Dents installed with 72%SMYS
pressure in pipe and cycled to failure at Ac = 72% SMYS
New standards for higher stress lines: The NPRM proposes to regulate Class 1 gas gathering lines with an MAOP that produces a hoop stress of 20% or more of SMYS
for metallic lines, or more than 125 psig for non-metallic lines, and that are at least 8 inches in outside diameter.
With alternative MAOP pipelines operating at up to 80% SMYS
, PHMSA wanted to eliminate any potential low-strength pipe in these pipelines.
PHMSA has already given a number of major pipelines approval to operate at 80 percent of SMYS
under special permits.
Cycle counting results in a dataset that reports all of the cycles counted from the input data along with the magnitude of the cycle (in terms of %SMYS
--a line operating at 50% of SMYS
that cycled from slack to M(A)OP would have 1 cycle through 50% SMYS
A similar exception is not allowed if the component other than pipe is being replaced or added to steel pipelines that operate at less than 30% of SMYS
8 Code that pipelines could operate safely at stress levels up to 80 percent of SMYS
Critical detection targets correspond to axial stress levels of 60% and 75% specified minimum yield strength (SMYS
) and monitoring detection targets correspond to the axial stress level of 90% SMYS
Under the proposed rule, companies would have to do a full integrity management (IM) program on lines operating at or below 20 percent SMYS
, located in or within a quarter-mile of a USA.
Those concerns and others aside, INGAA has made a counter proposal which includes submission of some of the new information PHMSA would like to have, such as the pipe arterial, the nominal pipe diameter, pipe coating, whether a low-stress pipeline is using the 30% SMYS
threshold and some other items.
But 20 percent of SMYS
or below exemption would cover 18 percent of those utility lines.
For lines operating above 40 SMYS
, the operator must either install a full encirclement split sleeve or replace the pipe.