Leak Rate Calculator

Atmospheric Leak Flow Rate Calculator

Identification Data


Fluid Data

State of matter
Pressure In
Atmospheric Pressure
Dynamic Viscosity
Ratio of Sp.Heats N/A
Molecular Weight g

Pipe Data

Pipe Diameter
Orifice Diameter
Leakage Time

Common Results

Pressure Drop bar Discharge Coefficient C
Velocity in pipe m/s Velocity in orifice m/s
Reynolds Number N/A Reynolds Flow Regime N/A
Beta Ratio Beta Volumetric Flow m3/h
Mass Flow Kg/h Mass Flow Kg/s
Leakage Quantity Kg

Results for gas state

Critical P Ratio N/A Critical P Out N/A
Expansion Factor N/A Molar Vol m3/Kmol
Match Number N/A Match Flow Regime N/A

How the Leak Rate Calculator works?

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All of our calculators work in a similar way. First you will find a block of information called "Identification Data". In this block we ask you to indicate the Tag, the Plant where the instrument is located and the Area. You also have the possibility to add some notes. This information will be attached to the report if you wish to provide it. It is not necessary to perform the calculation.
The next block of information is called "Fluid Data". In this block we ask you to indicate the the name of your fluid, state of matter, and other properties of your fluid. If you select gas, density is calculated based on the Pressure, Molecular Weight and Temperature properties.
The last input block is called "Pipe Data". Here we will need to provide the Pipe Diameter and the Oririce Diameter (usually estimated) and the amount of time elapsed since the first leakage.
Once everything is set you must click on Calculate! button. Then, all the resulting cells will be calculated. You can press this button until your results are inline with your expectations. Once everything is correct you can export your work to an ISA S20 format spreadsheet containing all your parameters and results. To be able to obtain this file you must click on Download button.
We hope you enjoy using this calculator.

Information and Definitions

Tagname Tagname of the instrument. This is the identifier of the field device, which is normally given to the location and function of the instrument.
Plant, Area and Notes Information Referred to the physical installation of the instrument. Plant and Process Area where the instrument is installed. Notes about the instrument.
Fluid Fluid Name or Composition. Fluid is called a type of continuous medium formed by some substance whose molecules have only a weak force of attraction. A fluid is a set of particles that are held together by weak cohesive forces and the walls of a container; The term encompasses liquids and gases.
State State of the matter. It could be Liquid, Gas or Steam.
Flow Mass of a substance which passes per unit of time. Mass flow in Kg/s units, flowing through the pipe.
Temperature Operating Temperature of the fluid in Celsius units. The flowing temperature is normally measured downstream from the orifice and must represent the average temperature of the flowing stream in degrees Celsius. Temperature has two effects on volume. A higher temperature means a less dense gas and higher flows, but when this higher flow is corrected to base temperature, the base flow is less.
Pressure In Considering the direction of the fluid, we define P1 as the pressure (gauge or absolut) existing in the pipeline before the restriction orifice. Pressure has two effects on volume. The higher pressure makes the gas denser so less volume flows through the meter. However, when the volume is expanded to base pressure, the volume is increased.
Dynamic Viscosity Viscosity is the measure of a fluid's resistance to flow. Dynamic viscosity is a measure of internal resistance.It measures the tangential force per unit area required to move one horizontal plane with respect to an other plane. It is commonly expressed, particularly in ASTM standards, as centipoise (cP) since the latter is equal to the SI multiple millipascal seconds (mPa·s).The viscosity of a fluid is highly temperature dependent.
Density Density is the relation of mass and volume.The density of a material varies with temperature and pressure. This variation is typically small for solids and liquids but much greater for gases.
Ratio of Sp.Heats Ratio of the heat capacity at constant pressure (CP) to heat capacity at constant volume (CV). It is sometimes also known as the isentropic expansion factor and is denoted by γ (gamma) for an ideal gas or κ (kappa), the isentropic exponent for a real gas.
Pipe Diameter Inside diameter of the pipe. All process calculations are based on the volume of the pipe which is the function of internal diameter of the pipe. As per standards, any pipe is specified by two non-dimensional numbers Nominal Diameter (in Inches as per American Standards or mm as per European standards) and Schedule (40, 80, 160,...). The outer diameter of the pipe is the diameter of outer surface of the pipe.
Pressure Ratio Pressure Ratio at which the discarge coefficient determined has the value C.
Reynolds (ReD) and Reynolds Flow Regime The Reynolds number (Re) is an important dimensionless quantity in fluid mechanics used to help predict flow patterns in different fluid flow situations. At low Reynolds numbers, flows tend to be dominated by laminar (sheet-like) flow, while at high Reynolds numbers turbulence results from differences in the fluid's speed and direction, which may sometimes intersect or even move counter to the overall direction of the flow.
Discharge Coefficient The discharge coefficient is a dimensionless number used to characterise the flow and pressure loss behaviour of nozzles and orifices in fluid systems.It depends on the orifice shape. The discharge coefficient can be obtained for any differential-pressure meter and any installation by calibrating it in a flowing fluid: for a particular orifice meter the discharge coefficient is a function of the Reynolds number. Over many years of experiment it has been found that the discharge coefficient can be predicted within a defined uncertainty provided that the orifice meter (i.e. the orifice plate and pipework) are constructed within the standards. If the discharge coefficient is to be used for an orifice meter without calibrating it in a flowing fluid, the discharge coefficient is usually taken from a published discharge coefficient equation. Therefore, the discharge coefficient equation is very important for orifice plates: an error of 0.1 % in discharge coefficient gives an error of 0.1 % in many flow measurements of natural gas. ISO 5167-1:2003 provides an equation for the orifice discharge coefficient calculation, Cd, as a function of Beta Ratio, Reynolds number, L1 and L2, where L1 is the distance of the upstream pressure tap from the orifice plate and L2 is the distance of the downstream pressure tap from the orifice plate.
Beta Ratio Beta Ratio is the ratio between the line inner diameter to bore size of the orifice. The flow coefficient is found to be stable between beta ratio of 0.2 to 0.7 below which the uncertainty in flow measurement increases. An orifice plate beta ratio of 0.6 means that the orifice plate bore diameter is 60% of the pipe internal diameter.

