bag_method Namespace Reference

Compressed air leak flow estimation using the bag fill-time method. More...

Classes
struct	Input
	Input parameters for the bag method compressed air leak calculation. More...
struct	Result
	Result of the bag method leak flow rate calculation. More...

Functions
Result	calculate (const Input &input)
	Estimates compressed air leak flow rate and annual consumption using the bag method.

Detailed Description

The bag method is a practical field technique for estimating compressed air leaks. A measurement bag (typically a pre-measured trash bag) is placed over the leak point and the time required to fill the bag is recorded. The fill time and known bag volume together determine the volumetric flow rate of the leak. This method is the second most accurate field technique for measuring compressed air consumption after inline flow meters.

See also

Bag Method Calculator

Function Documentation

calculate()

Result bag_method::calculate

(

const Input &

input

)

The leak flow rate is the bag volume divided by the fill time (converted to minutes). Annual consumption scales by operating hours and the minutes-per-hour factor, then converts to kiloscf.

Flow Rate:

\begin{equation}\label{eq:bag-method-flow-rate} Q_{leak} = \frac{V_{bag} \cdot 60}{t_{fill}} \end{equation}

where:

\(Q_{leak}\)	Compressed air leak flow rate \([\unit{ \scfm}]\)
\(V_{bag}\)	Pre-measured volume of the measurement bag \([\unit{ \cubicFoot}]\)
\(t_{fill}\)	Time for the bag to fill with leaked air \([\unit{ \second}]\)
\(60\)	Seconds per minute conversion \([\unit{ \second\per\minute}]\)

Annual Consumption:

\begin{equation}\label{eq:bag-method-annual-consumption} C_{annual} = \frac{Q_{leak} \cdot t_{op} \cdot 60}{1000} \end{equation}

where:

\(C_{annual}\)	Estimated annual air loss from the leak \([\unit{ \kscf}]\)
\(Q_{leak}\)	Compressed air leak flow rate \([\unit{ \scfm}]\)
\(t_{op}\)	Annual system operating time \([\unit{ \hour}]\)
\(60\)	Minutes per hour conversion \([\unit{ \minute\per\hour}]\)
\(1000\)	Standard cubic feet per kiloscf conversion \([\unit{ \unitless}]\)

Note

Bag fill time must be measured in seconds. Bag volume must be pre-measured in cubic feet. The flow rate \(Q_{leak}\) is at approximately standard atmospheric conditions.

Parameters

[in]

input

Input

Returns

Result containing flow_rate [scfm] and annual_consumption [kscf].