6 replies to this topic

[rana_nikhil2002]

Dear All,

I am working on insulation thickness calculation for Liquid and Vapour LPG line.
Design Pressure = 19.6 Bar
design Temp. = 0 to 60 C
Density of liquid LPG = 545 Kg/M3 and Vapure LPG = 9.9 Kg/m3
Amb. Temp = 60 C

Can any one please guide me to how I can find insulation thickness using above data.

Addition to this data :
Specific heat for liquid = 1548 J/Kg.K
Specifica hear for Vapour = 2061 J/Kg.K

Edited by rana_nikhil2002, 05 September 2012 - 10:29 PM.

[jrtailor09]

Dear nikhil,

Kindly recheck the Design temperature provided.

I feel it is not correct. There are lot discussion on insulation thickness calculation.

Better to follow standard guidelines instead of calculating thickness.

Regards,

[rana_nikhil2002]

Dear

This is a case of pipeline installed in Angola, Africa where ambient temp. could reach upto 50 to 60. So normal operating temp. of LPG product is 0 to 50 C.
For additional data this is Jetty where oil products and LPG needs to offloaded from ship and transfer to storage tanks.
Now, regarding LPG considering operating temp. 45 C and ambient Temp 60 C , there is heat transfer from outside to inside pipe. So there is possibility of Liquid LPG may generate vapour and there is possibility of explosion.
Please reply considering this situation and feel free if required more data

[ontherun]

I would consider a PIR type insulation at circa 50mm thick with foiled face. Aluminium would be a decent mechanical protection.


Hope this helps.

OTR

[Art Montemayor]

rana_nikhil2002:

The hottest place on earth ever recorded was Al-'Aziziyah in Libya where the temperature reached a scorching 136 degrees Fahrenheit (57.8 Celsius) on Sept. 13, 1922. This makes it the hottest place in the world to date.

And that was with a 1922 thermometer in a Libyan infrastructure at that time that surely didn’t have the latest technology in thermometers. That “record” hasn’t been equaled nor surpassed in the last 90 years – even with today’s more developed technology and instrumentation. This information also does not even mention HOW LONG that temperature was sustained (I suspect it peaked at around noon time in beautiful, downtown, Al-'Aziziyah). Additionally, that record is for the ambient air for that brief moment, not a steady and sustained condition.

Therefore, jrtailor09 has every logical, common sense reason to challenge your establishment of such an exaggerated temperature condition. Also,

• Are you assuming the LPG liquid in the pipeline would be static at the ambient peak temperature?
• If this is a Jetty where the LPG is offloaded, then it is at the seashore and that makes it even more improbable that the temperature would be that high due to the ambient humidity;
• Regardless of what you say, if the pipeline is filled with liquid LPG and it is forced to reach 60 ^oC --- or even 100 ^oC, that does not mean it will generate vapor (“boil”); it will only generate a higher pressure and probably reach a state of supercritical compression (as a supercritical fluid); that alone does not give cause for an explosion to occur.
• If you can fully justify a higher saturated temperature for the LPG, then why not just design the pipeline to sustain the maximum saturated pressure? That would be far more simpler than installing and maintaining insulation.

I have visited and worked in Angola. It is a beautiful country – far more beautiful than Libya and far cooler.

[kkala]

Not having expertise on the topic, I remember few demonstrations of software to estimate insulation thickness in pipes (1985). The criterion of insulation thickness was "heat loss reduced to 1% - 5% of bare pipe loss". The percentage 1% - 5% could be manually specified.

Editing note, 10 dec 2012: The post is not related to the topic, but to another post (written above the present one) asking whether there is any standard on heat loss form insulation to environment. Art Montemayor replied (around 1st Dec 2012) that there is no international standard on it, the query could be developed in another thread, the post of heat loss standard in this thread would be deleted. This apparently occurred.
Above is from memory; even though sense is given, wording may not be exact.

Edited by kkala, 10 December 2012 - 12:55 PM.

[Neelakantan]

hi nikhil!


Let us understand the problem clearly; any company involved in importing LPG through Jetty will definitely have standard insulation specifications (for both energy conservation and economics of insulation); if you are in the detailed engineering stage, this specificaiton shall be used for detailing; if you are in the stage of creating or verifying these specificaitons, then probably a senior engineer level of involvement is required.

Be clear about the design parameters; normally they are fixed values (max and minimum) and not a range.
I understand the value you are indicating are probably operating conditions?

Now understand that LPG is a mixture (of C₃ and C₄ and traces of C₂ and C₅s). Look at the envelope of the composition and you will understand Art's statment that the pressure would change if the line is static with liquid and gas. However, since this is a transfer line, it would be under pressure during unloading operation and probably, the pressure would be much more than the "flashing" pressure. I am sure the code would be talking about the unloading rate and the the line could be in use for a max of 24 hours. Rest of the time, the line would be decanted to the storage through a sump pump. and would be at low pressure (~.2 to 0.5 barg). So be clear about the design basis of the line and the operation methodology before deciding the need for insulation.

And i am really interested in the 0 deg C that you have indicated; is it during draining?

Finally, if insulation is required to be estimated manually, use the basics or 3eplus software to estimate the requirement. I dont want to suggest a number;

Regards
neelakantan