Abstract

The increase in operating temperatures of subsea installations will have a repercussion on the required temperature ratings of syntactic foam insulation systems. As of yet there is not ample information available indicating that current materials are going to be able to provide the required temperature ratings. Test results are presented indicating the role of microspheres and the coating of microspheres in the temperature rating. Test results are also presented on syntactic foams based on new resin systems that offer remarkable improvements compared to current systems.

Introduction

This paper presents results of development and testing programs focused on optimizing syntactic insulation, offering reliable long-term performance. Research programs have concentrated on achieving low waterabsorption at elevated temperature and pressure by studying the performance of various combinations of resin and microsphere systems. Through analysis it has become apparent that the performance of syntactic foams at high temperatures is closely related to the type of glass microsphere used. Detailed analysis of chemical processes occurring between the resin and the microsphere surface has shown thatthe composition of the glass and the coating applied to the spheres are major contributors to the performance ofthe insulation.

Development programs for thermoset syntactic foam systems have focused on both testing of these materials under various conditions and on manufacturing and application techniques associated with the materials. These programs have made considerable headway in proving that high temperature thermoset syntactic foams are currently available.

Additionally, these programs have provided encouraging direction, which will hopefully lead to the development of insulation capable of withstanding 130°C or higher in the near future.

State of the technology

Currently, insulation systems based on thermoset syntactic foams are marketed by a number of manufacturers and are applied to subsea systems throughout the world. The vast majority of the syntactic foams are applied to systems that have operating temperatures ranging from 20 °C to 90 °C, at depths up to 10,000 ft. Although the industry is working towards standardization of performance requirements for syntactic foams, there is no agreement on the maximum allowable water uptake of the insulation material due to pressure and temperature. Water uptake is considered themajor contributing factor to decreasing thermal insulationperformance. One of the main reasons for the ambiguity in performance requirements is the lack of test equipment able to simulate operating conditions and measure thermal or mechanical performance. Although some institutions offer test vessels that can simulate such operating conditions, the cost of testing in these vessels is prohibitive for mostdevelopment work.

What has become clear over the last 2 years is that because of the limited knowledge on the behavior of syntactic foams under operating conditions end users favor water absorption levels that are limited and stable over time when measured from coupons immersed in water at operating temperatures and/or pressures. By some opinions, predictions can be made of long term performance based on accelerated, short duration tests at higher temperatures and pressures.

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