how to calculate Hydrotest time

Date 07-15-2013 19:38

I'd say that your tank was designed and built to ASME VIII. In this case, the Code itself says how to perform the hydro test.
I'd also say that the material is SA 515 Gr 70, rather that SA 55. You forgot to type the number 1, am I right?

Giovanni S. Crisi
Sao Paulo - Brazil

By 803056

Date 07-16-2013 14:33

Most codes do not specify a time, only the test pressure. The pressure must be held long enough that all the pressure boundary welds can be checked for leaks.

Wait, there's more. Many customer specifications will include a time element to ensure the pressure is held long enough for the test fluid to follow the leak path and manifest as a dripping tell-tail. If the customer does not specify a time, the question becomes, "How fast can you check this thing?"

Personally, I believe every hydro should be held at pressure a minimum of 15 minutes. I have seen vessels under pressure go for an hour or more with no evidence of leakage and then, drip, drip, drip........

The longer they are held under pressure the better. Some leak paths are very small and torturous, thus they take time before the test fluid reaches the inspection surface. A well written project specification should include a time element for pressure testing.

Al

By G.S.Crisi (****)

Date 07-16-2013 18:42

Al,
Yes, the Code specify the time. The time "must be long enough for all the pressure boundary welds be checked for leaks", as you yourself have said. If it takes 20 minutes to check the welds, the time will be 20 minutes; if it takes one hour, the time will be one hour.
Back in my days of erector engineer I erected a vacuum tower in an oil refinery. The tower arrived at the job site completely dissassembled in pre-formed plates. All the welds were field welds. Hundreds of meters of welds were performed at site.
It took quite a long time (I don't remember exactly how much) to check every centimeter of weld. Not even a drop of water was detected. The welders were good, the welding foreman was good, the welding procedure was good and the radiographic testing was well carried out.

I agree with you about 15 minutes minimum time.

Cordially
Giovanni S. Crisi

By JTMcC

Date 07-16-2013 18:45

To satisfy my curiosity, are there really areas of work where a hydro is on for only 15 minutes?

In my experience all hydro (or nitrogen or whatever) pressure tests have to be held for hours. Usually 8, 12 or 24. But my experience is limited in scope.

J

By G.S.Crisi (****)

Date 07-16-2013 18:56

Suppose an ion exchange tank in a demineralized water plant. The tank diameter is 42 inches (roughly 1.000 millimeters) and its straight heigth is 8 feet or 94 inches (roughly 2.400 millimeters).
There will be two circumferential welds (the ones between the cylindrical section and the two dished ends) and one longitudinal weld (the one to close the cylinder after the plate has been rounded up).
It'll take five minutes to check the welds.

Giovanni S. Crisi

By 803056

Date 07-16-2013 19:24

I have clients producing vessels that are on the order of 6 to 8 inches in length and as small as 4 inches in diameter. They are still designed, fabricated, and inspected to Section VIII. Check for leaks: 30 seconds.

Like I said, I do not believe Section VIII has a minimum hold time before the visual examination for leaks is performed.

Best regards - Al

By JTMcC

Date 07-16-2013 20:36

OK that's really small.
But still, I'd think a small slag track would take more than 15 minutes to seep any liquid.

The test medium, in my observance, takes more than 15 minutes to equalize from temperature difference. I guess a visual leak test is quite a bit different than a gage reading over time. But 15 minutes seems crazy to my feeble mind.

J

By 803056

Date 07-16-2013 21:00

There ain't no slag in GTAW.

Al :razz:

By JTMcC

Date 07-16-2013 22:28

No, but there are defects that can let the magic internal fluids get to the outside. Let's call it a contamination track. Or a magical leak.

Otherwise there wouldn't be a pressure test at all, huh?

Is your stance that because it's GTAW, no test is needed, or just trying to be clever at the expense of accuracy?

15 minutes seems awfully short but nobody ask me.

J

By 803056

Date 07-16-2013 22:41

Just trying to make the point that only a welding process that employs a flux system can have a slag inclusion or as you put it a "slag track." Am I trying to be clever; no, accurate; yes.

Did I say the pressure test wasn't needed? No, nary a mention of that in my response.

Al

By Milton Gravitt (***)

Date 07-17-2013 00:58

It's was a long time ago but I welded on some gas lines that go in buildings and they had to hold pressure for I think 48 hours without dropping.

