When Dependability Matters. Gas Metering by Sierra.

Company
Santa Cruz Wastewater Treatment Facility, Santa Cruz, California

Costumer
Jim Sturdivant, Electrical Technician, and Al Locatelli, Co-Gen and Standby Generator Specialist

Application
Digester Gas Flow Measurement and Optimizing Gas Mixing for Fuel

OEM Product
5 Model 640S Steel-Mass Insertion Mass Flow Meters, 2 Model 240 Innova-Mass Inline Multiparameter Mass Flow Meters, and 5 Model 780S Flat-Trak Inline Mass Flow Meters with Flow Conditioning.

Mass Flow Solution
Santa Cruz Waste Water Treatment Facility uses Sierra’s Steel-Mass Model 640S to measure the anaerobic digester gas (ADG), a mixture of 60% methane and 40% carbon dioxide, produced by their four digesters.  This digester gas is then mixed with natural gas and used as fuel for their 820kW internal-combustion engines.

Historically, wastewater treatment facilities around the globe have used differential pressure devices for their gas measurements.  These devices proved to be expensive to maintain, clogged easily, and required a separate pressure and temperature transducer and flow computer to deliver true mass flow.  In the late 1980s, like many wastewater treatment plants, Santa Cruz Wastewater Treatment Facility made the switch from these costly, maintenance ridden differential pressure devices to thermal technology.  Thermal is an excellent choice because it measures true mass flow directly with one instrument, has excellent turndown and accuracy at low flows, and has a much lower cost-of-ownership.

Becoming increasingly disgruntled with the lack of customer service from their thermal mass flow meter vendor, in the spring of 2002, Santa Cruz Wastewater Treatment Facility decided to give Sierra a try.  Rob Anderson, Sierra’s Sales Representative from Manco Controls installed Sierra’s Innova-Mass Model 240 Inline Multiparameter Vortex Mass Flow Meter to measure the natural gas used in their cogeneration system.  Through Anderson’s persistence and excellent customer service, by 2007, Santa Cruz Wastewater Treatment Facility had replaced all of their meters with Sierra’s vortex and thermal mass flow meters. “Other vendors sell you something, and you never hear from them again to help you out…Rob has been pretty unique both in response time and reliability with helping us out,” says Al Locatelli, Co-Gen and Standby Generator Specialist.

Healthy Digesters Produce Abundant Bio-Gas Critical for Energy Production
Producing abundant, healthy amounts of biogas each day in their digesters is the cornerstone of Santa Cruz Wastewater Treatment Facility’s unique renewable energy program.  Acting like a large stomach, the solids from the wastewater treatment process are “digested” in four large domed digesters, heated to 98 degrees for optimal digester gas production.  When methane forming bacteria breakdown the acids in the digester, large amounts of anaerobic digester gas, made up of 60 % methane and 40% C02, are produced.  From readings taken from Sierra’s Steel-Mass Model 640S, facility operators, the “brains” of this stomach, use their Supervisory Control & Data Acquisition (SCADA) computer system to check that each digester is producing optimal amounts of digester gas.  If the digester gas readings are low, the “stomach” is upset, so the operators will check various process parameters like PH levels and alkalinity ratios, temperature and feed rates to increase the production of digester gas.

Luckily for Santa Cruz Wastewater Treatment Facility accurately measuring digester gas in wastewater applications is the ultimate “Killer App” for thermal technology.  Since digester applications operate at relatively low pressures, the Steel-Mass Model 640S creates virtually no pressure drop and accurately measures these low flow rates whereas an orifice plate could not be used at all. The Steel-Mass Model 640S also provides 2% of reading accuracy and 1% repeatability over a 40:1 turndown range, essential for digester gas applications. Jim Sturdivant, Electrical Technician, responsible for fixing broken equipment at the facility says “Sierra is a good quality product…the best thing about the Sierra meters is that I never have to look at them.”   Nothing pleases a technician more.

