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Odorizer and Flow Meter Solve Low-Flow Odorization Challenges

by | on | in Natural Gas Products | 1 Comment

Recently, GPL Odorizers and Linc Energy Systems were challenged by a client's problematic low-flow odorization site. Both companies worked together and conferred with Sage Metering, who designed the GPL 100 Thermal Mass Flow Meter for low-flow odorization use. Here is a case study on this application.


A natural gas distributor in central Tennessee had lost confidence in an odorization system at a low flow site. The client agreed to test a beta unit of the GPL 750 Odorizer at this challenging site. A thermal mass flow meter was installed to accommodate the low and intermittent gas flow to communicate with the odorant injection controller and ensure accurate and repeatable odorization. The GPL 750, an eco-friendly odorization system solved this challenging application.

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Challenging Low-Flow Odorization Application

A problematic natural gas odorization site was becoming a burden to a Tennessee natural gas distributor. Matt Stennett, the Chief Gas Engineer at the company's Smithville location, was odorizing natural gas coming into a town using an odorant injection style odorizer with a Williams Pump. There were issues with priming the odorant pump and because there were no remote communications to the odorizer, the client was forced to frequent the site to verify that the pump was working and delivering the odorant correctly.

This gas coming to the site was low flow and intermittent flow running at a maximum target flow of 12,000 SCFH. It was unclear, however, how low the gas flow was, but the meter at the site was a turbine meter. The turbine flowmeter is considered a traditional flow meter technology, along with differential pressure and positive displacement meters. The turbine meter is a favorite device used to measure gas flow, particularly for clean, medium-to-high steady streams of low-viscosity fluids. This meter style measures volumetric flow based on fluid flowing passed a free-spinning rotor, with each revolution agreeing with a particular volume of fluid. Turbine meters measure liquids as well as natural gas flow. The turbine meter, however, is notorious for having a low-flow cutoff at about 15% of the maximum flow capacity.

Solution - GPL Odorizer and Thermal Mass Flow Meter

GPL 750 OdorizerBeta GPL 750 Low Flow Odorization System

Members of Linc Energy Systems and GPL Odorizers met the client, Matt Stennett at the American Public Gas Association conference show in 2015 in Broomfield Colorado. At the time, the client mentioned that he had been performing countless service calls to keep an odorizer at a low-flow site functioning. I showed him our new low-flow odorizer and said that I was looking for a beta site to test the soon to be released GPL 750 Odorizer. In the weeks to come, we spoke further, and I sent him drawings of the proposed unit, along with specifications including a complimentary modem so that we could monitor how the unit was performing from our home office in Wheat Ridge Colorado.

Knowing that there was a turbine meter at the site, and not completely understanding how minimal the gas flow could run, we knew the turbine meter would not provide accurate data for the odorizer's controller. We consulted with Sage Metering, the manufacturer of premium thermal mass flow meters. The company designed a flow meter specifically for low and intermittent-flow odorization applications called the GPL 100 flow meter which has a low-end sensitivity of 5 SFPM.

GPL 100 thermal mass flow meterGPL 100 Thermal Mass Flow MeterWe installed the GPL 750 Odorizer along with the GPL 100 Thermal Mass Flow Meter at the Tennessee beta site. The flow meter reads the gas flowing into that town and sends a 4-20 mAmp signal to the Horner computer; the controller of the GPL 750 Odorizer. This odorizer employs proprietary drip technology and injects a fixed measure of odorant into the gas stream proportionate to the flow, ensuring accurate and repeatable odorization even in low or intermittent flow.

After a couple of months of operation, the client called and expressed concern that the Horner controller was showing much more flow (measured by the thermal mass flow meter) than the turbine meter's data. We explained that anytime the flow plummeted below 1800 SCFH the turbine meter was not registering the gas flow, because of its low-flow cutoff, and therefore the thermal mass flow meter data was more accurate.


When following up with the customer some time later to see how the odorizer was performing, the client was happy to say, "The GPL 750 has proven to be boringly reliable." Apparently, the customer had only needed to go to the site once to check an alarm, only to learn that there had been a power outage and he needed to reset the modem. According to Stennett, the GPL system allows "much more accurate injections during low-flow conditions and makes it possible to document, calculate, audit, and prove it to ourselves and our state regulatory agency." Stennett further stated, "The GPL 750 Odorizer solved one of our most challenging odorization applications. It demonstrated accurate and repeatable odorant injection even in no flow, low flow, and intermittent-flow conditions."


The GPL 750 Odorizer, along with the GPL 100 Thermal Mass Flow Meter solved the customer's challenging odorization application. The client no longer has to provide frequent service calls to the location.


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About The Author

Tom is a former engineer for Xcel Energy, where he designed gas meter and regulator applications. He has also worked for mechanical contractors and engineering firms approving gas meters and regulators in various applications. He currently manages the Linc Energy Meter and Regular Department and is working on flare gas measurement.


  • Guest
    flow meter Wednesday, 01 March 2017

    Measuring principle
    Many people are made uncomfortably cold by just a
    small draft. The thermal flow-measuring principle is
    based on the fact that heat is drawn from a heated
    body when a gas flows past.
    A thermal flowmeter contains two PT100 temperature
    sensors for this purpose. One sensor measures the
    current fluid temperature as a reference. The second
    sensor is heated and has a constant temperature
    differential relative to the first sensor at “zero flow”.
    As soon as the fluid begins to flow in the measuring
    tube, the heated temperature sensor cools off due to
    the fluid flowing past – the higher the flow velocity, the
    greater the cooling effect.
    The electric current required to maintain the
    temperature differential is thus a direct measure of
    mass flow

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