To successfully redirect water away from your job site, you must understand how to size your pipe properly when bypassing. If you incorrectly size your pipes, they’ll affect the performance of the entire pumping system. On the same hand, sizing pipes is essential because contractors must indicate the pipe sizes in their plans when they submit bids for their projects.
What is Bypassing?
During new construction or repairs, companies must pump wastewater around the pipes that require maintenance to prevent overflows. To do so without disrupting the normal flow, they create a temporary pipeline so fluids effortlessly flow through the pipes and discharge downstream to another location.
Bypass systems work great for various applications, particularly when you need to divert sewage through pipes in infrastructures and openings. You can also use a bypass system to repair storm drains and sanitary drains, which have been installed separately since the 1930’s.
How to Size Your Pipe Properly When Bypassing
First, you need to know exactly how much and where the flow will come from and where it needs to discharge. Take note of the distance of the area you’ll work in to estimate the length of pipes suitable for the job. Bypass pipes can be one size smaller than main pipes, but larger pipes are typically more ideal for longer distances, Discharge piping should be vented for longer distance piping, so adjust your pipes if needed. Additionally, the size of the pipes must match the peak flow, or the pipeline’s highest daily flow, if the pipe is too small it will create too much TDH or pressure on the pumps and drastically lower the performance of the pumping system; failure to consider the peak flow may result in costly spills.
You must also take friction loss and static lift into consideration. Friction loss happens when you increase the line size through the bypass to the receiving point of the system. Static lift is the height at which the water rises in the pipes before it reaches the pumps. Finally, don’t forget to think about the overall bypass system design when you select suction and discharge pipes.
Diameter plays a huge role in the pipes you use, as they must be large enough for the flow. The equation for pipe diameter is the square root of four multiplied by the flow rate divided by Pi multiplied by velocity. It’s also crucial that you’re familiar with the fluid’s temperature and viscosity which is the measurement of internal friction or thickness of the fluid flowing through the pipe. The less viscous the fluid, the more easily it can travel from one end of the pipe to the other. To reduce friction and velocity, you need to make sure all the pipes for your operation are the proper size.
Physicists and engineers use Poiseuille’s law to predict the velocity of water through a pipe. They use the equation mentioned above, where:
- ΔP = the velocity of the fluid
- μ = the dynamic viscosity, or the force a fluid needs to flow and overcome its own friction
- L = the length of the pipe
- Q = the volume of the fluid
- R = the pipe’s radius
This relationship assumes that the flow is laminar, or that it will move along smooth streamlines. If the flow is laminar, the fluid’s velocity is always constant. Thus, this law is an idealization more applicable to small capillaries than to water pipes. It may result in high flow rates, but companies or municipalities can still use Poiseuille’s law for their predictions.
Turbulence, or irregular movement, is almost always a factor when working with low viscosity fluids and larger or wider pipes, as friction is caused by the interaction of the fluid with the pipe walls. These factors are difficult to quantify, especially turbulence, and Poiseuille’s law doesn’t always give an accurate approximation. If you maintain constant pressure, however, this law can give you a good idea of how flow rate differs when you change the pipe dimensions.
The Hazen Williams coefficient can also be used to determine the type of pipe and size. In this case, you can also use the Reynolds number, or the ratio of inertia, to anticipate laminar or turbulent fluid flow in a pipe. This number is the sum of density multiplied by velocity multiplied by length divided by viscosity. Low numbers (lower than 2,000), for example, indicate laminar flow. Numbers above 3,500 show that the flow is turbulent.
Pipes in Practice
The Trans-Alaska Pipeline System is a prime example of effective pipe sizing. It’s one of the largest in the world; the pipeline spans 800 miles, and it’s four feet (or over a meter) in diameter. It starts in Prudhoe Bay and ends in the city of Valdez. The Trans-Alaska pipeline was built in the 1970’s to decrease oil prices across the nation, and it still moves millions of barrels of crude oil across Alaska every day. This amazing feat in engineering is possible due to the same physics that moves water into your house, sewage into treatment plants, and medicine through IV’s.
The Relationship Between Pipes and Pumps
To ensure a seamless bypass pumping project, always test the piping, as well as the pipeline itself, for leaks and pressure before operation. hydrostatic testing can be done to accomplish this.
Bypass systems can run dry and operate all day, so some contractors may not be able to automatically stop theirs from running if an issue occurs.
Once you know the flow of your operation and the depth level of the pipeline, select the proper pumps for your application. The pumps work above ground, which ensures the fluid reaches the discharge point. Using the right pumps is just as important to a sewage bypass system’s success as sizing the pipes and obtaining fittings that can withstand pressure. When you obtain the correct equipment, you reduce the likelihood of delays in your work that cost you time and money.
MWI carries robust pumps for a wide range of applications, including bypass pumping. We also provide exceptional water pump services, which include pump rental and 24/7 emergency pump repair services. When you request our help, our certified engineers will meticulously analyze your pumps’ performance and reliability. Plus, our experienced team can also design custom systems to meet your unique requirements. Contact us today for more information.