PRESSURE VESSEL STATIC HEAD ADJUSTMENT ADVICE REQUIRED 1

[staticmh]

Hi Folk,

Good morning!

I want to know that how static head adjustment can be performed in calculation while we are performing the hydro test in vertical position and vessel to be erect in vertical position.


i'm designing a vessel which is being verified on UG-99(b) & UG-99(C) for both shop and site.
I got an comment from client on my calculation that " Since the Vessel orientation is vertical, Static head shall be adjusted in the test pressure during hydro testing at horizontal position"

My vessel data is below stated:

O.D = 610mm
Thickness shell = 12mm
Shell Length = 2550mm
Orientation = Vertical
Shop Test = Shall be Horizontally
Site Test = Shall be horizontally

Could any body please guide me that how to encounter the client comment. As i have been read the code ASME SEC III Div. 1 and states that, for vertical position static head shall be include in the test pressure value.

whereas, for horizontal vessel there shall not be any severe static head to be calculate and nor included.

Furthermore, please advice with your experience.

 

[saplanti]

Your client’s comment is very clear. You are the designer, the vessel is vertical in working condition, and the test is in horizontal. They are asking you to include vertical position static head to the test pressure while the vessel tested in horizontal. It seems to be the additional static head is 2.55 metres -if it is full of liquid and the static head does not exceed this value- (convert this to your selected unit in your design) which is very low but your calculation shall show it that you have considered in the test.

I hope the answer is clear for you.

 

[david339933]

Standard Designation: BPV Section VIII Div 1
Edition/Addenda:
Para./Fig./Table No:
Subject Description: Section VIII, Division 1 (1992 Edition, 1993 Addenda); UG-99(b)
Date Issued: 01/12/1995
Record Number: BC94-414
Interpretation Number : VIII-1-95-27
Question(s) and Reply(ies):
Question (1): Does the last sentence of UG-99(b) of Section VIII, Division 1, "All loadings that may exist during this test shall be given consideration," require that the static head that exists in a tower in the vertical position must be considered when determining the test pressure in the horizontal position?

Reply (1): No.

Question (2): Does UG-99 specify in which position a vertical tower must be hydrotested?

Reply (2): No.

 

[staticmh]

@saplanti, Thank you very much for your reply.

I understand your all explanation, but as per my understanding the vessel static head shall be only act when it shall be hydro test in vertical position or while operating. then we have to look that what additional value of static head is calculating and whether it is taking during test pressure value calculation or not.

Whereas the hydro test position of this vessel is horizontal and the static head shall not be effect the pressure because of its lower head value i.e. let say O.D is 610mm and i assume that the vessel is full of liquid in horizontal position and maximum height of liquid during hydro test is 586mm.

so the static head pressure value shall be calculated as per below show:

p = rho * g* h
= 1000 * 9.81 * 0.585
= 5.73 Kpa

Now what to do this value ? please advice?

 

[saplanti]

The hydrostatic head effect is very insignificant for the hydrotest. In case very high vertical colums there may be some influence.

As David commented the code interpretation does not require this addition since they see the insignificance. However you may please them by showing that in your calculation, but the pressure indicator will may not see the value at all.

Sometimes you just please your client on some insignificant numbers instead of loosing your valuable time by discussing on the issue.

 

[staticmh]

Saplanti,

Thank you very much for your kind words.