Specifying Insulation for Marine Applications—Opportunities, Challenges, and Considerations
The marine sector presents special challenges when it comes to insulating materials. This article discusses the nature of the marine insulation environment, several challenges unique to the sector, and some considerations when specifying insulation for marine vessels. While there are many tested and approved materials, this will examine the properties of mineral wool and fiber glass.
From aquaculture and grain to defense and energy, the world’s marine sector literally directs the flow of goods that power and protect our planet. Closer to home, commissioned vessels operating on U.S. waters are integral to steering commerce. Consider the following data points showing the impact of American vessels on trade, energy, and transport capacity:
- According to the American Waterway Operators, water moves 60% of U.S. grain for export.1
- The single largest commodity that moves on
U.S. waterways is petroleum—244 million tons of petroleum are transported on American waters annually.
- One 15-ton barge-tow can move the equivalent of 216 rail cars or 1,050 semi-trailer trucks.
- More than 760 million tons of cargo are moved by the tugboat, towboat, and barge industry² each year.
Shipping also is integral to defense strategies and supporting peace on international waters. From aircraft carriers to submarines, the U.S. Department of the Navy lists 296 deployable battleships as of March 2020.3 Additionally, as the coastal defense, search and rescue, and maritime law enforcement branch of the U.S. Armed Forces, the U.S. Coast Guard operates nearly 2,000 vessels including cutters, ice breakers, and patrol boats. Other divisions of the military also commission seagoing vessels such as tugs, fireboats, and workboats. And, of course, there are myriad other marine applications ranging from cruise ships to the increasing use of oil tankers to store crude offshore. On April 24, the Wall Street Journal reported offshore storage of oil increased 76% since March 1, 2020, driven by a glut in supply coinciding with decreased demand during the global pandemic.
Across all these varied vessels, 1 common denominator applies: insulation that can withstand the rigors of the marine environment and comply with standards set by classifying bodies. Mechanical insulation is 1 technology that can help those specifying materials for vessels address the many challenges posed by the marine environment. Installed in onshore applications, mechanical insulation is essential to reduce process- or HVAC-related energy use, lower the load on mechanical equipment and systems, and reduce noise levels.
Insulation Challenges in the Marine Environment
The marine sector presents some unique challenges when it comes to insulating materials. Mobility is a key factor specific to seafaring vessels. Whereas a building remains at a fixed location across its lifetime, the very nature of marine applications means a vessel may operate in markedly different climates. For example, an aquaculture fleet off the frigid shores of Newfoundland may be redirected to much balmier fishing waters in southeast Asia as seasons change. The vessel will need thermal insulation installed to tolerate temperature variance while keeping crew members comfortable and cargo protected.
Another distinguishing consideration that sets insulation used in the marine environment apart from other applications is the liquid nature of the environment. Insulation systems in the marine environment must be able to withstand exposure to water as well as high levels of humidity. On vessels operating in the oil and gas sector, guarding against corrosion under insulation (CUI) is a huge concern, as moisture can collect and erode steel components on pipes and nearby equipment. Systems also must be sealed against the risk of water washing over the deck, posing a threat to equipment, quarters, and anything topside. Even small gaps in insulating cladding can let in enough water to cause significant corrosion issues. CUI also presents an economic cost. The NACE International Impact “International Measures of Prevention, Application, and Economics of Corrosion Technologies Study” published in 2016 notes: “The global cost of corrosion is estimated to be US $2.5 trillion, which is equivalent to 3.4% of the global Gross Domestic Product (GDP) (2013).”4 The report goes on to state that “using available corrosion control practices [could result in an estimated] savings of between 15 and 35% of the cost of corrosion.” Individual safety and environmental consequences are additional costs to consider when it comes to CUI.
A third challenge when thinking about insulation for the marine environment is the very limited space aboard most vessels. According to Peter Betti, Senior Project Manager at Performance Contracting, Inc. (PCI), many Navy vessels are designed with specifications requiring redundant equipment, making space a premium. “An engine room is essentially a power plant compressed into a very small area,” Mr. Betti says, noting that space is a significant constraint when installing marine insulation. As a practical example, consider outfitting a bulkhead area, where a 3″ fire protection product needs to be installed while
allowing a 5″ standoff from the bulkhead and accommodating heavy pieces of structural outfitting.
Classification Bodies Drive Standards
Who oversees and certifies the insulation materials used on national and international waters? Regulatory bodies represent both the shipyards and the ship owners. The International Maritime Organization (IMO), U.S. Navy, American Bureau of Shipping (ABS), and DNV-GL are some of the large organizations used to classify American vessels, among others; and International Convention for the Safety of Life at Sea (SOLAS) regulations established by the IMO5 guide the international safety of merchant ships. The SOLAS regulations were adopted more than a century ago, in response to the 1914 Titanic disaster, and multiple SOLAS amendments have followed. The U.S. Navy’s standards (navy.mil) govern vessels commissioned by the U.S. Navy; while the ABS also establishes standards as one of the world’s leading classification organizations addressing technical, operational, and regulatory challenges to support safe, secure, and responsible marine and offshore industries.
The standards used by these classification bodies are taken very seriously by engineers, shipbuilders, and shipyards. While insulation represents a very small part of the cost involved in building a ship, failure to select a material in compliance with standards set by classification bodies can bring about a standstill. According to Mr. Betti, “Insulation might cost 1 to 3% of the total cost of a project, but it can completely hold up the entire project if the wrong product is installed.” Understanding and abiding by the standards set by organizations such as IMO, navy.mil, and ABS is critical.
