API 570 (& B31.3) Piping Classification,
Intervals, and Categories
For Class 1, 2, and 3 piping, the period between thickness measurements for CMLs or
circuits should not exceed - answer one-half the remaining life.
Interval for Class 1 - answer on-half life or Five years for thickness and five years for
external VT, < 4 years left -Full remaining life up to 2 years
Interval for Class 2 - answer on-half life or Ten years for thickness and five years for
external VT, < 4 years left -Full remaining life up to 2 years.
Interval for Class 3 - answer on-half life or Ten years for thickness and Ten years for
external VT, < 4 years left -Full remaining life up to 2 years.
Interval for Class 4 - answer Optional for thickness and Optional for external VT.
Interval for injection Points - answer three years for thickness and By class for external
VT.
Interval for StA - answerno regulation on thickness measurements, external VT by
class, and 6 months for grade side of interface.
Owner/users shall maintain a record of process piping fluids handled, including -
answertheir classifications.
The operating temperature of a hydrocarbon stream relative to its flash point, boiling
point and auto-ignition temperature is a significant factor in - answerdefining potential
consequence of a release.
Operating temperature of hydrocarbon piping systems should be considered when -
answerassigning piping service class.
On-site ambient temperature gasoline is Class 2 because it is below the boiling point
but above its flash point, however, what would make it Class 1? - answerabove 550 °F,
gasoline should be Class 1 since auto-ignition can occur.
Class 1 Services are piping with the highest potential of resulting in - answeran
immediate emergency if a leak were to occur.
, Flammable services that can auto-refrigerate and lead to brittle fracture are what Class?
- answerExample of Class 1 piping.
Pressurized services that can rapidly vaporize during release, creating vapors that can
collect and form an explosive mixture, such as C2, C3, and C4 streams are what Class?
- answerExample of Class 1 piping.
Fluids that can rapidly vaporize are those with atmospheric boiling temperatures below -
answer50 °F (10 °C) or where the atmospheric boiling point is below the operating
temperature.
Hydrogen sulfide (greater than 3 % weight) in a gaseous stream is considered what
Class? - answerExample of Class 1 piping.
Anhydrous hydrogen chloride is an example of what Class? - answerExample of Class
1 piping.
Hydrofluoric acid is an example of what Class? - answerExample of Class 1 piping.
Piping over or adjacent to water and piping over public throughways are automatically
what Class? - answerClass 1 piping.
Flammable services operating above their auto-ignition temperature are considered
what Class? - answerClass 1 piping.
Services not included in other Classes are - answerClass 2.
Class 2 includes the majority of - answerunit process piping and selected off-site piping.
On-site hydrocarbons that will slowly vaporize during release such as those operating
below the boiling point but above the flash point are what Class of piping? -
answerClass 2.
On-site hydrogen, fuel gas, and natural gas are all Class - answerClass 2 piping.
On-site strong acids and caustics are part of what Class of piping? - answerClass 2.
Services that are either flammable but do not significantly vaporize when they leak or
flammable but are located in remote areas are in what Class? - answerin Class 3.
Services that are potentially harmful to human tissue but are located in remote areas
may be included in which class? - answerClass 3.
On-site hydrocarbons that will not significantly vaporize during release are Class -
answer3
Intervals, and Categories
For Class 1, 2, and 3 piping, the period between thickness measurements for CMLs or
circuits should not exceed - answer one-half the remaining life.
Interval for Class 1 - answer on-half life or Five years for thickness and five years for
external VT, < 4 years left -Full remaining life up to 2 years
Interval for Class 2 - answer on-half life or Ten years for thickness and five years for
external VT, < 4 years left -Full remaining life up to 2 years.
Interval for Class 3 - answer on-half life or Ten years for thickness and Ten years for
external VT, < 4 years left -Full remaining life up to 2 years.
Interval for Class 4 - answer Optional for thickness and Optional for external VT.
Interval for injection Points - answer three years for thickness and By class for external
VT.
Interval for StA - answerno regulation on thickness measurements, external VT by
class, and 6 months for grade side of interface.
Owner/users shall maintain a record of process piping fluids handled, including -
answertheir classifications.
The operating temperature of a hydrocarbon stream relative to its flash point, boiling
point and auto-ignition temperature is a significant factor in - answerdefining potential
consequence of a release.
Operating temperature of hydrocarbon piping systems should be considered when -
answerassigning piping service class.
On-site ambient temperature gasoline is Class 2 because it is below the boiling point
but above its flash point, however, what would make it Class 1? - answerabove 550 °F,
gasoline should be Class 1 since auto-ignition can occur.
Class 1 Services are piping with the highest potential of resulting in - answeran
immediate emergency if a leak were to occur.
, Flammable services that can auto-refrigerate and lead to brittle fracture are what Class?
- answerExample of Class 1 piping.
Pressurized services that can rapidly vaporize during release, creating vapors that can
collect and form an explosive mixture, such as C2, C3, and C4 streams are what Class?
- answerExample of Class 1 piping.
Fluids that can rapidly vaporize are those with atmospheric boiling temperatures below -
answer50 °F (10 °C) or where the atmospheric boiling point is below the operating
temperature.
Hydrogen sulfide (greater than 3 % weight) in a gaseous stream is considered what
Class? - answerExample of Class 1 piping.
Anhydrous hydrogen chloride is an example of what Class? - answerExample of Class
1 piping.
Hydrofluoric acid is an example of what Class? - answerExample of Class 1 piping.
Piping over or adjacent to water and piping over public throughways are automatically
what Class? - answerClass 1 piping.
Flammable services operating above their auto-ignition temperature are considered
what Class? - answerClass 1 piping.
Services not included in other Classes are - answerClass 2.
Class 2 includes the majority of - answerunit process piping and selected off-site piping.
On-site hydrocarbons that will slowly vaporize during release such as those operating
below the boiling point but above the flash point are what Class of piping? -
answerClass 2.
On-site hydrogen, fuel gas, and natural gas are all Class - answerClass 2 piping.
On-site strong acids and caustics are part of what Class of piping? - answerClass 2.
Services that are either flammable but do not significantly vaporize when they leak or
flammable but are located in remote areas are in what Class? - answerin Class 3.
Services that are potentially harmful to human tissue but are located in remote areas
may be included in which class? - answerClass 3.
On-site hydrocarbons that will not significantly vaporize during release are Class -
answer3