M.G.

By JTMcC

Date 07-18-2013 20:07

Thank you, 803056, after 30 years of tig, errr, GTAW welding I never realized a flux system wasn't employed.

I know the term slag track is a non AWS standard colloqialism, but is way different than an inclusion. It does contain multiple inclusions tho.

You must work around really dumb welders, eh?

J : )

By 803056

Date 07-19-2013 01:39 Edited 07-19-2013 01:43

Ouch!

It just validates my 10% / 80% / 10% rule. 10% excel, 80% make a good living, 10% should be doing something else.

With some good training it could be changed to 30% / 60% / 10%.

My goal is the latter.

Al :cool:

By JTMcC

Date 07-19-2013 02:56

I guess it wouldn't be prudent to start holding your breath. Human element and all : )

J

By 46.00

Date 07-19-2013 03:27

Al, I disagree, GTAW or TIG welding and also GMAW (MIG welding) are capable of generating slag or silicon deposits on the weld face which can be included into the weld metal, especially on multi run weld joints. Granted it is not going to be a common problem but in the name of accuracy it has to be acknowledged.

http://www.twi.co.uk/news-events/bulletin/archive/pre-1998-articles/1988-articles/how-tig-welding-procedure-affects-penetration-and-slag-island-formation-part-1/

By electrode (***)

Date 07-19-2013 06:38

46.00,

an interesting and valuable investigation.

Thank you for both revealing and sharing.

Regards!

By Joey

Date 07-19-2013 10:07

Slag Island? first time I heard this terminology. We don't have that Island in Smokey. What we have is rubbish island. :yell:

I will not use the term SLAG for GTAW process. :razz:

By electrode (***)

Date 07-19-2013 14:09

Sir,

apparently there's some unpleasant misunderstanding here.

Anyway, because it is I you're responding to, kindly permit me the attempt to clarify this in a quick and simply comprehendible way.

In my understanding basically 'JTMcC' raised an interesting aspect. Twice worth being seriously considered. I was under the impression that did happen - did it not?

In my understanding the fundamental question here is not the terminology. This rather I suspect is, if even, secondary important.

In fact, you could actually name the out coming result as you wish. The only consideration from my perspective since the 'slag' proves female; it preferably should represent some female's name. But, like I say, I'll leave this to you.

Anyway, and to make this clear, here's where fun is over with me as it now goes about welding. I rather consider the Welding Institute's investigation some well-considered, non-academic of course but simply practical approach to deal with something that can occur, even if you like, or worse, "believe" it or not. And that, even when using arc welding processes such as TIG (GTAW) that do not "employ" a specific "flux system".

So, we should basically estimate the investigation, appreciably revealed by 46.00, at least partly capable of proving JTMcC’s statement's correct. Also, I am sure that many of us, who have extensively welded TIG (GTAW), under particular circumstances, have been faced with either similar reaction products, byproducts or contaminations.

As a matter of fact, the study is providing, in my eyes, interesting and valuable, information on what's possible. Name it "slag tracks", "contamination tracks", "slag inclusions", "slag islands", or even "Linda" or "Margaret" (see above).

That again, at least in my interpretation, seems arising from oxidation; just recalling, that, from those gases or -mixtures respectively tested, the "tri-mix" (5H_2 + 25Ar + Helium) produces, maybe, an imbalance towards reducing atmosphere conditions hereby, maybe, dropping the oxygen content, from wherever it stems, for eliminating the reaction products.

"Accuracy" was mentioned. "In the name of accuracy", I for one do greatly appreciate 46,00's input.

This welding forum, due to some strange, but quite funny, excrescences admittedly yet hardly understandable to me, should be happy for having fellows around capable of soothing the sometimes, and with all due respect, unilateral conversations, thereby broadening our all's horizons.

Oh yes, respectfully considering you an adult I do ask your understanding for not using these kindergarten (emot)icons.

Thank you.

By Joey

Date 07-22-2013 08:37

electrode

Please accept my apology if my response caused you some discomfort. You could be emotionally sensitive by the emoticons being used here. The type of discontinuities should be carefully distinguish using the terminology that is recognized by the acceptance standard / code which spell out the acceptable limits for discontinuities. Will you agree to use the term slag island when interpreting radiographs for GTAW welds? What is the use of those Linda and Margaret, slag islands when you cannot relate them to the code you are using?

