July 1, 2020

Sealing the Deal for Sewage Pump Replacement

Seal Water System Design and Manufacturing

Seal water system for Terre Haute, IN.

In most situations, pump related or otherwise, there are multiple ways to overcome a challenge or solve a problem. With every project we face at Metropolitan, the priority is to address our customers’ needs, but there’s rarely only one right way to do so. The City of Terre Haute, Indiana recently found themselves in a similar position when it came time to replace the sewage pumps at its new main lift station.

In this case, the city needed to decide between two different pump setups: one that required the use of a seal water system and one that did not. In the end, Terre Haute settled on pumps requiring seal water and the engineers behind the project, Commonwealth Engineers, Inc., knew Metropolitan could deliver exactly what they needed. After all, we know pumps, we’re more than familiar with designing systems of every shape and size to fill a need, and our expertise extends well beyond our home state of Illinois.

The Need for a Seal Water System

The importance of a reliable pump system and its intended operation cannot be understated.

Systems with mechanical seals, a component that allows rotating shafts on pumps to operate while providing a trifecta of benefits including leakage prevention, pressure control, and contamination exclusion, can benefit from seal water systems to help maintain proper operating conditions.

A seal water system delivers a continuous flow of flushing liquid through a double mechanical seal. Each seal type has specific seal water flow and pressure requirement, but the flushing water has to be at a higher pressure than the discharge pressure of the main pump to keep the solids off the seal faces successfully.

Several factors can affect how much seal water a system consumes, including rotation speed, seal water temperature and pressure. Additionally, the main pump manufacturer specifies a minimum flow and pressure that each seal must have to operate reliably.

In general, these systems serve three main purposes:

    1. 1. Cool the seal
    1. 2. Lubricate the seal
    1. 3. Flush impurities out of the system

The pressurized seal water essentially acts as a small loop of barrier or buffer fluid. This potable water is forced into the seal housing thereby flushing contaminants away from the pump. The entire process typically requires a minimal amount of seal water, meaning the system in Terre Haute, responsible for flushing mechanical seals and packing stuffing boxes in the sewage pumps, needed to be low flow.

Designing a low flow system meant two things: proper piping and a reliable controller. In this application, type L copper piping was the best option. The thicker wall, when compared to type M, would better handle the pressure and coating any other piping at such narrow diameters —0.75” to 1.0”—would be too cumbersome and costly. As for the controller, the MetroTech III Pro Water Pressure Pump Controller was the clear choice.

If you’re familiar with any of our past projects involving the MetroTech III Pro variable speed water booster pump controller, or if you’ve installed one in the past, the controller’s adaptability made using this controller for a low-flow application a natural fit.

In fact, the MetroTech III Pro was designed into this project because it delivers precision and control and, regardless of the size of the application, both are essential for long-term operability. With pressure control, sophisticated communications and an intuitive touch screen for the operator interface, the controller ensures accurate and timely operation which are both crucial in this application. As the new sewage pumps turn on, the need for seal water is initiated and Metropolitan’s booster pump delivers the specified amount of water for the number of pumps running at that time. To eliminate the risk of pressure building up on our system, a pressure release valve is put in place and dumps back into the break tank.

To help everything in Terre Haute run as smoothly as possible, the intuitive MetroTech III also offers real-time troubleshooting to the team responsible for daily operation. Of course, our goal is to avoid troubleshooting all together which is why we perform a full array of tests before any Metropolitan system or components leave our Romeoville, Illinois facility.

Custom Design of Seal Water System

Angled view of seal water system.

Testing You Can Count On

Our experts are well versed in putting every piece of equipment through a full range of tests and our facility features extensive testing capabilities that were further enhanced in 2017. For larger projects, full system testing greatly reduces startup time and decreases the potential for errors—resulting in added costs and potential downtime—
after installation.

Our state-of-the-art, on-site test lab is designed to perform a full range of testing on all of our equipment. Testing capabilities include hydrostatic-pressure, hydraulic-performance, and hydronic-equipment performance testing on both individual items and large packaged/custom assemblies. Newer additions include automated testing with programmable logic controls (PLC), actuated throttling valves, calibrated instrumentation, and even witness testing with our customers.

With new sewer pumps and a reliable seal water system to help ensure everything runs as smoothly as possible, the City of Terre Haute is better equipped to serve its residents and guests now and into the future. And, as always, if they need anything in the years to come, we’ll be a phone call away to answer their questions and offer any services they may need.

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