Hydrotest Pressure on Vessel Nameplate
Hydrotest Pressure on Vessel Nameplate
(OP)
Hi,
In our project specification we've asked the Vendor to hydrotest vessel to 1.3 MAWP (new& cold). I've got a question from them - which hydrotest pressure shall be mentioned on the vessel nameplate, 1.3 x MAP new&cold or 1.3 MAWP (the pressure of the test done at the field)?
Their concern with noting the MAP N&C test pressure on the nameplate is that when they hydrostatic test in the field, they may refer to the nameplate and consider that this is correct and over stress the vessel. The only time that the 1.3 X MAP N&C pressure can be applied is when the vessel is in the shop.
On the other hand, 1.3 x MAP is the actual hydrotest pressure - shouldn't a vessel nameplate reflect the pressure a vessel actually was tested to?
What is your experience? I will appreciate your input.
Thanks.
In our project specification we've asked the Vendor to hydrotest vessel to 1.3 MAWP (new& cold). I've got a question from them - which hydrotest pressure shall be mentioned on the vessel nameplate, 1.3 x MAP new&cold or 1.3 MAWP (the pressure of the test done at the field)?
Their concern with noting the MAP N&C test pressure on the nameplate is that when they hydrostatic test in the field, they may refer to the nameplate and consider that this is correct and over stress the vessel. The only time that the 1.3 X MAP N&C pressure can be applied is when the vessel is in the shop.
On the other hand, 1.3 x MAP is the actual hydrotest pressure - shouldn't a vessel nameplate reflect the pressure a vessel actually was tested to?
What is your experience? I will appreciate your input.
Thanks.





RE: Hydrotest Pressure on Vessel Nameplate
The nameplate requires the MAWP and design temperature. A standard hydrotest is done at 1.3X MAWP with a minimum of 70 deg F water (field or shop). A calculated hydrotest pressure can be used in accordance with UG-99 2c. However, the MAWP is still stamped on the vessel nameplate. I have not seen MAP N&C used on nameplates for ASME Section VIII, Div 1 vessels.
In some cases the design pressure can be used as MAWP, but you need to stamp the nameplate per Figure UG-118.
The only scenario I could think of where the nameplate would be stamped differently is when a vessel will be installed in a Jurisdiction or country that requires MAP N&C to be stamped in lieu of MAWP.
RE: Hydrotest Pressure on Vessel Nameplate
ER
RE: Hydrotest Pressure on Vessel Nameplate
70deg. is not a required test temp. for SecVIII-Please see UG-99(h)but keep in mind the requirements of the NBIC for later testing. Also review UG-99(c)(d).
To determine test pressures review Appendix 3 and UG-99(b).
InnSk-I would not worry about a later test,the one doing the testing should consider the results. See ASME SecVIII UG-99(d) and NBIC RC-2051 and RC-3031.
RE: Hydrotest Pressure on Vessel Nameplate
RE: Hydrotest Pressure on Vessel Nameplate
Subsequent tests on the pressure vessel are normally pressure tests, and as deanc rightfully pointed out, follow NBIC rules (if applicable). I really see no reason to stamp hydrotest pressure when it is known that a hydrotest is conducted above MAWP.
RE: Hydrotest Pressure on Vessel Nameplate
With a tall vessel, the shop would most likely test in the horizontal. A subsequent field hydro with the vessel in the vertical position can cause the bottom head to see a pressure to which it has not been previously exposed nor designed for.
Another consideration for field hydrotesting is whether the foundation can support the weight of a large, normally vapor filled, vessel full of water. Often, the foundation cannot support that load.
Adding a hydrotest pressure to the nameplate adds no value and may encourage a test which will cause failure of the vessel or foundation.
jt
RE: Hydrotest Pressure on Vessel Nameplate
I have never seen a vessel designed that couldn't be filled with water in the operating position. It is a given that operations will manage to fill it to the brim. Most of the concern is of over stressing comes in the inadequately support tall vessel in the horizontal position.
Most PV programs will give you the weight empty, operating based on the input data and the weight full of water. All our foundations are designed to carry the heaviest weight of the vessel.
RE: Hydrotest Pressure on Vessel Nameplate
I'm sorry you haven't seen a vessel which couldn't be filled with water in the vertical position! What that tells me is that you haven't been involved with tall relatively low pressure vessels. Say an atmospheric column 150' T-T x 20' diameter at say 25 psi and 700°F. The head from a full water load would be 65 psi. So this vessel designed for perhaps 20' of liquid on the bottom would see roughly 100 psi on the bottom shell course and head during a vertical hydrotest. Nearly four times the design pressure...
I'm happy that your foundations are designed for a full water load. In my past life at a major E&C firm I ran into situations where the foundations were not adequately designed for a field hydro. I witnessed one hydro of a particularly tall (well over 200') field fab vessel where the structural engineer had surveyors out during the hydro to verify that the foundation wasn't beginning to tilt. That is not a great indication of confidence in the foundation...
jt
RE: Hydrotest Pressure on Vessel Nameplate
It was corporate policy never to push a foundation or anchor system on any vessel. A little steel, a few more yard of concrete, and a competent designer goes a long way in the engineering of supports. As I stated before all our vessels no matter how large are designed for sustained 140 mph winds from any direction, that in itself goes a long way to carrying the weight full of water. We have tested them all under these conditions.
We did pay a little extra in material for FV/15 psig columns for this capability but like every other company we could rely on operations to flood anything we could put out there and they obliged us.
Even on our structured packing columns we still use a 100% flood design. This is good way to start a column up, 80% flooded with 100% reflux. On some 90' internal condenser columns with tunnel trays with a 125,000 pph circulation we can flood it in a second or two.
Just for curiosity what would be a level of flood, liquid load, to design a column for use with valve trays?
RE: Hydrotest Pressure on Vessel Nameplate
RE: Hydrotest Pressure on Vessel Nameplate
Comments.
The more you learn, the less you are certain of.
RE: Hydrotest Pressure on Vessel Nameplate
As part of the rules for altering a pressure vessel, the NBIC requires a Form R-2 that has to be filled out and signed by the Inspector. On that form, is the hydrotest pressure that the item was tested to for the alteration. There is no reason to stamp this information on the vessel. If the nameplate was stamped with an R symbol indicating an alteration, the hydrotest information will be on Form R-2.
RE: Hydrotest Pressure on Vessel Nameplate
Steve Braune
Tank Industry Consultants
www.tankindustry.com