Page 58 - Pipeline Pigging Technology

Regulations: during and after rehabilitation

Method 1: This type can range from exposing the pipe in a hellhole of a few
ieet in length to a fairly long segment of several hundred feet. It is obvious that
on any segment that exceeds the maximum-allowable length for unsupported
line, pipe will have to be supported by either an earth plug or a temporary
pipe support. Also, the situation becomes more critical on a line containing
liquid. This is where the services of a very experienced stress engineer are
essential.

Method 2\ This type of project usually involves several miles of pipe and,
by the magnitude of the job, involves a wide range of the regulations, both for
gas and liquid lines. For example, some typical steps are:

1. remove the line from service and evacuate the product. (If stress-
corrosion cracking is suspected, then a hydrostatic test is per-
formed);
2. excavate the line and place on skids;
3. remove the deteriorated coating;
4. inspect the pipe surface for corrosion and damage;
5. replace all failed or damaged pipe;
6. prepare the surface and recoat the pipe;
7. place the pipe in the ditch;
8. backfill;
9. hydrostatic test;
10. tie-in and bring back into service; and
11. install cathodic-protection system.

In this type situation you have, in effect, the same circumstances as the
construction of a new system.

BASIC REGULATORY AREAS CONSIDERED

Let's look at some basic areas of the pipeline regulations that have to be
addressed, and briefly comment on each one; Figs 1 through 4 indicate those
parts of the respective regulations that could apply to either or both methods.
The basic areas are:

39