Leak Flow Rate Calculator References

1 International Organization of Standards (ISO 5167-1). 2003. Measurement of fluid flow by means of pressure differential devices inserted in circular cross-section conduits running full — Part 1: General principles and requirements.
2 International Organization of Standards (ISO 5167-2) 2003. Measurement of fluid flow by means of pressure differential devices inserted in circular cross-section conduits running full -- Part 2: Orifice plates.
3 American Society of Mechanical Engineers (ASME). 2001. Measurement of fluid flow using small bore precision orifice meters. ASME MFC-14M-2001.
4 U.S. Dept. of the Interior, Bureau of Reclamation, 2001 revised, 1997 third edition, Water Measurement Manual.
5 Michael Reader-Harris (2015) Orifice Plates and Venturi Tubes.
6 Miller, R. W., Flow Measurement Handbook, 3rd ed., McGraw-Hill, New York, 1996.
7 American Gas Association, AGA Gas Measurement Manual, American Gas Association, New York.
8 Wikipedia
9 Corrosionpedia
10 Orifice Plates and Venturi Tubes (2015) - Michael Reader-Harris
11 EMERSON Fundamentals of Orifice Meter Measurement
12 Search Data Center

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Frequently Asked Questions

Q1 What is a Leak Rate and Why is it Important?
A1 A leak rate refers to the rate at which a fluid or gas escapes from a sealed system or container. It is typically expressed in units like liters per minute or cubic centimeters per second. Leak rate calculations are essential in various industries, such as manufacturing, automotive, and HVAC, to ensure product quality and safety. Controlling and measuring leak rates are crucial to prevent environmental contamination, product loss, and safety hazards. Accurate calculations help in identifying and addressing leaks promptly, ensuring compliance with regulatory standards, and minimizing economic losses.
Q2 How Can I Calculate Leak Rates?
A2 Leak rate calculations depend on the specific context and the nature of the leak. Generally, the formula for calculating leak rate involves dividing the volume of fluid or gas that has leaked by the time it took for the leak to occur. The formula can be expressed as Leak Rate (LR) = Volume (V) / Time (t). However, this formula may need adjustments based on factors such as temperature, pressure, and the properties of the leaking substance. Specialized equipment like leak detectors, flow meters, or pressure decay tests can be employed for accurate measurements. Additionally, the choice of units for expressing leak rates should match the specific requirements of the industry or application.
Q3 What Factors Affect Leak Rate Calculations?
A3 Several factors influence leak rate calculations, including temperature, pressure, the size of the leak, and the properties of the leaking substance. Changes in temperature and pressure can alter the behavior of gases, affecting their ability to escape from a sealed system. Smaller leaks may be more challenging to detect and measure accurately. Different gases or fluids may exhibit unique behaviors, affecting their leak rates. Variations in material properties, such as viscosity and surface tension, can also impact leak rate calculations. Therefore, it's crucial to consider these factors and use appropriate correction factors or calibration methods to obtain precise results.
Q4 What Are the Applications of Leak Rate Calculations?
A4 Leak rate calculations find application in diverse industries. In the automotive sector, they are crucial for ensuring the integrity of fuel systems and air conditioning units. In manufacturing, leak rate measurements are essential in quality control to prevent defects and inefficiencies. In the oil and gas industry, they are used to monitor pipeline integrity and prevent environmental contamination. Leak rate calculations are also important in medical devices to ensure patient safety. These calculations play a vital role in complying with industry-specific regulations and standards and are a fundamental part of risk assessment and preventive maintenance programs. Accurate leak rate calculations are indispensable for maintaining safety, product quality, and environmental responsibility in various domains.