By electrode (***)

Date 07-22-2013 09:40

Sir,

my sincere thanks for both the apologies, unneeded actually but I do nonetheless much appreciate your friendly attitude, and your most reasonable questions.

1. "Will you agree to use the term slag island when interpreting radiographs for GTAW welds?"

Most likely - negative. You are surely right.

As long as "slag island" remains a term not properly dealt with by, adequately included into or explicitly connected to an appropriate code/standard, it will just remain as meaningless as "Linda", "Margaret" or whatsoever.

Moreover your question shows and confirms the difficulties when something or a phenomenon, i.e. strange "surface discontinuities" showing (maybe) "slag character" in GTAW), arises that actually "shouldn't" arise. And thus, as a consequence, hardly can be covered by any code or standard terminology.

It was my intention to just indicate that, even though the code(s) do(es) not cover it, it nonetheless exists and that TWI fellow, so my assumption, was just seeking some adequate way to describe it by using some (unfortunate?) mixture between terms used in the welding field (slag) and rather general terms (island).

I suppose, just to make clear that the phenomenon's occurrence shows some irregularity - which should not be proven however, by the well-known "welding slag" - due to having some very particular requirements to meet (as described in the codes or elsewhere).

2. "What is the use of those Linda and Margaret, slag islands when you cannot relate them to the code you are using?"

There's none. I do fully agree with you.
Especially yourself and those being inspectors, are certainly in high demand of codes and standard nomenclature most properly reflecting their daily practice.

And I guess here it is where we come full circle - again. As mentioned by 'MMyers' in connection to another (similar) thread, and I should like to quote this here:

"So, to limit discussion to only using standard terms and definitions as defined in a single code's book limits our ability to fully describe the topic and inherently leads to the possibility of errors. (...) Sure, the AWS definition is correct in essence, but it incorrectly provides scope by not defining the necessary qualification that flux is used in addition to the parent/filler metal - simply stating "material" is too vague and leads to confusion and incorrect conclusions. This is an artifact of the information distillation process."

I like that much. It shows great 'real world' experience.

I am sorry for being unable to say more. But like I already stated. This topic, from the engineering/scientific background is "not trivial".

In my personal experience this "not trivial" is (almost always) used by physicists as they're approaching their own mental boundaries.

However, I guess there's no big disagreement - if even - between yourself and myself.

On the contrary. Through your questions/comments you could prove - once more - some very well-known fact... the devil is in the details.

Thank you.

By G.S.Crisi (****)

Date 07-22-2013 17:53

Joey,
TWI is The Welding Institution of the United Kingdom of Great Britain and Northern Ireland. They speak the King's English over there. That's why you've never heard that terminology.
Never mind. Also here in Brazil the Portuguese we speak is far from being the one they speak in Portugal.
Giovanni S. Crisi

By Joey

Date 07-26-2013 04:13

Prof Crisi

My current destinations (Malaysia & Singapore) are using BS EN std.
I normally used the appropriate terminology in line with the standard.
I've never read the term Slag Island produced by TIG process in BS EN.

~Joey~

By lo-hi

Date 07-19-2013 21:16 Edited 07-19-2013 21:20

Aint supposed to be no slag in a gtaw weld

By 803056

Date 07-22-2013 20:00

Ain't supposed to be slag in any weld!

Al

By Jim Hughes (***)

Date 08-14-2013 11:04

803056
B31.1 says 10 min.

Thanks

By 803056

Date 08-14-2013 11:12

Hey Jim, where have you been hiding?

Good to hear from you.

Best regards - Al

By Jim Hughes (***)

Date 08-14-2013 11:52

Al,
have had some may-days on a couple of our mega projects and have had to travel a lot. Thanks for asking. Good to be missed. :)

Thanks
Jim

By welderbrent (*****)

Date 07-17-2013 03:26

Interesting.

A good number of years back, over 50% of my life ago, when I worked for a pipe manufacturing plant in the Pacific NW, we hydro tested pipe from 3" to 84". We manufactured pipe up to 144" but I'm pretty sure the test tanks didn't go that big. Anyway, your pressure is lower the larger the pipe. From there, it depends upon the code, the customer specs, and the purpose for the test. If only to find leaks, it doesn't take long at pressure. But I don't know of a formula. I'm sure some of the testing agencies could give you an answer if no one here comes up with a solid answer.

