Key factors that affect material selection in LNG service
LNG is a mixture of low-molecular-weight hydrocarbons that has been cooled down to liquid form for ease and safety of non-pressurized storage or transport. Multiple critical factors should be evaluated to determinate whether an insulation system should be considered for LNG service.
Demand for Clean Energy
and industrial insulation systems
The recent surge in demand for energy, clean energy in particular, catalyzed a positive series of events for companies specializing in the manufacture, fabrication , and installation of high-performance industrial insulation systems. The sheer volume of insulation required to protect the high investment in these facilities has been inspiring.
Two major threats to industrial insulation performance, moisture (liquid and vapor) and fire, are prominent in the engineering of liquefied natural gas (LNG) facilities.
Moisture Vapor transmission
With many of these facilities being in hot and humid climates, water vapor transmission (WVT) resistance is important. Pipes or vessels may be at continuous operating temperatures of nearly -270 °F (-168 °C), with ambient conditions at 90 °F (32 °C) or more with humidity of 90 percent.
In these conditions, the opportunity for moisture to be driven into the insulation is at its highest. Since the natural moisture drive is from hot to cold, one can see how the insulation material can significantly impact the system.
proper material selection
LNG is a mixture of low-molecular-weight hydrocarbons. The actual composition varies however; LNG is primarily methane with ethane, propane, butane, and nitrogen present as well. Risk of fire can be reduced by proper material and application selection. Often, there are fire credentials critical to evaluating whether an insulation system should be considered for LNG service. These may include but are not necessarily limited to the National Fire Protection Agency (NFPA), Coast Guard Approval (critical near or offshore), Underwriters Laboratories (UL), and Factory Mutual (FM).
Other key factors that affect material selection
- Dimensional stability: Cold or cryogenic service temperatures can cause dimensional channel changes leading to warping of the insulation on the pipe, leaving gaps. Along with high humidity, this can allow moisture entry that will promote ice buildup. This can be an expensive problem to repair.
- Compressive strength: Construction and maintenance of LNG pipe racks require tradesmen to work on and around the insulation. Physical damage can be limited by using insulation materials with high compressive strength, absorbing the point loads and traffic. In addition, high compressive strength is important for pipe supports, as weight loads can damage insulation at those locations.
- Combustibility: Fire protection properties are often an additional requirement for the system. This involves the use of fire-rated insulation materials, as well as stainless steel jacket and banding. This information is critical to the selection of the proper materials.
- Accessories selection: Selecting accessory materials that complement the insulation is also important. Extensive testing and proven performance history with the specified insulation are highly recommended.
- Insulation fabricator selection: Attention to detail in fabricating insulation for cold and cryogenic work is also an important aspect. Paying close attention to dimensions, minimizing through-fabrication joints (joints perpendicular to the pipe that pass through the entire thickness of the pipe insulation segment) and 100 percent sealing of those joints will contribute to a successful project.
It is suggested that a fabricator demonstrate the proper experience with cold and cryogenic work before an order is placed with them. As these projects tend to be very large in scope, the fabricator's capacity for sourcing materials and converting those materials into quality insulation systems is an important consideration as well.
- Contractor selection: There are highly competent contractors familiar with the critical cold and cryogenic insulation techniques. These companies are staffed and managed around performance in critical end uses, of which LNG is certainly one. The bid list may not be as large as one would like, but competence should win the day with LNG candidates. Historical profiles and reference lists should be considered for pre-qualifying an LNG insulation contractor. Financial stability is equally as important, as the contractor should have the ability to sustain the financial demands of a large, intense project with high levels of labor and material costs.