Jim Darby, a senior staff engineer and product manager for Marsh-McBirney, a Hach Co. brand, has seen it all in his 30+ years in the water and wastewater flow industry.
From experiences involving flow meters on nuclear submarines to municipal applications in the Boston area, Darby has a vast array of flow meter-related knowledge to draw upon.
Recently, Water & Wastes Digest spoke with Darby about his company Marsh-McBirney and other topics related to flow meters.
WWD: What are some of the current challenges regarding flow monitoring/metering?
Jim Darby: There are many challenges facing those involved with implementing and maintaining municipal flow measurement programs. Many of today’s issues are not new. Data quality, cost, safety and maintenance issues are typically high on the list of concerns for professionals and managers tasked with flow metering projects.
Today’s regulatory requirements are becoming more stringent, requiring more flow measurements. Increased measurements, coupled with the increased cost of compliance with confined space regulations, have a multiplying effect on monitoring program cost. Something often overlooked in the past is how much cost is associated with revisiting the site, especially when confined space entry is required to clean a fouled sensor. With more metering points and expensive safety procedures, maintenance is yet another cost multiplier—not to mention any lost or degraded data that may have occurred.
WWD: In your 30+ years of experience in the industry, what is the most unique or unusual flow-related problem or issue you have come across?
Darby: This is a tough one. There have certainly been many unique flow-metering issues faced over this time period.
In the early years Marsh-McBirney manufactured instruments to measure water flow in the ocean. I worked on solving a long-standing problem regarding angular accuracy and was granted a U.S. patent on the new sensor design. I also helped instrument the Polaris, Poseidon and Trident nuclear submarines as new missile systems were developed and tested. Our flow meters were used to measure flow around the missile tubes before and during launch.
In the municipal wastewater arena, the most memorable effort would probably be the Massachusetts Water Resource Authority (MWRA) project. This project involved installing 135 Flo-Dar flowmeters throughout the Boston metropolitan area. Many of these lines were very old and varied from 8 to 70 in. in diameter.
Additionally, we were just completing a surcharge velocity sensor that gave Flo-Dar the ability to measure flow during surcharge conditions. We had to complete successful testing at Alden Laboratory, upgrade our battery capacity to power the meter for a minimum of one year and provide cellular Internet connections for all these sites on a demanding schedule. Data from all these sites is now available for billing and planning purposes in near-real time on the MWRA server.
WWD: As a member of AWWA’s Standards Committee on Rate Type Flowmeters, are there any changes expected for the standards in 2007? If so, what are they?
Darby: The AWWA Standards Committee on Rate Type Flowmeters recently completed work on the AWWA Manual of Water Supply Practices M33. This manual, Flowmeters in Water Supply (M33), was published in late 2006. The committee is currently working on a Report on Magnetic Inductive Flowmeters (Magmeters). This document has passed the balloting stage and been approved by the committee.
WWD: What was your initial reaction when you learned that Hach would be purchasing Marsh McBirney?
Darby: Initially I had concerns about changes that would be coming. Over the years Marsh-McBirney was a great place to work and I was a little apprehensive. I resolved to go into the new relationship with an open mind and good attitude.
Very soon, my concerns were eliminated. The transition was handled professionally. I have been treated well and I feel that I will be able to continue to contribute to the new organization in the future as I have done in the past.
Marsh-McBirney has a top-notch support team that remains intact. They are not tasked with supporting the Hach analytical products and are able to concentrate on just Hach/ Marsh-McBirney flow products. This is a big plus for our flow customers.
WWD: Is there a piece of advice or recommendation regarding flow meters that you would like to pass along to a water or wastewater engineer who is involved with flow meters?
Darby: One piece of advice I would give is there is no one flowmeter that works well in every site. When planning a metering site, take the time to analyze the flow conditions and then pick the best meter for the application. Sites with very slow velocity, very high velocity, the combination of high velocity with low level, surcharging, clear flows and other attributes will allow you to rule out some meters from the selection process.
Whatever you choose, keep a close eye on maintenance requirements because they will be costly in the long run.
