What is the meaning of continuous gas consumption in instrument gas consumption

In the calculation of instrument air consumption and air compressor selection, continuous gas consumption it is a key parameter that directly reflects the continuous demand for compressed air under stable operating conditions. The following is a detailed explanation of continuous gas consumption:

definition of 1. continuous gas consumption

continuous gas consumption refers to the meter in. The amount of compressed air consumed continuously at a constant rate during normal operation, usually in units cubic meters per minute (m & sup3;/min) or liters per second (L/s). This parameter describes the average gas consumption characteristics of the instrument during uninterrupted operation, and is an important basis for evaluating the stability of the air source system and selecting the capacity of the air compressor.

Characteristics of 2. continuous gas consumption

1. stability:
   the continuous gas consumption remains relatively constant during the working cycle of the instrument and does not fluctuate significantly with time or operating state. For example, when the pneumatic actuator continues to push the valve, its air consumption remains basically unchanged.

2. Long-term:
   continuous gas consumption reflects the meter in long time running gas consumption demand, not instantaneous peaks or intermittent gas consumption. For example, the pneumatic instrument in the 24-hour uninterrupted monitoring process, the gas consumption is the continuous gas consumption.

3. Difference from instantaneous gas consumption:

   • instantaneous gas consumption: The peak gas consumption of the instrument at a specific operation moment (such as the rapid opening of the valve and the instantaneous action of the cylinder) is usually much higher than the continuous gas consumption.
   • continuous gas consumption: The average gas consumption of the instrument in the stable operation stage is the basic parameter of the gas source system design.

Application Scenarios for 3. Continuous Gas Consumption

1. pneumatic instrument:
   such as pressure transmitters, flow meters, etc., need to continue to consume compressed air to maintain measurement accuracy and signal transmission. For example, the continuous gas consumption of a pneumatic pressure transmitter during normal operation is 0.05 m & sup3;/min.

2. pneumatic actuator:
   such as pneumatic valves, cylinders, etc., in the continuous push or maintain the position of the need for stable gas supply. For example, the continuous gas consumption of a pneumatic valve in the fully open state is 0.2 m & sup3;/min.

3. Pneumatic tools:
   such as pneumatic wrenches, spray guns, etc., in the long-term operation (such as continuous tightening of bolts or spraying operations), the gas consumption can be regarded as continuous gas consumption. For example, the continuous gas consumption of a pneumatic spray gun during continuous spraying is 0.3 m & sup3;/min.

Calculation and Selection Significance of 4. Continuous Gas Consumption

1. calculate total gas consumption:
   in the design of the plant gas source system, it is necessary to count the continuous gas consumption of all instruments and consider the simultaneous use coefficient (K) to calculate the total gas consumption. For example:

   • instrument A: continuous gas consumption 0.05 m & sup3;/min
   • instrument B: continuous gas consumption 0.1 m & sup3;/min
   • instrument C: continuous gas consumption 0.15 m & sup3;/min
   • simultaneous use factor K = 0.8 (assuming that three instruments are not operated at full load at the same time)
   • total air consumption: q total =(0.05+0.1+0.15)× 0.8=0.24m & sup3;/min

2. select air compressor capacity:
   the rated displacement of the air compressor should be slightly larger than the calculated total air consumption, taking into account leakage, loss and future expansion requirements. For example, if the total air consumption is 0.24 m & sup3;/min, an air compressor with a displacement of 0.3 m & sup3;/min can be selected.

3. Optimizing the air supply system:
   through the reasonable distribution of continuous large gas meter to different gas supply circuit, or the use of gas storage tank buffer, can reduce the gas source pressure fluctuation, improve the stability of the system. For example, a pneumatic valve with a large amount of continuous gas consumption is separated from a meter with a small amount of gas consumption.

5. practical cases

case: Pneumatic instrument system of a chemical plant

• instrument List:
  • pressure transmitter (5 sets): each set of continuous gas consumption 0.03 m & sup3;/min
  • pneumatic valves (3 sets): each set of continuous gas consumption 0.1 m & sup3;/min
  • flowmeter (2 sets): each set of continuous gas consumption 0.05 m & sup3;/min
• calculation process:
  1. theoretical total gas consumption:
     Q theory = 5 × 0.03+3 × 0.1+2 × 0.05=0.15+0.3+0.1=0.55m & sup3;/min
  2. coefficient of simultaneous use (medium load, K = 0.7):
     Q actual = 0.55 × 0.7=0.385m & sup3;/min
  3. add 10% margin:
     Q final = 0.385 × 1.1 & asymp;0.42m & sup3;/min
• selection results:
  select displacement 0.5 m³/min pressure 7 bar the air compressor meets the system requirements and reserves room for expansion.