Basis of Specification
1. Design Pressure
Unless otherwise specified, the minimum corrosion allowance shall be:
Carbon Steel Alloy Steel: 1.5 mm
Ferritic Steel: 1.5.mm
Austenitic Stainless Steel for general purpose: 0 mm
The following minimum pipe wall thickness shall be used for carbon and low alloy steels of process and utility piping including the items mentioned above.
112“ and smaller
2" to 6"
8" to 12"
14" and over
Design temperature as given in the line list for each pipeline. Design temperature as given for each service in the service summary by Process Discipline or Process Licensor.
When maximum operating temperature (T) is given in line list or service summary, the design temperature (T) shall be as follows :
T = T 0+ (+20) 0 C, When T0 is between 0 to 200 0 C
T = T 0+ (+10 to + 20 ) 0 C , when T0 is over 200 0 C
T = T 0+ (-5) 0C, when T 0 is 00 C and under
Where = T = Design Temperature
T 0 = Maximum Operating Temperature
The design temperature of a piping system shall be the design temperature of connected equipment.
For un-insulated piping, the design temperature may be determined in accordance with ASME B 31.3.
The reducing co-efficient for piping components not specific in the ASME B 31.3 shall be 95% for fluid temperatures over 370 C .
4. FittingsLong radius (R= 1.5 D) but welding elbows shall be used wherever possible. Unless otherwise specified, flanged elbows shall not be used.
Pipe bends may be used in place of elbows, which shall not be used. Pipe bends may be used in place of elbows, but the minimum-bending radius shall be 5 times the nominal pipe size.
Miter bends may be used within the limitations specified in the ASME B 31.3.
- Where pipelines are connected to flanged equipment and valves.
- Where frequent dismantling of piping is required.
- Where clearance for dismantling equipment such as compressors and reactor heads is required.
- Where steel piping is connected to non-metallic or non-ferrous piping.
6. Flange Types6.1 Slip-on Flanges
6.2 Welding Neck Flanges
Welding neck flanges shall be used in all instances where slip-on flanges, socket weld flanges and screwed flanges are not permitted.
6.3 Socket Weld Flanges
Raised face flanges shall in general be used:
i. For flanges of 600 LB or lower rating in process services.
ii. For flanges of 1500 LB or lower rating in utility services.
iii. Regardless of the above limitations a) and b) for design temperatures not exceeding 4500C.
However requirements of basic documents shall not be diluted in this process.