N.Y. Comp. Codes R. & Regs. tit. 16, § 255.503 – General requirements.

(a) No person may operate a new segment of pipeline, or return to service a segment of pipeline that has been reconstructed, relocated, replaced, or reactivated until it has been tested in accordance with this Part to substantiate the proposed maximum allowable operating pressure and each leak has been located and eliminated.
(b) The test medium must be liquid, air, natural gas or inert gas that is:
1. (1) compatible with the material of which the pipeline is constructed;
2. (2) relatively free of sedimentary materials; and
3. (3) except for natural gas, nonflammable.
(c) If air, natural gas, or inert gas is used as the test medium, the following maximum hoop stress limitations apply:
Maximum hoop stress allowed as
percentage of SMYS
Class Natural Air or inert
Location gas gas
1 80 80
2 30 75
3 30 50
4 30 40
(d) Each weld used to tie-in a test segment of pipeline is excepted from the test requirements of this Part.
(e) If a component other than pipe is the only item being replaced or added to a pipeline, a strength test after installation is not required, if the manufacturer of the component certifies that:
1. (1) the component was tested to at least the pressure required for the pipeline to which it is being added;
2. (2) the component was manufactured under a quality control system that ensures that each item manufactured is at least equal in strength to a prototype and that the prototype was tested to at least the pressure required for the pipeline to which it is being added; or
3. (3) the component carries a pressure rating established through applicable ASME/ANSI, Manufacturers Standardization Society of the Valve and Fittings Industry, Inc. (MSS) specifications, or by unit strength calculations as described in section 255.143 of this Part.

Maximum hoop stress allowed as
percentage of SMYS
Class	Natural	Air or inert
Location	gas	gas
1	80	80
2	30	75
3	30	50
4	30	40