Pipe insulation — a crucial aspect of any facility’s infrastructure — is as useful as it is under appreciated. Process cooling applications heavily rely on pipe insulation to ensure the proper operating conditions for a given process.
The many types of insulation available and their various material compositions and manufacturer-intended usages lead to disputes over the correct type of insulation to specify for a particular process cooling application. This article will provide an overview of the numerous options and applications available for pipe insulation and a breakdown of several specific types of pipe insulation suited for process cooling applications.
Made from a variety of materials that achieve slightly different end results, the primary purpose of all types of pipe insulation is to create a barrier between the contents of a pipe and the outside environment. A lack of proper insulation on process cooling pipes can lead to decreased efficiency, increased condensation, unwanted freezing and even harm to people who come in contact with the pipes.
Although it has many applications, pipe insulation generally is classified as either thermal or acoustic. Thermal insulation is specifically designed to prevent the transmission of heat from one side of the insulation to the other. (Acoustic insulation is designed to achieve a similar result with sound.) Industrial process cooling applications are not often dependent on conforming to a specific decibel level, so this article will focus on discussing thermal insulation and its applications.
Applications for Thermal Insulation
Thermal insulation has several useful applications in terms of process cooling. Common applications for insulation in process cooling systems include condensation control, heat gain or loss prevention to ensure energy efficiency, freeze prevention and preventive safety.
Condensation Control. As is the case with any vessel full of liquid at a below-ambient temperature, colder pipes often develop condensed water vapor on their exterior. This undesirable effect can lead to corrosion and water damage.
Certain types of pipe insulation have been developed for condensation control. They provide a barrier that keeps airborne water vapor separate from the surface of the pipe and prevents condensation from forming.
Prevent Heat Gain or Loss. When pipes are operating at temperatures significantly above or below ambient temperature, heat transfer can occur as the material in the pipe attempts to adjust itself to the surrounding air temperature. This means that the energy exerted to achieve a certain temperature of the liquid within the pipe will be wasted once the temperature rises or falls due to the ambient temperature. The energy it takes to restore the pipe to its correct operating temperature is an added utility expense. Proper thermal pipe insulation placed on the exterior of the pipes helps keep cold products cold and warm products warm as they convey through the piping system.
Freeze Prevention. Exterior pipes or pipes in below-freezing environments are at risk of allowing the contents inside the pipe to freeze. This will create blockage and varying degrees of other damage. Water expands as it freezes, so a water pipe that freezes will likely rupture and shut down the entire process.
The goal of pipe insulation in these environments is to keep the temperature of the liquid inside the pipe at the desired level to create optimum process cooling conditions. Although insulation alone cannot stop the pipe from freezing, it can increase the time it takes for the pipe to freeze in conjunction with a heat trace system on the pipe. With insulation and heat trace cables used on outdoor pipes, the liquid has adequate time to get to its destination before the pipe becomes blocked.
Personnel Safety. Although safety is not the most common concern addressed by pipe insulation in process cooling applications, insulation is useful for preventing any injuries resulting from a person coming in contact with the surface of a pipe at a temperature that is unsafe to touch. Thermal insulation can be specified to allow human contact without danger by applying the correct thickness of insulation to the exterior of a pipe.
Pipe Insulation Material Choices
The unique requirements of process cooling applications necessitate pipe insulation composed of varying material combinations to achieve optimal operating conditions. Depending on the desired conditions, a number of insulation materials can perform this important function. Insulation materials commonly are rated by their performance in four key areas:
- Thermal conductivity.
- Water-vapor resistance.
Insulation contractors are able to select the type of pipe insulation best suited for process cooling applications.
Common insulation materials include mineral or glass wool, rigid or flexible foam, polyethylene or other polyurethane-based insulation types, calcium silicate, cellular glass and aerogel. This range of pipe insulation materials allows the contractor to select the best material choice for the conditions in the process cooling system.
For chilled-water and refrigeration systems with active condensation or water leaks, a mold-resistant flexible elastomeric thermal insulation with an expanded closed-cell structure often is recommended. This type of pipe insulation is particularly useful for preventing heat transfer and condensation drip in these systems. This flexible elastomeric thermal insulation is not made with any formaldehyde and is resistant to mold and mildew, making it suitable for regulating pipe temperatures.
In process cooling systems that experience extremely low temperatures, a blend of several materials to create a hybrid insulation is sometimes necessary. One example is a polyurethane-modified polyisocyanurate cellular plastic insulation that is used for multiple applications with extreme temperature differences. This type of hybrid insulation is efficient for many thermal insulation applications due to its rigidity over a wider range of temperatures than traditional polyurethane insulation types. Effective over the temperature range of -297 to 300°F (-183 to 149°C), hybrid polyisocyanurate insulation often is used on industrial and commercial pipes as well as tanks and vessels, shipping containers, structural panels and even roof insulation.
If sustainability is a concern, environmentally friendly, high-density molded insulation is suitable for process cooling and other applications ranging from 0 to 1000°F (-17 to 538°C). This type of insulation is formaldehyde-free, mold-resistant and made from inorganic glass fibers that provide both lifecycle longevity and high performance for low and high temperature applications. The material provides energy savings and condensation control while helping companies achieve indoor air quality and sustainability goals.
Process engineers are in the unique position to choose the type of insulation that is best suited to the needs of their individual application. This type of individualized selection will maximize the benefits and minimize any potentially negative consequences that a lack of pipe insulation could create. PC