Design Guide

R

Tank Heating Systems

CH

EM

EL

EX

Contents

IntroductionDesign Guide Overview 1Appropriate Applications 1Design Guide vs. TankCalc Plus 1Approvals 1Preliminary Steps 1Caution 1

Part I: Heat Loss CalculationsSurface Areas 2Step 1. Calculate the surface area of the tank. 3

Cylinder Surface Area 3Truncated Cone Surface Area 4

Step 2. Calculate the QV (heat loss through the insulated body). 4Step 3. Calculate the QS (heat loss through the base support). 6

Concrete Slab or Earth Foundation 6Legs 7Concrete Saddles 8Uninsulated Skirt 9

Step 4. Calculate the QA (heat loss through the accessories). 10Manholes 10Handholds 10

Step 5. Calculate the tank QT (overall heat loss) 11Step 6. Calculate the final-design heat loss 11Illustrative Example 12

Part II: Heater Selection and Sizing System Selection 13Plastic Tank Considerations 14RHS Model and Size Selection 15Illustrative Example 15RHS Tank Heater Dimensions 16

Part III: Heater Design Thermostatic Control of Tank Heaters 17Location, Spacing, and Arrangement of Heaters 17Questions 18

Specifications/Approvals 19

Design Worksheet 20

Notes 22

Introduction

Design Guide Overview

This design guide has three basic parts:• Part I provides heat-loss information based on various tank configurations

and temperatures and helps you calculate tank heat loss.• Part II helps you determine which Raychem Heating System—the Raychem

Heating System (RHS) tank heater or self-regulating heating cables—is rightfor you. If you choose an RHS tank heater, Part II helps you select the rightsystem model and size. If you choose a heat-tracing cable system, Part IIwill refer you to the right source.

• Part III contains design instructions for both systems.

Appropriate Applications

This design guide is appropriate for the following conditions:• Fully insulated tanks• Vertical and horizontal tanks• Low (water) and medium (light oils) viscosity fluids• Ordinary areas• Standard freeze protection and process temperature maintenance

Contact Raychem for designing systems that meet the following conditions:• Hazardous locations• High viscosity fluids (heavy oils)• Tanks smaller than 4 feet in diameter• Other unusual applications

Design Guide vs. TankCalc Plus

This guide presents a general approach to designing a heat-tracing system fora tank or vessel. The guide’s design and heat-loss assumptions are based onthose in Raychem’s TankCalc Plus software. The heat loss calculations madeusing this guide will be higher than the identical calculation in TankCalc due toengineering assumptions made in this guide. See your Raychem representativefor a copy of TankCalc.

Approvals

RHS tank heaters are approved for ordinary areas and Class I Division 2, ClassII, and III, Division 1 and 2 hazardous locations by Factory Mutual (FM) and theCanadian Standards Association (CSA).

Preliminary Steps

Before proceeding with your tank heating system's design, you should obtainthe information requested in the Design Worksheet at the end of this designguide and record the necessary information there.

1

Part I: Heat Loss Calculations

Surface Areas

The overall heat loss (QT) of an insulated tank can be expressed as:

QT = QV + QS + QA

where:

QV = Heat loss through the insulated body of the tankQS = Heat loss through the slab, legs, saddle, or other base supportQA = Heat loss through accessories such as manholes, handholds, ladders, or

handrails

Calculation of the tank’s overall heat loss (QT) requires six simple steps:

Step 1. Calculate the surface area of the tank.Step 2. Calculate QV (heat loss through the insulated body of the tank).Step 3. Calculate QS (heat loss through the base support).Step 4. Calculate QA (heat loss through the accessories).Step 5. Calculate QT (overall heat loss).Step 6. Calculate the final-design heat loss.

