Licensing exams can be challenging. Our Exam Study Guide helps you prepare by presenting questions similar to those on an actual exam. You can find many more sample questions on the TPO website at  www.tpomag.com/study.

WASTEWATER

By Rick Lallish

What condition may occur if old packing is not removed completely, before repacking a pump?

A. Tension-alignment problems

B. Shaft scoring

C. Excessive leaking from the magnetic seal

D. Packing gland misalignment

Answer: B. When changing the packing on a pump, it is imperative to remove all the old packing before installing new packing. If this is not done, shaft scoring will occur, leading to premature pump failure and leakage. Proper pump packing is vital for proper pump operation and maintenance. Replacing a shaft or pump can be costly. More information may be found in the Pumps and Pumping textbook from Skeet Arasmith, 9th edition, 2006.

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DRINKING WATER

By Drew Hoelscher

What mA signal should an operator expect if a chemical feed pump is operating at 75% flow capacity on a 4-20 mA current loop?

A. 4

B. 8

C. 16

D. 20

Answer: C. The 4-20 mA point-to-point or multipoint circuit is commonly used in the automation of process equipment at water treatment facilities. Using the mA signal transmitted from instruments and sensors to a controller is a crucial step in troubleshooting process equipment. For example, a 4 mA signal would indicate a chemical feed pump that is not operating and a 20 mA signal would indicate a chemical feed pump operating at 100% capacity.

About the authors

Rick Lallish is water pollution control program director and Drew Hoelscher is program director of drinking water operations at the Environmental Resources Training Center of Southern Illinois University Edwardsville.