Class of Piping System

Piping systems are subdivided into three classes, denoted as class I, class II and class III, for the purpose of acceptance of materials, selection of joints, heat treatment, welding, pressure testing and the certification of fittings. 

Classes I, II and III defined as by BV are as per table below: 

Media conveyed by the piping system	Class I	Class II (1) (4)	Class III (7)
Toxic media	without special safeguards	not applicable	not applicable
Corrosive media	without special safeguards (3)	with special safeguards (3)	not applicable
Flammable media:  heated above flashpoint, or  having flashpoint < 60°C  Liquefied gas	without special safeguards (3)	with special safeguards (3)	not applicable
Oxyacetylene	irrespective of p	not applicable	not applicable
Steam	p > 1,6 or T > 300	other (2)	p ≤ 0,7 and T ≤ 170
Thermal oil	p > 1,6 or T > 300	other (2)	p ≤ 0,7 and T ≤ 150
Fuel oil   Lubricating oil  Flammable hydraulic oil (5)	p > 1,6 or T > 150	other (2)	p ≤ 0,7 and T ≤ 60
Other media (5) (6)	p > 4 or T > 300	other (2)	p ≤ 1,6 and T ≤ 200

( 1 )    

Valves under static pressure on oil fuel tanks or lubricating oil tanks belong to class II. 

( 2 )    

Pressure and temperature conditions other than those required for class I and class III. 

( 3 )    

Safeguards for reducing leakage possibility and limiting its consequences: 

e.g. pipes led in positions where leakage of internal fluids will not cause a potential hazard or damage to surrounding areas which may include the use of pipe ducts, shielding, screening etc. 

( 4 )    

Valves and fittings fitted on the ship side and collision bulkhead belong to class II. See also [20.4.3] b). 

( 5 )    

Steering gear hydraulic piping system belongs to class I irrespective of p and T. 

( 6 )    

Including water, air, gases, non-flammable hydraulic oil. 

( 7 )    

The open ended pipes, irrespective of T, generally belong to class III (as drains, overflows, vents, exhaust gas lines, boiler escape pipes, etc.).