The heat-loss rates for insulated tank bodies (Table 2 and Chart 2 on page 5) arebased on the following IEEE 515 provisions:

• Fiberglass insulation• Tank located outdoors in winds greater than 20-mph• No insulating airspace between tank surface and insulation

The tank body heat-loss rates in Table 2 and Chart 2 assume a tank that is com-pletely full and insulated with a minimum of 1 inch of fiberglass. However, Table 3provides insulation factors for adjusting the tank-body heat loss to insulationsother than fiberglass.

2

STEP 1. Calculate the surface area of the tank.

Cylinder Surface Area

The surface area of the cylindrical tank (Figure 1) is equal to the area of the body(Abody) plus the area of both ends of the tank (Aend), or, in the case of a verticalcylinder resting on a slab, the area of the tank body (Abody) plus the area of the top(Aend). If the tank is a vertical cylinder resting on a slab, do not add in the bottomarea at this point.

Figure 1. Cylinder surface areas

To calculate the total surface area (AV) of the tank cylinder:

• Calculate the surface area of the body:

(Abody) = πDH

• Calculate the surface area of one or both ends:

(Aend) =πD2 or (Aend) = πD2

x 24 4

• Add the results.

For your convenience, Table 1 below provides both the end and body areas ofcylindrical tanks 6 to 20 feet in diameter and 8 to 25 feet high.

Table 1. Cylindrical Tank Surface Areas

Abody (ft 2)

H (ft)

D (ft) A end (ft 2) 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25

6 29 151 170 189 208 227 245 264 283 302 321 340 359 311 396 415 434 453 4717 39 176 198 220 242 264 286 308 330 352 374 396 418 440 462 484 506 528 5508 51 202 227 252 277 302 327 352 377 403 427 452 478 503 528 553 579 604 6299 64 227 255 283 311 340 368 396 425 453 481 509 538 566 594 622 650 679 70710 79 252 283 315 346 377 409 440 472 503 535 565 597 629 660 692 723 754 78611 95 277 311 346 381 415 450 484 519 553 588 622 657 692 726 761 795 830 86412 114 302 340 377 415 453 491 528 566 604 641 679 717 754 792 830 868 905 94313 133 327 368 409 450 491 531 572 613 654 695 736 776 817 858 899 940 981 102114 154 352 396 440 484 528 572 616 660 704 748 792 836 880 924 968 1012 1055 110015 177 377 425 472 519 566 613 660 707 754 802 849 896 943 990 1037 1084 1131 117916 202 403 453 503 553 604 654 704 754 805 855 905 955 1006 1056 1106 1157 1207 125717 227 427 481 535 588 641 695 748 802 855 908 962 1015 1069 1121 1175 1229 1282 133618 255 452 509 565 622 679 736 792 849 905 962 1018 1075 1131 1188 1244 1301 1357 141419 284 478 538 597 657 717 776 836 896 955 1015 1075 1135 1194 1254 1314 1373 1433 149320 315 503 566 629 692 754 817 880 943 1006 1069 1131 1194 1257 1320 1383 1446 1508 1571

Note: For area of horizontal tank, add area of both ends.

D

HD

H

3

Truncated Cone Surface Area

The total surface area (Av) of a truncated cone tank (Figure 2) is calculated as follows:

(Av) = (Abody) + (Atop) + (Abottom)*

* Do not include (Abottom) if tank bottom is resting on a slab.

Figure 2. Truncated Cone Surface Areas

STEP 2. Calculate the QV (heat loss through the insulated tank body).

Calculating the QV requires the following tank information:

• Maintain temperature (TM)

• Minimum ambient temperature (TA)

• Insulation thickness

You use the maintain and minimum ambient temperatures to arrive at the ∆ tem-perature. With the ∆T and the insulation thickness you calculate the QV.

To calculate the QV :

• Obtain the ∆T by subtracting the minimum ambient temperature (TA) from themaintain temperature (TM):

∆T = (TM) – (TA)

• Determine the heat loss rate for the application. (Table 2 and Chart 2 on page5 show the heat-loss rates per square foot for typical ∆ temperatures and insu-lation thicknesses.)

• Determine the insulation factor. (Table 3 on page 5 provides insulation factorsfor the most commonly used tank insulations.)

