ZLD-2 Type Orifice Plate Flowmeter for Coal Seam Borehole Gas Flow Measurement is manufactured based on the principle of orifice plate flowmeters. It is used for testing the gas emission flow rate from boreholes, specifically the initial gas emission rate (q), which serves as an indicator for predicting the risk of coal and gas outbursts in local excavation areas. With a complete multi-stage orifice plate flowmeter configuration and simple testing procedures, it is one of the commonly used gas parameter testing devices in coal mines and certification institutions.

ZLD-2 Type Orifice Plate Flowmeter for Coal Seam Borehole Gas Flow Measurement is made of acrylic material, which is shatter-resistant and corrosion-resistant. The scale is engraved in a concave surface, making it durable;
The device includes multi-stage orifice plates and other testing components that meet standards, with complete accessories, making it convenient to carry for underground operations;

ZLD-2 Type Orifice Plate Flowmeter for Coal Seam Borehole Gas Flow Measurement Technical Parameters
Range: 0–1.6 Kpa
Flow Measurement Range: 0–100 L/min
Instrument Weight: 0.8 kg
Flow Measurement Range: 0.1–100 L/min
Water Column Differential Pressure Reading: 0–160 mm
Instrument Resolution: 1 mmH2O

ZLD-2 Type Orifice Plate Flowmeter for Coal Seam Borehole Gas Flow Measurement Measurement Steps
1. Preparation Before Measurement
Fill the water column gauge with water and adjust both sides to the zero scale line; check the sealing performance of the instrument. If the seal fails, replace the "O" ring; based on coal seam conditions, estimate the flow rate and select a nozzle with a flow range that is relatively close. Install it on the nozzle base of the flowmeter.
2. Method and Steps
This flowmeter is used in conjunction with the JN-1 type sealing device. When predicting the risk of coal and gas outbursts in the working face and conducting effectiveness tests for outburst prevention, after drilling is completed, quickly insert the sealing device to seal the hole. Then, connect the exhaust pipe of the sealing device to the intake nozzle of the flowmeter using a hose, ensuring the water column gauge of the flowmeter remains in a vertical position. At this time, the gas emitted from the coal body passes through the measurement chamber, exhaust pipe, connecting hose, and flowmeter nozzle, creating a differential pressure on both sides of the water column gauge. Read the differential pressure value of the water column gauge.
The entire measurement process must be completed within 2 minutes.
Determination of ZLD-2 Multi-Stage Orifice Plate Flowmeter Indicators
The initial gas emission rate q (L/min) is calculated as follows:
Q = K × K1 × √Δh
Where: K—Flow coefficient of the selected nozzle, L/min·mm;
This coefficient is determined experimentally and provided in the instrument manual upon delivery.
K1—Gas concentration correction factor. Since the methane concentration in coal seam gas is typically above 95%, this coefficient is taken as 1.34;
Δh—Differential pressure reading of the water column gauge, mm.
The critical value of the initial gas emission rate indicator should be determined based on actual measurements from the coal seam of each mine. If no measured data is available, refer to the data listed in Table 1.
Table 1 Critical Values of Initial Gas Emission Rate Indicators for Outburst Risk Prediction
Volatile Matter of Coal 5–15 15–20 20–30 >30
qm 5.0 4.5 4.0 4.5
Table 2 Nozzle Series Table
Nozzle Number 1 2 3 4 5
Nozzle Aperture D (mm) 0.5 1.0 2.5 5.0 7.0
Nozzle Coefficient K (L/min·mm) 0.033 0.130 0.83 3.250 6.370
Flow Measurement Range (Methane) (L/min) 0.09–0.55 0.35–20.20 2.18–13.78 8.71–55.08 17.07–107.97
Five nozzles with different apertures are designed. Due to limitations in nozzle machining precision, the nozzle series for the same diameter may vary. Therefore, each nozzle must be calibrated on a calibration instrument before delivery to obtain the actual nozzle coefficient. Table 2 provides the nozzle series for the five designed nozzles.

Zhengzhou Aidi produces Orifice Plate Flowmeter for Coal Seam Borehole Gas Flow Measurement, supplying coal drill cuttings desorption instruments, deep hole sampling devices, pressure measuring instruments, geological exploration desorption instruments, borehole flowmeters, mine extraction and outburst prevention equipment, true density measuring instruments for coal, gas content measuring instruments, automatic initial gas emission rate measuring instruments, diffusion rate measuring instruments, gas parameter instruments for coal extraction pipelines, and borehole coal powder circulation devices.