Straight Tubular Elements

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Straight Tubular Elements

Tubular heaters can be formed into virtually any shape, brazed or welded to any metal surface, and cast into metals.

The tubular heater's basic construction consists of a computer-designed helical coil of 80% Nickel 20% Chromium alloy resistance wire fusion welded to the nickel-coated steel terminal cold pins. This assembly is precisely stretched and centered in the element metal sheath, which is then filled with Grade "A" Magnesium Oxide powder (MgO). The filled tube is then compacted by a roll reduction mill into a solid mass, permanently stabilizing the coil in the center of the tube while providing excellent heat transfer and dielectric strength between the coil and the sheath.
 
 

 
Standard Sheath Materials

 

The selection of a sheath material should be made based on the the chemical composition of the solution being heated, character of materials entering the solution, and the processes controls. The following are the most common tubular element sheath materials. For other materials consult Proheat.

Note: Maximum sheath temperatures refer to the maximum temperature of the element sheath material. Consideration must be given to maximum temperature and watt density the heated material can safely see.

Incoloy® 800   A Nickel (30-35%), Chromium (19-23%), Iron Alloy. The high nickel content of this alloy contributes to its resistance to scaling and corrosion. Used in air heating (also see Incoloy® 840) and immersion heating of potable water and other liquids.
Maximum sheath temperature is 1600°F (872°C).

316 Stainless Steel   A Chromium (16-18%), Nickel (11-14%), Iron Alloy with Molybdenum (2-3%) added to improve corrosion resistance in certain environments, especially those which would tend to cause pitting due to the presence of chlorides. Applications include deionized water.
Maximum sheath temperature is 1200°F (649°C).

Incoloy® 840   A Nickel (18-20%), Chromium (18-22%), Iron Alloy having about 10% less nickel than Incoloy 800. Used in many air heating applications where it has exhibited superior oxidation resistance at less cost.
Maximum sheath temperature is 1600°F (872°C).

Copper   Mainly used in clean water heating for washrooms, showers, rinse tanks and freeze protection of storage tanks.
Maximum sheath temperature is 350°F (177°C).

304 Stainless Steel   A Chromium (18-20%), Nickel (8-11%), Iron Alloy used in the food industry, sterilizing solutions, and many organic and inorganic chemicals.
Maximum sheath temperature is 1200°F (649°C).

Low Carbon Steel   Applications include fluid heat transfer media, tar, high to low viscosity petroleum oils, asphalt, wax, molten salt, and other solutions not corrosive to a steel sheath. 
Maximum sheath temperature is 750°F (399°C).

321 Stainless Steel   A Chromium (17-20%), Nickel (9-13%), Iron Alloy modified with the addition of titanium to prevent carbide precipitation and resulting intergranular corrosion that can take place in certain mediums when operating in the 800-1200°F (427-649°C) temperature range.
Maximum sheath temperature is 1200°F (649°C).


Electrical Limitations and Minimum/Maximum Sheath Lengths

 


Element
Diameter

Maximum
Voltage

Maximum
Amperage

Resistance in Ohms
per Heated Inch

Sheath Length

       
min
max

in

Mm

min

max

in

mm

in

mm

0.26

 6.6

250

15

0.1

17

11

279

200

5080

0.315

 8.0

480

30

0.06

21

11

279

200

5080

0.375

 9.5

480

30

0.04

21

11

279

230

5842

0.43

10.9

600

40

0.04

21

11

279

268

6807

0.475

12

600

40

0.04

21

11

279

275

6985

0.625

15.9

600

40

0.04

17

11

279

255

6475


Sheath and Heated Length Tolerance (applicable for all diameters)

 

 

