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MEASUR-Tools-Suite v1.0.11
The MEASUR Tools Suite is a collection of industrial efficiency calculations written in C++ and with bindings for compilation to WebAssembly.
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A compressed air leak survey is a systematic facility walk-down in which a technician locates, tags, and measures every audible or detectable compressed air leak. This calculator processes the full set of measurements and produces four summary outputs:
Each leak in the survey is processed individually and the results are summed. A single survey entry can represent multiple identical leaks through the units multiplier, which avoids the need to enter duplicate rows.
Measurement Methods
The calculator supports four leak flow-rate measurement methods. Only the method selected for each entry contributes to the calculation; the other three input structs are ignored.
| Method | Selector | Description |
|---|---|---|
| Estimate | 0 | Visual and audible assessment; see Estimate Method Calculator |
| Decibels | 1 | Ultrasonic detector reading; see Decibels Method Calculator |
| Bag | 2 | Bag fill-time measurement; see Bag Method Calculator |
| Orifice | 3 | Pressure and orifice geometry; see Orifice Method Calculator |
Cost Basis
The cost of a compressed air leak can be expressed in two ways:
Relevant formulas are documented below.
Combined instantaneous flow rate for one survey entry.
The total instantaneous flow rate for a survey entry is the per-leak flow rate returned by the selected measurement sub-calculator multiplied by the number of identical leak points. This represents the total compressor capacity being wasted by this group of leaks at any given moment.
\begin{equation}\label{eq:leak-survey-total-flow} Q_{total} = Q_{method} \cdot n \end{equation}
| \(Q_{total}\) | Combined instantaneous flow rate for this survey entry \([\unit{ \scfm}]\) |
| \(Q_{method}\) | Leak flow rate from the selected sub-calculator \([\unit{ \scfm}]\) |
| \(n\) | Number of identical leak points (units multiplier) \([\unit{ \unitless}]\) |
Annual air volume for survey entries using the estimate or orifice method.
For the estimate method, the sub-calculator's operating time is set to \(t_{op}\) (hours per year) before calling estimate_method::calculate. The returned annual consumption (in kscf) is multiplied by 1000 to convert to standard cubic feet, then scaled by the units multiplier.
For the estimate method:
\begin{equation}\label{eq:leak-survey-estimate-annual} V_{annual} = C_{annual} \cdot 1000 \cdot n \end{equation}
For the orifice method, and for the decibels method, the annual volume is
computed from the instantaneous flow rate and the annual operating hours:
\begin{equation}\label{eq:leak-survey-time-based-annual} V_{annual} = t_{op} \cdot Q_{total} \cdot 60 \end{equation}
| \(V_{annual}\) | Annual compressed air volume lost through this survey entry \([\unit{ \scf}]\) |
| \(C_{annual}\) | Annual consumption from estimate_method::calculate \([\unit{ \kscf}]\) |
| \(1000\) | Kiloscf to standard cubic feet conversion \([\unit{ \unitless}]\) |
| \(n\) | Number of identical leak points (units multiplier) \([\unit{ \unitless}]\) |
| \(t_{op}\) | Annual compressed air system operating time \([\unit{ \hour\per\year}]\) |
| \(Q_{total}\) | Combined instantaneous flow rate for this entry \([\unit{ \scfm}]\) |
| \(60\) | Minutes per hour conversion \([\unit{ \minute\per\hour}]\) |
Annual air volume for survey entries using the decibels method.
The decibels sub-calculator returns an instantaneous leak rate. The annual volume is computed from that rate, the annual operating time, and the minutes-per-hour conversion factor.
\begin{equation}\label{eq:leak-survey-decibels-annual} V_{annual} = t_{op} \cdot Q_{total} \cdot 60 \end{equation}
| \(V_{annual}\) | Annual compressed air volume lost through this survey entry \([\unit{ \scf}]\) |
| \(t_{op}\) | Annual compressed air system operating time \([\unit{ \hour\per\year}]\) |
| \(Q_{total}\) | Combined instantaneous flow rate for this entry \([\unit{ \scfm}]\) |
| \(60\) | Minutes per hour conversion \([\unit{ \minute\per\hour}]\) |
Annual air volume for survey entries using the bag method.
