8 replies to this topic

[ASH25320]

What should be the hydrotest pressure for a plant equipment after annual turnaround. Is there any standard which specifies the pressure? Presently we are hydrotesting at operaing pressure. Any information is Welcome. Thanks in Advance..

[Art Montemayor]

Ash:

You haven't told us what equipment it is that you are testing in your plant. We can't tell what is in your mind.

Are you hydrotesting pressure vessels? Or is it storage tanks? If you are pressurizing your process vessels to only operating pressure, you are definitely NOT HYDROTESTING.

[Qalander (Chem)]

As already advised by Art;

You should appreciate that since any plant has many many individual equipments, associated piping etc. and each has to be tested as per its design/service needs and recommended standard values if any.

You should first have a complete list prepared and the details of the above mentioned items must be listed in front of each one and the applicable type of recommended reference/value and mode

thereafter one may proceed to; definitely a huge exercise I understand.

Hope this helps to further elaborate.

Best regards
Qalander

[ASH25320]

it is pressure vessels along with piping & generally hydrotest is done after Annual shut dwn.

[Qalander (Chem)]

it is pressure vessels along with piping & generally hydrotest is done after Annual shut dwn.

We all do understand and realize that, and mostly have come across such activities many many time indeed!.

But your query remains unclear and vague as such very very difficult for the forum colleagues to help.

Probably as if you do not want to be helped!

Otherwise be specific, focused and more elaborate in your query/its details.

Best Regards
Qalander

[smalawi]

Hi,

As Art and Qalander indicated, you need to specify the name of your equipment and preferably manufacturing year.

The ASME pipe and pressure vessel code is what you need; it has been revised and some older equipment are built to the older version. The API 14E is also a good reference.

Hydrotesting is typically done to establish the strength of the welds and overall vessel / pipe material strength. X-ray only establishs the welds' quality, not strength.

In the old days (I think circa 1996 and before, you need to confirm) the hydrotest was done by testing at 150 % of the design pressure, basically at the yield strength of the vessel / pipe. Post-1996, this rule changed for vessel and now it's 130 % only.

The hydrotest is only required when the equipment is first commissioned. As such, for columns / large vessels, this test is done at the manufacturing site. Once erected, this test is rarely redone, as the foundation is seldom designed for the full weight full of water. Some tricks have to be used - such as dummy boxes. Hydrotesting is required when there is changes to the structural integrity of the vessel / pipe such as cutting / wielding. Local code also governs here.

Another issue for thick wall vessels is that these can not be hydrotested under cold conditions. The wall has to be heated above the minimum pressurizing temperature (MPT). If not, the vessel wall will crack! These are tested in the field by high pressure gas such as hydrogen after gradually being heated above the MPT.

For heat exchangers, hydrotesting is used to check the leakage in both tube / shell sides. It is normally performed after cleaning.

cheers,

sm

[John Meerabux]

ASH,

As SM pointed out, 150% of Operating Pressure in the past (and in some existing standards outside US's ASME code, we still use 150% in Australia, AS1210) is used for a hydrotest. However, only once after the vessel has been manufactured, until the vessel is modified and requires reevaluation.

You can check what code and operating conditions the pressure vessel is manufactured and designed to by looking at the nameplate. This is not something you do regularly to the same equipment.

John Meerabux

[zehuachem]

Hi, ASH,
I think the intention of your test is just to find is there any leakage of water. Am I right?

[Qalander (Chem)]

Hi, ASH,
I think the intention of your test is just to find is there any leakage of water. Am I right?

If I am not mistaken then, the main Aim/ Goal/ Objective is to Check/ Evaluate/ Establish.

1) Mechanical Integrity

2) Continued Fitness or otherwise for intended service and

3) Re-rating,De-rating or further refurbishment requirements.

Consequent to the works(if any) performed during this Mega repair,maintenance,clean-up etc. activity.

Hope this helps.

Best regards
Qalander