Accurate Flow Measurement for High Viscosity Liquids
May 16 2023
In the realm of measuring the flow of petroleum liquids and petrochemical additive injection fluids, Positive Displacement flow measurement devices, such as Titan Enterprises' Oval Gear (OG) flowmeters, reign as a highly favoured option. These flow meters continue to be a dependable choice in today's advanced process control settings for several reasons. They excel in harsh environments, boast high-pressure capabilities, and offer long-term reliability with minimal maintenance requirements. Moreover, they are particularly well-suited for handling viscous fluids.
For the precise measurement of high viscosity liquids such as fuels, thick oils, bitumen, resin, and tar, specialised devices with precision engineering are necessary. Oval gear meters are designed with teeth that serve the dual purpose of driving the gear and sealing the central path. The unique shape of the ovals in these meters generates the differential force required, rather than relying solely on the gear teeth on the lobe. The size and shape of the oval gears can be customised to suit the specific resolution and flow requirements of the process application.
When metering high viscosity liquids in an application, the pressure drop becomes the primary limiting factor. Flow measurement devices equipped with Oval Gears offer a larger surface area, leading to a significant increase in the driving pressure across the gears. As a result, these devices exhibit a wider flow range capability and lower pressure drop compared to other positive displacement meter types.
Neil Hannay, Titan Enterprises’ Senior Development Engineer, explained: “The higher the viscosity of a liquid, the more pressure will be required to ‘force’ the liquid into the flowmeter and around the oval gears. It’s important to bear this in mind when selecting the correct size of oval gear flowmeter for your application. For example, more pressure will be required to push through resin than diesel.”
Titans' Oval Gear (OG) flowmeters exhibit remarkable resistance to the impact of fluctuating liquid viscosity, density, and temperature. As the viscosity of the liquid increases, the measurement accuracy of these flowmeters actually improves, achieving a nominal accuracy of 1% to approximately 0.1% of the flow rate at higher viscosities. Even at viscosities exceeding 1000 cSt, Titan offers specially profiled gears with their standard OG models to accommodate the additional liquid flow while maintaining high accuracy.
To cater to specific high-pressure demands, chemical compatibility, and safety considerations in potentially explosive atmospheres, Titan Enterprises provides customised options and adaptive designs for its Oval Gear meters. The range includes models with ATEX compliance and IP65/NEMA 4 protection, ensuring safe operation even in harsh environments. These meters are built to withstand challenging conditions, such as explosive or corrosive atmospheres, while maintaining accurate and reliable measurements.
Titan's Oval Gear meters undergo in-house pressure testing, with custom-designed models capable of being tested up to 950 bar and calibrated against diesel fuel upon request. In the chemical industry, oval gear flowmeters are frequently employed alongside batch controllers to enable the automated dispensing of predetermined volumes of chemicals.
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