Assessment Method for Compressed-Air Energy Consumption, Leakage Rate, and Life-Cycle Cost of Pneumatic Industrial Manipulators

00executive summary

A Pneumatic Industrial Manipulator converts compressed air into load balancing, lifting, clamping, rotation, brake release, and vacuum generation. Recording only the compressor nameplate power or equipment inlet pressure cannot determine the air consumed per one thousand cycles by one machine, leakage during line stoppages, the location of pressure losses, or whether an energy-efficiency retrofit will pay back. ISO 11011:2013 divides a compressed-air system into supply, transmission, and demand subsystems and requires a complete assessment comprising acquired data, analysis results, and a written report [1]. This report applies that system boundary to one manipulator and establishes a calculation method using a common time base for electricity metering, total flow, branch flow, dynamic pressure, and production counts.

This article uniformly uses the standard reference atmosphere of ISO 8778:2003 to express the free air volume, that is, 20 °C, 100 kPa absolute pressure, 65% relative humidity, and written as m³(ANR)[8]. When the field instrument uses other references, the data is first converted to the same reference state and then added. On the supply side, the average specific power of the system measured during the same period is SP_sys This produces an allocated energy-consumption metric; actual electricity savings and economic benefits shall use only the same-load-bin marginal power–flow model or normalized whole-plant measurements before and after the retrofit. On the equipment side, integrate flow to calculate production and leakage air use. On the distribution side, evaluate every synchronized pressure sample for the peak-flow action and minimum-inlet-pressure action. ISO 1217:2009 defines the boundary for compressor-flow and power acceptance data [4]; the ISO 6358 series supports steady-state flow characterization of components and assemblies and calculation of system flow capacity within its scope [5][6][7]. Neither replaces contemporaneous on-site measurement.

Core conclusion

• Energy-consumption calculations shall use free-air volume at a common reference state. If gauge pressure, absolute pressure, actual-condition volume, and m³(ANR) are mixed, the report fails the data-quality gate.
• This article uses the conservative upper bound of the annual branch leakage volume proportion R_leak,U Grading: no more than 5% is grade A, more than 5% and no more than 10% is grade B, both pass; more than 10% is fail. The leakage proportion in the U.S. Department of Energy data uses compressor capacity or system air supply as the accounting boundary [9], which is different from the denominator of the annual branch volume of a single device in this article. The two percentages cannot be directly converted; this report fixes 10% as the upper limit of project release.
• The pressure item must be passed only if the conservative upper bound of the total pressure loss rate from the exhaust measuring point of the compressor unit to the inlet of the key actuator does not exceed 10%, and the conservative lower bound of the dynamic minimum inlet pressure of the equipment is not lower than the design lower limit; if any condition fails, it will be judged as failed [9].
• For one machine, use m³(ANR) per 1,000 cycles and allocated kWh per 1,000 cycles as energy-efficiency metrics, and separately report production air use, leakage air use, and idle pressure-retention air use. Allocated electricity consumption is not evidence of actual electricity savings.
• Overall release uses a one-out-of-six rejection rule covering data, leakage, pressure, energy efficiency, economics, and functional safety. Leakage, pressure, energy-efficiency, and economic criteria are evaluated at expanded-uncertainty bounds in the unfavorable direction. The project passes only when all six criteria pass.

01Research objects, system boundaries and terminology

The scope includes the Pneumatic Industrial Manipulator body, end-effector tooling, vacuum generator, local air receiver, filter-regulator assemblies, hoses, and equipment branch. The supply subsystem includes compressors, cooling, drying, filtration, and auxiliary electricity. The transmission subsystem includes headers, ring mains, branch lines, and terminal connections. The demand subsystem begins at the equipment-branch isolation valve and ends at actuator exhausts, vacuum-generator exhausts, and process blow-off outlets. ISO 4414:2010 and GB/T 7932-2017 cover general rules and safety requirements for pneumatic systems and components on machinery [2][3]. An energy-efficiency retrofit shall not impair loss-of-pressure protection, residual-energy release, isolation, pressure limiting, gripping retention, or inadvertent-release prevention.

A “cycle” is defined from workpiece pickup authorization through completed release and return to the starting state for the next pickup. Count rework, no-load, and commissioning cycles separately; do not include them in conforming production cycles. Whenever the equipment branch remains pressurized during production, changeover, breaks, or off-shift periods, include all of that time in pressurized hours.

Each sampling point can only be classified into one operating status, and the status code is fixed as:P Qualified production,R rework,S commissioning or empty loop,C changeover,I Idle with pressure,F Fault with pressure,D Relieve stress. When the controller does not have a status code, the status will be reconstructed based on cycle permission signals, equipment alarms, branch isolation valve feedback and shift records; if any one of the four types of signals is missing, the status itemized report will fail the data judgment.P The state forms production air use,R/S/C/I/F separate rows,D The non-zero flow rate in the status is treated as the zero point of the instrument or the internal leakage of the isolation valve is abnormal. In this way, the air required to complete production, the eliminable air consumption and the air used for safe pressure maintenance can be separated to avoid counting off-duty leakage into the efficiency of a single operation.

