Tube to tubesheet leakage in shell & tube heat exchangers

[amitss_sam]

Following is the worst thing I faced last month in one Solvent extraction plant.
There is one shell & tube heat exchanger (tubeside vegetable oil & shellside is steam @ 3 barg at operating condition). We hydrotested this vessel at 6 barg. This vessel is designed for 4 barg pressure both sides. For tubes to tubesheet joint, we done expansion of tubes which we do regularly. Tube material is SA249 TP304 ERW schedule 40, size: 1 1/2" OD (38mm). After 20 days of plant working, there is leakage from this tube to tubesheet joint. I am trying to figure out the reason why this happen.
Please note that there is no seal welding.

[aseptman]

Dear amitss
At the given pressure conditions there is no issue with Expanded only T-TS joint.
What are your temperature conditions? Was the exchanger fixed tubesheet one like AEM or BEM ?
If the diff in shell and tube ave temperatures is more may be thermal expansion is culprite?

[duazo2009]

Following is the worst thing I faced last month in one Solvent extraction plant.
There is one shell & tube heat exchanger (tubeside vegetable oil & shellside is steam @ 3 barg at operating condition). We hydrotested this vessel at 6 barg. This vessel is designed for 4 barg pressure both sides. For tubes to tubesheet joint, we done expansion of tubes which we do regularly. Tube material is SA249 TP304 ERW schedule 40, size: 1 1/2" OD (38mm). After 20 days of plant working, there is leakage from this tube to tubesheet joint. I am trying to figure out the reason why this happen.
Please note that there is no seal welding.

Amits _sam

what type of joint you’ve used; it is expanded and enhanced with two or more grooves, expanded and enhanced with single groove or it was expanded but not enhanced. Either any of these joint type, have you calculated and determine the tube to tubesheet joint load in the periphery of bundle at Operating and hydrotest conditions?

The maximum effective tube-to-tubesheet joint load is calculated per TEMA RCB-7.25, and the maximum axial load is determined per ASME VIII-1 Appendix A-2. As TEMA RCB-7.25 only considers the tubes at the periphery of the bundle, the assumption is made that the peripheral tubes are the most highly stressed. For certain conditions of loading and/or geometry, additional consideration of the tube stress distribution throughout the tube bundle may be warranted (see TEMA RGP-RCB-7 for additional information).

Cheers,

duazo2009

[amitss_sam]

there i kept 2 grooves inside every hole. Groove depth is 0.8mm. tubeside temperature was 90 degree 7 shell side is steam @ 3 barg. Total there are 89 tubes. Out of them 12 tubes leakage happened which are at centre of tube bundle. This is fixed tubesheet type heat exchanger. What u mean by enhanced ? I didnt done any calculation for strength.

[duazo2009]

there i kept 2 grooves inside every hole. Groove depth is 0.8mm. tubeside temperature was 90 degree 7 shell side is steam @ 3 barg. Total there are 89 tubes. Out of them 12 tubes leakage happened which are at centre of tube bundle. This is fixed tubesheet type heat exchanger. What u mean by enhanced ? I didnt done any calculation for strength.

Amitss_sam

Please refer this sample calculation which is similar:

TEMA RCB-7.25 Tube To Tubesheet Joint Loads - Periphery Of Bundle, New
Equations used Wj = pi*Fq*Pt**G2/(4*N) Fq is from RCB-7.161 (8th Ed)

Pt* = P2 P2 and P3 are from RCB-7.23
(TEMA 8th Ed)
Pt* = -P3
Pt* = P2 - P3
Lmax = At*Sa*fe*fr*fy*fT, where fT = (Po + PT)/Po Lmax is the allowable load from ASME VIII-1, Apendix A-2
Joint Type k, expanded, not enhanced
Operating

Wj > Lmax indicates that the joint strength is not adequate for the New condition. Wj = pi*4.228*108.9495*552/(4*2,331.00) = 469.4972 lb
Interface pressure Po not specified; ft = 1 assumed.
Lmax = 0.0786*9,500*0.042*0.6*1*1 = 18.82123 lb fy = SyTS/SyTube = 33,000/22,500 = 1.4667, fy = 1
Tube side hydrotest

Wj <= Lmax indicates the joint strength is adequate for the New condition. Wj = pi*4.2492*6.9554*552/(4*2,331.00) = 30.12293 lb
Interface pressure Po not specified; ft = 1 assumed.
Lmax = 0.0786*36,000*0.042*0.6*0.95*1 = 67.75644 lb fy = SyTS/SyTube = 38,000/40,000 = 0.95
Shell side hydrotest

Wj <= Lmax indicates the joint strength is adequate for the New condition. Wj = pi*4.2492*0.8642*552/(4*2,331.00) = 3.742685 lb
Interface pressure Po not specified; ft = 1 assumed.
Lmax = 0.0786*36,000*0.042*0.6*0.95*1 = 67.75644 lb fy = SyTS/SyTube = 38,000/40,000 = 0.95

Note: An expanded joint is a produced by applying an expansion force inside the portion of the tube to be engaged in the tubesheet. The design temperature for an expanded joint should not in the creep range (i.e. time-dependent) for the selected tubesheet or tube material. The maximum operating temperature should be limited such that the interface pressure due to expanding the tube at joint fabrication plus the interface pressure due to differential thermal expansion does not exceed 58 percent of the smaller of the tube or tubesheet yield strength as listed in ASME Section II, Part D, Table Y-2 for the operating temperature,. Expanded Length - Enter the length of the expanded portion of the tube for tube-to-tubesheet joint types (k) and (h). For TEMA exchanger designs, see TEMA RCB-7.5 for specific requirements regarding minimum expansion lengths.
Factor fr - Input the joint efficiency factor for the tube-to-tubesheet joint determined per test results in accordance with ASME VIII-1Appendix A-4 or Table A-4. The joint efficiency factor should be less than 1.0.
Interface Pressure Po - Interface pressure between the tube and tubesheet that remains after expanding the tube at fabrication. This input must be greater than or equal to zero. The combination of tube and tubesheet material used has a pronounced affect on the interface pressure Po. A method for calculating the residual contact pressure is outlined in Mechanical Design Of Heat Exchangers And Pressure Vessel Components by Singh and Soler in section 7.8.
Interface Pressure PT - Interface pressure between the tube and tubesheet due to differential thermal growth. This input can be any number (negative, positive or zero).

[amitss_sam]

thnka duazo. i will check this.

[Mikepehli]

pls
ERW electrical resistance tubes? the tube welded seam joint ? Sounds peculiar for S&T heater. Can you recheck the tube spec?
I would never used ERW pipes for rolling expansion due to the seam weld HAZ and metal hardening
I would look as first step if the tube is the correct one
Specify how did you expand the tubes?
How did you measure the expansion?
How many times did you expand these tubes?
Metal relaxation?
Metal cold work hardened, the tube issue?
The tube joint to tube sheet is the correct one? can you review and answer your findings.
m