Abstract
Multilayer spraying of rigid polyurethane foam provides an excellent way of insulating storage tanks for liquefied hydrocarbons such as LNG. The viability of such an insulating system depends both on the initial quality of the foam and on its response to the different environments which the foam may encounter during its service life.
As part of a larger programme to develop rigid polyurethane insulation foams for both marine and land storage tanks, several techniques were developed for assessing the quality and performance of the foam. Nitrogen and cyclohexane were used as probes to examine the interfaces between successive layers of foam? it was shown that very careful control of the spray technique is needed. Random deposition of isolated spray droplets outside the main foam laydown pattern leads to substantial porosity of the interface. Each successive layer must be sanded to expose fresh surface which should then be maintained substantially free from adsorbed water until the next foam layer is applied.
A chromatographic technique was developed using the polyurethane foam itself as the chromatographic fixed phase to study the interactions with gaseous environments likely to be encountered in service. These included the stored hydrocarbon liquids, nitrogen, oxygen, carbon dioxide and water (the components of air) and the various compounds which might be present in exhaust gas inerting systems. Hydrocarbons have no effect on the foam. However, there is a strong chemical interaction with oxides of sulphur and nitrogen which have severe deleterious effects on foam properties.
Get full access to this article
View all access options for this article.