LBJ Series Metal Scraper Flow Meters

Overview:

The LBJ series metal scraper flowmeter (referred to as the flowmeter) is a positive-displacement type flow instrument. It is designed for the continuous or intermittent, highly precise measurement of liquid flow rates in pipelines. Featuring high measurement accuracy, smooth operation, low noise, zero pulsation, large flow capacity, resistance to sludge and sand, long service life, strong viscosity adaptability, and ease of maintenance, this flowmeter is widely used across industries such as petroleum, chemical processing, light industry, transportation, and commerce. It is particularly well-suited for measuring industrial media like crude oil, residual oil, refined petroleum products, and light hydrocarbons. 
This flowmeter features on-site indication with direct digital readout, as well as the ability to output electrical pulse signals for use with display instruments and computer systems, enabling centralized, long-distance control and management of pipeline flow.

Structure and Working Principle of Flow Meters:

1. Structure of the Flow Meter

The flowmeter consists of several key components: the main body (flow transmitter), connecting parts, and the meter head (indicator). The main body primarily includes a rotor, cams, camshaft, scraper blades, connecting rods, rollers, as well as cover plates and the housing. Inside the housing, there’s a circular hollow cylinder—the rotor itself is a hollow, thin-walled cylinder that rotates freely. When the flowmeter uses two pairs of scraper blades, four slots are radially cut into the rotor’s cylindrical wall at 90° intervals. For three pairs of scraper blades, six slots are arranged at 60° intervals instead. These scraper blades slide within their respective slots, allowing them to extend outward or retract inward. Each set of four blades is connected by two cross-linked rods positioned at right angles to one another, while three pairs of blades are linked via three rods that intersect in space at 60° angles—ensuring they never collide. Between the scraper blades and the cams, there’s a bearing mechanism; all four or six bearings roll smoothly along a stationary, specially shaped cam. This design enables the scraper blades to alternately extend out of the rotor and then retract back inside, maintaining precise measurement. Additionally, the flowmeter’s main body (the flow transmitter) features a dual-shell construction. This innovative design effectively eliminates measurement inaccuracies caused by external forces such as pressure differences and pipeline tension-induced deformation of the flowmeter cavity, while also making maintenance and calibration of the device much more convenient. 
Repair and maintenance.

The flowmeter's indicator features two sets of cumulative counting mechanisms: the small-character counter displays the total accumulated count of the flowmeter, while the large-character counter shows the cumulative count at a specific moment and can be reset to zero.

2. How flow meters work

When the liquid being measured flows through the flowmeter, it drives the scraper blades and rotor to rotate. At the same time, the scrapers extend or retract radially along a specialized trajectory. Notably, the distance between the end faces of every pair of opposing scrapers remains constant. As the scrapers continuously rotate, this creates a fixed metering space (metering chamber) within the cavities of the adjacent rotor housings and between the upper and lower cover plates. With each full rotation of the rotor, exactly four (or six) identical, closed volumes of liquid—precisely corresponding to the metering chamber’s capacity—are discharged. (Refer to Figure 1.) The rotor’s rotational motion is then transmitted via a sealed coupling and transmission system to the counting mechanism, directly indicating the total volume of liquid that has passed through the flowmeter. 
The flowmeter equipped with a pulse transmitter can output electrical pulse signals, which can be processed by a computer or electronic display instrument to indicate both the cumulative and instantaneous flow rates of the liquid passing through the meter—enabling seamless control of various automated systems.

3. Combined configurations of flow meters

The flowmeter employs a modular assembly design, consisting of a main unit (the flow transmitter), a precision adjuster, a pulse transmitter, a heat sink, and a counter. With the exception of the transmitter, all other components are standard, universally available parts, allowing users to freely combine and select among the four configurations shown in Figure 2, based on their specific needs.

Technical specifications

1. Main Technical Parameters    
Accuracy Level:

±0.2% (range ratio of 10:1), with repeatability better than +0.03%. 
±0.1% (range ratio of 5:1), with repeatability better than ±0.03%; 
±0.5% (range ratio of 10:1), with repeatability better than ±0.05%. 
Explosion-proof rating: Ex db ⅡBT4

Protection rating: IP67

Display format: Large-digit counter—5-digit large digits with zero-reset capability, and 8-digit small digits without zero-reset.

Smart Flow Totalizer: 4-digit instantaneous flow rate: 000.0 to 999.9 m³/h, 8-digit totalized flow: 0000.0000 to 9999.9999 m³/h

Output signals: Pulse signal, dual-channel pulse signal, pulse signal 4–20mA (three-wire system), 1–5V, 4–20mA + HART protocol (three-wire system), MODBUS, and RS485 communication protocol. (Remote transmission distance up to ≤300m).

Power supply: DC 12V–24V

Technical Specifications Table

Note: The medium viscosity ranges from 0.3 mPa·s to 3000 mPa·s. 
Note: When the fluid viscosity exceeds 100 mPa·s, the maximum flow rate must be multiplied by the following factor:

2. Pipe Connection Flange

The connection flanges for the flow meters are manufactured according to the above-mentioned standard. If the user’s site requires a different standard, the flanges can be produced according to the user’s specified flange standards.

3. Implementation Standard 
This enterprise standard: JB/T 9242-2015 "Positive Displacement Flow Meters" and Q/ZAY 15-2023 "LBJ Series Metal Vane Flow Meters."

4. Characteristic Curve

① Gasoline 0.7 mPa·s 
② Water: 1 mPa·s 
③ Light diesel oil, 3.5 mPa·s 
④ Heavy oil 100 mPa·s 
 

5. Flow Meter Overall Dimensions

Flow meter external dimensions

Note: *Items marked are custom-sized; adjustments can be made if the user has specific requirements.