• Calculate the total heat loss through the tank body:

QV = AV x Heat loss rate x Insulation factor

4

D

d

SH

π2

(D+d) SAbody =

= π2

(D+d) + H2(D+d)2

4

Atop =π D2

4

Abottom =π d2

4

Table 2. Heat Loss Rate per Square Foot (watts/ft 2)

Insulation Thickness

∆T 1" 1 1/2" 2" 3" 4"

50°F 3.4 2.3 1.7 1.2 0.9100°F 7.1 4.8 3.6 2.4 1.8150°F 11.0 7.5 5.6 3.7 2.8200°F 15.3 10.3 7.7 5.2 3.9250°F 20.0 13.5 10.2 6.8 5.1300°F 24.9 16.8 12.7 8.5 6.5

Chart 2. Heat Loss Rate per Square Foot (watts/ft2)

Table 3. Insulation Factors for Typical Insulations

Insulation types Insulation Factor k Factor*

Fiberglass 1.00 0.270Cellular glass 1.46 0.395Calcium silicate (Type 1) 1.48 0.400Expanded perlite 1.85 0.499Flexible elastomer 1.15 0.311Mineral fiber blanket 1.26 0.340Polyisocyanurate 0.67 0.180Rigid polyurethane, preform 0.60 0.161Rigid polyurethane, spray 0.60 0.161Rock wool/mineral wool 1.06 0.287

* Based on a 50°F mean temperature with units BTU/hr–°F–ft2/in.

0

20

10

30

15

5

25 1" of insulation

1 1⁄2"

2"

3"4"

50° 100° 150°

∆T (°F)

Hea

t Los

s (w

atts

/ft2 )

200° 250° 300°

5

STEP 3. Calculate the QS (heat loss through the base support).

The following heat-loss tables and accompanying charts (3A–3D) provide typicalbase-support heat losses (QS) through the following types of base support:

• Concrete slab or earth foundation• Legs• Concrete saddles• Uninsulated skirt

Concrete Slab or Earth Foundation

Based on the ∆T and tank diameter, select the QS from the table or chart below.

Table 3A. Heat Loss for a Concrete Slab or Earth Foundation

Tank ∆T (°F)

Diameter (ft) 50 ° 100° 150° 200° 250° 300°

5 137 278 451 566 711 85710 283 573 864 1154 1452 170320 566 1163 1760 2325 2922 348830 848 1767 2616 3535 4383 523140 1131 2388 3518 4649 5906 703750 1374 2945 4320 5891 7265 8836

Chart 3A. Heat loss for a concrete slab or earth foundation.

10000

8000

6000

4000

2000

0

9000

7000

5000

3000

1000

50° 100° 150° 200° 250° 300°

D = 5 feet

D = 10 feet

D = 20 feet

D = 30 feet

D = 40 feet

D = 50 feet

∆T (°F)

Hea

t Los

s (W

)

6

Legs

Determine the heat loss for legs (QS) as follows:

• Based on the ∆T and tank diameter, select the heat loss from the table orchart below.

• The heat loss is on a per leg basis; therefore, multiply the heat loss by thenumber of legs.

Table 3B. Heat Loss for a Leg Support

Tank ∆T (°F)Diameter (ft) 50 ° 100° 150° 200° 250° 300°

5 26 52 77 103 129 15510 and above 85 169 351 336 420 505

Chart 3B. Heat loss for a leg support.

600

400

200

0

500

300

100

D = 5 feet

D = 10 feet and up

50° 100° 150°

∆T (°F)

Hea

t Los

s (W

)

200° 250° 300°

7

Concrete Saddles

Determine the heat loss for saddles (QS) as follows:

• Based on the ∆T and tank diameter, select the heat loss (QS) from the table orchart below.

• Multiply the heat loss you select by the number of saddle supports.

