hydrotest pressure for in-service pressure vessel

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hydrotest pressure for in-service pressure vessel

Postby sakib321 » 09 Jul 2011, 14:37

the newly fabricated pressure vessel were hydrotested as per UG 99 but my question is that which criteria we need to follow for the pressure vessel that are in service. i have read API 510 but not find any specified criteria (it shows pressure test depends upon the inspector)

one more question which is related to it is that does aging factor of pressure vessel count while considering the hydrotest pressure or it is tested at pressure which is specified by designer at time of designing.?
Sakib Jalal
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Re: hydrotest pressure for in-service pressure vessel

Postby ashfaqanwer » 09 Jul 2011, 15:29

Hydrostatic test for in-service pressure vessel in not frequently done until or unless there is some major repair work carried out.
Even when repairs are carried out, NDTs are used to qualify them and if inspector understands that the repairs sound OK he doesn't insist for pressure test.
Guidelines are available in NBIC on repair works of boilers and pressure vessels and their hydrostatic testing after repairs.
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Re: hydrotest pressure for in-service pressure vessel

Postby ben » 09 Jul 2011, 17:11

Do you want to get some general information on this or have a case on your desk?
Pressure vessels are not subjected to hydrostatic test pressure without any special reason i-e; major repairs.
If deemed necessary then the pressure must not exceed the test pressure when done after manufacturing that is code recommended. See the vendor's data.
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Re: hydrotest pressure for in-service pressure vessel

Postby mechcolor » 09 Jul 2011, 22:22

See para 4.4.1 of NBIC part 3 where hydrostatic pressure has been recommended as 1.5 of max. allowable working pressure. And this is the maximum value. You must decide after looking at the vendor's data sheet.
Yes aging factor is always considered whenever a pressure equipment is to be pressurized at a value above design / MAWP and therefore not recommended. NDTs if can replace hydrostatic test are preferred.
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Re: hydrotest pressure for in-service pressure vessel

Postby Nabeel Ahmed Qureshi » 10 Jul 2011, 09:22

What criteria shall be followed for Heat Exchangers? Leak Testing on defined frequency or Hydrotesting? At our site we do Hydrotesting of all Exchangers at a defined frequency. Any inputs/practices sharing shall be highly appreciable.
NAQ
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Re: hydrotest pressure for in-service pressure vessel

Postby Nabeel Ahmed Qureshi » 10 Jul 2011, 09:26

Also, the Hydro is done 1.3 times of Design pressure. However, if the exchanger health is doubtful due to excessive corrosion / tube leakages we reduce it to 1.1 or even to only Design Pressure. At few instances, we had to restrict ourselves to 1.3 of operating pressure due to extremely bad health of exchanger.
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Re: hydrotest pressure for in-service pressure vessel

Postby kaleemfaaras » 10 Jul 2011, 11:16

Quoting from API 572 para 10.8.2 "Pressure & Vacuum Testing"
"When a pressure vessel is fabricated, it is tested for integrity
and tightness in accordance with the standard or construction
code to which it was built. (In addition to integrity
and tightness, the pressure test can also result in beneÞcial
stress redistribution at defects.) These methods of testing may
also be used to subsequently inspect for leaks and to check
repair work. When major repair work such as replacing a
head, a large nozzle, or a section of the shell plate is performed,
the vessel should be tested as if it were just installed.

In certain circumstances, the applicable construction code
requirements for inspection of vessels in service also require
periodic pressure testing, even though no repair work has
been necessary. For code rules concerning tests of vessels in
service, see API 510 and NB-23. The ASME Code, although
a new vessel fabrication code, may be followed in principle in
many cases.
"

It means that the vessel can be pressure tested at 1.3 times the design following the rules of ASME code for new vessel construction. However decision stays with the site inspector and the applicable regulations, where applicable.

sakib321 wrote:the newly fabricated pressure vessel were hydrotested as per UG 99 but my question is that which criteria we need to follow for the pressure vessel that are in service. i have read API 510 but not find any specified criteria (it shows pressure test depends upon the inspector)

one more question which is related to it is that does aging factor of pressure vessel count while considering the hydrotest pressure or it is tested at pressure which is specified by designer at time of designing.?
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Re: hydrotest pressure for in-service pressure vessel

Postby kaleemfaaras » 10 Jul 2011, 11:20

For your case, I am again quoting from API 572 para 10.8.3 "Testing Exchangers"
"When an exchanger is removed from service, it is often
desirable to apply a test to either the shell side or the tube side
before dismantling.
The pressures to be used when testing will depend on the
operating and design pressures of the unit. These pressures
should be determined locally in accordance with individual
practice or jurisdictional requirements. Before applying pressure
to the shell side only of an exchanger, the inspector
should be sure that tubes of the bundle are of sufÞcient wall
thickness to withstand the external pressure. In addition the
channel side test pressure and the shell side test pressure
should be checked against one another and care should be
taken that one side or the other of the exchanger is not excessively
pressured when testing. Particular care should be taken
with any high-pressure exchangers where the tubesheets were
designed basis differential pressure."

Hope it helps.

Nabeel Ahmed Qureshi wrote:What criteria shall be followed for Heat Exchangers? Leak Testing on defined frequency or Hydrotesting? At our site we do Hydrotesting of all Exchangers at a defined frequency. Any inputs/practices sharing shall be highly appreciable.
NAQ
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Re: hydrotest pressure for in-service pressure vessel

Postby kaleemfaaras » 10 Jul 2011, 11:25

Please note that API 572 is about Inspection of Pressure Vessels (Towers, Drums, Reactors, Heat Exchangers & Condensers)
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Re: hydrotest pressure for in-service pressure vessel

Postby kaleemfaaras » 10 Jul 2011, 11:55

Also please see the excerpt from para 6.5 "Pressure test" of API 510:
"When the authorized pressure vessel inspector believes that
a pressure test is necessary or when, after certain repairs or
alterations, the inspector believes that one is necessary (see
7.2.9), the test shall be conducted at a pressure in accordance
with the construction code used for determining the maximum
allowable working pressure.
"
So if the construction code in your case is ASME VIII Div. 1, you can pressure test at 1.3 times design.
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