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MAWP VS Hydrostatic Test

08/18/2009 3:56 AM

My pipeline is pipe 16", API 5L Gr.X52. thickness 9,53mm

Design pressure is 1450 Psi.

The pipe was successfully conducted factory hydrostatic test for 5 second with test pressure 2000 Psi.

I was calculated if the MAWP is 1755 Psi.

Could i perform pipeline hydrostatic test with pressure 1,25 x DP = 1850 Psi?

Is it will failure?

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#1

Re: MAWP VS Hydrostatic Test

08/18/2009 4:32 AM

Why 1850 instead of 1755 if the design pressure is 1450psi? Why not 1755psi?

What is in the pipe at the design pressure?

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#2

Re: MAWP VS Hydrostatic Test

08/18/2009 5:59 AM

Well..

If your MAWP is 1755 psi, you will not be able to perform hydrostatic test more than the value of MAWP that you have specified.

You told us that the factory (supplier) of yours could perform the hydrostatic test up to 2000 psi. BUT REMEMBER, it is only for 5 second!!

You need to give restriction or lets say the critical pressure point for your pipe. And the critical point itself is MAWP.

Please recalculate your pipe thickness if your MAWP < Test Pressure.

Where is the country of origin of your pipe manufacturer?

Hope this helps. Please correct me if i am wrong.

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#3

Re: MAWP VS Hydrostatic Test

08/18/2009 10:01 AM

Give few more details like what is the design temperature and what is hydro test temperature and as per which code your pipe line is supposed to be designed , So that I can understand your case and help you better way

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#4

Re: MAWP VS Hydrostatic Test

08/18/2009 10:15 PM

The temperature test & design is 30 and 38 oC

We use code ANSI B31.4

We have to perform hydrostatic test in 1,25 x DP =1850 Psi, based on para. 437.4.

Because of hydrostatic test pressure is greater than MAWP, what is the pipeline must be fail?

There is a restriction on test pressure must be less than MAWP?

I think, why the pipe cauld withstand in factory test pressure (2000 Psi) is the Ultimate strength of the pipe is higher than 2000 Psi.. if we see the strength-strain curve, there no influence of time

Best hope, the problem can be solved perfectly

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#5

Re: MAWP VS Hydrostatic Test

08/19/2009 2:03 AM

Good Morning AvatarIndo:

1. Factory Hydro Test according to API 5L is in correspondance with the material Yeild Point, Thickness and Diameter. Chek in this code tables if the factoty Hydro Test was Right.

2. Pipe line construction API 1104 1,5xDP 2205psi

3. Operation MAWP have no correspondance with points 1 and 2

Then, if the factory test was right, you need to review Cals. and possible you bought wrong size or wrong material pipe.

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Guru
Engineering Fields - Piping Design Engineering - New Member Egypt - Member - Member since 02/18/2007

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#6

Re: MAWP VS Hydrostatic Test

08/19/2009 3:13 AM

We have to differentiate between mill hydrostatic test (carried out at mill for single segment(s) of pipe) and hydrostatic test for whole loop(s) of piping system after complete fabrication and erection.

The ASME code B31 covers the hydrostatic test after fabrication and erection of piping system, where in this case the Hydrostatic Test Pressure = 1.5 Design Pressure x (Sat ambient temp./ Sat design temp. )

• Therefore, the hydrostatic test pressure = 1.5 x 1450 (Sat ambient temp./ Sat design temp. ) = 2175 PSI

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#7
In reply to #6

Re: MAWP VS Hydrostatic Test

08/19/2009 3:32 AM

Mr Abdel..

Actually i am interested on this topic.

What if the hydrostatic pressure exceeds MAWP? Lets say the temperature is ambient / normal.

In vessel, we have PSV (pressure safety valve). The set point of PSV is equal or less than MAWP. So if working pressure is raising up to MAWP, the PSV will open.

So, i assume here MAWP is a critical or limit point of equipment, if the pressure exceeds the MAWP, vessel will rupture.

Please correct me if i am wrong.. Thanks.