Cogeneration System Uses Biogas for Engine Fuel
According to Al Locatelli, Co-Gen and Standby Generator Specialist, preparing this raw biogas into fuel for their internal combustion engines is no simple task, but it’s what makes Santa Cruz Wastewater Treatment Facility unique. Their Waukesha 7042 GLD 820KW engine, coined Cogeneration 1, burns a mixture of digester gas and purchased natural gas. The natural gas is mixed with air to lower the BTU levels closer to digester gas.  This biogas enters a manifold system, goes through an iron sponge scrubber to remove hydrogen sulfide (H2S), a harmful greenhouse gas, and a chiller unit to remove the moisture from the gas.  Compressed from 7 inches of water column to 3 psi, the gas enters a second carbon scrubber to remove siloxanes which can harm the engines.

In their static inline mixer controlled by a loop processor, this cleaned and compressed biogas is mixed with the diluted natural gas to maintain the optimal gas blend of 80% digester gas and 20% purchased natural gas. If the mass flow rate of digester gas decreases, more diluted natural gas enters the blend. Essentially the diluted natural gas compensates for the fluctuations in digester gas production, ensuring that very little digester gas has to be flared off.  After passing through a particle filter, this mixed gas is finally ready to fuel up the Waukesha 7042 GLD engine.  To improve engine performance, Locatelli explains that a high BTU shot of natural gas is injected into the pre-combustion engine chamber using admission valves to ignite the lean fuel mixture in the cylinders.  Natural gas readings taken from the Flat-Trak Model 780S help Locatelli diagnose potential engine problems and tune the engine for increased efficiency.  Although most of their biogas is used to fuel Cogeneration 1, sometimes, especially when Cogeneration 1 is down, the digester gas pressure increases and a pressure transducer loop processor automatically opens a valve to flare off the excess digester gas.  For EPA reporting purposes, this flared gas is measured with Sierra’s Steel-Mass Model 640S.  By reusing their methane, Santa Cruz Wastewater Treatment Facility prevents 41 tons of CO2 emissions from polluting our atmosphere, a potent greenhouse gas.

Each day, operators check the gas readings taken by the Flat-Trak Model 780S  and  Innova-Mass Model 240 which are connected to the Supervisory Control & Data Acquisition (SCADA) computer system, allowing them to  manage this complex cogeneration system and trend historical data of gas usage.  Working and relying on Sierra every day, Locatelli says, “from what I see from other vendors, Sierra is the top of the line.”  He is even more pleased with the lack of maintenance problems. “We started using these meters in 2003 and have had no problems,” declares Locatelli.

Energy Savings—A Balancing Act
By using the sophisticated SCADA system and their Power Monitoring System, which automatically calculates their monthly energy bill, Dave Meyers, Senior Plant Operator, makes important energy saving decisions each day.  Using about 1.3 megawatts, the plant can’t run solely on the 820kW produced by Cogeneration 1.  Meyers explains that during the week, between Noon and 6pm Monday through Friday, May through October, energy rates jump from 11 cents a kilowatt hour to 11 dollars a kilowatt hour which includes on peak demand charges.  To break these peak demand times, he decides to fire-up their Waukesha 3521 GLD lean burn engine, coined Cogeneration 2, which produces 500kW of energy, but runs solely on purchased natural gas.  Meyers and other operators save Santa Cruz Wastewater Treatment Facility money on energy by choosing to pay for the natural gas to run Cogeneration 2 during peak demand times rather than importing energy from PG&E at $11 a kilowatt hour.

Conclusion
Sierra’s accurate mass flow measurements help quantify these savings by giving accurate mass flow rates of digester gas production, digester gas burned in the cogeneration system, and digester gas flared to the atmosphere all monitored by the Monterey Air Board twice a month.

When Rugged Reliability Matters.  District Energy Management by Innova-Mass®.

Customer
Harvey Vershum, Energy Manager at the University of Toledo, Ohio

Application
Distributed Steam Metering

Product
Sierra’s Innova-Mass® Model 241 Multiparameter Mass Flow Meter

Mass Flow Solution
The University of Toledo has installed 11 Innova-Mass® meters throughout the UT campus to measure the total steam output from their central steam plant and to submeter the amount of steam to each building in order to know the exact steam consumption, generated and distributed, throughout the campus.