02Measurement architecture and data quality threshold

The metering points are arranged according to the energy flow direction: the total electricity meter records the input electric energy of the supply system; the total supply flow meter records the m³(ANR) delivered to the conveying system; the equipment branch flow meter records the total air consumption of the Pneumatic Industrial Manipulator; the four synchronous pressure channels are fixed as P0 Downstream of the compressor unit exhaust check valve and upstream of the first aftertreatment element,P1 Main pipe inlet downstream of all air handling equipment,P2 The end of the main pipe and upstream of the equipment branch isolation valve,P3 Entrance to key execution components; the controller records cycles, product models, operating status and alarms. When there are multiple pressure critical actuators, move them separately P3 Complete independent testing and each position must pass. When multiple air compressors are connected in parallel, the total electrical energy and total free air flow are summed using the same time window.

This method sets the upper limit of relative expansion uncertainty of branch flow to 5%, the upper limit of relative expansion uncertainty of electric energy to 2%, and the upper limit of relative expansion uncertainty of pressure to 2%. The uncertainty budget must include calibration, repeatability, reference state conversion, clocks, state classification and annual extrapolation; data items will not pass when only citing the instrument nameplate accuracy. If any item exceeds the upper limit, the energy efficiency comparison will not enter the economic evaluation. The baseline period and the post-retrofit evaluation period use the same product weights, qualified cycle definitions and annual pressure hours; when the product structure changes, it is normalized according to the frozen weight, and the two unnormalized totals are not directly compared.

Freeze product weights before review starts w_j, use the company’s approved annual production plan for weighting; if no annual plan exists, use the qualified-cycle share of each model over 7 consecutive baseline days. Every weighted model shall complete at least 30 qualified cycles in both the baseline and post-retrofit periods; otherwise, the data item fails. Calculate normalized air-consumption intensity using the following equation and the same set of w_j, and Σw_j=1：

The clock error between branch flow and circulation status must not exceed 100 ms, and the clock error between power and total supply flow must not exceed 1 s; four pressure channels perform the same DAQ with a 1 sample limit. Missing samples are not interpolated; if the total missing rate exceeds 5%, the missing segment covers the peak action, or there is any missing point during the leak test, the data item will not pass directly. Instrument expanded uncertainty by coverage factor k=2 report. The standard uncertainty of annual compressed-air consumption in the two periods is u_base=U_base/2、u_after=U_after/2, the correlation coefficient is ρ When:

U_base、U_after It is the absolute expanded uncertainty of annual compressed-air consumption in the two periods. Records should only be used if there is documented evidence of independence of the calibration chain, instrumentation, sampling and scaling errors. ρ; In the absence of any evidence, a conservative upper bound is always used. U_ΔV=U_base+U_after。ΔV_L>0 only then is an air-saving improvement demonstrated; a value of zero also fails. All derived hard gates use the following conservative-direction bounds:

Data items are not passed when the denominator is not greater than zero. Energy efficiency items must be met at the same time η_air,L≥5% with ΔV_L>0;Leakage items must meet R_leak,U≤10%. See Chapters 06 and 08 for the pressure and economic boundary formulas respectively.

03Compressed Air Baseline and Energy Efficiency Indicators

Use the contemporaneous measured system-average specific power only to calculate the allocated energy-consumption metric:

E_sys Includes electricity consumed within the assessment boundary by compressor main motors, cooling fans, dryers, condensate drains, and auxiliary controls;V_supply m³(ANR) delivered to the pipeline network during the same period. Using only compressor nameplate power misses partial loading, unloading and auxiliary equipment losses. ISO 1217:2009 stipulates the flow and power acceptance test methods of positive displacement compressors. The data is used to check the rated point and is not used as a substitute value for the annual specific power on site [4].E_device,alloc with I_e,alloc It is a cost allocation indicator and cannot be written as the actual power saving of the air compressor station.

Calculate actual electricity savings with the same-load-bin marginal power–flow model. Assign synchronized 1 min averages of total plant flow and total active power to the load bins b; Each load bin used shall contain at least 30 complete samples in both the baseline and post-retrofit periods. The sample-flow range shall cover the pre- and post-retrofit flow within that bin, and the compressor start/stop sequence, control mode, supply-pressure setting, and air-treatment-equipment operating combination shall be identical. Fit a least-squares straight line to each bin P_b=α_b+m_bq_b Fitting the measured active power and free air flow, fixed SP_marg,b=m_b/60；m_b Use kW/[m³/min(ANR)], so SP_marg,b Use kWh/m³(ANR). expanded uncertainty U_SP,b Also includes regression slope, meter, and total flow meter components:

Any load bin has insufficient samples, post-retrofit flow falls outside the measured curve range, the compressor sequence or control mode changes,m_b≤0, or U_SP,b/SP_marg,b>10% When, the binning model is invalid. The whole-station normalized substitution method combines the production combination, compressor sequence, control mode, compressor inlet temperature 5 °C range and air supply set pressure 0.02 MPa range to form a working condition layer g; There must be no less than 30 complete 1 min active power samples before and after each layer, and the same group of approved annual hours must be used H_g：

ΔE_full,L instead of ΔE_actual,L Enter the economic calculations. If neither the binned marginal model nor the full-site normalized substitution method meets the data threshold in this section, the economic term will not pass.

