient.
How to use the graph for more accurate calculations
Convection curve correction factors:
For losses from top surfaces or from horizontal pipes
  • Multiply convection curve value by 1.29
For side surfaces and vertical pipes
  • Use convection curve directly
For bottom surfaces
  • Mulitply convection curve value by 0.63
Radiation Curve Correction Factors
The radiation curve shows losses from a perfect blackbody and are not dependent upon position. Commonly used block materials lose less heat by radiation than a blackbody, so correction factors are applied. These corrections are the emissivity (e) values.
Total Heat Losses =
  • Radiation losses (curve value times e)
  • + Convection losses (top)
  • + Convection losses (sides)
  • + Convection losses (bottom)
  • = Conduction losses (where applicable)
Helpful Hint
The graphs for losses from uninsulated and insulated surfaces are hard to read at low temperatures close to ambient. Here are two easy-to-use calculations that are only rule-of-thumb approximations, but they are reasonably accurate when used within the limits noted.
Rule #1
Losses from an uninsulated surface (with an emissivity close to 1.0): (This applies only to temperatures between ambient and about 250ºF).
Rule #2
Losses from an insulated surface: (This insulation is assumed to be 1 inch thick and have a K-value of about 0.5 Btu-in/hr-ft2-°F. Use only for surfaces less than 800°F.)
Heat Losses from Insulated, Water & Metal Surfaces

1. Based upon combined natural convection and radiation losses into 70ºF environment.

2. Insulation characteristics

k = 0.67 @ 200ºF

k = 0.83 @ 1000ºF.

3. For molded ceramic fiber products and packed or tightly packed insulation, losses will be lower than values shown.

For 2 or 3 inches Insulation: multiply by 0.84 For 4 or 5 inches Insulation:

multiply by 0.81

For 6 inches Insulation:

multiply by 0.79

Heat Losses from Oil or Paraffin Surfaces
8. MATERIAL EMISSIVITY AND SPECIFIC HEAT:
Some Material Emissivities / Metals

Material

Specific Heat Btu/lb.-°F

Emissivity

Polished Surface

Medium Oxide

Heavy Oxide

Blackbody
Aluminum
Brass
Copper
Inocoloy®800


0.24
0.10
0.10
0.12


0.09
0.04
0.04
0.20

0.75
0.11
0.35
0.03
0.60

1.00
0.22
0.60
0.65
0.92

Inconel® 600
Iron, Cast
Lead, Solid
Magnesium
Nickel 200

0.11
0.12
0.03
0.23
0.11

0.20
-
-
-
-

0.60
0.80
0.28
-
-

0.92
0.85
-
-
-

Nichrome,-80-20
Solder, 50-50
Steel
mild
stainless 304
stainless 430

0.11
0.04

0.12
0.11
0.11

-
-

0.10
0.17
0.17

-
-
-

0.75
0.57
0.57

-
-

0.85
0.85
0.85

Tin
Zinc

0.056
0.10

-
-

-
0.25

-
-

Some Material Emissivities/Non-Metals

Material

Specific Heat
Btu/lb.-°F

Emissivity

Asbestos
Asphalt
Brickwork
Carbon
Glass

0.25
0.40
0.22
0.20
0.20

Most Non-Metals: 90

Paper
Plastic
Rubber
Silicon Carbide
Textiles
Wood, Oak

0.45
0.2-0.5
0.40
0.20-0.23
-
0.57

9. RTD TOLERANCES, CLASSES AND COMPARISONS
Platinum RTD Tolerance Values

Temperature °C

Resistance Value Ω

Tolerance DIN-IEC-751

Class A
°C (Ω)

Class B
°C (Ω)

-200
-100
0
100
200

18.52
60.26
100.00
138.51
175.86

±0.55-(±0.24)
±0.35-(±0.14)
±0.15-(±0.06)
±0.35-(±0.13)
±0.55-(±0.20)

±1.3-(±0.56)
±0.8-(±0.32)
±0.3-(±0.12)
±0.8-(±0.30)
±1.3-(±0.48)

