001 Front Cover

Metal Protection Tubes

Technical lnformation, Applications, and Suggestions

Illletal Protection Tubes'

Some General Suggestions For Effective Metal Protection Tube Use: / Carelully select the proper protection tube alloy for your process to maximize the service life.

{ tilse a thick walled tube, such as schedule 80, double extra heavy, or Richards heavy duty SP size for longer service life. { tlse a thin walled tube, such as schedule 40, or smaller O.D. tube, if you require a quicker temperature response time. / t tne protection tube will be subject to severe mechanical shock or abrasion, use the Richards heavy duty SP size. / Protection tubes should be inserted into fluids a minimum of six times the O.D. of the tube. / Protection tubes should be inserted into gases a minimum of eight times the O.D. of the tube. / lnsertion lengths for furnaces and salt baths are typically a minimum of 6" (152.4mm). / Protection tubes, which pass through a hot zone (muffle furnace), should be inserted at least 12" (304.8mm). / ln molten salt baths, angle assembly tube lengths should be a minimum of 18", to protect the elbow from level changes. / t tne elbow on angle assemblies will be subject to high temperatures, an all alloy bent type tube should be used. / neptace all metal protection tubes on a regular basis, since they will become become porous over time. / Never shorten the life of new thermocouple elements by placing them into old, worn-out, porous, protection tubes / Protection tube overall lengths should be long enough to insure that the head temperature will not exceed 400"For 2O4"C. { tlse large O.D. or thick walled protection tubes where sagging is a problem at elevated temperatures. / trlote that metal tubes are somewhat porous above 1500"F or 815"C, so in some cases a ceramic inner tube is also used.

Norninal Pipe Size Dimensions. t 1/8" .41 10.4 .27 .068 6.9

H

H lld

5.6

.22 .095

7.6

114"

.088

.30 119

.36

.54

9.1

13.,,7

]Fil m .55 .147 14.0 tEt .74 .154 18.8 FI .96 .179 24.4 .42 .126 14.7

3/9 "

12,4

.49

.68 1V.2

.091

11 .B 4'.7 4

6.4 7.37

.25 .29

.466

.187

.1 09

112"

.62

.84

21 .3

15i,.7

10.9 7,87

.614

5.53

.218

.43

15.6

314"

24.8

.31

.82 113

1.05

26,,7

E 3qt H E

l

9.14

1"

.250 20.7 6,35

.60 .36 15.2

.815

.1 33 26,7

33,5

1.05

1.32

1 114" 1 112"

22.8 9.65

.90 ,38

.250 29.5 6.35

1.28

1 .16

32.5

.140

.191

1 .38

35.1

1 .66

42,.2

27,9 10.16

34.0 7.13

1.10 .40

.200

1.34 .281

38.1

.145 40.9

1 .50

48.3

1 .90

1 .61

2"

1.69 d 2.13 .375 54.1 9.,52 1 .77 ,55 45.,0 13.97 .343 42.9 8.71 1.50 .44 38.1 11 ,18

.154

.218 49.3

1.94

52.6

2.38 60.3 2.07

2112"

.203

2.32 .276 59.0 lFt 2.90 .300 73.7 ffi 3.36 .318 85.4 @t 3.83 .337 97,2 s,56 |

62.7

2.88 73.0 2.47

58.4 15.24

2.30

66.5

3"

.60

11 ,12

2.62

77,9

.438

3.50 88.9 3.07 .216

3112"

69.3 16,26

2.73

.64

.226

3.55

4.00

90.1

101 .6

4"

87.4 13.48 3.15

.67 80.1

17.O2

3.44

4.03 .237 102.3

.531

4.50

1:14.3

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