The HUALIU Gas Roots Flowmeter (model HL-LLQ) is a high-accuracy, high-reliability, wide-range gas metering instrument, widely used for custody transfer and process monitoring of non-corrosive gases such as natural gas, city coal gas, propane, nitrogen and various industrial inert gases. The intelligent version integrates flow, temperature and pressure sensors and an intelligent flow computer on the Roots flowmeter body; both the pressure and temperature sensors can be calibrated and verified independently, making replacement, maintenance and use more convenient.

The instrument consists of a housing, conjugate rotors and an intelligent flow computer, among other components. Under the action of the differential pressure between the gas inlet and outlet, a pair of conjugate rotors in the measuring chamber maintains the correct relative position via precision-machined timing gears, keeping optimum working clearances between the rotors, between the rotors and the housing, and between the rotors and the wall plates, thus achieving continuous non-contact sealing. Each full rotation of the rotors discharges four times the effective volume of the measuring chamber, completing precise positive-displacement metering. Accuracy remains stable over long-term operation and is unaffected by the medium.

The product is compact and low in power consumption, with a turndown ratio up to 90:1, low starting flow and low pressure loss. The meter coefficient can be automatically linearized in nine segments according to the flow-frequency signal, balancing metering accuracy across a wide range. E²PROM data storage permanently retains user and factory parameters during power loss. The basic version provides working-condition, standard-condition and calibration pulse outputs, with optional 4~20mA analog output and RS485 communication; the B-type meter additionally features GPRS wireless transmission, facilitating the construction of remote monitoring and data-traceability management systems.