300
400
500
600
650

212.05
247.09
280.98
313.71
329.64

±0.75-(±0.27)
±0.95-(±0.33)
±1.15-(±0.38)
±1.35-(±0.43)
±1.45-(±0.46)

±1.8-(±0.64)
±2.3-(±0.79)
±2.8-(±0.93)
±3.3-(±1.06)
±3.6-(±1.13)

RTD Tolerance Class Definitions
DIN class A: ± [ (0.15 + 0.002 | t | ] °C
DIN class B: ± [ (0.30 + 0.005 | t | ] °C
RTD Resistance Wire Comparisons

Element Metal

Temperature Range

Benefits

Base Resistance

TCR (Ω/Ω/°C)

Platinum

-260 to 850°C
(-436 to 1562°F)

Best stability, good linearity

100 Ω at 0°C

0.00385 (DIN-IEC-761), 0.003916 (JIS 1604-1981)

Copper

-100 to 260°C
(-148 to 500°F)

Best linearity

10 Ω at 25°C

0.00427

Nickel

-100 to 260°C
(-148 to 500°F)

Low cost, High Sensitivity

 

 

10. HEATER SHEATH COMPATIBILITY GUIDE

SOLUTION

TYPE OF HEATER

 

SOLUTION

TYPE OF HEATER

 

SOLUTION

TYPE OF HEATER

 

 

 

 

 

Acetic .................................. PTFE* or Quartz

 

Copper Cyanide ................. 304 Stainless Steel

 

Nitric Hydrochloric Acids... PTFE* or Quartz

Acetane 70, 80 .................................... PTFE*

 

Copper Fluoborate ............................... PTFE*

 

Nitric Phosphoric ....................... Quartz

Actane Salt .......................................... PTFE*

 

Copper Pyrophosphate ..... 304 Stainless Steel

 

Oil ................................................ Steel

Acid Sulfate .......................... PTFE* or Quartz

 

Copper Strike .................... 304 Stainless Steel

 

Oleic Acid ..................... PTFE* or Quartz

Alcorite ................................ PTFE* or Quartz

 

Copper Sulfate ..................... PTFE* or Quartz

 

Oxalic Acid.....................PTFE* or Quartz

Alkaline Cleaners (Electrified)....... 304 Stainless Steel

 

Cyanide ............................ 304 Stainless Steel

 

Paint Stripper (Alkaline) ........ 304 Stainless Steel

Alkaline Soaking Cleaners .... 304 Stainless Steel

 

Deionized Water .......... 316 Stainless Steel or Titanium

 

Perchlorethylene .......... 316 Stainless Steel

Alodine (most formulas) ....... 316 Stainless Steel

 

Deoxidizer (Etching) ...............PTFE* or Quartz

 

Phosphoric Acid (No Fluoride) ....... PTFE* or Quartz

Alstan ............................... 304 Stainless Steel

 

Deoxidizer Non-Chromated ....... 316 Stainless Steel

 

Phosphate Cleaner ..... 304 Stainless Steel

Aluminum Bright Dip ............ PTFE* or Quartz

 

Dichromic Seal ..................................... Steel

 

Phosphate .................. 316 Stainless Steel

Aluminum Cleaners .............. 304 Stainless Steel

 

Diethylene Glycol ................ 304 Stainless Steel

 

Potassium Acid Sulfate ..... PTFE* or Quartz

Aluminum Chloride .............. PTFE* or Quartz

 

Diversey, 511, 514 ................................ PTFE*

 

Potassium Cyanide ........ 304 Stainless Steel

Aluminum Sulfate ................ 304 Stainless Steel

 

Dow Therm ...................... 316 Stainless Steel

 

Potassium Hydroxide .... 304 Stainless Steel

Ammonia ............................ 304 Stainless Steel

 

Dye Solutions .................... 304 Stainless Steel

 