5 Key Areas to Consider When Specifying Insulation in the Marine Sector
Fire Resistance—a Top Priority
Across all categories of vessels and all classification organizations, fire resistance is a top driver for insulation materials. Offshore drilling rigs, commercial merchant ships, and naval vessels are all subject to disaster in the event of a fire. Unlike commercial buildings, crew and passengers may be miles from a safe, land-based evacuation point. For this reason, non-combustible materials are imperative on drilling rigs, ships, and navy vessels to guard against fire outbreak. In an on-board environment, where the crew typically has very limited options for egress, the fire-resistant properties of suitably tested insulation materials make it a reliable option for marine insulation applications.
Regulations for SOLAS Chapter II-2 are designed to ensure that fires are avoided in the first place.6 For example, materials such as carpets and wall coverings are strictly controlled to reduce risk. Next, focus is placed on rapid detection of fires, followed by guidelines to ensure that any fire that occurs is contained. A wide variety of fire-suppression systems are available to contain fires. Designing ships to facilitate easy evacuation for crew and passengers is a key element of the chapter. SOLAS also includes annexes on fire protection materials and required approval test methods. The guidelines prohibit installation of any combustible material except on cold-surface systems.
The fire-resistant properties of insulation are especially important here. One material well known for its fire-resistant properties is mineral wool. Used in commercial buildings for decades, mineral wool is among the most tested insulating materials for helping protect decks and bulkheads. Fire-tested to ASTM E119, mineral wool has been shown to withstand temperatures well above 2,000°F. Fiber glass products are another commonly used material and have been tested to meet IMO 164.109 non-combustible material (SOLAS) guidelines and ASTM C547 standards.
The weight of the insulation system in the context of the entire vessel’s weight—i.e., including fuel, generators, equipment, and other materials—must be considered. Commercial ships may be laden with diesel fuel and massive generators, adding to the overall weight of the ship. As weight limits are a big consideration in shipping, there should be a strong, inverse relationship between the amount and location of mechanical insulation installed and the combined weight of generators and fuel.
Based on recent research, a material’s weight is not necessarily the best indication of its strength. Advancements in building science are allowing lighter insulation system components to deliver increased compressive strength.
Salt water can present an especially hostile environment for materials in the marine sector. A study reported on Marinelink.com reviewed more than 1,000 failure cases across 5 specialist laboratories in the United States, Europe, and Asia, and found that more than a quarter (27%) of failures occur in tubes and piping across components in the maritime and oil and gas sectors.7
Condensation collecting in areas such as cold-service systems can be a concern in the marine environment. For that reason, installing a vapor barrier on cold-service systems and any area where condensation may present a concern should be considered a best practice. In a humid environment, it can be challenging for products to stay sealed,
making a confident closure/sealing system especially important.
As the jacketing on marine-rated fiber glass insulation products helps protect pipes from moisture infiltration, it also helps defend against CUI, thereby protecting a vessel against potential process failure, damage to equipment, and increased potential for leaks.
Noise reduction requires acoustic insulation, and acoustics is an area of increased attention in the marine sector. Sound vibrations traveling across a vessel can create issues ranging from comfort to personal well-being and safety. Sound vibrations even can contribute to structural concerns. According to Mr. Betti, concerns about the safety of marine operators and sailors recently prompted both the IMO and the Navy to increase vessels’ acoustical performance requirements.
The combination of so much steel and mechanical systems in tight quarters can make acoustics a particular challenge in the marine space. For crews living on larger vessels, adequate noise reduction is necessary to reduce sound and structure-borne noise between cabins and from 1 deck to another. When it comes to reducing sound transmission, structural design (ships have bulkheads, as opposed to walls), as well as the type of insulation used in the bulkhead, should be considered. Depending on construction details, different materials can be used to support acoustics, each with varying degrees of effectiveness. Testing allows us to validate various system designs to recommend the best insulation system.
An important consideration is sound transmission classification (STC), a composite rating derived from sound attenuation performance at a variety of sound frequencies that is widely used to rate interior configurations. However, for a specific frequency of sound, the composite STC may not be the best comparison of 1 assembly to another. For example, mechanical system noise in an engine room will have different frequencies compared to conversation in living quarters. STC is a composite rating addressing how well a partition attenuates airborne sound. Considering individual frequencies, though, can help improve acoustic performance and impact the type of insulation used. Note that insulation
by itself does not have an STC rating. Rather, STC ratings reflect acoustical performance for an entire system.
The International Organization for Standardization (ISO), a non-governmental organization, published ISO 20283-5:2016 providing guidelines for the measurement, evaluation, and reporting of vibration regarding habitability for all people on board passenger and merchant ships, especially crew. While not a U.S. standard, overall frequency-weighted root means squared (RMS) vibration values in the frequency range from 1 Hz to 8 Hz are given as guideline values for different areas on ships.6
The thermal conductivity properties of insulation mitigate and reduce the transfer of heat between the vessel area and the exterior environment. Shell boundaries, hulls, and decks separate interior temperature and humidity-conditioned areas from the environment. Depending on the time of year, the temperature range between external ambient temperature above the waterline and seawater can vary dramatically. Seawater ranges from ~90°F to 28°F, the temperature at which it freezes. Shell boundaries above the waterline will be exposed to solar radiation and ambient temperatures ranging from 120°F to -60°F. With such a temperature range, Mr. Betti says properly insulating side shells can result in operational savings and a return on investment in a matter of months. If not insulated, a vessel’s stiffeners can act as heat transfer fins, significantly increasing overall heat transmission.
Diverse Marine-Certified Products Navigate a Complex Environment
As reflected in the applications above, marine insulation is required to perform many functions, ranging from fire resistance to managing acoustics. Ultimately, there is no silver-bullet, one-size-fits-all insulating material for every marine application. Some manufacturers are taking note of the opportunities the marine sector provides. Just as strategically specified insulation meets diverse performance requirements on land, marine-certified products stand up to challenges at sea and on domestic waters.
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