Have a Great Day, Brent

By ctacker (****)

Date 07-17-2013 04:02

Was that pipe plant in Longview WA?

By Shane Feder (****)

Date 07-17-2013 06:41

Guys,
The length of time it takes to check all joints (welded, bolted or threaded) is the minimum length of time required for the test.
In addition
B31.3 Clause 345.2.2 (a) - 10 minutes minimum
B31.1 Clause 137.4.5 10 minutes minimum
ASME VIII Div 1 - my interpretation of UG 99 (g) is test pressure is 1.3 x MAWP. Once this is achieved pressure is reduced to test pressure divided by 1.3 and all welds are checked for leaks.

JT,
Please correct me if I am wrong but a lot of your work seems to be pipelines so visual inspection cannot be made of the welds - that is why the hydrotest duration is so long.
Regards,
Shane

By electrode (***)

Date 07-17-2013 08:37

Shane,

just a quick comment - if I may.

Some '3rd stage guild navigators' around here but especially your advice does always prove enlightening to me.

Reminds me a little of that, coming from 'nantong'.

Thank you.

By ssbn727 (*****)

Date 07-18-2013 06:02

That the sort of comment should be kept private and NOT in an open forum electrode. :mad:

By 46.00

Date 07-19-2013 03:29

Why?
......and why the 'mad' emoticon?

By JTMcC

Date 07-18-2013 20:43

Brent,

Whatever the pipe mills are doing, it's not transfereing across the big water.

I've seen as many as 7 pipe joints (in a 30 mile section) unzip (let go at the longitudinal factory seam) under hydro, all chinese manufacture. Of course when the pipe mills are all working full tilt it can be hard to buy line pipe domestic so gas/oil companies get what they can get.
Anencdotally only, Viet Nam, Indonesian, and Phillipines pipe seems to be a lot better than china pipe.

The US manufacturers are going to great length to increase their capacity, good on them. The mainline boom will not end in my lifetime, those corridors laid in the 50's/60's are worn out and only large (multi million $) fines will make the owners replace them. It's coming to a neighborhood near you!
The companies are all happy happy until their 75 year old line blows up and kills somebody. Then it's all hands on deck and hire a PR firm to rehabilitate our image and tell the world how sorry we are and we love people. There are thousands of miles of worn out big bore line underground right now that was laid in the 40's, 50's and 60's. Worn plumb flat out today. Lines you've never heard of.

Normal working pressure in new main line const today is 2000 psi on big bore. Hydro is well above that but the china product leaves a lot of bad gaps in QC and that's a large, large cost.
Hydro it, blowout the pipe, move tractors (on big truck lowboys plus the flag cars),mechanics,welders,laborers,operators,skids, inspectors (welding inspectors, ditch inspectors, sandblast and dope inspectors, rehab inspectors) + environmental, survey, archeologists back 40 miles cause the line pipe let go. Woohoo, you're looking at heavy bid killing cost all because you had to buy junk pipe.

Buy American.

J

By welderbrent (*****)

Date 07-17-2013 14:00 Edited 07-17-2013 14:25

Maybe I am missing something. Seems to me we are all coming from personal past experiences without actually knowing which phase of construction this is about.

But, Vignesh has not enlightened us as to rather this is in the shop manufacturing stage of members, plant manufacturing of product, rebuild of facilities, etc. And, as Shane points out, it also needs to be mentioned how many joints, connections, total length, and more to come to any conclusions even with other factors being equal.

We have seen comments that are applicable depending upon phase of production, applicable code, and/or customer specs, or even manufacturer's specifications.

But, we don't know exactly what is asked and thus how to find an exact answer. At least, I don't.

Hydrotesting can be used to determine many things: holes that show immediate leaks, lack of fusion and other problems that show in a few minutes, welding problems that will allow a total blowout because the product could not hold pressure for the prescribed time, and more.

Besides working at the pipe plant mentioned above, I have welded pipe many times. One one such project we were running four lines about 200 ft long each with all kinds of elevation and lateral changes. Thus 90's, 45's, inline butt splices, etc. Dodging all kinds of things that were in the way of getting from point A to point B. Half way through we find a length of pipe with holes that I can stick the end of 5/32 electrode all the way through the wall of the pipe. Now, this pipe was supposedly tested at the manufacturing plant to standard hydrotest at time of manufacture. Shipped from Asia to Seattle to Portland to my job. Notice the plural on the term 'holes'. Not just one. Several down the seam.

