8 Considerations When Designing Jacketed Pipe and Tubing Systems
For process engineers and plant managers in the sanitary processing industry, you're always looking for ways to improve your system efficiencies.
In the language of processing systems, jacketed pipe and tubing is essentially tubes within tubes. The inner tube, or pipe, is used to transport the product.
Surrounding this product-carrying tube is an outer tube, or jacket, that contains a media fluid — such as steam, hot or cold water, or glycol.
This jacket has inlet and outlet ports for the media, which is pumped through the outer tube to either heat or cool the materials flowing in the inner, product-carrying tube.
Jacketed piping and tubing can be an effective solution in process piping systems that are used to convey very viscous fluids — such as honey. In this case, the outer pipe jacket contains a heated liquid that warms the fluid flowing through the product pipe, making it easier to pump through process lines.
When used to control the viscosity of a fluid, jacketed pipe or tubing is ideal for products that are shear sensitive, or which contain large particles.
Typically, jacketed pipe systems can operate at a wide range of temperatures. For example, the jacketed tubing systems built by CSI are designed for media temperatures ranging from 34°F to 205°F, and product temperatures ranging from 24°F to 300°F.
8 Considerations in Designing Jacketed Tubing Systems
Jacketed tube systems are more complex than standard process piping, and they require more engineering to ensure that they perform as intended. In designing and laying out jacketed systems, there are a number of considerations that must be taken into account.
1. Fluid Pressure
The fluid flowing in the product side of the tubing must operate at a higher pressure than the fluid flowing in the media side of the tubing. This ensures that in the event that an unforeseen failure occurs in the process piping, the product is pushed into the media tube, rather than being drawn into the product line and causing product contamination.
2. Media Port Locations
The media inlet port for the system should be located at the lowest point in the process piping, and conversely, the outlet port should be located at the highest point. This ensures that the media will fully fill the jacketed pipe before exiting the system, and perform the job for which it is intended.
3. Slope
Jacketed piping should also be installed with a 1% slope in the line in order to facilitate complete system draining.
4. Fluid Flow
The system needs to be designed so that the media fluid flows in the opposite direction of the product flow. This improves the desired rate of the heating or cooling of the product.
5. Pipe Breaks and Joints
Tubed piping systems should be designed with a minimum number of piping breaks, or joints. Each break, both for the media and product lines, has both a direct cost impact (i.e., the physical costs of the components) and an indirect cost impact (i.e., the preventative maintenance costs) on the overall cost of the system.
6. Annular Space
Optimize the annular space between the product and media tubes. This prevents the product from solidifying or scorching, as well as similar problems.
7. Piping Stress
High stresses can result in the jacketed tubing system if the product core and media jackets operate at significantly different temperatures, or are made of different materials. For this reason, it’s a good practice to perform a piping stress analysis on a jacketed piping system, anticipating all core/jacket temperature combinations and external loading.
8. System Components and Layout
Finally, consider the following when designing a jacketed tubing system:
- Requirements for peripheral insulation around the jacketed tube (e.g., wrapped fiberglass or polyfoam).
- Thermal differences and expansions between the product and media lines, taking into account cycle times and durations.
- Types of piping section connectors used (i.e., expansion joints versus welded connectors).
- The potential for crevice corrosion on the media side (this has an impact on the materials used in the construction of the jacket).
- Internal supports needed for the product piping.
- The requirements (if any) for turbulence mechanisms in the pipeline such as flow disruptors, fins, and wraps.
Jacketed Pipe and Tube Connectors
As may be imagined, connectors used in jacketed tubing systems are also more complex than those found in standard process piping. Considerations must be given to the types of connectors use for the product-carrying pipe (i.e., the inner tube), the media pipe or jacket (i.e., the outer tube), and the types of connectors used (if any) to connect together the media pipes being used in two separate jacketed systems.
In this latter case, the assumption is that each jacketed subsystem in a larger process piping system can share a common media source, and so the media fluid can travel from one jacketed system to another.
The typical connectors used for each application include the following:
- In product pipes, the fluid being transported is considered to be sanitary, and any typical sanitary connector pipe connector may be used (e.g., butt weld fittings, Tri-Clamp® connectors, and bevel seat fittings).
- For the media pipes, the fluid being transported is not sanitary, and so a sanitary pipe connector is not required. Typically, National Pipe Thread connectors are used as the connectors for the media pipes.
- To connect two separate sections of media-carrying pipes between jacketed subsystems, hose connectors are commonly used.
With respect to the wide variety of connectors that may be used in jacketed tubing systems, CSI has considerable experience in designing and building these types of systems. We work with our customers to fit nearly any type of jacketed tubing connector required to meet a particular application.
Pipe Jackets or Tube Jackets?
On initial consideration, jacketed fluid processing systems made with pipes versus tubes would appear to be preferable based on the strength and durability of pipes. However, pipe jacket systems do bring considerable downsides:
- Using pipe as a jacket adds a lot of weight to the system, requiring the mounting structure (hangers, supports, piping racks, etc.) to be constructed of heavier-gauge materials in order to support the extra weight
- Jacketed system products with a mechanical external finish—often a requirement in sanitary system applications—are more readily available, commercially, as tubing in comparison to piping. Using pipes adds an additional cost, then, in order to achieve a uniform cleanable surface.
CSI has received questions from customers about the pressure ratings for tube-based jacketed systems versus pipe-based systems. In short, the theoretical bursting pressure of tube-based jacketed systems far exceeds the operating pressures of typical media systems. In other words, other media system components would fail before pressure could collapse or rupture the internal product tube.
Next Steps
Jacketed piping or tubing can be an effective solution in process piping systems that are used to convey very viscous fluids — such as honey.
But these specialized piping systems are complex, and require some expertise to design and install them properly. Here, CSI can help.
We’re experts in process piping system design, engineering, and construction, and can help you with your requirements for a jacketed tubing system. Call us at 417-831-1411 for more information.
ABOUT CSI
Central States Industrial Equipment (CSI) is a leader in distribution of hygienic pipe, valves, fittings, pumps, heat exchangers, and MRO supplies for hygienic industrial processors, with four distribution facilities across the U.S. CSI also provides detail design and execution for hygienic process systems in the food, dairy, beverage, pharmaceutical, biotechnology, and personal care industries. Specializing in process piping, system start-ups, and cleaning systems, CSI leverages technology, intellectual property, and industry expertise to deliver solutions to processing problems. More information can be found at www.csidesigns.com.