The evaluation report presents four indicators: production air-consumption intensity I_prod, leakage air-consumption intensity I_leak, total air-consumption intensity I_air and allocated energy-consumption intensity I_e,alloc. A reduction in total compressed-air consumption accompanied by a proportional drop in cycle count does not constitute an energy-efficiency improvement. The post-retrofit reduction in total air-consumption intensity is defined as:

The passing condition for energy efficiency items is point value η_air≥5%, conservative lower bound η_air,L≥5%, and according to the coverage factor k=2 Conservative lower bound of calculated throttle amount ΔV_L>0. If any of the conditions fails, the energy efficiency item will fail. The report must give both the raw difference, the expanded uncertainty, and the conservative lower bound, and not just the percentage.

04Effective air consumption of Pneumatic Industrial Manipulator

Direct integration by the equipment-branch flow meter produces the official measured result:

Integral variable dt Measured in min.b(t) for time t The inlet pressure level of the equipment belongs to, and the pressure level width is fixed at 0.02 MPa;k(t) Steady-state valve position combinations mapped to the PLC output.q_leak,s,b,k It is the leakage baseline measured in Section 05.1 under the same condition, pressure range and valve position combination. Every one that has appeared s-b-k All combinations must have a baseline; if any combination is missing, the sub-item report will not pass.V_total is the total integral of the branch flow meter;V_prod with V_R/V_S/V_C/V_I/V_F It is the functional sub-item after deducting the leakage baseline of the same period. Evaluate total volume closure within a 7-day window |V_total-(V_prod+V_R+V_S+V_C+V_I+V_F+V_leak)|/V_total It must not exceed 2%. If it exceeds 2%, the individual report will not be passed. Any sampling point appears q_ANR<q_leak,s,b,k When there is no need to truncate the result to prove closure, the leakage baseline of the combination must be retested first; if the situation still occurs after retesting, the data item will not pass. Rework R and debug or empty loop S Included in the total, but not included in qualified production air use.

The theoretical free air volume of a double-acting cylinder is only used to check the flow order of magnitude. The bore area is A_b, the piston rod area is A_r, the itinerary is L, the extended and retracted air supply absolute pressures are respectively p_1,abs、p_2,abs, the air supply temperature is T_1、T_2 When, the theoretical value of a complete reciprocation is:

in the formula p_abs = p_gauge + p_atm. Dead space, hose charging and exhausting, buffering, valve terminal pilot, brakes, tooling units and vacuum generator are included separately. The pneumatic balancing circuit is not equivalent to the full volume discharge of the cylinder every time, so the official results reported only take the flow integral. The vacuum generator is integrated according to the actual opening time; continuous air blowing, false normally open exhaust and idle vacuum keep all in V_I, not included in the effective production work.

Multiple models of equipment are grouped into two-dimensional groups by status and model. The integration window of each cycle starts from the rising edge of the grabbing permission and ends at the rising edge of the next cycle's starting state confirmation signal; the pressure time without confirmation signal between the two cycles is included I, shall not be spread into adjacent cycles. The flow meter is in D The average value of the continuous 60 s state is used as the zero point verification value for the day. When the absolute value exceeds 0.5% of the full scale of the instrument, the branch flow data for the day will not pass. Flow integration simultaneously retains the 1 s original sequence, per-cycle results, and daily summary, and the cumulative volume difference between the three layers of data must not exceed 0.5%.

ISO 6358-1:2013 with its 2020 and 2026 amendments, and ISO 6358-2:2019 with its 2026 amendment, are used to test the flow characteristics of fixed- or variable-flow-path components within their stated scopes [5][6]. ISO 6358-3:2014 uses known component and piping characteristics to calculate steady-state system flow capacity [7]. Do not apply equations outside the applicable part's scope to cylinders, air receivers, check devices with cracking pressure, quick-exhaust valves, or internally piloted regulators. For a regulator, use the manufacturer's pressure–flow curve covering the project set pressure and actual upstream-pressure, downstream-pressure, and flow ranges. If that curve is unavailable, use synchronized measurements of upstream pressure, downstream pressure, and flow; do not substitute an ISO 6358 calculation.

05Leak rate measurement, conversion and classification

05.1 Branch mass flow meter method

The equipment leakage release value is preferably a branch mass flow meter. For every state that appears in Chapter 04 s, 0.02 MPa pressure level b and steady-state valve position combination k, reproduce the combination in test mode, remove the workpiece and suspended load, lock mechanical motion, disable blow-off, vacuum-generator, and actuator commands, and record continuously for 30 min. Safety functions that require continuous compressed air for risk control shall be metered on a separate branch and classified as functional air use, not leakage. If safety-function air use cannot be separated from leakage, the s-b-k Combined data does not pass.