Potassium Hydrochloric ..... PTFE* or Quartz

Ammonia Persulfate ............. PTFE* or Quartz

 

Ebonal C ........................................... Titanium

 

Potassium Permanganate........... PTFE* or Titanium

Ammonium Bi Fluoride......................... PTFE*

 

Electroless Copper .............................. PTFE*

 

Rhodium ........................ PTFE* or Quartz

Ammonium Chloride ........................ Titanium

 

Electroless Nickel ............... PTFE* or Titanium

 

Rochelle Salt Cyanide .........304 Stainless Steel

Ammonium Nitrate ............. 316 Stainless Steel

 

Electroless Tin (Acid) ........... PTFE* or Quartz

 

Ruthenium Plating..............PTFE* or Quartz

Anodizing (Aluminum).............. PTFE* or Quartz

 

Electroless Tin (Alkaline) .... 316 Stainless Steel

 

Salt (Actine) .................................. PTFE*

ARP 28, 80 Blackening Salts... PTFE* or Quartz

 

Electro Cleaner .................. 304 Stainless Steel

 

Sea Water .................................. Titanium

Arsenic ............................. 304 Stainless Steel

 

Electro Polishing ................... PTFE* or Quartz

 

Silver Bromide ........... 316 Stainless Steel

Barium Chloride .............. Quartz or Titanium

 

Enthone 80 Acid ................................. PTFE*

 

Silver Cyanide ........... 304 Stainless Steel

Benzoic Acid ................................... Titanium

 

Ethylene Glycol .................................... Steel

 

Silver Lume ............... 304 Stainless Steel

Black Nickel ......................... PTFE* or Quartz

 

Ferric Ammonium Oxide ..... 316 Stainless Steel

 

Silver Nitrate ............. 316 Stainless Steel

Black Oxide (Hi-Temp) ....... 304 Stainless Steel

 

Ferric Chloride ....... PTFE*, Quartz, or Titanium

 

Sodium Bisulfate .......... PTFE* or Quartz

Black Oxide (Low-Temp) .................. Titanium

 

Ferric Nitrate ..................... 304 Stainless Steel

 

Sodium Carbonate .................... Titanium

Bonderizing ....................... 316 Stainless Steel

 

Ferric Sulfate .................... 304 Stainless Steel

 

Sodium Chlorate ........................ Titanium

Boric Acid ........................................ Titanium

 

Fluoborate ............................................ PTFE*

 

Sodium Chloride .......................... Titanium

Brass Cyanide .................. 304 Stainless Steel

 

Formic Acid ..................... 316 Stainless Steel

 

Sodium Cyanide ......... 304 Stainless Steel

Bright Nickel ........... PTFE*, Quartz, or Titanium

 

Glycerol ........................... 304 Stainless Steel

 

Sodium Dichromate (Hot Seal) ... 316 Stainless Steel

Bright Copper Cyanide ....... 304 Stainless Steel

 

Immersion Gold ................ 304 Stainless Steel

 

Sodium Hydroxide ......................... Steel

Bronze (Alkaline)................. 304 Stainless Steel

 

Gold-Acid .............. PTFE*, Quartz, or Titanium

 

Sodium Hypochlorite .................... PTFE*

Brown Oxide ................................... Titanium

 

Gold Cyanide .................... 304 Stainless Steel

 

Sodium Persulfate ......... PTFE* or Quartz

Burnite ................................. PTFE* or Quartz

 

Grey Nickel ............ PTFE*, Quartz, or Titanium

 

Stannate ....................................... Steel

Butyric Acid .................................... Titanium

 

Hot Seal Dichromate ......... 316 Stainless Steel

 

Stanostar .................... PTFE* or Quartz

Cadmium Black ................... PTFE* or Quartz

 

Hydrochloric Acid ................. PTFE* or Quartz

 

Stearic Acid .............................. Quartz

Cadmium (Alkaline) ............ 304 Stainless Steel

 

Hydrofluoric Acid ................................. PTFE*

 

