Trenchless Tech Forum – Tips for Sewer Bypass Pump Startup Success
Every sewer bypass pump project has potential pitfalls. Sound planning and setup can pave the way for startup success, and reduce the risks of spills and leakages. Here are three tips to help a project team achieve startup success.
Size the System Right
Worker and environmental safety always need to be at the forefront of a bypass operation. Anyone working in a confined space such as a sewer should be properly equipped – as well as trained and supervised.
Companies need to determine the maximum anticipated flow and design the bypass system, accordingly. A good first step is create a professional drawing to show what the pump system will look like, and how it will address project needs and constraints. This is an area where a fluid solutions provider can help, if needed.
Be sure to select the right pumps and hoses. Diesel-driven centrifugal pumps are the typical choice. However, if the suction lift is too great, electrical or hydraulic submersibles may be required.
In sizing the system, the total dynamic suction lift should be no greater than 28 ft. The recommended minimum suction depth is 6 ft. A suction lift that’s too high or too low can cause performance loss or equipment damage. Also, control velocity and plan for it not exceed 12 ft per second. To avoid rupturing or flattening the discharge pipe, make sure you are introducing and evacuating the right amount of air.
To maintain uptime, build in redundancy and easy access. Jobsites should have backup pumps on hand and system design needs to make it easy to swap pumps in and out as needed. In set up, project teams need to create good access points for fueling, maintenance and isolation gate valves.
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Inspect and Test before Startup
Fixing issues is much more complicated after a pump system goes live. A few important steps can help reduce the risk of problems. Start by checking all pump lubricant and fuel levels. A team doesn’t want to let a bypass fail due to a lack of basic pump maintenance.
A telemetry system can automatically send alerts for problems involving fuel level, oil pressure, coolant temperature, flow rate, suction and discharge pressure and more. Before startup, check the telemetry system, if one is being used, to make sure it is connected and all sensors are sending signals.
Outfit the suction system with a vacuum gauge on the priming and suction side, and a pressure gauge on the discharge side for continuous monitoring. Also, it is always a good idea to test the bypass system by filling it with fresh water to check for leaks.
And before every startup, attach an updated emergency response plan and contact list to every pump.
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Troubleshoot Startup Failures
Sometimes, even with all planning done well, and after checking and rechecking every component, the system might not start. Here are four common trouble spots to eliminate the most likely culprits.
There’s a lot of sophisticated planning that goes into the automatic priming system on a centrifugal pump, but when something goes wrong, the cause may be simple. Check to see if someone left the drain valve open or the priming system valve closed.
Look for the easy fixes first. The answer could be as simple as a five-dollar gasket that is cut or missing inside the suction hose. Another common issue is if the check valve is open — even just a little — there is potential for an air leak. The check valve is a hard rubber flapper that has a lip seal around its circumference. Over time it can wear out. If check valves do not make a positive seal, there will be an air leak.
Lastly, the suction lift can be tricky and depends on several factors. Remember, suction lift should be not greater than 28 ft. Water levels fluctuate in sewer system. If the depth is greater than 28 ft, the pump will not prime. It’s possible the water level increased just when the team was trying to start up the system. If the team is using a trailer-mounted pump, there’s a quick remedy that may make the difference. Remove the wheels to get the pump lower to the ground.
A sewer bypass pumping project can be a large and costly undertaking. It is recommended that companies always consult with an expert regarding the specific circumstances, applicable rules and regulations related to a specific site and situation.
Troy Underwood is a vertical sales specialist at United Rentals.