For each combination, use a sampling interval no greater than 1 s, hold equipment inlet pressure at the pressure-bin center ±0.01 MPa, and maintain valid-data coverage of at least 95%. Invalidate the entire test segment if any motion command or functional-air-use command occurs.q_leak,s,b,k Take the arithmetic mean of the effective samples of this combination; expand the uncertainty U_q,s,b,k Includes flowmeter calibration, repeatability, reference-state conversion, zero offset, and pressure stability. Measure the baseline and post-retrofit periods separately; do not reuse the leakage value from the other period.

The report records the 20 °C, 100 kPa absolute, 65% relative humidity configuration when the mass flow meter outputs the ISO 8778 reference status directly. Instrument output working condition volume flow q_op , according to the compression factor given in the calibration certificate Z Conversion:

p_op,abs and T_op Acquire it with the same timestamp as flow. Reject the data set if records for absolute pressure, absolute temperature, compressibility factor, or humidity configuration are missing. Internal valve leakage, non-zero-air-consumption condensate drains, and air consumed by instrument impulse lines are all included as in-boundary leakage.

05.2 Review method for pressure drop during production shutdown

Use the pressure-decay method only when all of the following conditions are met: the workpiece and suspended load have been removed; mechanical parts are locked; compressed air is locked out and tagged out; the safety holding circuit is physically isolated from the test section; the controlled P&ID, pipe-segment list, air-receiver list, and component BOM provide 100% item-by-item coverage of the isolated volume; and the test permit is signed by the equipment and safety owners. Do not start a pressure-decay test if any condition is missing.

System rises to work gauge pressure for controlled recipe recording p_1,g Then cut off the compressed-air supply, and the end point is fixed at p_2,g=0.50p_1,g, obtained by linear interpolation of the moment when the pressure time series crosses this value. t. The DOE's 1.25 factor is used only at this half-pressure endpoint and corrects the average leakage during the pressure drop to the initial system pressure [9][11]. Calculated by endpoint absolute temperature:

V_sys Use m³,p_1,abs、p_2,abs with p_ANR=100 kPa(abs) Using the same pressure units,T_1、T_2 with T_ANR=293.15 K Use K,Z_1、Z_2、Z_ANR Get the calibration certificate or controlled physical property table,t Use min.|T_2-T_1|>2 K, any compression factor is missing, any volume item lacks a controlled size, the minimum end pressure touches the lower limit of the safety circuit design, or the pressure curve does not cross the precise half-pressure point, the results are invalid. The relative deviation between the two tests is |q_1-q_2|/[(q_1+q_2)/2] Calculate and take the arithmetic mean if it does not exceed 10%.

When the pressure drop review value differs by more than 10% from the mass flow meter result at the same initial pressure level, the leakage data will not pass. The pressure drop review value does not replace the state-pressure-valve position combination results in Section 05.1, nor is it directly applicable to the annual leakage volume.

05.3 Load/unload cycle screening method

The load time is released only when a single fixed-speed compressor supplies air independently, the compressor is under load/unload control, all non-leakage air use is closed, the output is controlled full load flow when loaded, the output is zero when unloaded, and the load and unload switching pressures of 10 cycles respectively fall within ±1% of their respective 10-time average values. T_on and unloading time T_off arithmetic mean. The proportion of leakage to compressor capacity is calculated according to the DOE method [9]:

The percentage is not published if any of the prerequisites fails. This method is only used for total leakage screening of supply systems; use the results of Section 05.1 for individual equipment. The two methods have different boundaries and do not directly average the two percentages.

05.4 Proportion of equipment leakage air

V_device,year The air supply volume of the same branch under pressure throughout the year, including production, rework, commissioning, model change, idleness, failure and leakage. The leakage volume must not be added to the value already integrated by the branch flow meter. V_device,year;Only when using the sub-item model to estimate the annual total, the V_leak,year Added to each functional sub-item. Released for use as defined in Chapter 02 R_leak,U, point values are for display only.

The third edition of the U.S. Department of Energy Sourcebook describes leakage in well-maintained compressed-air systems as below 5%～10%, while poorly maintained systems may reach 20%～30% [9]; its load/unload method expresses results relative to compressor capacity or the full-system supply boundary. This article R_leak The annual leakage volume corresponding to a single equipment branch is divided by the annual total air supply volume of the branch. The denominators are different, so the DOE ratio is not converted into the equipment ratio. This article independently stipulates R_leak,U≤10% It is the upper limit for project passing; this threshold is only used in this evaluation method. When a safety-related pressure-holding circuit leak is detected, the equipment safety criteria take precedence over the energy consumption level; after the leak repair is completed, all six retests in Chapter 11 are performed.

06Pressure loss, flow capacity and minimum pressure criteria

For pressure evaluation, use the action with peak flow and the action with minimum inlet pressure. First record synchronized flow and pressure for each pneumatic action of every production model over 10 repetitions. Select the action with the highest dynamic-flow peak, and select the minimum-inlet-pressure action as P3 the item with the lowest minimum value; if both are the same, retain only one. During formal evaluation, record each selected action for 30 consecutive cycles. The dynamic-flow channel and four pressure channels shall use the same 1 kHz sampling clock, with a combined -3 dB bandwidth of at least 200 Hz.

