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contactfarhan
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Join Date: Oct 2011
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Full Vacuum (FV) Design Pressure

02/01/2013 12:22 PM

Gentlemen,

Please explain me what is the meaning of full vacuum for design pressure for a vessel.

I have inspected a vessel whose data plate shown design pressure of 5+FV, what does this means?

Also after some repairs on this, what will be the test pressure for this vessel?

Seeking an expert reply and opinion.

Regards

Farhan
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lyn
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#1

Re: Full Vacuum (FV) Dsign Pressure

02/01/2013 12:37 PM

A picture is worth a thousand words.

Here's how not to do it!

Railroad Tank Car Experiment
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JPool
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#2
In reply to #1

Re: Full Vacuum (FV) Dsign Pressure

02/01/2013 1:19 PM

Lyn, no matter how many time I see that video, it never gets old.

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lyn
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#5
In reply to #2

Re: Full Vacuum (FV) Dsign Pressure

02/01/2013 3:37 PM
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dhayanandhan
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#8
In reply to #1

Re: Full Vacuum (FV) Dsign Pressure

10/09/2013 5:03 AM

Dear Mr.lyn,

Good Posting.

About 4 years back I was a witness for Implosion of 1000 MM dia., 6 MM thick, MS Round Pipe, at a vaccuum of 24 Inches i.e. 600 MM Vaccuum. The Circular Pipe became flat of 200 MM through out the length of 12 Metres.

DHAYANANDHAN.S
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JNB
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#3

Re: Full Vacuum (FV) Design Pressure

02/01/2013 1:25 PM

Full Vacuum design pressure means the vessel is rated to be used at any vacuum level that can be achieved under standard atmospheric pressure conditions. It is usually associated with a temperature range as well. Note that this assumes all materials that contact the vessel are compatible with it and do not cause unacceptable levels of physical or chemical corrosion and abrasion.

A plate rating 5+FV likely means that the vessel is rated to be used from 5 (whatever the units are, if there are none you have a serious problem and should be on the phone to the manufacturer if using under pressure!!) down to full vacuum. You do have to make sure that this is for the vesssel and not any jacketing as each has to be rated seperately- jackets are not often vacuum rated though.

Any structural repairs that would affect the integrity of the vessel (eg. wall repairs to a tank, not just extending the legs on it) will definitely require recertification to the appropriate code by a competent person. Therefore, the only person that can tell you what the pressure capacity will be afterwards will be the engineer dealing with it.
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contactfarhan
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#6
In reply to #3

Re: Full Vacuum (FV) Design Pressure

02/02/2013 2:26 AM

Dear JNB, Thanx alot for your valuable comments, Sorry i forgot to put units it is 5+FV barg. at 225 Deg C.
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SolarEagle
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#4

Re: Full Vacuum (FV) Dsign Pressure

02/01/2013 2:37 PM

Full vacuum would mean 0 psi inside and normal atmospheric pressure outside...

as an example...

"The meaning of "4.5 MPa/FV" is that the pressure vessel or similar component is designed for a pressure of 4.5 Mega Pascals (gauge pressure), or Full Vacuum conditions. One Mega Pascal = Millions of Pascals. One MPa (gauge pressure) = 145.03 PSIG. The term FV means Full Vacuum, generally taken as 1 Atmosphere Pressure External to the vessel, with zero absolute pressure inside, equivalent to 15 PSIG External Pressure. "

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PWSlack
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#7

Re: Full Vacuum (FV) Design Pressure

02/02/2013 9:22 AM

Remember also that the vessel will have test records - records of hydraulic testing that have been witnessed by the Engineer/Surveyor for the company supplying burst/collapse indemnity insurance for the facility. The records will be in the facility's General Register, for review and re-test at intervals for insurance purposes. The magnitude of the test pressure applied to the vessel, and its working pressure for insurance purposes, will be noted on the certificate. It is important to check this, as the safe working pressure as determined by that company, may be changing with time. Vessels do deteriorate, particularly those containing steam and compressed air, as the thichkness of the vessel wall falls with time, due to corrosion.

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contactfarhan (1); dhayanandhan (1); JNB (1); JPool (1); lyn (2); PWSlack (1); SolarEagle (1)

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