How to calculate the gas consumption of a piece of equipment

Guide for calculation method and implementation of gas consumption of equipment

accurate calculation of equipment gas consumption is the key to optimize the compressed air system and reduce operating costs. The following is a systematic calculation method based on engineering practice and technical standards:

1. basic parameter acquisition

1. access to equipment technical documents
   • refer to the “List of Pneumatic Components” in the equipment manual, and record the model and rated air consumption of all pneumatic components. For example, the SMC type standard cylinder air consumption formula is:
     Q=fracpI4timesD2timesStimesfracP 11.01325timesfrac160
     (Q is air consumption m/min,D is cylinder diameter m,S is stroke m,P is working pressure MPa)
   • record the design working pressure of the equipment (usually marked as “working air pressure” parameter, in MPa).
2. Verification of measured method
   • install a thermal mass flow meter at the air inlet of the equipment (range accuracy ± 1%), continuously record gas consumption data for 72 hours.
   • Draw a “time-flow” curve to identify the peak gas consumption (usually during the start-up phase) and steady-state values.

2. sub-item calculation method

1. air consumption calculation of pneumatic components
   • continuous running element(e. g. pneumatic motor):
     Q=fracPtimesVtimesn60timeseta
     (P is the shaft power kW,V is the specific power kW/ m³/min, n is the speed rpm,η is the mechanical efficiency)
   • intermittent operation element(e. g. clamping cylinder):
     Q=sum(qItimestI)
     (qi is the air consumption of a single action, ti is the action frequency times/minute)
2. Pipeline leakage assessment
   • the ultrasonic leak detector shall be used for testing according to GB/T 26204-Classification and Testing Methods for Leakage of Compressed Air Pipes:
     • micro-leakage: ≤0.5L/min
     • small leakage: 0.5-2L/min
     • medium leakage: 2-10L/min
     • large leakage:> 10L/min
   • calculation of total leakage:Qleak=sum(LItimesKI)
     (Li is the flow rate at each leakage point, and Ki is the pressure correction coefficient)

3. comprehensive calculation model

1. gas consumption of single equipment
   Qequipment=Qcomponenttimes(1 S) Qleak
   (S is the safety factor, the recommended value is 0.1-0.2)

2. gas consumption of multiple equipment systems
   Qsystem=(sumQequipmentItimesCI)timesK
   (Ci is the simultaneous use factor and K is the line loss factor, usually 1.1-1.3)

calculation Example of 4. Typical Application Scenarios

5. optimization recommendations

1. selection optimization
   • low air consumption components are preferred, such as thin cylinders (15% energy saving compared to standard types -20%).
   • Centralized gas supply is adopted to reduce the pressure loss of branch pipelines.
2. Operation optimization
   • implement zone pressure control, and depressurize operation during non-production hours (every 0. 1MPa, energy saving of about 7%).
   • Establish a gas consumption monitoring platform to display the gas consumption data of each equipment in real time.
3. Maintenance Management
   • the pipeline pressure holding test shall be carried out every quarter (pressure drop ≤ 0.02MPa /h).
   • Replace old components, such as upgrading ordinary solenoid valves to energy-saving type (pressure drop reduced by 50%).

6. special working conditions

1. pulse gas equipment(e. g. sandblasting machine)
   • using the “peak-average” conversion algorithm:Qaverage=QpeaktimesD
     (D is the duty cycle, if the sandblasting time accounts for 30%, then D = 0.3)
2. Variable condition equipment(such as CNC machining center)
   • phasing calculation:Qtotal=Qstandbytimest1+Qprocessingtimest2
     (t1 is the proportion of standby time, t2 is the proportion of processing time)

conclusion
the gas consumption calculation of the equipment shall follow the three-level calculation system of “component-level measurement → system-level modeling → working condition correction. It is suggested that enterprises should establish a database of equipment gas consumption, and realize dynamic monitoring and intelligent analysis combined with Internet of things technology, so as to provide data support for energy-saving transformation of compressed air system. By optimizing the selection, operation control and maintenance management, the system energy efficiency can be improved by 15% -30% the payback period is usually within 1-2 years.