The first LNG plant began operation in 1917 in West Virginia, US, using mineral wool pipe insulation that had been in use since the 1840s. Cellular glass came into prominence in the 1930s, with rigid cellular plastics, such as

polyisocyanurate (PIR), emerging around the 1950s. Concurrently, there was an increasing global need to impose standardised

levels of quality or attainment within material technologies, engineering, and construction. Charles Dudley became the driving force behind the American Society for Testing and Materials (ASTM), mostly driven by rapid advancement in railroad technologies and the ensuing failures. Today, ASTM governs over an immense landscape of products and test methods, including insulation applications.

Risk mitigation

Ted Berglund and Joseph Hughes, Dyplast, USA, take a detailed look at LNG insulation system risk mitigation.

BEYOND STANDARDS

LNGINDUSTRY REPRINTED FROM JULY 2016

The organisation now known as ISO was initiated in 1926 as the International Federation of the National Standardising Associations. Deutsches Institut für Normung (DIN) standards began to advance in Germany in 1936 and, of course, there were similar advancements of other standards, such as ASME, ANSI, EN, NACE, NORSOK, SSPC, API, etc.

CINI, the International Standard for Industrial Insulation, emerged in 1988 and is evolving into a dominant global standard for thermal insulation in LNG applications. International companies, such as Shell, DSM, DOW, AkzoNobel and the former Hoogovens, jointly set up CINI, concluding that there was a considerable need for improved insulation system quality standards. LNG engineering firms, such as CB&I, KBR, Chiyoda, etc., increasingly incorporate CINI standards into their insulation specifications – at least somewhat driven by CINI’s focus on having the physical properties of insulants increasingly measured at in-situ conditions. For example, thermal conductivities, strengths, tensile E-modulus, etc., must be measured at temperatures down to -165°C (-265°F).

PrefaceExperience has demonstrated that insulation systems within LNG facilities are often ‘under-designed’ when compared to other mechanical systems. Decades of lessons learned from under-designing other mechanical systems, such as piping materials, welding, compressors, relief valves, etc., have led to a keen awareness among LNG engineers regarding impacts on safety, plant reliability, process efficiency, energy loss, and environmental compliance.

Unfortunately, the repercussions of under-designed insulation systems were often less obvious, yet had similar manifestations, as well as loss of product due to boil-off, increased maintenance costs from valve freeze-ups, and sometimes curtailments in production or even personal injury. Related costs and foregone profits could have been avoided with improved compliance with existing standards and implementation of a broader risk mitigation programme.

The purpose of this article is to offer a macro-level discussion of the following:

� The role of standards in mitigating insulation risks.

� Which standards are becoming dominant for LNG insulation.

� Where standards must be supplemented with broader risk mitigation.

The encouraging trends within CINI and ASTM add more value to LNG engineers tasked with selecting cryogenic insulants and designing cryogenic insulation systems. Compared to using standards and test methods that generally provide information only at ambient temperatures, CINI’s 2014 revision and ASTM C591-15, to a lesser extent, require testing of physical properties at lower temperatures, down to the LNG process range.

The increased due diligence executed by specifiers/engineers by insisting that suppliers comply with the latest standards and test methods is also encouraging. Furthermore, engineers are increasingly diligent as they strive to compare physical properties across competitive insulants that are unfortunately measured by disparate test protocols.

CINI vs ASTMThe 2015 versions of several ASTM governing insulation standards, such as C591 for PIR insulation and C552 for cellular glass, implemented requirements for thermal conductivity (ƛ) measurements from down to at least -129°C (-200°F). Note that leading insulant manufacturers typically also measure ƛ at LNG temperatures. ASTM does not yet require other physical properties to be measured at cryogenic temperatures.

While ASTM should be applauded for taking this significant step, CINI-2014 took the additional step to require that LNG insulation suppliers demonstrate compliance with an array of additional physical properties measured at -165°C (-265°F).

Thus, today’s LNG engineers seeking to take advantage of the latest in supportive standards to mitigate risk should consider CINI.

CINIAs noted, CINI standards presently go beyond ASTM to require that additional physical properties of insulants must be measured at LNG temperatures and comply with minimum CINI standards in order to be deemed acceptable in an LNG application. Additionally, CINI establishes which ASTM test

Figure 1. Elba Island LNG tank.

Figure 2. Elba Island LNG facility (blue pipe is LNG; white pipe is gas).

REPRINTED FROM JULY 2016 LNGINDUSTRY

method or EN equivalent must be used to measure each physical property.

A few physical properties established as requisite by CINI are independent of temperature (such as closed cell content), and others are measured at ambient temperatures since they are simply inapplicable or unmeasurable at -165°C (such as water absorption). These include:

� Density.

� Maximum service temperatures.

� Closed cell content (presumably does not vary with temperature).

� Chloride content (presumably does not vary with temperature).

� Water absorption – a complex subject since, at LNG temperatures, water is not absorbed, yet water may of course be absorbed within insulation at ambient temperatures and subsequently cooled to cryogenic temperatures. Presumably CINI has considered this and established its maximum water adsorption measured at ambient temperature.

� Water vapour permeability – water vapour permeability at cryogenic temperatures is similarly problematic.

