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Helping China Deliver Cleaner Coal Power

SteelMass 640S Thermal Mass Flow Meter

To keep pace with the electricity demands of its rapidly growing economy, China’s coal-fired power plant construction is booming. Conscious of their environmental impact, China has focused on building efficient, low polluting plants. One imperative is to balanceYiyan Power Plantthe fuel to air ratio in the boilers. More accurate fuel to air ratios result in increased boiler efficiency and a reduction in greenhouse gases.

Traditionally, coal plants used averaging pitot tubes (annubars) or other differential pressure-type (dP) devices. In a dP device, the flow is calculated by measuring the pressure drop over an obstruction inserted in the flow. These holes are prone to plugging from coal dust. Annubars are also mid-accuracy and poor turndown devices, and as volumetric devices, they don’t directly measure mass flow. The inaccuracies caused by these issues have long caused inefficient combustion and increased emissions.


The Hunan Electric Power Design Institute’s state-of-the-art coal-fired plant design for their 2008 Yiyang City installation provides a dramatic example of how Sierra is helping fill the demand for a cleaner process.

Building on the strengths of Yiyang I, built in 2001, Yiyang II required 16 high-precision mass flow meters for the measurement of combustion airflow to the boilers. After extensive testing of a wide variety of flow meters, the design engineers settled on Sierra’s SteelMass™ 640S meter. Almost immediately upon installation, YiYang II demonstrated increased accuracy and the ability to operate reliably at temperatures as high as 400°C (750°F).

Accuracy is inherent in the SteelMass 640S sensor due to the use of Sierra’s proprietary Dry-Sense™ Sensor Technology, a swaging process to press the velocity sensor into the thermowell. This creates a very stable sensor that does not require frequent calibration. Other thermal flow manufacturers use epoxies or glues to hold the sensing element in place, which can expand or contract over time creating “flow drift” that requires recalibration.

Sierra’s mass flow measurement solutions have significantly increased efficiencies in the Chinese coal-fired sector, while reducing maintenance costs and emissions. In fact, the improvements in these areas have been so dramatic that Yiyang I is now scheduled to be retrofitted with Sierra instrumentation.

Here’s what makes Sierra’s SteelMass 640S an ideal choice:
  • Measures mass flow directly with no temperature or pressure compensation required
  • Operates at high temperatures in the range of 400°C (750°F)
  • Offers 100:1 turndown as compared to 4:1 turndown for traditional differential pressure devices
  • Single point insertion means low installation costs and easy retrofitting
  • Insertion meters may be hot-tapped for easy cleaning
  • With no holes to get clogged, it operates smoothly in dirty flows, unlike more problematic averaging pitot tubes (annubars) and other differential pressure devices