HIPPS (High Integrity Pressure Protection Systems) are rapidly gaining ground in the LNG sector as an alternative to pressure relief systems with ultimate line of defence. Situated between high-pressure upstream and low-pressure downstream sections of an installation, they contain media if over-pressurisation is likely to occur. These engineered systems form part of advanced LNG safety systems and high-pressure shutdown technologies.

The core benefit of HIPPS is that the system is activated before over-pressurisation, automatically bringing high-risk processes to a safe state. With traditional pressure relief systems, a relief valve is triggered to vent during over-pressurisation. This allows excess gas or fluid to escape into the surrounding environment. HIPPS offers LNG overpressure mitigation and is recognised as a mission-critical safety system.

Superior downstream protection 

A HIPPS is a sophisticated valve-based safety instrumented system (SIS) designed to protect equipment from over-pressurisation scenarios that could result in full emergency shutdown. As a SIL 3–capable system and high‑reliability pipeline protection solution, these systems offer superior protection of downstream assets on any LNG plant, vessel or facility.

Traditionally, installations facing the strictest environmental regulations were at the forefront of HIPPS uptake as the systems out-perform standard safety regulations. However, associated economic advantages are now more widely recognised and driving further interest. Operators see HIPPS as a cost-effective LNG protection system and an OPEX-saving pressure protection technology.

As an emergency response solution, HIPPS deployment is far less costly than lengthy emergency shutdowns and all the repercussions they entail. When a relief valve is activated, operators face heavy costs surrounding intervention and lost production. HIPPS reduces unplanned downtime, supports LNG asset protection, and strengthens compliance with IEC 61511 safety lifecycle requirements.

But the benefits of HIPPS go further than simply reducing costs in the event of an incident. Deploying HIPPS in a pipeline unlocks the potential for lower downstream design pressures. So, the required wall thickness for downstream assets decreases, allowing de-rated pipework to be used, which brings potential size, weight and cost advantages, as well as having a positive impact on flow rates and throughput. This directly supports CAPEX optimisation and LNG pipeline protection strategies.

So, while environmental requirements initially drove LNG HIPPS uptake, it’s now widely recognised that there are three scenarios where the systems should be brought to the table. If the surrounding environment needs to be protected, the economic feasibility of a development needs to be improved or the risk profile of a facility needs to be reduced, HIPPS is an attractive and viable alternative to simple relief systems. HIPPS are equally effective in new projects or when adding to or upgrading existing installations. They support both FLNG and FSRU project safety upgrades and are adaptable for brownfield modernisation programmes.

The art of HIPPS integration 

HIPPS have a high degree of redundancy to maximise safety for site personnel, the general public and the environment, as well as high-value production assets. They are comprised of integrated technologies arranged in a complete functional loop, with three fundamental components: 

1. Pressure Transmitters monitor pipeline pressure and convey a signal to a logic solver.  

2. The Logic Solver captures signals from the pressure transmitters and performs a 2oo3 voting logic.  

3. The Final Element (normally two shut-off valves) provides corrective action to bring the process to a safe state.  

This architecture aligns with SIL 2 / SIL 3 compliant HIPPS design and functional safety lifecycle requirements. The use of redundant shutdown valves supports high-integrity pipeline isolation.

This configuration maximises performance and reliability. The 2oo3 (two out of three) methodology enhances the systems’ ability to detect problems, while reducing the likelihood of a response being triggered unnecessarily. Should one of the pressure transmitters fail, it won’t compromise functionality as two high pressure readings are required for activation. Likewise, if one of the valves in the final element fails, the second valve acts as a back-up to maintain the isolation of the high-pressure source. This also minimises common cause failure risk and aligns with LNG process safety solutions.

Clearly, in an ideal world, safety systems would never need to be activated. Plant designers and engineers should continually strive for inherent safety. HIPPS are the last line of defence and shouldn’t be considered an alternative to designing out potential over-pressurisation problems. Holistic thinking and intelligent design reviews are essential to enhance overall safety and get the most out of HIPPS. 

Front-end planning for LNG’s Line of Defence

When projects don’t allow adequate time for detailed assessment upfront, it can result in the installation of HIPPS with an inappropriate safety integrity level (SIL) specified. This affects pipeline risk analysis, LNG process safety performance, and SIL compliance.

Engaging a HIPPS integrator at an early stage is another crucial step. Ideally, they should be independent, so they have the freedom to draw on the best technologies to meet specific needs of an individual plant application. Independent HIPPS integrators provide project-ready HIPPS solutions and custom engineering support aligned with IEC 61508 and IEC 61511.

Opting for two different valve designs, such as a gate valve and a ball valve, from independent suppliers is a more effective way to maximise redundancy, enhancing overall safety and reliability. This is considered best practice in LNG engineering services and LNG safety architecture.

There’s no denying that the deployment of HIPPS can complex and challenging. To counter this, their development and integration should draw on the combined expertise of electronic and software engineers as well as mechanical engineers. A functional safety management system (FSMS) and validated SIL 3 components enhance reliability.

This consultative ‘one-stop-shop’ approach makes for a structured, cost and time saving solution. It also supports LNG project risk reduction and improved operational integrity.

The eight phases of HIPPS 

Each phase of a HIPPS project is dictated by safety lifecycle standard IEC 61511, including decommissioning at end of life. A partnership approach with clearly defined responsibilities enables operators to benefit from the specialist expertise of HIPPS integrators and other third parties.  

1. Hazard and risk assessment or Hazard and operability study (HAZOP) (end user responsibility) 

2. Allocation of safety functions to protection layers (end user responsibility) 

3. Safety requirements specification (end user responsibility) 

4. Design and engineering of safety instrumented system (HIPPS integrator responsibility) 

5. Installation and commissioning (HIPPS integrator responsibility) followed by validation (certifying body responsibility, e.g. TUV) 

6. Operation and maintenance (end user and HIPPS integrator, shared responsibility) 

7. Modification (HIPPS integrator responsibility) 

8. Decommissioning (end user and HIPPS integrator, shared responsibility) 

Application spotlight: FSRU HIPPS 

Engineers from Severn recently integrated, supplied and commissioned a HIPPS for an LNG Floating Storage and Regasification Unit (FSRU) being built by DSME in Korea. This involved advanced HIPPS installation services and LNG regasification protection.

The vessel, BW Magna, has a 173,400 cubic metre capacity and the HIPPS has been installed to protect the pipeline during the unloading of gas. This enhances safety for the FSRU itself, as well as the downstream equipment and pipeline in the docking terminals it connects with. 

HIPPS are not mandatory on FSRUs, but it’s increasingly recognised that they provide a superior level of safety and reliability. The system supplied to DSME operates at a working pressure of 117 barg. It comprises two 18” 900-class manual valves, a Sella Controls logic solver and three pressure transmitters. 

Additional safety measures on the FSRU include alarms, a shutdown system, blow down system and safety valves, as per industry-specified standards. The benefit of adding HIPPS is that it is a simple, proven solution which can operate independently of the wider vessel system.  

Conclusion 

The design, build and testing of HIPPS poses many challenges, compounded by a lack of defined standards for design parameters. This calls for a high level of interaction between the end user, HIPPS integrator and other parties throughout the eight phases of HIPPS development and deployment aligning with LNG’s Line of Defence. However, the investment of time, money and effort reaps dividends in the shape of superior safety and environmental credentials combined with associated economic advantages. These three factors are coming under increasing scrutiny in all areas of the energy industry. LNG players who invest in the best safety systems now will be one step ahead.