Implementation Options for the Subsea High Integrity Pipeline Protection System (HIPPS) Solution
Authors: Hoseth Jacob G. , Willmann Endre , Roberts Paul 
Published: October 2008

The economy of subsea production systems must be improved to maintain the viability of future projects. However any cost saving solutions must recognize strict safety requirements.

Further; reducing the rated working pressure of a pipeline below the maximum working pressure of the well, presents an interesting dichotomy between safety and production downtime.

This paper reports various methods to down rate equipment protected by HIPPS, with respect to the above issues.

In addition to discussion and analysis, some HIPPS design options to be qualified in an ongoing qualification project are presented. The qualification testing is scheduled to be finalized by the end of 1997.

Introduction

Subsea production flowlines are normally rated for the full wellhead shut-in pressure, but often utilized to a small fraction of this capacity to flow the product. The excess capacity may in some cases be prohibitively expensive for the field development. It is therefore a market desire to have protection systems available in order to rate the pipeline closer to the flowing pressure. HIPPS is one such system, in that it allows rapid closure of the inflow to the pipeline upon an unwanted pressure increase. This pressure increase may be the result of an unexpected obstruction of the line further downstream.

HIPPS, or HIPS as it has also been called, has never before been utilized subsea. Offshore topsides and onshore applications are numerous, some of which are referred to in OTC Paper 7828 /Ref.: 1/.

A two-year HIPPS qualification project was started in January 1996, with the aim of having a fully qualified suite of components and systems for subsea HIPPS applications ready by the end of 1997. The testing includes integration testing of the components and sub-systems. The authors behind this paper are team members of this qualification project. The paper reports on some of the system analyses that have been performed to support selection of components and their requirements.

The scope of this paper includes effects on the subsea system outside the exclusion zone of the topside facility. All equipment within this zone is assumed to be designed according to present practice. HIPPS may also have substantial positive effects on the integrity of the pressure containment systems within the exclusion zone, since high pressure situations are less likely to occur than without HIPPS.

HIPPS Risk

Expected risk associated with introduction of HIPPS may be split in three main areas for analysis. The three areas are:Expected number of HIPPS demandsReliability of HIPPSConsequence of simultaneous demand and HIPPS failure

These areas are discussed and analyzed, in reverse order, in the following sections.

Pipeline or Flowline Consequences

The consequences of a HIPPS failure upon a demand depends on the stored volume, pressure, type of fluid, etc. in the system and the probability of its release.

Difference between the maximum obtainable pressure and the maximum allowable pressure for the pipeline is one of the main drivers for this mentioned probability. This difference may be selected for each application depending on field specific requirements and configurations. In other words: