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opinion1055
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Join Date: Aug 2014
Posts: 8

Design Temperature & Design Pressure

08/26/2014 2:26 AM

Hello friends,

Am in stress analysis & I have a doubt.

In most cases i happen to work for very OLD Plant expansion projects.The input from client will be certain OLD existing documents. Most cases from scratch.

Suppose i have a line list that show only Operating pressure and temperature and not Design temp. and pressure, then how can i judge its design temp and pressure.

Is it a multiplication factor like 1.2 times or 1.5 times etc ?

Why I'm asking this is bcoz,
I have an iso of system 8"-P- line with Op.temp = 134 deg C, & Design temp = 38 deg C & Op.Press = 1.01 Bar, & Design Press = 19.64 Bar ( The line is connected to Stripper Column).

In the isometric(23 yrs old ), design parameter specified is actually the B16.5, 150# flange rating temp-press.
Client is asking to use this as design value.
But how can I use this in CAESAR Stress Analysis ?
It not logical.
That is why I raised this question.

Please advice..Thanks in advance
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PWSlack
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#1

Re: Design temparature & Design Pressure

08/26/2014 4:48 AM

In what condition is the 23-year-old pipework?

"A chain is only as strong as its weakest link." - Anon.

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opinion1055
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Join Date: Aug 2014
Posts: 8
#2
In reply to #1

Re: Design temparature & Design Pressure

08/26/2014 5:40 AM

The pipe is working good. And is in KSA.

Since the stripper is replaced with new, a major portion of the line has to be redesigned and Stress checked.
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shaff
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#3
In reply to #2

Re: Design temparature & Design Pressure

08/26/2014 6:34 AM

1. Assuming the material is CS.

2. Re check on your Operating Temperature and Pressure. Confirm them from client. Design values written on isometrics are often the max limits of the corresponding pipe class. Better get the operating conditions confirmed.

3. Now assuming you have confirmed the operating temperature to be 135 DegC and Pressure to be 1.01 Barg, you probably can refer to "TABLE 2-1.1 Pressure Temperature Ratings for Group 1.1 Materials" of ASME B16.5 and propose the client a Design temperature of 150 DegC which has a Working Pressure limit of 15.8 Barg (under 150# rating). Note that here the design pressure is well above operating pressure so "I feel" it would not be a problem. But design temperature is 15 DegC more than operating (1.1 times the operating), which "I feel" may be a concern to client. But propose and check back with them

3. Considering the above proposal is rejected, you can again go back to the same table and pick design temperature as 200 DegC and design pressure of 13.8bar. these values "I feel" are definitely above the operating conditions you stated. Note that these values are for 150# and you are increasing the temperature and limiting the pressure values.

4. Analyse the piping with this design limits and see if they work fine.

Before you do any analysis, confirmation from client, on the values you take is essential. Working in middle east, you would always work in this type of revamp projects only which are always atleast 25 years old plants :) We call it "Forensic Engineering"
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opinion1055
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#7
In reply to #3

Re: Design temparature & Design Pressure

08/27/2014 1:25 AM

Thanking you Shaff for you time and reply.. !!!!!
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PWSlack
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#4
In reply to #2

Re: Design temparature & Design Pressure

08/26/2014 6:35 AM

What test protocols took place when the line was created 23 years ago? What has changed since?

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lyn
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#5

Re: Design Temparature & Design Pressure

08/26/2014 9:09 AM

Where's the piping engineer?

If the client writes his desired design parameters into the contract, then that becomes the baseline.

Finally, total dependence on CAESAR to do the analysis on a 23 year old pipeline merely indicates that you need to hire a structural engineer who can use a pencil and a piece of paper to do the analysis.

The local authorities and the insurance carrier may have opinions about this work, too.
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MJCronin
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#6

Re: Design Temparature & Design Pressure

08/26/2014 3:22 PM

Opinion....

You are correct. Once design information reaches about 20 years old it is no longer valid for a CAESAR-II piping stress analysis.

The multiplication factor that you desire is 1.3345....

Old information is of little use to a young new stress analysis engineer

I suggest that you contract for professional help.

Also, get someone to help you with this piping mess.

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opinion1055
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Posts: 8
#8
In reply to #6

Re: Design Temparature & Design Pressure

08/27/2014 1:27 AM

Thankiing you MJCronin !!!!!!!!!!
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Crabtree
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#9
In reply to #8

Re: Design Temparature & Design Pressure

08/27/2014 7:03 AM

Congratulations. You've won the award for exclamation mark use given out by the Andy Germany Appreciation Society.

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Whitephone
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#10

Re: Design Temparature & Design Pressure

08/27/2014 10:09 AM

API 570 Section 7 (Inspection data evaluation, Analisys and recording)
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dclarihew
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Join Date: Sep 2009
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#11

Re: Design Temperature & Design Pressure

08/27/2014 8:31 PM

Another question to ask is "at what maximum pressure is this system protected?". Does the piping form part of the same pressure system as the vessel, and hence protected by the vessel relief valve, or does it have ultimate overpressure protection from another device - a relief valve, rupture disc, HIPPS etc? In any case, the piping design pressure cannot be lower than the set pressure of the relevant overpressure protection device.
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Anonymous Poster #1
#12

Re: Design Temperature & Design Pressure

08/28/2014 12:06 AM

Very good discussion. voted for shaff . As usual, CR4's mega stars lyn,pwslack and crabtree performed very well and voted for them too.
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Anonymous Poster (1); Crabtree (1); dclarihew (1); lyn (1); MJCronin (1); opinion1055 (3); PWSlack (2); shaff (1); Whitephone (1)

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