Aeration system pipe supports are typically spaced in the industry to provide long-term performance and service of aeration piping systems. In the spacing of these pipe supports, there are several variables that must be considered and evaluated to create a proper design. Clearly, there is a desire to have the pipe supports function properly while using the minimum number in order to control economics for the system. The design criteria that are appropriate for pipe supports are itemized below for sizing of the aeration systems.
Multiple types of pipe supports are available; however, all of those pipe supports are typically sized considering the following criteria:
- What is the diameter of the pipe?
- What is the material of construction of the pipe?
- What are the mechanical characteristics of the pipe materials?
- What is the thickness of the piping?
- What is the temperature of the aeration basin fluid and mix liquor?
- What is the temperature of the air in the piping?
- What type of diffuser, and number of diffusers in each segment of piping between pipe supports.
- Buoyancy of the pipe and of the air diffusers between supports when in operation.
- Weight of the segment of pipe between supports during the installation.
- Structural analysis of loads is based on the above data to control deflection and fiber stress.
All the above items are taken into consideration when doing the calculations for pipe support spacing and the number pipe supports. The maximum allowable deflection of the piping when in operation to maintain airflow between the diffusers uniform is also a criteria. Typically, the pipe deflection allowable between pipe supports is controlled to a maximum deflection of the piping of 12.5mm or 0.5”.
In addition to the design on the spacing of the pipe supports, the amount of hold down capability of the floor anchor bolts must also to be considered. Various design criteria are employed; however, the typical design for floor anchor bolts on pullout is generally 10 times the buoyancy, or up lift forces that may be generated by the piping and the diffusers as calculated above. These anchor bolts can be designed for as little as 4 times pullout with a considerable confidence; however, most of the systems use the 10 times safety factor as a specification.
Multiple types of the pipe supports are employed; however, all of these supports use the same general criteria for their sizing and spacing. When dealing with stainless steel or metal pipe typically, the piping will be rigid enough and the structural capacity of the metal material allows pipe support spacing that will be in the range of 4m to 5m.
For plastic piping systems, the calculations are done as shown above. In most cases, the supports are arrayed at spacings of 2.0m to 3m maximum.
The above are general design criteria for spacing and location of pipe supports, for application to any type of piping. Specialty applications and special designs are available. Special cases will be reviewed individually.