The pressure loss is calculated sample by sample for all formal evaluation waveforms and bounded in the unfavorable direction of the expanded uncertainty.p_0、p_1、p_2、p_3 They are four-point synchronous gauge pressure,U_0、U_1、U_2、U_3 For the corresponding absolute expanded uncertainty:

i Traverse the 30 waveforms of all selected actions,t Iterate through each sample; data items are not passed if any denominator is not greater than zero. DOE Sourcebook points out that the pressure loss from the compressor discharge to the final point of use should be far less than 10% of the discharge pressure, and the maximum design pressure drop of the main pipe is 1% to 2%[9]. This article puts R_Δp,total,U≤10% as the project upper limit and put R_Δp,main,U≤2% As the upper limit for newly built or reconstructed main pipes; both serve as the release thresholds for total pressure drop and main pipe pressure drop respectively. See Chapter 11 for the judgment caliber. Equipment must also meet p_3,min,L≥p_required,min,g；p_required,min,g Only the lowest working gauge pressure of the controlled design file is taken. If the file is missing, the pressure item will not pass.

Increasing the exhaust pressure of the air compressor cannot replace the elimination of end throttling. When the flow rate is insufficient, check the filter, plug-in, hose, valve island and muffler according to the measured dynamic peak flow rate; use ISO 6358 data for components within the applicable scope of the standard, and use ISO 6358-3 calculations for component combinations. For pressure regulators, only use the manufacturer's pressure-flow curve specified in Chapter 04 or simultaneous actual measurements. After the retrofit, all 30 waveforms of each selected action enter the boundary calculation and the pressure and function criteria all pass, and the pressure item is passed.

Pressure drop segmented fixed use P0-P1、P1-P2、P2-P3 Three segments of synchronized samples. The pressure drop in any section accounts for P0-P3 If the total pressure drop exceeds 40% at the same time, this section is listed as the first rectification order; this ratio is not calculated when the total pressure drop is not greater than zero. This ratio only determines the order of rectification and does not change the 2% main and 10% total pressure drop thresholds. The upper limit of the pressure sensor range must not exceed 2 times the controlled design work gauge pressure, and the four-point zero point difference must be less than 0.5% of the full scale in the pressure relief state, otherwise the pressure data will not pass.

07Electricity consumption attribution and annual cost

Calculate the annual allocated electricity consumption and allocated electricity cost for a single machine using the contemporaneous system-average specific power [10]:

c_e Get the comprehensive electricity unit price of the enterprise's bill, in yuan/kWh. The above three items can only be marked as "allocation" and cannot be written as actual energy savings or cashable benefits. Actual annual electricity savings and electricity bill savings are calculated according to load division in Chapter 03:

When time-of-use electricity prices exist, load bins are split according to electricity price periods at the same time;c_e,b,L Get the lower bound of the unit price of the corresponding billed electricity. Demand electricity charges can only be included if the modification reduces the maximum demand within the billing window and the bill record gives a definite amount; in the absence of this evidence, it is fixed at zero. Maintenance, spare parts, and line outage losses only use the amounts with vouchers in the financial or maintenance system; items without vouchers are fixed at zero, and industry averages are not allowed to be filled.

Calculate the supply-system average specific power on a rolling monthly basis. Use volume-weighted values for all allocated energy-consumption metrics. SP_sys,common=(E_sys,base+E_sys,after)/(V_supply,base+V_supply,after), no verbal weighting rules are set. Actual power savings always use the same load bin SP_marg,b Or the difference between actual measurements before and after normalization of the whole site, do not use SP_sys,common。

Annual volume shall not be calculated by multiplying a single shift by 365. For production, multiply the normalized intensity for each model by the approved annual cycle count. For leakage, multiply leakage flow for each state–pressure-bin–valve-position combination by annual pressurized hours. For changeover, idle, and fault components, use the functional average flow for each combination over 7 consecutive days together with the annual combination hours from the company's production-planning system. The fixed annual model is:

Each state in the formula q_s,b,k To deduct the same period q_leak,s,b,k Functional average flow after. The same volume can only appear once. First use real-world testing within the 7-day evaluation window N_j、H_s,b,k Calculate the component model and compare it with the original total points of the window branch; annual extrapolation is not allowed when the difference exceeds 2%. The frozen year will be used only after it has been closed for 7 days N_j、H_s,b,k Extrapolation. After 12 months of project operation, review the annual model using the full-year integrated branch consumption. If the deviation exceeds 5%, invalidate this economic conclusion as of the review date and repeat all six evaluations in Chapter 11 within 5 working days.

