scope:

PURPOSE OF FIELD TESTING

Hydrostatic testing is universally known and accepted as the primary means of demonstrating the fitness for service of a pressurized component. It is the responsibility of the owner, through its agents (engineer, contractor, or hydro-test company) to develop its own safe and appropriate hydro-test plan, taking into consideration all the elements presented in this and other reference documents, in order to assess and accept the installed pipeline from the contractor. After hydrotest, a pipeline or pressure vessel component may usually be expected to safely contain its intended operating pressure. However, even after a successful hydro-test, leakage or forced ruptures may occur later, for a variety of other reasons. The pre-commissioning hydro-test is simply one tool for evaluating a pipeline. The purposes of hydrostatic field testing of polyethylene pressure pipes using water are several, including:

• To assess the installed structural integrity of the pipeline for acceptability.

• To try to reveal the occurrence of faults or defects in the pipe laying procedures, as exemplified by damaged pipe or fusion joints non-conforming to the qualified fusion procedures.

• To try to reveal the occurrence of faults in the assembly procedures for pipeline components, as exemplified by tapping bands or saddles, flange sets, or Mechanical Joint assemblies.

• To try to validate that the pipeline will sustain an acceptable level of overpressure slightly greater than its design pressure, without leakage.

Note: Field testing is not intended to supplement or replace product standard test requirements.

The factors which affect the hydro-testing of HDPE pipe during commissioning procedures are: the creep characteristics of the PE pipe, the percentage volume of trapped air in the pipeline, and temperature variations. The self-limiting creep expansion of HDPE pipe is normal behavior for plastic materials when an internal pressure is applied, and is not an indication of a leak.