We have a CASE to be studied as follows:

1. An un-insulated piping system connected to equipment having service temperature of maximum + 60°C.
2. Piping system is exposed to atmospheric condition as the system is un-insulated, above ground and outdoor installation.
3. Black body metal temperature due to solar radiation is predicted to be maximum +85°C as per furnished data.
4. Winter minimum dry bulb temperature minus 3°C.
5. Climatological data.
Month Mean Mean Monthly Daily
Daily Daily Mean°C Variation
Max°C Min°C of temp. °c
January 18.4 7.9 13.1 10.5
February21.0 8.6 14.9 12.4
March 25.6 13.3 19.5 12.3
April 32.2 19.0 25.6 13.2
May 38.2 24.6 31.7 13.6
June 44.0 27.6 36.4 16.4
July 45.6 29.6 38.2 16.0
August 45.2 28.4 37.3 16.8
September41.5 24.9 33.7 16.6
October 35.5 20.6 28.1 14.9
November26.5 15.0 20.7 11.5
December20.0 8.3 14.0 11.7

6. What temperature load conditions are to be considered for the Analysis ? Is it

i. 21.1°C to 60°C
(or)
ii. 21.1°C to 85°C
(or)
iii. 21.1°C to minus 3°C
(or)
iv. minus 3°C to 85°C
(or)
v. Any other combination and / or range of temperature condition.

We will request your views on URGENT basis.

Regards

Manivannan
Pipe Stress Engineer-ICD
Heavy Engineering Industries & Shipbuilding Co.
PO Box : 10155;
Shuaiba-65452
State of Kuwait
Fax : 00965 326 2142
Mob. : 009656765627
E-mail : psmani@heisco.com

hello manivannan...


i think is would be wise to use the max temperature for expansion check and the least temperature for contaction check. I think you piping system is not so critical since the temperature is so minimal but it is always safe to check the system. i hope i have contribute something.

regards,
ian

Hello Manivannan,

What piping Code are you working to?

Remember that in the B31 Pressure Piping Codes the thermal expansion/contraction is addressed by evaluating the calculated maximum expansion/contraction stress RANGE and comparing it to the maximum allowable expansion/contraction stress RANGE (Sa)

Sa = f x (1.25 x Sc + 0.25 x Sh)

1. You will need to calculate the absolute maximum expansion/contraction temperature range from ambient temperature to hottest temperature added to the absolute maximum expansion/contraction temperature range from ambient temperature to coldest temperature. This will give you an absolute value for the maximum delta T range.

2. Using the calculated maximum delta T range and leaving CAESAR II at its default ambient temperature of 21.1 degrees C., use your absolute value for delta T as your design temperature and you will calculate your maximum thermal expansion/contraction stress range. This maximum thermal expansion/contraction stress range will then be compared to the maximum allowable expansion/contraction stress RANGE (Sa)

3. Any temperature excursions that are enveloped by this maximum temperature range will comprise "partial cycles". You will have to determine how many partial cycles you will expect in the service life of the piping system and consult the design Code for rules for reducing the allowable stress range accordingly (i.e., this would alter the value for the "f" factor used in the B31 Pressure Piping Codes for calculating the maximum allowable expansion contraction stress range Sa). Basically, if the sum of the total number of maximum expansion/contraction cycles added to the number of equivilent cycles (resulting from the total number of partial expansion/contraction cycles - read the Code to learn how to determine equivalent cycles from partial cycles) is less than 7000 the value for factor "f" will be 1.0. The value for "f" will decrease as the number of expansion/contraction cycles increases beyond 7000.

Any equipment loadings (forces and moments) calculated by these analyses should be disregarded.

4. To check your equipment loadings (loadings transferred to the equipment by the attached piping) you will want to do an analysis using default 21.1 degrees C. to the coldest temperature. Also you will want to do an analysis using default 21.1 degrees C. to the hottest temperature. The loadings calculated for the maximum pipe expansion loadings and for the maximum pipe contraction loadings should be compared to the equipment manufacturers' specified maximum allowable loadings. The thermal expansion/contraction stresses calculated by these analyses should be disregarded.