Intermediate Calculations for Tubesheets Extended as Flange:
Two major additions to the tubesheet calculations occur when a tubesheet is extended as a flange. First, a moment is added to the pressure moment, which governs the thickness of most tubesheets. Second, a moment exists on the portion of the tubesheet, which serves as the flange, and the effects of this moment must be evaluated. The TEMA standard requires that these conditions be evaluated using the rules in the ASME Code, Appendix 2. Those rules, in turn, require the complete evaluation of bending moments on the flange. It is those bending moment calculations, which are reflected in this section of the output. The flange design rules in PD 5500 are also very similar to the ASME Appendix 2 rules.
These calculations represent the basic bolt loading for the flanged portion of the tubesheet, and will be the same for the mating flange. The actual bending moments may change when compared to the mating flange. The flanged extension of the tubesheet is calculated as a ring type flange. Since no stresses are shown, you need to check the adequacy of the bolting by comparing the required bolt area to the actual bolt area. The bolt spacing correction factor is automatically included in the bending moment, such that the moment is the force times the distance times the bolt correction.
Geometric Constants, Pressure and Thickness Calculations:
The tube diameter, pitch, and pattern are used to calculate the term 'eta' in the tubesheet thickness equation. These rules are same for triangular, rotated triangular, square, and rotated square layouts. When a tubesheet may be controlled by shear stress, the program requires the perimeter and area of the tubesheet for the shear calculation. You will receive an error message when these values are required but not given. The result will be conservative if you overestimate the area and underestimate the perimeter.
The G dimension is calculated based on the exchanger type and either the diameter of the pressure component or the mean diameter of the gasket. TEMA standard states that for all the floating tubesheet (except divided), the G shall be the G used for the stationary tubesheet. The T type floating tubesheet should also be checked with actual gasket G of the floating tubesheet. In these cases, user can enter the G dimension of the stationary tubesheet.
Similarly, the F dimension is calculated based on the exchanger type and the type of connection to the shell and channel. These calculations are based on Table RCB-7.132 and Table RCB-7.133.
Differential Expansion Pressure:
The program contains tables of Young's modulus and the coefficient of thermal expansion. It selects these values from the tables based on the materials classification you enter on the material editing screen of the input spreadsheet. You should verify that the program has selected the right identification number for the material. You should also check the values to ensure that they agree with your expectations. A good place to find this data, and the source of these tables in the program, is the TEMA Standard, tables D-10 and D-11. The following table displays the program identification numbers for the materials in this standard:
Chart Number |
Cross Ref. to Elastic Chart |
|
---|---|---|
1 |
3 |
TE-1 : Carbon and Low Alloy Steels |
2 |
4 |
B31.3 : 5Cr - 9Cr |
3 |
6 |
B31.3 : 18Cr - 8Ni |
4 |
6 |
TE-1 : 27Cr |
5 |
6 |
B31.3 : 25Cr20Ni |
6 |
8 |
B31.3 : 67Ni30Cu |
7 |
1 |
B31.3 : 3.5Ni |
8 |
10 |
B31.3 : Aluminum |
9 |
7 |
B31.3 : Cast Iron |
10 |
13 |
B31.3 : Bronze |
11 |
12 |
B31.3 : Brass |
12 |
9 |
B31.3 : 70 Cu - 30Ni |
13 |
6 |
B31.3 : Ni - Fe - Cr |
14 |
6 |
B31.3 : Ni - Cr - Fe |
15 |
7 |
B31.3 : Ductile Iron |
16 |
14 |
TEMA : Plain Carbon Stl & C - Mn Stl. |
17 |
14 |
TEMA : C - Si, C - 1/2Mo & Cr - 1/2Mo |
18 |
14 |
TEMA : C - Mn - Si, 1-1/4Cr - 1/2Mo & 3Cr - 1Mo |
19 |
14 |
TEMA : Mn - Mo |
20 |
20 |
TEMA : 2 - 1/2 & 3 - 1/2Ni |
21 |
17 |
TEMA : 2 - 1/4Cr - 1Mo |
22 |
18 |
TEMA : 5Cr - 1/2Mo |
23 |
18 |
TEMA : 7Cr - 1/2Mo & 9Cr - 1Mo |
24 |
19 |
TEMA : 12Cr & 13Cr |
25 |
19 |
TEMA : 15Cr & 17 Cr |
26 |
15 |
TEMA : TP316 & TP317 |
27 |
15 |
TEMA : TP304 |
28 |
15 |
TEMA : TP321 |
29 |
15 |
TEMA : TP347 |
