Thermowells

Product and Ordering Information

Nomograph

The Nomograph and Table 4 below may be applied in calculating wall thickness. The following example demonstrates the use of the nomograph in a typical problem situation.

Problem: To find maximum operating pressure of a thermowell, 304 stainless steel material, with a .385 inch bore and .750 minimum outside diameter whose maximum operating temperature will be 700°F.

Solution: Maximum allowable stress (Table 4) 10,500 PSI.Wall thickness (Min.) = .182.
A) Align 10,500 on right scale with .182 on wall thickness scale and mark intersection on pivot line.
B) Align pivot point intersection with correct outside diameter.
C) Read maximum pressure on left scale (5100 PSIG).

Table 4 - Allowable Stress Values (PSI)1

Material Temperature °F
0 300 500 700 900 1100 1300
Aluminum (1100)
Aluminum (6061-T6)
Nickel
Steel2
304 S. Stl.
316 S. Stl.
310 S. StI .
321 - 347 S. Stl.
410 S. StI .
446 S. Stl.
A182-F11
A182-F22
Copper
Admiralty Brass
Monel 400
Inconel 600
Incoloy 8003
Hastelloy B4
Hastelloy X5
2,350
6,000
10,000
11,250 
18,750
18,750
18,750
18,750
15,000
17,500
16,150
17,500
6,000
10,000
16,600
20,000
15,600
25,000 
23,350 
1,850
5,000
10,000
11,000 
13,750
16,400
14,600
15,300
13,800
16,100
16,150
17,500
5,000
10,000
13,600
18,800
12,100
24,750 
18,850 
-
-
9,500
10,250 
11,400
15,500
12,600
13,500
12,850
15,000
16,150
17,500
-
-
13,100
18,500
10,400
21,450 
16,000 
-
-
-
9,000 
10,500
15,100
11,300
12,200
12,050
-
16,150
17,500
-
-
13,100
18,500
9,600
- 
15,500 
-
-
-
7,750 
10,000
11,650
10,300
11,300
9,650
-
13,100
14,000
-
-
8,000
16,000
9,100
- 
15,500 
-
-
-
6,500 
8,250
8,500
9,450
9,100
2,900
-
4,000
4,200
-
-
-
3,000
8,800
- 
15,500 
-
-
-
- 
3,400
3,500
4,000
2,200
-
-
-
-
-
-
-
-
4,150
- 
9,500 
  1. Values from ASME Boiler and Pressure Vessel Code Section VlIl - Unfired Pressure Vessels,1965.
  2. ASME Spec. Min. Tensile = 45,000 PSI
  3. ASME Code (See Note 1), Case 1325 (special ruling)
  4. ASME Code (See Note 1), Case 1323 (special ruling)
  5. ASME Code (See Note 1), Case 1321 (special ruling)