08Full life cycle costs and investment thresholds

This article uses a fixed evaluation period of 5 years. project discount rate r Only enterprise-approved values are used; economic items are not passed in the absence of approved values. The discount rate in the calculation input in Chapter 09 is fixed at 5%, and other options are calculated based on the enterprise-approved value. Point value full life cycle cost and net present value are calculated as follows:

Calculation to keep the boundary and use investment to reach the upper boundary C_invest,U and a lower bound on annual net savings S_y,L=C_base,y-C_after,y-U_S,y For input:

n It is the year when the undiscounted cumulative net savings reaches the upper bound of investment for the first time. The net savings during the year are calculated as even occurrences; there is no such situation within 5 years. n, any year S_y,L≤0 Or when the denominator is not greater than zero,PB_U Defined as infinity. When the annual net savings are equal, the above formula simplifies to PB_U=C_invest,U/S_1,L. Residual values, tax benefits and financing costs only enter the model if the contract or financial system gives a firm amount. The passing conditions for economic items are fixed as NPV_save,L>0 and PB_U≤3.0 years;Point value is not used for release. If any condition fails, the economic item fails. Even if the economic item passes, as long as the pressure, function or safety item fails, the overall project will still fail.

The baseline scenario and the retrofit scenario use the same annual cycle number, electricity price series and discount rate. When there is no energy price growth rate approved by the enterprise, the five-year electricity price growth rate is fixed at 0%; when there is no contract residual value, the residual value is fixed at 0%. The lower bound of actual power saving is only based on the binned marginal model in Chapters 03 and 07 or the normalized actual measurement of the whole station, and the average specific power sharing value is not allowed to enter S_y,L. The calculation retains unrounded values. The amount in the table is displayed to 0.01 yuan, the volume is displayed to 0.1 m³, and the ratio is displayed to 0.01 percentage points. The unrounded values are used for judgment to prevent the critical value from changing the conclusion due to display rounding.

09Complete calculation and determination of branch circuits for single equipment

The fixed inputs in this chapter are: 180,000 conforming cycles/year, 3,000 production h, and 4,000 pressurized branch h; the retrofit consists of repairing leaks, shortening the vacuum-supply command window, and reducing terminal flow-path resistance; investment upper bound 4,000.00 yuan; all-in electricity price and its lower bound both 0.80 yuan/kWh; 5-year discount rate 5%; and electricity-price growth, maintenance differential, spare-parts differential, line-stoppage differential, demand-charge differential, and residual value all 0. The average system specific power of 0.115 kWh/m³(ANR) is used only for allocation metrics.

09.1 Data, leakage and uncertainty

The data-quality parameters for the calculation case are fixed as follows: seven-day data coverage, 98.6%; relative expanded uncertainty in annual compressed-air use arising from flow measurement, reference state, clock, state classification, and annual extrapolation, 4.0% for both the baseline and post-retrofit cases; the corresponding absolute expanded uncertainties are 33,960 × 4%=1,358.4 m³ and 12,720 × 4%=508.8 m³. The relative expanded uncertainty of the marginal power-flow model is listed in Section 09.3; the relative expanded uncertainty for the four pressure channels is 1.2%. The instrument calibration status is set to "valid", the pressure channel deviation is set to no more than 1 ms, and the combined bandwidth is set to 250 Hz. According to the criteria in Chapter 02, the data item passes.

Set a 0.70 MPa pressure level for the calculation conditions.P/R/S/C/I/F All steady-state valve position combinations within the six states are set to a 30-minute calculation window according to Section 05.1, and the action and intentional air usage commands are both taken as 0; the flow input of all combinations is taken as 0.080 m³/min (ANR) before the modification and 0.002 m³/min (ANR) after the modification. The relative expanded uncertainty of the leakage flow rate in the two periods is both 4.0%, that is U_q,base=0.0032 m³/min、U_q,after=0.00008 m³/min. The annual number of pressurized hours is used as an accurate input,U_H=0：

Leakage quantity uses the branch-flow method. The input difference between the 7-day branch total integral and state-component model is 0%, meeting the 2% closure criterion. Rework, commissioning, changeover, idle functional air use, and fault-state functional air use are fixed at 0; total branch air use consists only of production air use and leakage air use.

09.2 Keeping boundaries on gas usage, leakage and energy efficiency

Production air-consumption intensity decreases from 82 to 68 m³(ANR) per 1,000 cycles, corresponding to annual production air use of 14,760 and 12,240 m³(ANR), respectively.

The upper bound of the leakage rate is calculated according to the unfavorable direction:

The throttle point value is 21,240 m³(ANR)/year. There is no documented evidence for the correlation between the two periods, and a linear conservative upper bound is fixed:U_ΔV=1,358.4+508.8=1,867.2 m³，ΔV_L=21,240-1,867.2=19,372.8 m³. The intensity expansion uncertainties are respectively 7.5467 and 2.8267 m³ per 1,000 cycles：

η_air,L≥5% and ΔV_L>0, the energy efficiency item passed; after retrofit R_leak,U=4.0881%≤5%, the leakage item is grade A and passed.

