Category D Fluid Service
Any ASME B31.3 Fluid Service Types that fulfilled all the requirements stated here; are categorized as Category D.
The first condition is that the fluid handled is non-flammable, non-toxic, and not damaging to human tissues.
The second condition is design pressure. For this service, the design gauge pressure does not exceed 150 psi. The normal atmospheric pressure is approx. 15 psi. So, this service handles moderate pressure.
The third condition is design temperature. The design temperature is between –29 and 186 degrees centigrade for this service. So, like pressure, this service handles moderate temperatures.
You can say that most utility lines, such as water, air, etc., fall under this type of fluid.
Piping is designed as per ASME B 31.3, chapter I to VI for metallic and chapter VII for non-metallic and lined piping. Normally carbon steel pipes such as ASTM A 53 and API 5L GR B are used. It may be galvanized or painted.
Category M Fluid Service
Category M fluid is highly toxic. Very small exposure caused by leakage can create permanent damage to body parts even if you take prompt measures.
So, all such fluids and if the owner of the facility, based on his experience, feels that safety measures requirements for Normal Fluid Service do not sufficiently provide the leak tightness required to protect personnel from exposure are part of this group.
Category-M fluid service piping is designed by chapter VIII rules of ASME B 31.3. Therefore, you must take enough safeguarding while designing the piping for category-M fluid service.
High-Pressure Fluid service.
ASME B31.3 says that a fluid service for which the owner specifies Chapter IX for piping design and construction is called high-pressure fluid service.
Usually, any service that requires a flange class exceeding 2500 is called high-pressure fluid service.
Non-metallic or metallic lined piping components are not permitted in the high-pressure piping category.
Elevated Temperature Fluid Service.
ASME B31.3 says that a fluid service in which the piping metal temperature is sustained equal to or greater than Tcr.
Tcr is corrected temperature 25°C below the temperature identifying the start of time-dependent properties. Creep is one of the time-dependent properties of a material. That means when your design temperature is high enough to affect stress value, it is considered an Elevated temperature fluid service.
While designing piping for Elevated temperature fluid service, you must consider this mechanical property for safe design.
High Purity Fluid Service.
ASME B31.3 says that a fluid service that requires alternative fabrication methods, inspection, examination, and testing is not covered elsewhere in the Code, with the intent to produce a controlled level of cleanness.
When process fluid requires the cleanest environment to avoid any metal-induced impurity, additional standards are used to design these piping. Industries such as pharma and food processing may require this type of cleanness in piping when piping systems are defined as high purity, ultra-high purity, hygienic, or aseptic.
Normal fluid service.
As the name suggests, if the fluid service for a pipeline is not any of the earlier discussed, it is a normal service.
So, you go through the categories such as high pressure, temperature, purity, Category D and M, and then whatever is left is called normal service.
Therefore, most piping designs covered in ASME B31.3 are for this normal fluid service piping category.
It is designed and constructed as per chapters I to VI for metallic piping and as per chapter VII for non-metallic and lined piping.
This is all about ASME B31.3 Fluid Service Types.