Chart 3C. Heat Loss for a Concrete Saddle

Tank ∆T (°F)Diameter (ft) 50 ° 100° 150° 200° 250° 300°

5 93 186 275 368 461 55310 145 290 430 576 721 86615 198 395 586 783 981 117920 250 500 741 991 1241 1491

Table 3C. Heat loss for a concrete saddle.

1600

1400

600

200

0

800

1200

1000

400

50° 100° 150° 200° 250° 300°

D = 5 feet

D = 10 feet

D =15 feet

D = 20 feet

∆T (°F)

Hea

t Los

s (W

)

8

Uninsulated Skirt

Based on the ∆T and tank diameter, select the QS from the table or chart below.

Table 3D. Heat Loss for an Uninsulated Skirt

Tank ∆T (°F)Diameter (ft) 50° 100° 150° 200° 250° 300°

5 402 805 1193 1595 1998 240010 806 1612 2389 3195 4000 480615 1209 2419 3585 4794 6003 721220 1613 3225 4780 6393 8006 9619

Chart 3D. Heat loss for an uninsulated skirt.

10000

8000

6000

4000

2000

0

9000

7000

5000

3000

1000

50° 100° 150° 200° 250° 300°

D = 5 feet

D = 10 feet

D = 15 feet

D = 20 feet

∆T (°F)

Hea

t Los

s (W

)

9

STEP 4. Calculate the QA (heat loss through the accessories).

The following heat-loss tables and accompanying charts (4A–4D) provide typicalaccessory heat losses (QS) through the following types of accessories:• Manholes• Handholds• Ladders• Handrails

Manholes

Select the heat loss for a manhole from the table or chart below. The heat loss isbased on a 2-foot-diameter cover and a 1-foot-tall base. The base and cover areuninsulated.

Table 4A. Manhole Heat Losses

∆T (°F)50° 100° 150° 200° 250° 300°

Heat Loss (W) 564 1120 1680 2237 2807 3401

Chart 4A. Manhole heat losses.

Handholds

Calculate the heat loss for handholds as follows:

• Select the heat loss from the table or chart below based on the ∆ temperature.Heat loss from the table or chart is based on a 0.5-foot-diameter, uninsulatedsurface.

• Multiply the heat loss you select by the number of handholds.

Table 4B. Heat Loss for a Handhold

∆T (°F)50° 100° 150° 200° 250° 300°

Heat Loss (W) 90 178 265 351 437 526

3000

2000

1000

0

2500

1500

500

50° 100° 150°∆T (°F)

Hea

t Los

s (W

)

200° 250° 300°

3500

10

Chart 4B. Heat loss for a handhold.

STEP 5. Calculate the tank QT (overall heat loss).

Add the heat loss rates (QV, QS, and QA) from Steps 2, 3, and 4.

Outdoor application

QT = QV + QS + QA

Indoor application

QT = 0.9 x (QV + QS + QA)

STEP 6. Calculate final-design heat loss.

Raychem recommends that the final-design heat loss should include a 20 per-cent safety factor, to satisfy IEEE 515 and manufacturing tolerances.

Final design heat loss = QT x 1.20

Note that this same heat-loss calculation approach is appropriate for insulatedpolypropylene and fiber-reinforced plastic (FRP) tanks.

600

400

200

0

500

300

100

50° 100° 150°∆T (°F)

Hea

t Los

s (W

)200° 250° 300°

11

Illustrative Example

Tank Checklist

Maintenance temperature 110°FMinimum ambient temperature –10°FTank material MetalTank shape Vertical cylinderTank dimensions 10-foot diameter; 12 feet highInsulation type FiberglassInsulation thickness 2 inchesTank support type Concrete slabTank accessories 1 manholeTank location Outdoors

STEP 1. From Chart 1, the area (AV) of the tank sides and top is377 + 79 = 456 square feet

STEP 2. ∆T = 110°F – (–10°F) = 120°FFor 2 inches of insulation and 120°F ∆T, the surface heat loss rate is4.4 watts/square foot. The insulation factor for fiberglass is 1.0.

