Further to the trailing mail, I would like to add some more points. The
basic criteria for any hydrotest (piping, equipment or pipeline) is that
the hydro test pressure shall not exceed 0.9 times of yield strength of
the materials which is being hydro tested.
The maximum hydro test pressure is arrived based on factor of safety
multiplied by the times of design pressure. For ex. All onplot piping,
the factor of safety is 0.6 and hydro test pressure is 1.5 times of
design pressure. Hence, 0.6 x 1.5 = 0.9, same way for pipeline, the
factor of safety is 0.72 and hydrotest pressure is 1.25 times of design
pressure, which comes 0.9. (the times of design pressure may vary
depends on factor of safety)
It means that at any point of time the hydrotest pressure shall not
exceed 90% of yield strength of the material and also it is decided
based on design factor or factor of saftey. If it exceeds this limit,
the material shall undergo permanent/ plastic deformation and this shall
not be rectified. Hence as long as the hydro test pressure is within
this limit, the system will work (immaterial of number of times).
Regards,
L. Prabhu kumar,
Sr. Principal Engineer,
Equipments & Materials Dept.,
Saipem India Projects Limited,
Nungambakkam High Road, Chennai - 600 034, India.
Tel:+91 44 43906588, Ext.: 588, Fax:+91 44 66840345,
Mobile Ph. No.: +91 9003010978.
L. Prabhu kumar,
Sr. Principal Engineer,
Equipments & Materials Dept.,
Saipem India Projects Limited,
Nungambakkam High Road, Chennai - 600 034, India.
Tel:+91 44 43906588, Ext.: 588, Fax:+91 44 66840345,
Mobile Ph. No.: +91 9003010978.
-----Original Message-----
From: materials-welding@googlegroups.com
[mailto:materials-welding@googlegroups.com] On Behalf Of Darcy Morin
Sent: Tuesday, May 04, 2010 7:49 PM
To: materials-welding@googlegroups.com
Subject: Re: [MW:5064] Hydrotest of Piping System
Further, ASME B31.3 utilizes a 3:1 safety factor in the Allowable
Stress Design of piping systems. So, it is unlikely that a 150%
hydrotest will weaken the system.
On 2010-05-04, at 0:37, Kathalingam Babu <kathalingam.qaqc@ppl.com.sg>
wrote:
> Hi
>
> On top of below mail, the materials will be weaken only if the test
> pressure exceeds the yield strength of the materials.
>
> In all codes, the test pressure will consider the above fact and
> test temperature, so the weakening of materials is rare if you
> follow appropriate fabrication procedures.
>
> Consideration shall be given what was the cause of failure, rather
> than how many time hydrotest allowed.
>
> Rgds,
>
> K.Babu
>
>
> ----- Original Message ----- From: "Kathalingam Babu"
<kathalingam.qaqc@ppl.com.sg
> >
> To: <materials-welding@googlegroups.com>
> Sent: Tuesday, May 04, 2010 2:22 PM
> Subject: Re: [MW:5042] Hydrotest of Piping System
>
>
>> Hi
>>
>> For your info, if the system fails , it doesn't mean, your weaking
>> the materials.
>>
>> I don't think , there is any restriction on how many times the
>> hydrotest allowed.
>>
>> Rgds,
>>
>> K.Babu
>> Singapore
>>
>>
>> ----- Original Message ----- From: "dhinesh gnanadhas"
<dhineshlhmm@gmail.com
>> >
>> To: "Materials & Welding" <materials-welding@googlegroups.com>
>> Sent: Tuesday, May 04, 2010 2:03 PM
>> Subject: [MW:5042] Hydrotest of Piping System
>>
>>
>>> Hi.
>>>
>>> If the piping system getting fails in every test. Howmany times we
>>> can
>>> do the hydro test for the same piping system?
>>>
>>> If we are doing the the hydrotest, we are weakening the pipe
>>> material.
>>> So, Howmany times the same system can be allowed to retest?
>>>
>>> --
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>>>
>
>
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> The views expressed/exchnaged in this group are members personel
> views and meant for educational purposes only, Users must take their
> own decisions w.r.t. applicable code/standard/contract documents.
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The views expressed/exchnaged in this group are members personel views
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decisions w.r.t. applicable code/standard/contract documents.
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