On the Safe Side: The “ROOT” of the Problem

Check out this interesting safety article about a near miss and a gate valve.

If you have been in this business long enough, there most likely has been at least one incident that, from a safety standpoint, was a “near miss.” These occurrences are normally not reported, and the only value gained is that the particular involved personnel take note and not make the same error again. The purpose of this article is to share with you a NEAR MISS. By passing this information along, we hope it will prevent you from having to make a more serious accident report.

The Situation: During the daily check of a pneumatic ejector station an operator noticed that one pot was cycling at a much higher rate than the other. After investigation, the operator concluded the discharge check valve was not closing properly, and wastewater was flowing back into the pot from the 6 inch force main after each cycle. The operator went back to the plant to pick up his assistant and necessary tools.

At the Station: Upon returning to the station, the operator and his assistant lowered a bucket containing the necessary tools to the station floor and then the operator climbed down the tube to the working chamber followed by the assistant. The operator then began the steps necessary to isolated the two pots in the station: Step 1, close the 6 inch gate valves on the inlet side of each pot; Step 2, initiate a discharge cycle to empty the pots and then close the 6 inch gate valves on the discharge side of the pot; Step 3, close the valves of the air supply to each pot.

The above isolation procedure had been used by the operator in the past to clear objects from the check valves so the next routine step was to remove the bolts and nuts from the cover of the check valve in question. With all of the bolts removed and placed in a coffee can, the operator used a screw driver and hammer to free the cover, which resulted in a rapid inflow of wastewater into the station. While the operator retrieved the check valve cover from the rising wastewater, the assistant was heading up the ladder. The operator pushed the cover into place and then sat on the cover to reduce the wastewater flow into the station. Then he felt under the water and found some of the bolts and nuts which had been scattered on the floor when the coffee can was kicked over during the excitement of the moment. The sump pump in the station dewatered the chamber and so with the check valve cover in place and secured and with the good pot placed back on line, the operator called it a day.

What went wrong? A mass of roots had come down the line and was interfering with both the check valve and the complete closing of the gate valve. The operator had completed a collection system course and, after the incident, recalled the instructor giving a simple rule of thumb for the number of turns to fully close a gate valve, three times the diameter in inches plus three turns, so that in this case the six inch valve would require 21 turns to be fully closed. (Note: Check with the valve manufacturer for the actual number of turns)

Corrective Actions: Know the number of turns required to close gate valve and count them while closing. Never take all of the bolts out before loosening a cover that may be under pressure. SHARE your NEAR MISS stories so they stay a NEAR MISS.

Do you have a near miss to share? Contact us at www.newea.org

On the Safe Side is provided by the NEWEA Safety Committee to help increase safety awareness in everyday activities. Thank you to Chris Hipkiss of NHWPCA Safety Committee and Winnipesaukee River Basin Program WWTF in Franklin, NH for sharing this article with us.