30 |
15 |
TEMA : 25 Cr-12Ni, 23 Cr-12Ni, 25Cr-20Ni |
31 |
23 |
TEMA : Aluminum 3003 |
32 |
23 |
TEMA : Aluminum 6061 |
33 |
32 |
TEMA : Titanium, Grades 1, 2, 3, 7 |
34 |
21 |
TEMA : Ni-Cu (Alloy 400) |
35 |
24 |
TEMA : Ni - Cr - Cr - Fe (Alloy 600) |
36 |
25 |
TEMA : Ni - Fe - Cr (Alloy 800 & 800H) |
37 |
35 |
TEMA : Ni - Fe - Cr - Mo - Cu (Alloy 825) |
38 |
34 |
TEMA : Ni - Mo (Alloy B) |
39 |
27 |
TEMA : Ni - Mo-Cr (Alloy 276) |
40 |
28 |
TEMA : Nickel (Alloy 200) |
41 |
33 |
TEMA : 70-30 Cu - Ni |
42 |
22 |
TEMA : 90 - 10 & 80 - 20 Cu - Ni |
43 |
29 |
TEMA : Copper |
44 |
30 |
TEMA : Brass |
45 |
29 |
TEMA : Aluminum Bronze |
46 |
29 |
TEMA : Copper - Silicon |
47 |
31 |
TEMA : Admiralty |
48 |
37 |
TEMA : Zirconium |
49 |
15 |
TEMA : Cr - Ni - Fe - Mo - Cu - Cb (Alloy 20Cb) |
50 |
38 |
TEMA : Ni - Cr -Mo - Cb (Alloy 625) |
51 |
39 |
TEMA : Tantalum |
52 |
40 |
TEMA : Tantalum with 2.5% Tungsten |
53 |
43 |
TEMA : 17 - 19 CR ( TP 439 ) |
54 |
44 |
TEMA : AL-6XN |
55 |
47 |
TEMA : 2205 (S311803) |
56 |
48 |
TEMA : 3RE60 (S31500) |
57 |
41 |
TEMA : 7 MO (S32900) |
58 |
42 |
TEMA : 7 MO PLUS (S32950) |
59 |
45 |
TEMA : AL 29-4-2 |
60 |
46 |
TEMA : SEA-CURE |
61 |
16 |
TEMA : C-Si, C-1/2 Mo & Cr- 1/2Mo |
62 |
16 |
TEMA : C-Mn-Si, 1-1/4Cr-1/2Mo & 3 CR - 1Mo |
63 |
17 |
TEMA : C-Mn-Si 1-1/4Cr-1/2Mo & 3 CR - 1Mo |
When PD 5500 is selected, then the material band is mapped to nearest TEMA number, which is then used to look up the Young's modulus and the coefficient of thermal expansion. This is necessary since PD 5500 does not provide tables of thermal expansion versus temperature.
When a fixed tubesheet is analyzed, the program calculates the following information:
-
The minimum tubesheet thickness per RCB-7.131.
-
The values G, F, and ETA per RCB-7.132 and RCB-7.133
-
The equivalent differential expansion pressure per RCB-7.161
-
The equivalent bolting pressure per RCB-7.162
-
The effective shell side design pressure per RCB-7.163
-
The effective tube side design pressure per RCB-7.164
-
The required thickness per RCB-7.132 or RCB-7.133
-
The shell longitudinal stress per RCB-7.22
-
The tube longitudinal stress per RCB-7.23
-
The allowable tube compressive stress per RCB-7.24
-
The tube to tubesheet joint loads per RCB-7.25
If the tube or shell longitudinal stresses are being exceeded, it can be caused by the differential thermal expansion between the tubes and the shell. For example, when a tube is under compressive stress and the shell is under tensile stress, this indicates that the tube is trying to expand more than the shell. In this case an expansion joint can be used to relieve this axial stress. You can either put a thin expansion joint by checking the appropriate box (designed using the Thin Joint module) or a thick expansion joint (which can be designed the Tubesheet module or the Thick Joint module).
Display of Results on Status Bar
As the user enters the data, program performs the calculation and displays the important results on the status bar. Any error messages are also displayed. This allows a quick design of the tubesheet and makes it easier to try various configurations to select the best one. Any failures are indicated in red. Here is a sample:
-
Design a Thick Expansion Joint in the Tubesheet Module
After you input the thick expansion joint geometry in the Tubesheet module, the program uses the following process to design the expansion joint:
-
Compute the expansion joint spring rate
-
Use the expansion joint spring rate in the fixed tubesheet calculations
-
Use the results of the tubesheet calculation, along with the prime pressures (P’s, P’t, Pd) to compute the expansion joint stresses.
-
Run a corresponding expansion joint calculation for each tubesheet load case. The program displays the results for the worst case. (detailed results are also available).
-
The procedure followed when designing PD 5500 tubesheets is similar to the one shown here.
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The software can also perform finite element analysis (FEA) on certain thick expansion joint properties. For more information, see Finite Element Analysis (FEA) and ASME or TEMA Expansion Joints.
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