Business Impact
Sierra’s Multiparameter Mass Flow Meter

…has replaced their old, inaccurate condensate method of estimating steam flow, giving them repeatable distributed steam measurements.  Innova-Mass® accurately measures every unit of steam usage on campus, shows where there is an increase in steam consumption, and proves that energy saving changes are working to save the university money on energy costs.

Harvey Vershum was no exception.  However, like many facilities managers, he began to realize that using the condensate method may not be very accurate and the rotors on the turbine meters would break and had to be replaced every year—a costly and time-consuming process.  In the 1980s, Vershum contacted Tom Tumlin, a Sierra representative and now president of Portage Controls in Medina, OH, to replace his rotors at $500 a pop.

The Innova-Mass® Has Captured Over 80% of the District Energy Market
Over the years, Tumlin would prompt Vershum, “take the turbine meters out and replace them with Sierra.”

With its capability of measuring five parameters with one process connection and calculating true mass flow directly, without separate temperature and pressure sensors, Tumlin knew that Innova-Mass® would not only be easier for Vershum to operate but decrease his installation costs and overall cost-of-ownership.  Known as the “steam meter” for the industry, Innova-Mass® has captured over 80% of the District Energy market worldwide, and as a member of IDEA, Sierra has been a leading contributor to improving district energy technology. Tumlin’s persistence and market knowledge paid off.

Vershum Has Less Maintenance and No Moving Parts with Innova-Mass®
In 2003, Vershum finally decided to give Sierra a try.  He replaced one of his insertion turbine meters and installed his first in-line Innova-Mass® meter .  He was so pleased with its “accuracy and reduced maintenance” that in 2004 he replaced even more of his meters with Sierra.  With its easy installation, no moving parts, and greater configuration flexibility, Vershum was sold on Sierra’s Innova-Mass®.  He has never looked back.

In 2005, the Medical College at Toledo merged with the University of Toledo, and Harvey Vershum became the Director of Energy Management for both campuses.  And again, in 2007 he chose Sierra to outfit 27 buildings on the campus with Innova- Mass, installing 7 insertion meters and 3 in-line meters for distributed metering at the University of Toledo.  Tom Tumlin readily partnered with Vershum during this installation process.  He drove to the University of  Toledo, toured the entire campus, looking at 12 inch pipes, 4 inch pipes, elbows, and straight lines, planning the best place to install the meters.

Tumlin remembers “going from building to building, running around hot basements, sometimes in steam tunnels or metering pits.”  For Tumlin, this is the norm.  He always checks the meter location, confirms pipe size, steam pressure and estimated flow rate.  This is the Sierra way—building partnership with customers throughout the entire process.

Tumlin reports proudly that Vershum “has not lost a meter.  It goes in and doesn’t break”.

Facilities Managers Love the Ease-of-Use of Innova-Mass®
In the past with volumetric turbine meters, Vershum and other facilities managers had to calibrate the meters for a specific temperature, pressure, and pipe size with specific flow rates and units.  This proved to be very tedious and time-consuming work.  With its easy-to-use menu, changing ranges, outputs and totalizers and engineering units is simply done, either locally at the meter or remotely using HART or MODBUS.

“Sierra does this on the head…no pain no strain,” says Tumlin.  And Vershum loves the “ability to remote mount the head.”  He explains that sometimes the meters are in locations that would be impossible to reach without a ladder.  The remote mounted head allows him to position the display where it can be read quickly.

The University of Toledo Campus Saves Money on Energy Costs
With Sierra installed, now Harvey Vershum can make informed energy saving decisions for the University of Toledo campus.  He said, Sierra has given him the ability to track the steam usage.  He has been able to verify the savings after he removed his old steam absorbers and installed new high efficiency electric chillers.  The bottom line is that Harvey Vershum has saved University of Toledo money on energy costs and can do his job more easily, quickly, and with less hassle.

In January of 2008, Harvey Vershum ordered 5 more 241 Innova-Mass® Multiparameter Mass Flow Meters and will bid on 8 more later in the year.