09.3 Actual Electricity Savings and Conservative Economic Bounds

The load-bin input matrix uses 60 complete 1 min samples both before and after the retrofit. Compressor start/stop sequence, control mode, 0.70 MPa supply setting, and air-treatment operating combination are held the same. Three load bins cover all pre- and post-retrofit flow. The sum of expanded uncertainties in the air savings across the bins is fixed at 1,867.2 m³, and the expanded uncertainty in marginal specific power for every bin is 0.005 kWh/m³(ANR):

The actual energy saving point value is 2,380.32 kWh/year; the guard value is (5,520-500)×(0.100-0.005)+(10,080-880)×(0.112-0.005)+(5,640-487.2)×(0.124-0.005)=2,074.4832 kWh/year. The annual energy savings point value is 2,380.32 × 0.80=1,904.256 yuan, the lower bound is 2,074.4832 × 0.80=1,659.58656 yuan。

The present value coefficient of equivalent costs in 5 years is 4.32947667. The net present value savings point value is 1,904.256 × 4.32947667-4,000=4,244.43 yuan;The lower bound of net present value savings is 1,659.58656 × 4.32947667-4,000=3,185.14 yuan. The point value payback period is 4,000/1,904.256=2.10 years;The annual lower bound is equal, and the upper bound of the payback period is 4,000/1,659.58656=2.41 years。NPV_save,L=3,185.14>0 and PB_U=2.41≤3.0 years, economic items passed.

09.4 Pressure, functional safety and overall judgment

The pressure calibration conditions are fixed as follows: the minimum working gauge pressure of the key actuator is 0.60 MPa; the peak flow action and the minimum inlet pressure action are the same action; the number of action waveform samples is 30. The following pressure parameters take the most unfavorable value in the input matrix:P0 is 0.70 MPa,U_0=0.0084 MPa;Pre-retrofit P3 The lowest point is 0.61 MPa,U_3=0.00732 MPa;after retrofit P3 The lowest point is 0.65 MPa,U_3=0.0078 MPa：

If the upper bound of the total pressure drop before the retrofit exceeds 10%, the pressure item fails; after the retrofit, the upper bound of the total pressure drop does not exceed 10%, and the lowest pressure lower bound is higher than 0.60 MPa, the pressure item passes. This calculation condition does not include new or reconstructed main pipes, and the 2% main pipe additional threshold is not triggered.

The functional-safety verification matrix includes six items: load holding after loss of air supply, emergency stop, braking, gripping confirmation, prevention of inadvertent release, and residual-energy management. For each item, record the load, initial state, command, holding duration, and binary acceptance criteria. All six binary states are pass, and the number of safety bypasses is 0. Under the inputs and calculations in this chapter, all six gates—data, leakage, pressure, energy efficiency, economics, and functional safety—pass; the overall result is pass.

10Transformation priorities and retesting process

Perform the retrofit in this fixed sequence: first, after removing the workpiece and suspended load, mechanically securing motion, and completing lockout/tagout, isolate abandoned branches, idle equipment, and non-zero-air-consumption condensate drains; second, repair leakage at fittings, hoses, valves, and seals; third, clean or replace filters, push-in fittings, hoses, valve terminals, and silencers based on the segmented pressure-drop results, and evaluate regulators using manufacturer curves or synchronized measurements; fourth, reduce the local pressure setting in 0.02 MPa increments, performing all pressure-waveform and functional-safety tests in Chapter 06 at each setting. Fix the released setting at the value that satisfies R_Δp,total,U≤10%、p_3,min,L≥p_required,min,g And the minimum tested setting is 100% passed for functional safety; the fifth step is to establish a PLC whitelist window for each air blowing and vacuum generator command, and the window start and end signals and duration are written into the controlled recipe. If a command is 1 outside the window in any cycle, it will be judged as failed; the sixth step is to complete all functional safety tests; the seventh step is to repeat the 7-day energy efficiency measurement. First increase the air compressor pressure or add a new air compressor without entering the first six steps.

Retesting uses frozen product weights and identical cycle definitions. Section 05.1 Each state-pressure-valve position combination is re-recorded for 30 minutes; the pressure test covers all waveforms of the two types of actions defined in Chapter 06; the safety test covers all functions of gas shut-off holding, emergency stop, braking, clamping confirmation, inadvertent-release prevention, residual energy processing and project risk assessment. If any one of these fails, the device may not be put into production in energy-saving mode.

After the project is released, it will be calculated every month using the latest complete monthly data. I_air,norm, retest leakage quarterly in accordance with Section 05.1, and repeat all six Chapter 11 evaluations after any replacement of a hose, valve terminal, regulator, vacuum generator, pressure setting, or control program. If the conservative lower bound of monthly normalized air-consumption intensity rises by more than 10% above the release value, or the quarterly R_leak,U>10%, locate all leaks within 5 working days and initiate all six retests;p_3,min,L Exit energy-saving mode immediately if it falls below the design lower limit or any safety function fails. To resume production, root cause records, completed maintenance work orders, six re-test passing records, and signatures of equipment and safety responsible persons must be present. Without any record, restoration is not allowed. All original records, formula versions and judgment tables are kept for no less than 5 years to cover the complete LCC evaluation period of this report and form a record chain for continuous improvement of energy performance [12].