QV = AV x Heat Loss Rate x Insulation Factor

Interpolation on the graph is needed to determine the heat loss rate.

Heat loss rate = 3.6 + (120°F - 100°F) (5.6 - 3.6)150°F - 100°F

Heat loss rate = 4.4 w/ft

For this exampleQV = 456 x 4.4 x 1.0 = 2007 watts

STEP 3. Using the graph in Step 3 to determine the heat loss (QS) through theconcrete slab for a tank diameter of 10 feet and a ∆T of 120°F:

QS = 689 watts

STEP 4. For a ∆T of 120°F, the manhole heat loss can be determined fromStep 4:

QA = 1344 watts

STEP 5. QT = QV + QS + QA

QT = 2007 + 689 + 1344 = 4040 watts

STEP 6. Calculate final-design heat loss, which includes a safety factor of 20percent.

Design heat loss = 4040 watts x 1.20 = 4848 watts

12

Part II: Heater Selection and Sizing

System Selection

To select the appropriate Raychem heater for a tank, many factors have to beconsidered. Use following guidelines to determine the best product for your appli-cation, but if you have any questions, contact your Raychem sales representative.

RHS Tank HeatersChoose an RHS tank heater for the following special applications:• A space constrained tank• A heat-loss application requiring fluid heat-up• Tanks with high heat loss

If you choose an RHS tank heater, proceed to “RHS Model and Size Selection” onpage 15.

Self-regulating Heating Cables

Choose a self-regulating heating cable for the following special applications:• A tank containing temperature-sensitive fluids• Tank materials such as PVC and polyethylene• Applications requiring:

— Shut-off at a specific temperature— Uniform heating

• An application in a Class I Division 1 hazardous area (refer to the RaychemFactory Mutual Approved Auto-Trace Heat Tracing Systems for Division 1Locations Application and Installation Guide, H53622)

If you choose self-regulating heating cables, please consult one of the followingdesign guides for model and size selection and for additional design information:• Auto-Trace Heat Tracing Systems for Ordinary and Division 2 Areas Design

Guide, H51149• Factory Mutual Approved Auto-Trace Heat Tracing Systems for Division 1

Locations Application and Installation Guide, H53622.

13

Plastic Tank Considerations

When designing heating systems for plastic tanks, the user must be careful tokeep the wall temperature below the recommended maximum material tempera-ture. The following steps will quickly help you determine if your specific applicationis appropriate for the tank material.

STEP 1. Determine the power density of the -L heater, Qa. a) Qa = 295 Btu/ft2-hr for nominal voltages of 120 Vac and 240 Vacb) For voltages other than 120 Vac and 240 Vac,

(Qa) adjusted = (Qa) * (V/ Vnominal)2

STEP 2. Determine the maximum fluid maintain temperature, Tf.

STEP 3. Determine the fluid gradient, ∆Tf. The fluid gradient will depend on fluidtype and temperature. For applications not involving temperature sensi-tive fluids, the following values may be used for simplicity. ∆Tf = 10°F for fluids similar to water ∆Tf = 30°F for fluids similar to warm light oils ∆Tf = 100°F for fluids similar to warm heavy oils

STEP 4. Calculate the tank wall gradient, ∆Tw. The gradient depends on wallthickness, t and material conductivity, k. ∆Tw = Qa * t / k

Wall thickness is expressed in inches. Typical conductivity values forhigh temperature plastics are: k = 1.7 Btu-in/hr-ft2 -°F for polypropylene k = 2.1 Btu-in/hr-ft2-°F for fiber-reinforced plastic (FRP)

STEP 5. Calculate the maximum outer wall temperature, Tout-max. Tout-max = Tf + ∆Tf + ∆Tw

The user should contact the tank manufacturer to determine the type andtemperature capability of the tank material. The maximum temperature forpolypropylene and FRP is typically 220°F. Other plastics like PVC andpolyethylene have much lower temperature capabilities and are more suit-able for use with Raychem's self-regulating heating cable product line.