� pH-value – somewhat akin to water adsorption, CINI does not make it clear why/how the pH of an insulant has an impact at -165°C. Presumably it does have an impact.

� Leachable chloride content.

� Dimensional tolerances.

� Flame spread index (FSI) – flame spread per ASTM E84; the maximum FSI value is not set by CINI, but rather by local codes and the design specification.

CINI exceeds ASTM requirements by dictating that, in addition to thermal conductivity, the following physical properties must also be measured at LNG temperatures:

� Compressive strength.

� Linear thermal expansion coefficient.

� Tensile strength.

� Tensile E-modulus.

� Poisson’s ratio.Also, importantly in cryogenic applications, increased

contraction stresses can occur in the insulation materials due to the temperature differentials across the insulant. Such stresses require an insulant with increased tensile strength, a reduced tensile modulus, and a reduced linear thermal expansion coefficient. At service temperatures below -50°C, CINI asserts that the cryogenic thermal stress resistance (CTSR) factor of, for instance, PIR insulation foam shall comply in the X, Y and Z direction with the following relation:

The factors in the equation are defined in the CINI specification. CINI is striving to establish safety factors within a complex environment where stresses vary within the layers of the insulation.

LNG insulation system risk mitigation beyond standardsRisks in the context of an insulation system arise from a multitude of process, environmental, and situational factors. Process factors

are generally well understood and quantifiable, and include the following issues:

� Process temperatures and the expected variations.

� Pipe metallurgy and corrosion risks.

� Expansion/contraction.

� Pipe diameter/weight, etc.

Similarly, environmental factors are generally well-quantified: � Ambient temperature variations.

� Solar radiation intensity.

� Ambient humidity swings.

� Rainfall.

� Wind.Situational factors are generally not quantifiable and include

issues such as operator and maintenance crew training, spare parts availability, proximate insulation fabrication shops, water wash-down practices, etc.

Thus, the quantification of the expected variability among the aforementioned factors establishes the framework for a basic design of the insulation system: insulant material, thickness, number of layers, pipe coatings, butt and longitudinal joint design,

possible inclusion of inner-layer vapour barriers, metallurgy and gauge of jackets, sealing of jacket seams, number of expansion joints, number of pipe hangars, etc. Considering the factors, a liquefaction facility in Nigeria has an inherent set of risks quite different from a regasification plant in Canada.

After the insulation system’s basic design is proposed, the risk mitigation process continues by assessing the risks inherent within the basic design, and then prioritising the risks in terms of magnitude and probability of occurrence. In addition to operational risks, consideration must be given to delivery, storage, installation, commissioning, and maintenance protocols. The ‘ideal’ insulation system design is not in fact ideal if poor on-site storage compromises its integrity. An ideal system design for

Figure 3. Elba Island LNG facility.

modular components shipped across long distances may be different than a non-modularised plant, and so forth.

However, what happens, for instance, when the insulation system operates for two weeks at ambient air temperatures above the nominal maximum; or what if steam blows to clean pipe during pre-commissioning exceed maximum design temperatures of the insulation system? Additionally, there are situational factors that arise during operations that may not have been previously considered, such as the potential for mechanical abuse (e.g. forklift bumps), chemical abuse from equipment cleaning, excessive vibration, etc., and, of course, the unpredictable risk of typhoons, explosions, and fires.

Risk mitigation primerRisks addressed in the prior paragraphs can be generally addressed either at the design stage, or during the operational phase. While it is true that, generally, risks are most cost-effectively mitigated at the design phase, the reality is more complex. A comprehensive risk analysis is necessary to make such determinations. For instance, mechanical abuse can be mitigated by insulation with greater compressive strength, thicker jackets, stairs over pipe likely to be stepped on, warning signs, etc., depending on the circumstance.

Design risk mitigationRisks can be mitigated at the design stage by increasing the design factor. In essence, this equates to expanding the assumed nominal range of expected process, environmental, or situational factors. Alternatively, risks can be mitigated by adding a safety factor. In other words, simply adding X% more thickness, Y% more strength or by coating a pipe for corrosion that would not have otherwise been coated, etc. Note that definitions such as

safety factor, safety margin, design margin, etc. vary by industry and even within different contractors. Stakeholders should insist on clear understandings.

Operational phase risk mitigationAn LNG plant manager should be armed with an understanding of what risks have been considered, to what extent they have been accommodated within the design, and which risks may need to be mitigated in-situ. The formidable obligations of the plant manager then become: tracking identified risks; prioritising new risks; quantifying the ongoing relevance of old vs new risks; planning for the materialisation of foreseeable risks; and evaluating effectiveness of the risk management programme throughout the project.

There should be macro key performance indicators (KPIs) that, when they stray from predictions, may help identify problems. Example KPIs include auto-consumption, LNG recovery, rundown to tank, gas shortfall, high emissions, utilisation, etc. However, root cause analysis of any deficiencies additionally requires good log-taking, trending and archiving, as well as audio/visual alertness from operators.

SummaryCINI standards are a great step forward in the effort to mitigate insulation system risks at LNG facilities. They identify which physical properties are the most pertinent, establish minimum/maximum values, dictate the requisite ASTM or EN test methods, and require that many physical properties be measured at LNG temperatures.

However, a good risk mitigation programme should track, anticipate and plan for failures or problems that should not occur.

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