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Guru
Engineering Fields - Piping Design Engineering - New Member Egypt - Member - Member since 02/18/2007

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#8
In reply to #7

Re: MAWP VS Hydrostatic Test

08/19/2009 3:59 AM

During hydrostatic test, the test pressure must be higher than MAWP by at least 1.3 times as per ASME BPV Code. But during operation of the equipment, no way to allow for the pressure inside the vessel to attain or to be higher than the design pressure, MAWP.

For this reason, the critical equipment must be furnished with a pressure releasing system (e.g safety valve, rupture disk, pressure control system,... etc.) to be adjusted at set pressure less than the MAWP by about 5-10%.

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Guru
Engineering Fields - Piping Design Engineering - New Member Egypt - Member - Member since 02/18/2007

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#10
In reply to #7

Re: MAWP VS Hydrostatic Test

08/19/2009 10:19 AM

What if the hydrostatic pressure exceeds MAWP?

That is true, the hydrostatic test pressure must be greater than the design pressure MAWP, and by applying the hydrostatic pressure as per code rules and recommendations, there is no risk on the vessel.

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#16
In reply to #7

Re: MAWP VS Hydrostatic Test

05/30/2013 1:27 PM

Dear Mr.premium (and Mr.Abdel Haleem Galala also)

You have referred "What if the hydrostatic pressure exceeds MAWP? "

During my 1st year of service, my Chief Engineer, was informing us that the Test Pressure can be more than the Standards. The reason/explanation what he was giving was 'THE STRESS INDUCED AT THE WORKING PRESSURE and TEMPERATURE, the SAME AMOUNT OF STRESS IS TO BE INDUCED WHILE TESTING AT AMBIENT TEMPERATURE."

Certainly the above reason calls for a higher pressure than the Standards. For 220 psi, (300 Deg.C working Temp.) the Standard Test Pressure calls for 330 psi, but he used ask us to test at 525 psi, and the value 525 psi is derived from the material characteristic graph, supplied by the Tube supplier, as the 525 psi at room temperature will induce the same stress at working pressure and temp. He used witness the test. The simple logic as told by him, "if any failure of tubes, let it fail now"

I request comments from CR4 Members on this type of approach.

DHAYANANDHAN.S

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#9

Re: MAWP VS Hydrostatic Test

08/19/2009 6:17 AM

Yes, but the field Hydrotest never could be more than the fabricator Hydro test. That s why i Thing that you have a trouble with the Calcs.

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Guru
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#11
In reply to #9

Re: MAWP VS Hydrostatic Test

08/20/2009 1:26 AM

Yes, but the field Hydrotest never could be more than the fabricator Hydro test.

What do you mean?

It is very important to know that the hydrotest carried out as per code after full completion of fabrication work is called "Hydrostatic Test Pressure" whatever this test was carried out at workshop or at field, and its value remains the same as per code.

And this Hydrostatic Test is differs than that pressure test carried out at mill after production of pipe itself.

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#12
In reply to #11

Re: MAWP VS Hydrostatic Test

08/20/2009 2:24 AM

GM Adbel

The Hydrotest at fabricator shop is suppose to be performed one by one (Lenght) up to 90 or 92% YP to ensure the integrity of the long or spiral weld and the pipe body. AvatarIndo said 2000 psi (API 5L)

The Hydrotest at field is to ensure the pipe line integrity (including circunpherential buttwelds, branch, olets...) This test will be done at 1,5 desing Pressure plus temp. )Here i don t know why they are using B 31 4 instead of API 1104 for PIPELINE). Wherever, this pressure never can be more than 2000 psi. Then and according with you: Therefore, the hydrostatic test pressure = 1.5 x 1450 (Sat ambient temp./ Sat design temp. ) = 2175 PSI

And this is more than 92% YP ( Something is wrong, the DP or the selected material, or thickness or possible me)

MAWP is a pressure to be reference after SU and during operations.

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#13

Re: MAWP VS Hydrostatic Test

08/20/2009 10:39 PM

Could we back to early topics?

The topic is about pipeline.

