VACUUM INSULATED PIPE (VIP)

Background

Large diameter vacuum insulated piping (“VIP”) was first pioneered and used in LNG export terminals in the late 1990s, followed by continual development by a handful of oil & gas industries with mixed results.   It was not until the early 2010s that reliable and maintenance-free VIP designs became available, based on lessons learnt from earlier designs and plant operations.

Jord’s experienced team has designed and commissioned several VIP systems that are successfully operating at major LNG export terminals in Australia (QCLNG and APLNG) and USA (Cameron and Freeport).  The know-how of this team is enabling ongoing prototyping and development of this technology. Our drive is to continue to improve performance, safety, reliability, durability and maintainability.

Our latest VIP design offers significant technical and commercial improvements over VIP systems built in the 2010s and conventional foam insulation systems.

Figure 1. LNG Export Terminals with Vacuum Insulated Pipe Systems

Design Layout

VIP shares the same stainless-steel core pipes with conventional PIR/PUR systems but is contained by an external pipe in a ‘pipe-in-pipe’ configuration.  The radial gap or annular space between the pipes is insulated with multiple layers of highly reflective aluminium foil to reject radiation heat input. This space is also evacuated to high vacuum levels to eliminate heat transfer media for conduction and convection.

We offer two different types of VIP models, as shown in Fig 2 below.  Each has its distinctive benefits and applications.  The only difference between ‘Type A’ and ‘Type B’ is the location of the expansion joint (bellows).

Jord VIP – Type A

The VIP ‘Type A’, with an internal expansion joint (bellows), enables the core pipe to self-compensate for its thermal contractions (approx. 3mm per meter pipe length) due to cyclic temperature changes from neutral status to -162oC during normal operation.

The jacket pipe is subjected to environmental heating and cooling from low temperatures at winter nights to 75oC pipe skin temperature due to solar heating during summer days.   Thermal movements in the jacket due to varying weather conditions are about ±0.04% of pipe length, and can be safely restrained by rigid pipe supports and adjoining pipe spools within allowable design stress limits.

Therefore, each VIP spool (up to 36m long) remains practically unchanged in length at all operating conditions. The great advantage of this for LNG Terminals is that no expansion loops are required in up to 1 km straight length.

Pipe supports are welded to the jacket pipe to form an integral part of the VIP spool and bolted directly onto pipe racks, modules or plinths at jobsites.    The pipe supports are capable of resisting much higher loading than the conventional PIR/PUR pipe supports, in particular, axial thrust load due to thermal contraction/expansion between expansion loops and dynamic loads induced by abrupt LNG flow changes, eg hydraulic shock or commonly known as ‘water-hammer-effect’.

Figure 2. General arrangement of Jord VIP spool – Indicative only

Jord VIP – Type B

The VIP ‘Type B’ is configured to allow like-for-like replacement of the conventional PIR system by retaining the identical core pipe layout.  Externally, however, PIR foam is replaced by vacuum containment.  Expansion Loops are required for this model but at extended intervals up to 360m.

BENEFITS OF VIP

Improved Thermal Insulation

The principle behind superior thermal insulation is the vacuum or the absence of major heat transfer media including: (a) conduction via solids and (b) convection via gas/fluid.   The conventional mechanical insulation media such as polyisocyanurate (PIR) and polyurethane (PUR) largely rely upon inherent thermal conductivity coefficient and insulation thickness to achieve acceptable performance when fresh.  However, insulation performance degrades over time due to ingress of air (and moisture) as a result of eventual wear and tear of vapour barriers.

For example, 190mm thick PIR or 350mm PUR yields approximately 28 W/m2  heat flux to LNG when newly installed and 40 to 50 W/m2 after 5 to 10 years of operation.

VIP is more compact at 45mm radial vacuum gap and typically yields approximately 3 W/m2  or 10 times better than PIR as illustrated.  Its insulation performance remains consistent over time provided that operating vacuum is not compromised by accident.   The current VIP manufacturing technology offers life-long vacuum during normal operation, usually 40 years.

By reducing the heat flux by 10 fold, Boil Off Gas (BOG) is significantly reduced. Therefore, it may be possible to downsize BOG return pipe sizes and associated BOG treatment systems.   Also, Hold Time (elapsed time to LNG boiling) is increased from 3 days (PIR/PUR) to 30 days (VIP), meaning that LNG can be temporarily stored inside the LNG loading pipeline for up to 30 days or between ship loadings without recirculation or cooling.

