MCE International carries out the engineering and design of HIPPS systems at the Teesside ( UK ), headquarters of MCE Group. Within the engineering package is a complete turnkey development of the systems, including design, procurement, build and commissioning. In addition, MCE can offer the incorporation of Valvtechnologies ( VTI ) high performance, zero leakage, metal seated ball valves within the architecture of the system.

General

In general, the HIPPS design should satisfy:

* The required SIL by calculation, based on component reliability

* Fault tolerance requirements

As a rule of thumb, many operators choose to design HIPPS at a target SIL 3, regardless of pressure relief device type.

It should be noted also that in the UK, ALARP ( as low as reasonably practicable ) plays an important role when considering risk in the derivation of the safety case associated with any HIPPS application. Reference to, and conformance with, safety standard IEC 61508 will be an essential requirement of the HIPPS design process.

The overview drawing attached shows the MCE HIPPS package. This is intended to show capability in supporting the engineering design requirements for a HIPPS application. However, the engineering exercise in its entirety will involve much deeper engineering work including detailed electrical, mechanical, and control system design, calculations and safety conformance verifications

As a broad definition, HIPPS, High Integrity Pressure Protection System, is a term applied to an instrument based protective system installed in a situation where downstream plant is not fully rated to the potential pressures it may be exposed to in a fault condition.

Industry is increasingly utilizing HIPPS to reduce flare loading and to prevent negative environmental impacts associated with the traditional techniques of pressure relief venting.

The actual composition of a HIPPS system is relatively simple and includes pressure sensing instrumentation, 2 out of 3 (2oo3) or 1 out of 2 (1oo2) voting logic, and two actuated shutdown valves. It would also include remote signaling of alarms.

In terms of application, the use of HIPPS is determined by definition within a safety case and hazard analysis for the particular installation ( pressure system ) under consideration. The safety case should identify the extent of the safe design carried out for the pressure system. If the safety case identifies an installation that itself can be defined as an 'inherently safe system' then it would be deemed 'fully rated' and HIPPS would not be required. However, if the case for an inherently safe system cannot be proven then the utilization of HIPPS can be justified.

The Safety Case

The safety case and hazard analysis would necessarily involve assessment of all possible overpressure conditions to satisfy the application of a HIPPS solution. Within the hazard analysis a safety integrity level ( SIL ) will be determined for the HIPPS and the installation will also need to satisfy fault tolerance requirements. Installed equipment such as subsea isolation valves upstream of the riser would be an example whereby the HIPPS SIL would be reduced.

SIL Levels

Actual determination of SIL is based around equivalent performance comparisons against pressure relief devices. For instance, for spring operated pressure relief devices a minimum target SIL 3 would be used; for pilot operated devices SIL 2 would be adopted.

In general, SIL can be defined in four discrete bands as follows:

SIL 4 highest and most onerous target to achieve requiring state of the art techniques ( usually avoided )
SIL 3 less onerous than SIL 4 but still requiring the use of sophisticated design techniques
SIL 2 requiring good design and operating practice to a level akin to ISO9001
SIL 1 the minimum level but still requiring good design practice
Calculation of SIL for HIPPS is, in essence, relatively straightforward since it is based on equipment reliability data, but common cause failure considerations during operation add an 'unknown' element to the equation. Such failure conditions generally relate to the mechanical valves used on the HIPPS installation where process conditions can cause detrimental effects on their long-term operation.

Technical Competence and ISO Accreditation

MCE International has established a fully operational multi-discipline design team based at the Teesside facility in the UK. The skills of the team extend into:

* Engineering consultancy
* Project engineering, management and control
* Project planning
* HV electrical system design
* Control system design
* Safety system design
* Control systems software
* Mechanical system design

The competence of the team to undertake the engineering, design, and build of a HIPPS skid are clearly demonstrable by the context of the detail engineering inherent in projects currently under execution.

In addition, when proposing solutions to prospective customers conformance to ISO accreditation will be imperative. MCE has accreditation to ISO9001:2000 that includes engineering and design services. A recent audit by the MCE accreditation body, SGS Yarsley found no corrective actions required in the design operations resident in MCE International.