Illustrative Example

Tank ChecklistFluid Water Maintenance temp. 50°FTank material FRP Tank wall thickness 1⁄2”RHS heater RHS-L-XXX Voltage 277 VacArea Classification Ordinary

STEP 1. Calculate adjusted heater power density ,(Qa) adjusted = (295) * (277/ 240)2 = 393

STEP 2. Determine fluid maintain temperature, Tf = 50°F

STEP 3. Determine fluid gradient for water, ∆Tf = 10°F

STEP 4. Calculate wall gradient for a FRP tank with 1⁄2” wall thickness,∆Tw = (393 * 0.5) / 2.1 = 94°F

STEP 5. Calculate maximum outer wall temperature,Tout-max = 50°F + 10°F + 94°F = 154°F

Maximum material temperature for FRP is approximately 220°F. Therefore, theapplication is compatible with the tank material.

14

RHS Model and Size Selection

Tank material and power density determine which RHS tank heater series to select.

The number of heaters you will need depends on the amount of heat distributionthe application requires. A large number of low-powered heaters will disperse theheat better than fewer high-powered heaters. Raychem recommends distributingthe heat over as much wall surface as is economically feasible. If you have anyquestions, contact your Raychem sales representative.

Metal Tanks

RHS-H series heaters are used for metal tanks. RHS-H heaters have a power den-sity of 1.9 watt/in2 at specified voltage with integrated thermostatic overtemperatureprotection.

The table below lists the RHS-H configurations available. To determine the numberof heaters required, divide the final-design heat loss for the tank by the heater'spower output as shown in the table.

Catalog Number Dimensions Voltage (Vac) Power Output (W)

RHS-H-500-1 14" x 24" 120 500RHS-H-1000-1 24" x 26" 120 1000RHS-H-1400-1 24" x 36" 120 1400RHS-H-500-2 14" x 24" 240 500RHS-H-1000-2 24" x 26" 240 1000RHS-H-1400-2 24" x 36" 240 1400

Polypropylene, FRP and Metal Tanks

RHS-L series heaters are for plastic or metal tanks. RHS-L heaters have a powerdensity of 0.6 watt/in2 at specified voltage with integrated thermostatic overtemper-ature protection. The following RHS-L configurations are available:

Catalog Number Dimensions Voltage (Vac) Power Output (W)

RHS-L-150-1 14" x 24" 120 150RHS-L-300-1 24" x 26" 120 300RHS-L-420-1 24" x 36" 120 420RHS-L-150-2 14" x 24" 240 150RHS-L-300-2 24" x 26" 240 300RHS-L-420-2 24" x 36" 240 420

Power Adjustment Factors

For all heaters with the -2 option, power output is calculated at 240 Vac. If thesource voltage is either 208 Vac or 277 Vac, the following power output correctionfactors should be used.

208 Vac: Power output factor = 0.75277 Vac: Power output factor = 1.33

15

RHS Tank Heater Dimensions

Dimensions (inches)

RHS Model A B C D E F

RHS-L-150-WRHS-H-500-W

14 24 4.875 8.875 4 5.125

RHS-L-300-WRHS-H-1000-W

24 26 9.95 13.75 4 5.125

RHS-L-420-WRHS-H-1400-W

24 36 9.75 13.75 4 5.125

A

B

D

C

F

E

16

Part III: Heater Design

Thermostatic Control of Tank Heaters

RHS Tank HeatersThermostatic control is required with RHS tank heaters.

There are two kinds of sensors for indicating temperature: “in-fluid” and “on-surface”sensors.

The “in-fluid” approach uses a thermowell protruding through the tank wall and intothe fluid. Control of the heater is achieved by using a solid-state control device thatreceives its input from an RTD inside the thermowell.