Reduced Expansion Loops

Expansion Loops are placed every 100m to 120m for conventional PIR/PUR pipeline to absorb thermal contractions (3mm per meter) in core pipeline when operating at cryogenic temperatures, i.e. pipe contraction is 300mm to 360mm between expansion loops.

Jord’s latest VIP design offers structural advantages that can significantly reduce expansion loops, i.e. significant reduction in CAPEX related to pipe material procurement, insulation, civil construction, and a simplified piping installation process.

VIP ‘Type A’ is equipped with an internal expansion joint to self-compensate for thermal contractions in core pipes without affecting overall pipe spool lengths.  Therefore, external Expansion Loops are not normally required if ‘Type A’ is used.   Thermal movements in jacket pipes due to daily solar radiation and weather changes are negligible (approx. 0.04% of pipe length) and restrained within allowable stress limits in the jacket pipes and supports.

VIP ‘Type B’ does not have expansion joints in core pipes to provide like-for-like replacement of the conventional PIR/PUR pipes for customers not accepting ‘Type A’.    Differential thermal movement between the inner and outer pipes is compensated by bellows fitted in the jacket pipe.  This system requires an expansion loop every 360m (max) as opposed to typical 120m.  The extended span is possible because rigid pipe supports are rated at much higher axial loading (100T).

Reduced Pressure Drop

A fewer number of loops reduces pressure drop in the LNG loading lines by approx. 15 kPa per loop at typical LNG flow rate of 4m/s.

With the application of VIP, it is possible to lower the design pressure or downsize pump capacity and pipe thickness.  CAPEX savings will be significant.   Alternatively, LNG flow can be speeded up to shorten ship-loading times for expedited delivery.

Integrated Pipe Support

Each VIP spool is supplied with welded pipe supports.  Pipe support heights can be custom designed to suit client requirements in the event that VIP ties into non-VIP pipelines or valve clusters, specific heights can be accommodated.

Pipe support is designed to safely resist every conceivable loading condition during normal and abnormal operations.  It is rated at 100T axial loads, whereas, a typical High-Density PUR clamp-on support is limited to 8 to 10T (for 38” line) above which bonded/glued foam layers break and dislodge from core pipe.

Bolted pipe support provides rigid fixed point while guided support slide axially to relieve thermally-induced stress upon reaching frictional limits at the ground interface.

Secondary Confinement for Environmental Protection

One of the many added benefits of the VIP system is secondary confinement.   In an unlikely event of core pipe leakage, LNG can be temporarily confined within the jacket pipe spool and prevent uncontrolled spillages to the surroundings which is hazardous.   A premium VIP model is available to offer full secondary containment to protect the environment from uncontrolled LNG spillages.

Superior Protection

Corrosion.   VIP spools offer ‘immunity’ to corrosion as the core pipe is fully contained and preserved within a vacuum condition (no moisture/oxygen).  By eliminating corrosion and minimising the chance of core pipe damage, the VIP spools will yield reliable and dependable performance during the life of plant with little or no maintenance.

External Impact & Weather Containment.  The core pipe is fully contained within the sturdy jacket pipes and physically protected from potential mechanical impacts, accidents, the elements, and possible sabotage or malicious acts/vandalism.

Fire safety.      The VIP system may return to normal operation even after fires with simple cosmetic repairs on heat affected components, such as external paint and external safety cap O-ring.  Core pipes and vacuum insulation materials are not affected by postulated fire conditions.

Operation and Maintenance

Every VIP spool is 100% factory-tested prior to delivery to ensure reliable and maintenance-free operation during the entire plant life (25+ years).  Anticipated design life of VIP is 40 years.  Minor paint touch-ups may be required on a needs basis. No capital spares are required.

Expedited Installation and Reduced Project Risk

Every VIP spool, measuring up to 36m long and 20T, is delivered pre-tested, sealed with life-long vacuum and ready for lifting onto designated locations, leaving only spool-to-spool interfaces to be welded followed by joint insulation using the spot-insultation kit provided.

Pressure testing on site-erected piping (entire lengths) is mandatory and normally carried out with exclusion/safety zones secured and cordoned off because of high stored energy during pressure testing. However, VIP spools are delivered pre-tested at factory, thus only the field-welds at spool joints need to be ‘locally’ pressure tested without having to warrant site evacuation.  Cost savings will be substantial.

Overall project risk is proportionally reduced thereby saving significant time and labour cost.