LPG Flow Meter

I. Purpose:

The LPG(liquefied petroleum gas) flow meter is an important component of the LPG dispenser. Comprising four symmetrical pistons, each cycle of operation results in the discharge of 0.5 liters of oil. Its design incorporates features such as connecting rod limitations, an integrated check valve at the inlet, double leather wrists piston, and one-way bearings at the output end. These elements contribute to the flow meter’s remarkable attributes, including high precision in measurement, excellent wear resistance, and an extended operational lifespan. With its compact structure, user-friendly operation, easy maintenance, and visually appealing exterior, this flow meter finds applications in the filling and refueling services of gases, kerosene, diesel, gasoline, and mixed fuels.

II. Working Principle:

The pump directs LPG into the flow meter, where the pressure variance between the inlet and outlet propels the pistons into action. This movement initiates a sequence involving connecting rods, crankshafts, and distribution valves, resulting in the reciprocating motion of the pistons. With each cycle, the four pistons collectively discharge 0.5 liters of liquefied gas.

Simultaneously, the distribution valve propels the outer rotor component, with magnets inducing rotation in the inner rotor component through magnetic field forces.

III. Structure, Technical Parameters, and Environmental Conditions:

Structure: The LPG flow meter comprises a housing, upper cover, inner rotor component, outer rotor component, isolation sleeve, bottom cover, crankshaft, connecting rod, piston, distribution valve, distribution valve seat, and adjustment device. Materials chosen for design adhere to standardized specifications, such as 9Cr18 for the crankshaft, 3Cr13 for the connecting rod, FD-3 modified tetrafluoroethylene for the piston, and nitrile rubber for sealing.

Technical Parameters:

a) Displacement per revolution: 0.5L

b) Accuracy error: ±0.1%

c) Repeatability error: ≤0.1%

d) Minimum adjustment amount: 0.05%

e) Maximum flow rate: 35 L/min

f) Minimum flow rate: 5 L/min

g)Operating stability: Following continuous operation for 100 hours at the maximum flow rate, the measurement accuracy should not exceed ±0.1%, with a repeatability error not exceeding 0.1%. The minimum permissible error for the maximum measured value is ±0.3%, with a repeatability error not exceeding 0.15%.

Environmental Conditions:

a) Temperature: -25°C to +55°C

b) Relative humidity: 30% to 90%

c) Atmospheric pressure: 86KPa to 106 KPa

IV. Structural Diagram and Installation Dimension Diagram

Structural Diagram and Installation Dimension Diagram

1 Slotted coupling 2 One way bearing 3 Isolation sleeve
4 Inner rotor magnet 5 Outer rotor magnet 6 Outer rotor assembly
7 Upper cap 8 Distribution valve 9 Adjustment end cap
10 Piston assembly 11 Cylinder liner 12 Bottom cap
13 Crankshaft 14 Connecting rod 15 End cap
16 Shell 17 Distribution valve seat

V. Testing and Adjustment:

The LPG flow meter will be shipped from the factory after being rigorously tested and qualified. If you need to change the parameters, you can adjust them according to the following instructions.

Accurate flow meter adjustment:

a) Figure 1 shows the opening of the lead seal above the flow meter handle. After removing the sealing wire and sealing pin, rotate the handle clockwise or counterclockwise. Turning it clockwise will reduce the amount of oil, turning it counterclockwise will increase the amount of oil.

b) The flow meter contains 15 adjustment holes. Each adjustment handle can adjust the distance of a whole hole or half a hole. Each time one hole pitch is adjusted, the adjustment amount is approximately 0.038%. When adjusting, make sure the sealing pin is on the left side. After completing the adjustment, insert the pin and seal the lead seal.

Flowmeter Accuracy Adjustment
Figure 1 :Flowmeter Accuracy Adjustment

Explanation: Before leaving the factory, the LPG dispenser undergoes metering calibration by the manufacturer. The flow meter adjustment device and counter are sealed. Post-factory, accuracy adjustments must be carried out by the metrological management department, with new seals added.

VI. Installation, Common Simple Fault Analysis:

Installation: The flow meter must be horizontally positioned and securely fixed. Connect the pump outlet to the flow meter inlet, and the flow meter outlet to the outlet pipe. Ensure the sealing of connection surfaces to prevent leakage.

Usage: As a measuring device, the flow meter must undergo regular calibration by relevant departments according to regulations.

Maintenance: The flow meter should be placed in a dry and well-ventilated room, ensuring protection against moisture, rain, rust, fire, and low temperatures. During transportation and storage, seal the inlet and outlet with caps.

VII. Common Simple Fault Analysis:


a. Check whether sealing components corresponding to the leakage site are damaged or aged. If so, replace the damaged sealing components.

b. Inspect the casting at the leakage site for sand holes or cracks. Replace defective castings.

c. Check for loose bolts at the leakage site and tighten them.

Inaccurate Metering:

a. Inspect the surface of the distribution valve and distribution valve seat for scratches or damage. If present, replace the distribution valve or distribution valve seat. (Note: When replacing the distribution valve seat, assemble and grind it after installation on the housing to ensure a smooth surface.)

b. Check for damage to the diaphragm and replace it. (Note: Clean the inner surface of the cylinder liner before replacement.)

c. Inspect for damage to the unidirectional bearing and replace it.

No Counting:

a. Check whether the elastic pin between the slotted coupling and the sensor is single-sided or disconnected. Replace the elastic pin.

b. Check whether the inner rotor component is frozen. Simply reassemble it after thawing.

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