Could i temporary take conclusion:

1.Hydrostatic test pressure shall be less than mill test pressure

2.The main restriction of hydrostatic test is The highest test pressure is shall be less than 1,3 MAWP

Correct me if i wrong....

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Guru
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#14
In reply to #13

Re: MAWP VS Hydrostatic Test

08/21/2009 1:41 AM

At first, we have to define and select exactly which code we have to apply, because the rules and conditions applied to such a code can be differs from that of the other code. For example : the rules of applying the hydrostatic test for power piping (ASME B31.1) can be differed than that of process piping (ASME B31.3) , and the both shall be differed than those of liquid pipeline (ASME B31.4) and so on.

If our case is a "Pipeline", we have to define which type of pipeline: liquid pipeline (ASME B31.4) or gas pipeline (ASME B31.8). If we considered that the system is a liquid pipeline, so we have to apply the rules of ASME B31.4. The following paragraphs are quoted from that code:

QUOTED

437.4 Test Pressure

437.4.1 Hydrostatic Testing of Internal Pressure Piping

(a) Portions of piping systems to be operated at a hoop stress of more than 20% of the SMYS of the pipe shall be subjected at any point to a hydrostatic proof test equivalent to not less than 1.25 times the internal design pressure at that point (see para. 401.2.2) for not less than 4 hr. When lines are tested at pressures that develop a hoop stress, based on nominal wall thickness, in excess of 90% of the SMYS of the pipe, special care shall be used to prevent over strain of the pipe.

1. Those portions of piping systems where all of the pressured components are visually inspected during the proof test to determine that there is no leakage require no further test. This can include lengths of pipe that are pretested for use as replacement sections.

2 . On those portions of piping systems not visually inspected while under test, the proof test shall be followed by a reduced pressure leak test equivalent to not less than 1.1 times the internal design pressure for not less than 4 hr.

(b) API RP 1110 may be used for guidance for the hydrostatic test.

(c) The hydrostatic test shall be conducted with water, except liquid petroleum that does not vaporize rapidly may be used, provided

1. the pipeline section under test is not offshore and is outside of cities and other populated areas, and each building within 300 ft (90 m) of the test section is unoccupied while the test pressure is equal to or greater than a pressure which produces a hoop stress of 50% of the specific minimum yield strength of the pipe.

2. the test section is kept under surveillance by regular patrols during test

3. communication is maintained along the test section

(d) If the testing medium in the system will be subject to thermal expansion during the test, provisions shall be made for relief of excess pressure. Effects of temperature changes shall be taken into account when interpretations are made of recorded test pressures.

(e) After completion of the hydrostatic test, it is important in cold weather that the lines, valves, and fittings be drained completely of any water to avoid damage due to freezing.

(f) Carbon dioxide pipelines, valves, and fittings shall be dewatered and dried prior to placing in service to prevent the possibility of forming a corrosive compound from carbon dioxide and water.

437.4.3 Leak Testing. A 1 hr hydrostatic or pneumatic leak test may be used for piping systems to be operated at a hoop stress of 20% or less of the SMYS of the pipe. The hydrostatic test pressure shall be not less than 1.25 times the internal design pressure. The pneumatic test gage pressure shall be 100 psi (7 bar) or that pressure which would produce a nominal hoop stress of 25% of the SMYS of the pipe, whichever is less.

UNQUOTED

So, as per ASME B31.4, I think you could perform pipeline hydrostatic test with pressure 1.25 x 1450 = 1812.5 psi

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#15
In reply to #14

Re: MAWP VS Hydrostatic Test

08/21/2009 2:08 AM

So, as per ASME B31.4, Para. 437.4.1(a), which states that if a portion of your piping system operates at a hoop stress more than 20% of the SMYS, you can perform pipeline hydrostatic test not less than 1.25 times the internal design pressure at that point.

So, and only for that case where hoop > 20% SMYS (and you have to prove that condition), the Hydrostatic Test Pressure shall be not less than 1.25 MAWP = 1.25 x 1450 = 1812.5 psi

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