A Hybrid Approach for Effective CUI Management

Introduction

Corrosion under insulation (CUI) is a common damage mechanism in the hydrocarbon production and processing industries, typically manifesting as localized corrosion/pitting [1]. CUI is generally triggered by moisture-saturated thermal insulation, where the time of wetness (TOW), in addition to other factors (chemistry, design, temperature, etc.), govern the rate of CUI propagation [2-3]. In addition to CUI, moisture-soaked thermal insulation can cause heat dissipation from thermally insulated assets. It is estimated that moisture content as low as 5% within thermal insulation can increase heat loss by 25% in a typical thermally insulated system wrapped with fibrous stone wool insulation [4]. Heat conservation in piping is crucial to the efficiency of processing facilities such as steam-assisted gravity drainage (SAGD) facilities since the heat/enthalpy of the steam is directly proportional to the heavy oil recovery rate.

In addition, there have been numerous reports from the Alberta Energy Regulator that refer to incidents of novel stress corrosion cracking (SCC) on thermally insulated pipeline grade steels (e.g., X52, X60, X70) where wet insulation was discovered [5]. The heat of the pipe may boil out a small portion of trapped moisture (which may escape from the jacketing laps), but any remaining moisture within thermally insulated systems poses heat loss, CUI, and even SCC risks. Industry codes and standards recommend the use of low-point drains to allow for drainage of trapped moisture. However, moisture in the insulation is bounded by the surface tension between the insulation and the pipe, which generally requires more than gravity-assisted drainage to clear [6]. Low-point drains can partially remove moisture, but they may not be effective enough to mitigate CUI risk(s) and thermal losses [7]. Recent advancements in insulation manufacturing have introduced innovative products that purport to absorb less moisture than traditional fibrous stone wool insulations. Unfortunately, for most owner-operators, upgrading their existing thermally insulated infrastructure with new insulation materials is not practical or feasible from an economic and/or environmental standpoint.

Due to the technology gaps for insulation drying measures, CUI and thermal losses continue to be an industry challenge. Recently, the American Petroleum Institute (API) introduced a climate action framework (CAF) to facilitate initiatives and technologies that can help reduce carbon emissions/footprints from the operation of hydrocarbon facilities in various sectors (i.e., upstream, midstream, and downstream) [8]. In the authors’ opinion, finding solutions to safely and effectively remove moisture from existing insulation, as opposed to replacing with new materials, is an important step in furtherance of the CAF initiative. The primary reason being that insulation is generally single-use and made of non-degradable materials. So, when looking at the vast amount of insulation used in existing operations around the world, destroying it or depositing it in landfills would have a significant negative impact on the environment and companies’ carbon footprint. In the case study presented in this article, we field-tested a hybrid design insulation ventilation system (IVS) that utilizes low-point drainage and insulation breathability to remove moisture from moisture-saturated thermal insulation [9].