API 650 DOUBT: HIDROSTATIC TEST. 5

[PINOLERO]

Hi Everybody:
Could anyone help me with the following doubt?:
We just finished to build a 5,000m3 API 650 tank. We are planning the hydrostatic test, however, we are not installed the firefighting pipeline which will be supported on the tank shell. We neither installed the datum plate at bottom of the tank. Can we do the hydrostatic test even though we are going to do further welding jobs at the tank shell and bottom after this test?.
Thank in advance for your help
Best Regards,

 

[Eddycurrentguy]

You COULD (if you wanted to) hydrotest before completion, but you would not be in compliance with several sections... Not withstanding that, the integrity of the completed unit would not be demonstrated.



S.4.14.2 Inspection of Welds by Liquid Penetrant Method
The following component welds shall be examined by the liquid penetrant method before the hydrostatic test of the tank:
a. The shell-to-bottom inside attachment weld.
b. All welds of opening connections in tank shell that are not completely radiographed, including nozzle and manhole neck welds
and neck-to-flange welds.
c. All welds of attachments to shells, such as stiffeners, compression rings, clips, and other nonpressure parts for which the thickness
of both parts joined is greater than 19 mm (3/4 in.).
d. All butt-welded joints in tank annular plates on which backing strips are to remain.

 

[PINOLERO]

Eddy:
Thanks you for your soon response.
The support for the water pipeline will be installed at the exterior of the tank's shell. Do you think S.4.14.2 C applied in this case considering that the pipeline is not part of the tank?
What is your opinion if we do the hydrostatic test and then we install a datum plate at the bottom of the tank and we performed a liquid penetrant test for this welding?
Best Regards,

 

[IFRs]

Eddy - please clarify where API prohibits this. Your reference of S.14.2.1 is for Stainless tanks - the OP did not say his was stainless.

 

[Kiwi2671]

Pinolero,
Hydrotest must be done before external piping is attached.

5.3.5 Testing of the Shell
After the entire tank is completed but before any permanent
external piping is connected to the tank, the shell (except
for the shell of tanks designed in accordance with Appendix
F) shall be tested by one of the following methods:

a. If water is available for testing the shell, the tank shall be
filled with water as follows: (1) to the maximum design liquid
level, H; (2) for a tank with a tight roof, to 50 mm (2 in.)
above the weld connecting the roof plate or compression bar
to the top angle or shell; or (3) to a level lower than that specified
in subitem 1 or 2 when restricted by overflows, an
internal floating roof, or other freeboard by agreement
between the purchaser and the manufacturer. The tank shall
be inspected frequently during the filling operation, and any
welded joints above the test-water level shall be examined in
accordance with item b.
b. If sufficient water to fill the tank is not available, the tank
may be tested by (1) painting all of the joints on the inside
with a highly penetrating oil, such as automobile spring oil,
and carefully examining the outside of the joints for leakage;

The only exemption is if you have a tank manufactured in accordance with Appendix F
Regards,
Kiwi

 

[IFRs]

Kiwi - As I read that section, I think it is intended to address piping that is bolted to tank flanges that may stress when the tank settles. There is no prohibition against piping that is simply resting on supports where the supports are attached to the shell as long as the piping is not connected to piping not on the shell.

Pinolero - please clarify if this is an Appendix S or F tank.

 

[PINOLERO]

Hi everybody:

The tank is a iron steel tank, so it is not an appendix S tank. The tank is 10 meters high by 25 meter of diameter, therefore I do not believe belong to appendix F (correct me if I am wrong).

The pipeline to attach on the tanks is outside and will use the tank shell just as support to later (after the hydraulic test is performed) connect it with the foam chamber of the tank.

My concern is that the pipeline support will be welded to the tank and this (pipeline of 4 inches full of water) could produce stress in the metal sheet of the tank and its welding and if there is a failure you won't detected since you already performed the hydrostatic test. Do I have reason to be concerned?

Thank you for your help.

 

[IFRs]

The size of the tank does not determine if it is an Appendix F tank - the internal pressure does. Does the internal pressure make it an Appendix F tank? With a properly designed series of supports you should not have any issues with stress. Still, you and the owner should agree to this.

 

[PINOLERO]

Thank you IFRs. Yes, the tank is an appendix F tanks.
I am grateful for your help.
Best Regards,

 

[TANKO]

you have not to weld anything on the shell after hydrotest.

 

[PINOLERO]

Hi Tanko: Thank you for your response. Why do do you say that? This is a external welding?. Something in the code that prohibits this?
Thank you.

 

[TANKO]

We built many tanks according to API 650 & EN....I don t remeber which part of the code...but it is not possible to weld a support directly on the shell, bottom (both external and internal) after hydrotest...You can weld above another additional plate on the shell but you can not weld directly on the shell otherwise you have to do another time the hydrotest.

 

[Duwe6]

Tanko has given you the 'elegant' answer. Attache the necessary pipe supports now, and run the pipe later. If the pipe people cannout give you the support design, apply reinforcing pads [now] to receive the supports later. Welding on a repad after hydro is 'legal', but welding to the pressure boundary is not.

 

[PINOLERO]

Thank you Duwe6. Good recommendation.
Best Regards,