The “on-surface” approach uses bulb and capillary thermostats to control tankheaters by sensing temperatures on the outside surface of the tank wall. TheRaychem BCK-35 clamp kit is used to attach the bulb sensor to the wall. Also useAT-180 aluminum tape over the bulb. Primary thermostats should be located midwaybetween RHS heaters. If your application has high-heat-loss supports or acces-sories, place the primary thermostat midway between the RHS heater and the sup-port or accessory. The primary thermostat bulb should be placed horizontally on thetank.

RHS tank heaters have integrated, resettable thermostats that provide overtemperatureprotection in the event of a primary thermostat failure. The RHS integrated thermo-stat should not be used as the primary means of temperature control.

17

18

Location, Spacing, and Arrangement of Heaters

For vertical tanks, locate the heater on the lower one-third of the tank wall. Spiralself-regulating heating cables around the tank as indicated on Figure 3. Optimumspacing between spirals is 6 inches and minimum spacing is 3 inches. Use AT-180 to attach self-regulating heating cable to the tank. Arrange heaters on hor-izontal tanks and vertical cones as shown in Figures 4 and 5, respectively.

Figure 3: Vertical tanks with RHS (Figure A) and self-regulating heating cables(Figure B) heaters.

Figure 4: Horizontal tanks with RHS (Figure A) and self-regulating heating cables(Figure B) heaters.

Figure 5: Truncated cones with RHS (Figure A) and self-regulating heating cables(Figure B) heaters.

Questions

For more detailed answers to specific application problems, contact your localRaychem representative.

A B

A B

Primarythermostatbulb

Primarythermostatbulb

A B

Specifications/Approvals

RHS Tank Heaters

DescriptionThe RHS family of tank heaters consists of constant-wattage heating pads suitable forinstallation on metal and plastic tanks. The heaters come with power outputs up to1400 watts. Contact Raychem for customizing RHS heaters for special applications.

Voltage 120–277 VacWatt density 0.6 and 1.9 W/in2 at rated voltage.Corrosion resistance Stainless steel and silicone rubber construction T-ratings T2C (446°F/230°C) for -H series heaters

T4A (248°F/120°C) for -L series heatersMaximum exposure temperature 366°F (166°C)Maximum maintain temperature Up to 200°F (93°C) for -H series heaters

Up to 120°F (49°C) for -L series heaters

For use on metal tanks only

Power Voltage Nominal OverallCatalog Number Density (W/in 2) (Vac) Output (W) Dimensions

RHS-H-500-1 1.9 120 500 14" x 24"RHS-H-1000-1 1.9 120 1000 24" x 26"RHS-H-1400-1 1.9 120 1400 24" x 36"RHS-H-500-2 1.9 240 500 14" x 24"RHS-H-1000-2 1.9 240 1000 24" x 26"RHS-H-1400-2 1.9 240 1400 24" x 36"

For use on polypropylene, FRP, and metal tanks

Power Voltage Nominal OverallCatalog Number Density (W/in 2) (Vac) Output (W) Dimensions

RHS-L-150-1 0.6 120 150 14" x 24"RHS-L-300-1 0.6 120 300 24" x 26"RHS-L-420-1 0.6 120 420 24" x 36"RHS-L-150-2 0.6 240 150 14" x 24"RHS-L-300-2 0.6 240 300 24" x 26"RHS-L-420-2 0.6 240 420 24" x 36"

RHS Installation Kit

DescriptionThe RHS Installation Kit (P/N 844869) is FM Approved and CSA Certified for usewith RHS tank heaters. The RHS Installation Kit contains a caulking gun, two RTVadhesive tubes, a wedge, one 30-foot roll of AT-180 tape, and a trowel for mount-ing up to two RHS tank heaters.

Approvals

®F MAPPROVED

19

Ordinary and Hazardous Locations

Class I, Div. 2, Groups B, C, DClass II, Div. 1 & 2, Groups E, F, GClass IIIAll hazardous location applications must be engineered by Raychem.