Length

Sheath Length
Tolerance

Heated Length
Tolerance

Minimum Unheated
Length Each End

in

mm

in

mm

in

mm

in

mm

11-20

279-508

±3/32

 2

±1/4

 6

1

25

21-50

509-1270

±1/8

 3

±1/2

13

1-1/4

32

51-80

1271-2032

±5/32

 4

±7/8

22

1-1/2

38

81-110

2033-2794

±3/16

 5

±1-1/8

29

1-5/8

42

111-140

2795-3556

±7/32

 6

±1-3/8

35

1-3/4

44

141-170

3557-4318

±1/4

 6

±1-5/8

41

2

51

171-200

4319-5080

±3/8

10

±1-7/8

48

2-1/4

57

201-UP

5081-up

±1/2

13

±2-3/8

60

2-1/2

64


Mounting Methods

 


Type MC- Mounting Collar

Plated steel mounting collars are locked in place with a set-screw and serve as an adjustable stop for through the wall mounting. Collars are shipped in bulk unless otherwise specified.

Element
Diameter

"A"

"B"

in

mm

in

mm

in

mm

0.26

 6.6

5/16

7.1

5/8

15.9

0.315

 8.0

3/8

8.7

3/4

19

0.375

 9.5

7/16

11.1

7/8

22.2

0.43

10.9

7/16

11.1

7/8

22.2

0.475

12

7/16

11.1

1

25.4

Type LR --Locator Ring

Locator rings are permanently attached to the heater sheath and are used to limit the movement of the heater while allowing for expansion and contraction of the heater sheath. When ordering specify location from end of sheath.

Type MF --Mounting Bracket

The 16 gauge Stainless Steel Mounting bracket is an economical way to mount the heater in non-pressurized, non liquid applications. Unless otherwise specified the bracket will be located 1/2" (13 mm) from the edge of the heater sheath. Custom brackets of any size, thickness and material can also be supplied to meet your requirements.

 

Type B --Watertight Bulkhead Fittings

Bulkhead fittings provide a leak-proof method for mounting tubular heating elements through tank walls. A gasket, plated steel washer and brass hex jam nuts are included. Specify if a stainless steel washer and jam nut are required when ordering stainless steel fittings. Standard mounting location is the threaded end of the bulkhead flush with the end of the element sheath. For other mounting locations specify distance from end of sheath to gasket surface on bulkhead. Fittings are silver brazed or TIG welded to the element, depending on fitting material and customer application. Fittings in table are the most commonly used. Special fittings can be manufactured to meet your requirements. Specify: material, flange type, thread type and length.

Tubular
Diameter

Fitting
Material

Flange
Type

"A"

"B"

"C"

Thread Size (UNF)

in
mm
   
in
mm
in
mm
in
mm
 

0.26

 6.6

Brass

Round

3/4

19

1/2

12.7

5/8

16

1/2-20

0.26

 6.6

Stn. Stl.

Round

3/4

19

1/2

12.7

5/8

16

1/2-20

0.315

 8.0

Brass

Round

3/4

19

1/2

12.7

5/8

16

1/2-20

0.315

 8.0

Stn. Stl.

Round

3/4

19

1/2

12.7

5/8

16

1/2-20

0.375

 9.5

Brass

Round

3/4

19

1/2

12.7

5/8

16

1/2-20

0.375

 9.5

Stn. Stl.

Round

3/4

19

1/2

12.7

5/8

16

1¼2-20

0.43

10.9

Brass

Round or Hex

7/8

22

3/4

19

7/8

22

5/8-18

0.43

10.9

Stn. Stl.

Round or Hex

7/8

22

3/4

19

7/8

22

5/8-18

0.43

10.9

Steel

Round

7/8

22

3/4

19

7/8

22

5/8-18

0.475

12.1

Brass

Round

7/8

22

3/4

19

7/8

22

5/8-18

0.475

12.1

Stn. Stl.

Round

7/8

22

3/4

19

7/8

22

5/8-18

0.475

12.1

Steel

Round

7/8

22

3/4

19

7/8

22

5/8-18

0.475

12.1

Brass

Round

1

25

3/4

19

7/8

22

3/4-16

0.475

12.1

Stn. Stl.

Round

1

25

3/4

19

7/8

22

3/4-16

0.625

15.9

Stn. Stl.

Round

1-1/8

32

3/4

19

1

25

7/8-14