My job came to an immediate halt. Two days later a big meeting with manufacturer's reps, customer brass (large international operation), local pipe distributors reps, engineers, you name it.

Now, my specs were to fabricate this system, tap water, chilled water, high temp water, and a return line, then test it to about 3X it's normal operating pressure which would have put us at about 150 lbs. Oh, these were 4" lines. The new direction was to complete the project and then, since testing was obviously not what it should have been at point of manufacture, bring in a testing facility that took each line up to about 1000 lbs and held for 10 min. At that point, the lab rat, had to jump down in the ditch where these lines were all cribbed, and walk the line striking the pipe with a ball peen hammer at each welded joint.

I don't remember how many total joints I had, but there were no leaks anywhere and no blowouts from either the pipe seams nor my welds.

Point, purpose of the testing, applicable code, customer specs? We don't know thus far from the OP.

ctacker, no, it was the original Northwest Pipe and Casing when it was in Clackamas, OR.

Have a Great Day, Brent

By vignesh5585 (*)

Date 07-18-2013 02:02

thax all

By lo-hi

Date 07-19-2013 21:44

I have welded on underground steam mains that were hydro tested to 150 lbs and supposed to be held for 4 hours. This was in a ditch on a concrete runway, the inspector would witness the beginning of the test and return 4 hours later. If the test started in the morning, after about 2-3 hours in the blazing hot sun, water would start seeping out of the gauge and it was junk. Start your test in the afternoon and the vacuum would almost pull the little needle into the 3/8 pipe nipple. It would have been comical if it hadn't been so hot.

By 46.00

Date 07-20-2013 00:35

B31.3 (2011 and previous)states minimum of 10 minutes.

By dbigkahunna (****)

Date 07-22-2013 03:30

hydro test can by used as a leak test, but its main use is establishing the integrity of the system, tank or vessel. A pipe system can be tested to 80%, 95%, 100% or higher depending upon what the engineer want and the system use. Tanks and vessels are usually tested to 100% of their design pressure. A hydro on a vessel may be restricted due to the weight of the water required to test to 100%.
Do not confuse leak testing with hydrotesting. If I was testing a pipeline system at 1340psi I could care less about looking at the welds for leaks. I am not getting within 50 feet of any pipe under test over 250psi. Most pipeline companies have restricted how close personnel can get to a piping system if it is over 100 psi. I know, understand and have seen inspectors visually inspecting welds with 1340 psi on the pipe. Does not make it right nor safe.

By ssbn727 (*****)

Date 07-25-2013 02:40 Edited 07-25-2013 02:46

I agree Dbig k!

"A pipe system can be tested to 80%, 95%, 100% or higher depending upon what the engineer want and the system use. Tanks and vessels are usually tested to 100% of their design pressure. A hydro on a vessel may be restricted due to the weight of the water required to test to 100%."

Reciting what is written in a code or a standard doesn't mean that one must follow it to the letter because, they're only establishing what the very least is required, and DbigK has reminded us all that engineering requirements/contract specs always overrules minimum codes and/or standards requirements as long as the minimum requirements are met...

Dbigk also reminds us all that there should be no confusion between a leak test and hydrotesting...

On another note:
They may use the Kings English over there in the UK but over here, we use a smorgasboard of adopted words from many languages besides the King's English alone...
Since this is the American Welding Society and NOT The Welding Institute of the UK, any relatively newer participants of this forum should learn how to read and write American English and NOT the opposite as some may be more used to... So stop presuming that we need to learn how the King's English must be written & read in here because it's not going to happen here no matter how hard one may insist on it! :eek:

Finally, Your opinion on these beloved emoticons are at the very least ridiculous, and it is another feature in this forum that we use because we can! And they have been here way before any of the most recent critic's of of them have, so learn to adapt and accept them because when in Rome... Need I explain any further? I think NOT!!! :yell:

Respectfully to most in here,
Henry

By 46.00

Date 07-25-2013 04:36 Edited 07-25-2013 04:39

dbigkahunna, I am quoting some ASME clauses here as I'm not sure I fully understand your post.

Am I correct in understanding that you are mainly talking about pipelines under API 1104 etc. because I have never had these restrictions on process pipework and that includes such US based companies such as CB&I and Jacobs Eng. amongst others?