T-ratings:Low-watt heaters: T4AHigh-watt heaters (Class I): T2CHigh-watt heaters (Class II & III): Contact Raychem

Design Worksheet

Tank Information

Tank reference

Maintenance temperature (°F/°C)

Minimum ambient temperature (°F/°C)

Maximum ambient temperature (°F/°C)

Max. heater exposure temp. (power off) (°F/°C)(must be less than 366°F (166°C)

Process maintenance (°F/°C)operating temperature (power off)

Start-up temperature (°F/°C)

Insulation type and thickness

Tank wall material ❏ Metal ❏ Plastic

Tank location ❏ Outdoors ❏ Indoors

Maximum circuit breaker load Amps

Supply voltage Vac

Chemical exposure ❏ None ❏ Mild inorganic ❏ Organic/corrosive

Tank location ❏ Indoors ❏ Outdoors

Required approvals ❏ FM ❏ CSA

Area classification ❏ Nonhazardous ❏ Hazardous

If hazardous:Class ____________ Div. ____________ Group ____________

Flammable substance(s) ____________

T-rating(s) ____________

Ignition temperature(s) ____________ (°F/°C)

____________ (°F/°C

20

21

Tank Top/Ends(Select one)

❏ Flat

❏ Half dome

❏ Full dome

❏ Cone

Tank Body(Select one)

❏ Vertical cylinder

❏ Horizontal cylinder

❏ Rectangular

❏ Spherical

Tank Bottom/Ends(Select one)

❏ Flat

❏ Half dome

❏ Truncated cone

❏ Truncated pyramid

Supports(Select one)

❏ Legs

❏ Open skirt

❏ Saddle

❏ Slab

Accessories(Select all that apply)

❏ ManholesInsulated sides: ❏ Yes ❏ NoInsulated top: ❏ Yes ❏ No

❏ HandholdsInsulated sides: ❏ Yes ❏ NoInsulated top: ❏ Yes ❏ No

❏ Ladders

❏ Hand rails

Height (ft/m)

Diameter (ft/m)

Diameter (ft/m)

Length (ft/m)

Diameter (ft/m)

Height (ft/m)

Height (ft/m)

Quantity

Quantity

Quantity

Quantity

Contact pts

Contact pts

Height (ft/m)

Length (ft/m)

Width (ft/m)

Diameter (ft/m)

Length (ft/m)

Cross sect. (in2/cm2)

Cross sect. (in2/cm2)

Cross sect. (in2/cm2)

Diameter (ft/m)

Diameter (ft/m)

Cross sect. (in2/cm2)

Cross sect. (in2/cm2)

Height (ft/m)

Width (ft/m)

Perimeter (in/cm)

Perimeter (in/cm)

Perimeter (in/cm)

Height (ft/m)

Height (ft/m)

Perimeter (in/cm)

Perimeter (in/cm)

Notes

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Chemelex, Raychem, and TankCalc are trademarks of Raychem Corporation.

All information, including illustrations, is believed to be reliable. Users, however, shouldindependently evaluate the suitability of each product for their application. Raychem makesno warranties as to the accuracy or completeness of the information, and disclaims any lia-bility regarding its use. Raychem’s only obligations are those in the Standard Terms andConditions of Sale for this product, and in no case will Raychem be liable for any incidental,indirect, or consequential damages arising from the sale, resale, use, or misuse of theproduct. Specifications are subject to change without notice. In addition, Raychem reservesthe right to make changes—without notification to the Buyer—to materials or processingthat do not affect compliance with any applicable specification.

Raychem CorporationChemelex DivisionIndustrial Products Group300 Constitution DriveMenlo Park, California 94025-1164Tel (800) 545-6258Fax (415) 361-6711

Raychem Canada, Ltd.6303 Airport Road, Ste 101Mississauga, OntarioCanada L4V 1R8Tel (800) 387-3993Tel (905) 671-1680Fax (905) 671-0972

Raychem S.A.I.C.Carlos Pellegrini 1363, Piso 81011 Capital FederalBuenos Aires, ArgentinaTel (54) 1/394-5150Fax (54) 1/326-9985