11FMEA, risk control and general release rules

Overall release uses a one-out-of-six rejection rule. The project passes only if all six of the following criteria pass:

1. Data items: coverage, instrumentation, synchronization, bandwidth, repeatability, 7-day closure, and uncertainty budget all satisfy Chapter 02.
2. Leaked items:R_leak,U≤10%。
3. Pressure item:R_Δp,total,U≤10% and p_3,min,L≥p_required,min,g;When the project includes new or reconstructed main pipes, additional requirements must be met R_Δp,main,U≤2%。
4. Energy efficiency items:η_air,L≥5% and the conservative lower bound of air savings ΔV_L>0。
5. Economic items:NPV_save,L>0 and PB_U≤3.0 years。
6. Functional safety items: 100% pass of all functional and safety tests listed in the controlled risk assessment, with zero safety bypasses; failure when risk assessment, binary acceptance criteria, or any test record is missing.

If any item fails, the overall project will be judged as failed; after any rectification is completed, all six items will be re-executed, and partial retest will not be used instead.

12Research conclusion

The compressed-air economics of a Pneumatic Industrial Manipulator cannot be demonstrated by inlet pressure, compressor nameplate data, or a single flow screenshot. A complete evidence chain comprises a common reference state, integrated equipment-branch flow, leakage measurements by state–pressure-bin–valve-position combination, four-channel dynamic pressure, production-cycle counts, a same-load marginal power–flow model, and financial records. The leakage-rate upper bound of 10%, total pressure-drop upper bound of 10%, air-use-improvement lower bound of 5%, positive net-present-value lower bound, and 3-year payback-period upper bound specified in this report jointly form the engineering release rule.

This method is used for energy efficiency baseline, modification review, procurement life-cycle cost comparison and operation and maintenance retesting. When the formal measurement records, risk assessments, design documents and test reports of the equipment project simultaneously meet the six thresholds in Chapter 11, the conclusion is "passed the evaluation of this method"; if any threshold fails, the conclusion is "failed".

The standard status verification base date is 2026-08-15: ISO 11011:2013, ISO 4414:2010, ISO 8778:2003, ISO 6358-1:2013, ISO 6358-2:2019, ISO 6358-3:2014 and ISO 50001:2018 are all in ISO Published status; ISO 1217:2009 is still a published version and in the revision stage; GB/T 7932-2017 is marked as current on the National Standard Information Public Service Platform. Chapters 05 and 12 are included in the ISO 6358 and ISO 50001 amendments published as of that date. When a project is started after the verification base date, the standard list must be re-compared on the project establishment date; if the comparison is not completed, the data items will not pass.

References

1. ISO 11011:2013. Compressed air — Energy efficiency — Assessment. https://www.iso.org/standard/46580.html
2. ISO 4414:2010. Pneumatic fluid power — General rules and safety requirements for systems and their components. https://www.iso.org/standard/44790.html
3. GB/T 7932-2017 "General rules and safety requirements for pneumatic systems and their components". https://openstd.samr.gov.cn/bzgk/std/newGbInfo?hcno=8F5EDDC1CD00C550340316DBCEC789DD
4. ISO 1217:2009. Displacement compressors — Acceptance tests; Amendment 1:2016. https://www.iso.org/standard/44769.html
5. ISO 6358-1:2013, Amendment 1:2020 and Amendment 2:2026. Pneumatic fluid power — Determination of flow-rate characteristics of components using compressible fluids — Part 1: General rules and test methods for steady-state flow. https://www.iso.org/standard/56612.html
6. ISO 6358-2:2019, Amendment 1:2026. Pneumatic fluid power — Determination of flow-rate characteristics of components using compressible fluids — Part 2: Alternative test methods. https://www.iso.org/standard/71270.html
7. ISO 6358-3:2014. Pneumatic fluid power — Determination of flow-rate characteristics of components using compressible fluids — Part 3: Method for calculating steady-state flow-rate characteristics of systems. https://www.iso.org/standard/56616.html
8. ISO 8778:2003. Pneumatic fluid power — Standard reference atmosphere. https://www.iso.org/standard/26559.html
9. U.S. Department of Energy. Improving Compressed Air System Performance: A Sourcebook for Industry, Third Edition. https://www.energy.gov/sites/default/files/2016/03/f30/Improving%20Compressed%20Air%20Sourcebook%20version%203.pdf
10. U.S. Department of Energy. Determine the Cost of Compressed Air for Your Plant, Compressed Air Tip Sheet #1. https://www.energy.gov/sites/default/files/2014/05/f16/compressed_air1.pdf
11. U.S. Department of Energy / National Renewable Energy Laboratory. Uniform Methods Project, Chapter 22: Compressed Air Evaluation Protocol. https://www.energy.gov/sites/prod/files/2015/01/f19/UMPChapter22-compressed-air-evaluation.pdf
12. ISO 50001:2018, Amendment 1:2024. Energy management systems — Requirements with guidance for use. https://www.iso.org/standard/69426.html