Sulfamate Nickel ........ PTFE*, Quartz, or Titanium

Cadmium Fluoborate ........................... PTFE*

 

Hydrogen Peroxide ............. PTFE* or Quartz

 

Sulfur .......................... PTFE* or Quartz

Calcium Chloride ............................. Titanium

 

Indium ................................ PTFE* or Quartz

 

Sulfur Peroxide ........... PTFE* or Quartz

Calcium Hypochlorite ....................... Titanium

 

Iridite (4-75,4-73,14,14-2,14-9)...... 316 Stainless Steel

 

Sulfuric Acid ............... PTFE* or Quartz

Carbonic Acid .................................. Titanium

 

Iridite (1,2,3,4-C,7,8,15) ....... PTFE* or Quartz

 

Sulphamic Acid ............... PTFE* or Quartz

Caustic Etch ........................................ Steel

 

Iron Fluoborate .................................... PTFE*

 

Tannic Acid ........................... Titanium

Caustics .............................................. Steel

 

Iron Phosphate ................... 316 Stainless Steel

 

Tin Nickel ...................................... PTFE*

Caustics (highly concentrated 20% and over)... Steel

 

Isoprep (186,187,188) ....... 316 Stainless Steel

 

Tin Plating (Acid) (Stanus/Sulphate)...PTFE* or Quartz

Chlorine/Wet ....................... PTFE* or Quartz

 

Isoprep Acid Salts ............................... PTFE*

 

Tin Plating Acid (Fluoborate) ........... PTFE*

Chloride ............... PTFE*, Quartz or Titanium

 

Jetal .................................. 304 Stainless Steel

 

Tin Plating (Alkaline) .... 304 Stainless Steel

Chlorosulfuric Acid .......................... Titanium

 

Lead Acetate .................... 304 Stainless Steel

 

Trichlorethylene .......... 316 Stainless Steel

Chromic Anodizing ............... PTFE* or Quartz

 

Lime Saturated Water (Alkaline)......316 Stainless Steel

 

Trioxide (Pickle) ............. PTFE* or Quartz

Chromic Acetate .................. PTFE* or Quartz

 

Linseed Oil ........................ 304 Stainless Steel

 

Turco (4181, 4338) ..... 316 Stainless Steel

Chromic Nickel .................... PTFE* or Quartz

 

Magnesium Hydroxide........ 304 Stainless Steel

 

Unichrome ...................... PTFE* or Quartz

Chromium (No Fluorides)............PTFE*,Quartz, or Titanium

 

Magnesium Nitrate ............... PTFE* or Quartz

 

Water ......... 316 Stainless Steel or Quartz

Chromium (Fluoride) ............................ PTFE*

 

Manganese Phosphate ..... 316 Stainless Steel

 

Wood’s Nickel Strike .... Titanium, PTFE*, or Quartz

Citric Acid ........................................ Titanium

 

McDermid 629 .................................... PTFE*

 

Yellow Dichromate .......... PTFE* or Quartz

Clear Chromate .................... PTFE* or Quartz

 

Mercuric Chloride ............................ Titanium

 

Zinc Acid ...................... PTFE* or Titanium

Cobalt Nickel ........... PTFE*, Quartz, or Titanium

 

Muriatic Acid ....................... PTFE* or Quartz

 

Zinc Ammonium Chloride........ Quartz or Titanium

Cobalt Plating .................. 304 Stainless Steel

 

Nickel (Plating Solution) (Watts) ...PTFE*, Quartz, or Titanium

 

Zinc Cyanide................ 304 Stainless Steel

Cobra Etch .......................................... PTFE*

 

Nickel Acetate Seal ......... 316 Stainless Steel

 

Zinc Phosphate ........... 316 Stainless Steel

Copper Acid ......................... PTFE* or Quartz

 

Nickel Chloride .................................... Titanium

 

Zincate .................... 304 Stainless Steel

Copper Bright Acid .............. PTFE* or Quartz

 

Nitric Acid ............................... PTFE* or Quartz

 

 

 


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