The bag sub-calculator returns an annual consumption in kscf that already accounts for the operating time and number of units specified in the bag method input. The survey applies its own units multiplier to this result without the 1000× conversion to standard cubic feet. The reported annual_total_flow_rate therefore carries units of kscf for bag-method entries, while estimate, decibels, and orifice entries contribute in scf.
\begin{equation}\label{eq:leak-survey-bag-annual} V_{annual} = C_{bag} \cdot n \end{equation}
| \(V_{annual}\) | Annual compressed air volume for this survey entry \([\unit{ \kscf}]\) |
| \(C_{bag}\) | Annual consumption from bag_method::calculate \([\unit{ \kscf}]\) |
| \(n\) | Number of identical leak points (units multiplier) \([\unit{ \unitless}]\) |
bag_method::Input.operating_time field governs the period over which annual consumption is computed for bag-method entries; it is not overridden by the survey's hours_per_year field (unlike the estimate method). Annual electrical energy consumed by the compressor to replace leaked air.
When the electricity cost basis is selected (utility_type = 1), the compressor's specific power (kW per cfm of air delivery) is used to convert the annual air volume into electrical energy. Dividing the specific power by 60 converts from kW/(ft³/min) to kW·hr/scf so that multiplying by the annual volume (in scf) yields kilowatt-hours.
\begin{equation}\label{eq:leak-survey-electricity} E_{annual} = \frac{k_{sp}}{60} \cdot V_{annual} \end{equation}
| \(E_{annual}\) | Annual electrical energy consumed to replace leaked air \([\unit{ \kilo\watt\hour}]\) |
| \(k_{sp}\) | Compressor specific power \([\unit{ \kilo\watt\minute\per\cubicFoot}]\) |
| \(60\) | Minutes per hour conversion \([\unit{ \minute\per\hour}]\) |
| \(V_{annual}\) | Annual compressed air volume for this survey entry \([\unit{ \scf}]\) |
Annual monetary cost of leaked air when electricity is the cost basis.
The annual electricity cost is the product of the annual electrical energy consumed (see Annual Electricity Formula) and the electricity utility rate. This basis is appropriate when the operator wishes to compare leak repair costs directly to the compressor electricity bill.
\begin{equation}\label{eq:leak-survey-electricity-cost} C_{cost} = E_{annual} \cdot r_{elec} \end{equation}
| \(C_{cost}\) | Annual electricity cost of leaked air \([\unit{ \dollar\per\year}]\) |
| \(E_{annual}\) | Annual electrical energy consumed \([\unit{ \kilo\watt\hour}]\) |
| \(r_{elec}\) | Electricity utility rate \([\unit{ \dollar\per\kilo\watt\hour}]\) |
Annual monetary cost of leaked air when compressed air is the cost basis.
When the compressed air cost basis is selected (utility_type = 0), the annual cost is the product of the compressed air utility rate and the annual air volume. This basis is appropriate when the facility purchases compressed air from an external supplier or has an internally established cost-per-scf transfer price.
\begin{equation}\label{eq:leak-survey-ca-cost} C_{cost} = r_{ca} \cdot V_{annual} \end{equation}
| \(C_{cost}\) | Annual compressed air cost of leaked air \([\unit{ \dollar\per\year}]\) |
| \(r_{ca}\) | Compressed air utility rate \([\unit{ \dollar\per\cubic\foot}]\) |
| \(V_{annual}\) | Annual compressed air volume for this survey entry \([\unit{ \scf}]\) |
utility_type = 0 (compressed air), annual_total_electricity in the compressed_air_leak_survey::Result remains zero. Only annual_total_electricity_cost is populated. Modules | |
| Total Flow Rate Formula | |
| Combined instantaneous flow rate for one survey entry. | |
| Annual Volume Formula — Estimate and Orifice Methods | |
| Annual air volume for survey entries using the estimate or orifice method. | |
| Annual Volume Formula — Decibels Method | |
| Annual air volume for survey entries using the decibels method. | |
| Annual Volume Formula — Bag Method | |
| Annual air volume for survey entries using the bag method. | |
| Annual Electricity Formula | |
| Annual electrical energy consumed by the compressor to replace leaked air. | |
| Annual Electricity Cost Formula | |
| Annual monetary cost of leaked air when electricity is the cost basis. | |
| Annual Compressed Air Cost Formula | |
| Annual monetary cost of leaked air when compressed air is the cost basis. | |
Files | |
| file | compressed_air_leak_survey.h |
| Declarations for the compressed air leak survey aggregate calculation. | |
Namespaces | |
| namespace | compressed_air_leak_survey |
| Aggregated compressed air leak survey calculation. | |
Classes | |
| struct | compressed_air_leak_survey::Input |
| Input parameters for one leak entry in a compressed air leak survey. More... | |
| struct | compressed_air_leak_survey::Result |
| Aggregate result of a compressed air leak survey. More... | |
1.9.8