I believe Hydro testing is the safest way of proving a system is leak tight and fit for service or as you put it “establishing the integrity”. I would guess that if a system leaked, it would not be integral? Would you class deformation under pressure as not integral?
Again, I am only quoting ASME standards and fully appreciate that other standards may have completely different requirements but that is where I wish to gain knowledge as I mainly work under ASME controls!

ASME B31.3 (2011)
“345 TESTING
345.1 Required Leak Test
Prior to initial operation, and after completion of the applicable examinations required by para. 341, each piping system shall be tested to ensure tightness. The test shall be a hydrostatic leak test in accordance with para.345.4 except as provided herein…….bla bla bla”

ASME 8 Div 1 (2008)
“UG-99 STANDARD HYDROSTATIC TEST
(g) Following the application of the hydrostatic test pressure, an inspection shall be made of all joints and connections. This inspection shall be made at a pressure not less than the test pressure divided by 1.3.
Except for leakage that might occur at temporary test closures for those openings intended for welded connections, leakage is not allowed at the time of the required visual inspection.
Leakage from temporary seals shall be directed away so as to avoid masking leaks from other joints.”

So at least under ASME B31.3, a hydrostatic test is considered a leak test not an integrity test?

Under ASME 8, ALL connections must be visually inspected whilst under some sort of pressure which could be substantial i.e above 100psi or even 250psi? :grin:

Henry, I am also slightly confused by your post!

I imagine you comments regarding emoticons and the Kings English were directed toward electrode’s response to Joey’s comment on Slag Islands? To be honest I don’t think ‘electrode’s’ native tongue is the ‘King’s English’, I may be wrong but I'm fairly confident as a UK citizen that his is not, although he can most assuredly speak and write better English than I can his or any other language!

However, I admit I am not a big fan of the over use of emoticons! But that is just my opinion and it is up to the user to decide how others perceive there professionalism by the use of them! I'm not trying to influence anyone, just my own inconsequential opinion!

BTW Henry, I would have really appreciated your educated input on the resulting thread that Al started from this post about slag islands! :confused:

I was sort of hoping that you could have found a lost link or two! I was pretty sure you would have a wealth of info on this phenomena!

PS has anyone noticed that the OP’s figures don’t really add up and show no calcs have been done?

“Spec:
Design pressure :17 kg/cm2g

Hydrotest pressure : 22.1 kg/cm2g

Hydrotest temp: 17c to 48 c

Material Spec:
shell: SA 55 GR 70
thickness:40mm
mawp:17kg/cm2g
calculated min thickness:32 mm”
Let see who spots the mistake!

By electrode (***)

Date 07-26-2013 09:34

46.00,

in regard to:

"PS has anyone noticed that the OP’s figures don’t really add up and show no calcs have been done?

“Spec:
Design pressure :17 kg/cm2g
Hydrotest pressure : 22.1 kg/cm2g
Hydrotest temp: 17c to 48 c
Material Spec:
shell: SA 55 GR 70
thickness:40mm
mawp:17kg/cm2g
calculated min thickness:32 mm”
Let see who spots the mistake!"

Forgive me my ignorance, but can you help me?

I must admit that I am struggling a little on different code- abbreviation- and unit correlation; however, I am interested in what you mean.

Is it the test pressure and the resulting calculated wall thickness?

Many thanks.*

* For everything.

By bert lee (**)

Date 07-26-2013 16:32 Edited 07-26-2013 16:43

46.00

quote : I disagree, GTAW or TIG welding and also GMAW (MIG welding) are capable of generating slag or silicon deposits

when you disagree....can you share your actual experience with slag deposits on tig process? do you make a report to indicate "slag"? what inspection code can be used to asses the slag produced by tig process?

bert

By 46.00

Date 07-27-2013 22:14

bert please see the thread about 'Slag tracks versus Silicon Islands / Oxides' which is a continuation of this thread.

electrode, I may have been premature in calling a mistake but when design pressure and MAWP (Maximum Allowable Working Pressure) are the same, alarm bells sort of go off in my mind! It shows that no calculations have been done for the vessel thickness/Pressure as the two values should never be the same. But it is code compliant.........

By electrode (***)

Date 07-28-2013 08:32

Thank you 46.00.

Yes, that makes sense - I see.

By bert lee (**)

Date 07-28-2013 14:11

design pressure = MAWP

working pressure = / or less than design pressure