The Ideal Gas Law & Leak Testing Video

The Ideal Gas Law & Leak Testing Video

In this video we will discuss the ideal gas law and its effects on leak testing.

During leak testing, changes in pressure can occur due to changes in temperature, volume, and number of moles of the gas. Since parameters like pressure, volume, and amount of air are involved in this process, it is governed by the ideal gas law.

PV = nRT

Where:

P = the Pressure of the air (or gas) enclosed in the container, measured in atmospheres

V = the Volume of the container occupied by the gas, measured in Liters

n = the Number of moles of the gas

R is the Ideal gas constant with a value of 8.314

& T = the Absolute temperature of the gas, measured in Kelvin

Changes in pressure, temperature, and volume are related and a change in any single parameter can affect other parameters.

When the temperature of air rises, the average kinetic energy and velocity of the particles increases.  This raises both the pressure and temperature.

When the test part is pressurized, the walls of the part can undergo expansion. This causes a change in the volume of the part. With an increase in area, the overall pressure drops. Similarly, a decrease in volume causes an increase in pressure, so long as the temperature and number of moles are constant. If the number of particles increases, this exerted force per unit area also increases.

Using the ideal gas law, a suitable relation can be derived that allows determination of leak rates through pressure loss in the part. A leak rate can be seen as the volume of gas that escapes through the part per second.

During a leak test, if the separation of the results, or Delta P, between leaking and non-leaking parts is not great enough, the repeatability of the process will be compromised. This is due to environmental factors influencing the pressure and temperature of the part under test.

The selection of Fill and Settle times during the test influence the part’s ability to come to equilibrium, which directly affects the test outcome. The greatest contributor to successful test outcomes is the Fill step. At higher test pressures, a longer fill step will allow the thermodynamic process to reach equilibrium. Parts that have more compliance, or capability to experience expansion, also need to reach a point of equilibrium. The ideal gas law illustrates how reducing or nullifying pressure or thermodynamic change will influence test repeatability by causing greater separation in the ΔP, thus improving the test.

If you have questions about leak testing your part or application visit zaxisinc.com, email sales@zaxisinc.com or call us directly at 801-264-1000.

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The Ideal Gas Law & Leak Testing Video

During leak testing, changes in pressure can occur due to changes in temperature, volume, and number of moles of the gas.

Ideal Gas Law & Its Effects on Leak Testing

Pressure, volume, moles, and temperature During leak testing, changes in pressure in the test part...

Press Release – zHMI

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Ideal Gas Law & Its Effects on Leak Testing

Ideal Gas Law & Its Effects on Leak Testing

Pressure, volume, moles, and temperature

During leak testing, changes in pressure in the test part are of primary interest. When a test part is filled with air (or any other gas), it initially expands inside the part to occupy its volume. When the part finally reaches the test pressure, the air inside contracts. This rapid expansion and contraction of air changes its temperature and volume. The test part also undergoes slight changes in temperature and volume because of changes in temperature and volume of the air. 

In order to detect the leakage, the changes in pressure must be taken into consideration. The changes in pressure can occur due to changes in temperature, volume, and number of moles of the gas. Since parameters like pressure, volume, and amount of air are involved in this process, it is governed by the ideal gas law. Mathematically, the law is expressed as:

Ideal Gas Law & Leak Testing Information Video

P = Pressure of the air (or gas) enclosed in the container

 

V = Volume of the container occupied by the gas

 

n = Number of moles of the gas

 

T = Absolute temperature of the gas

 

R = Ideal gas constant with a value of 0.0821 dm3 atm K-1 mol-1

 

According to equation (1), the product of the pressure and volume of any quantity of an ideal gas is equal to the product of the number of moles, ideal gas constant, and the absolute temperature of the gas. It can be seen from equation (1) that changes in pressure, temperature, and volume are related and a change in any single parameter can affect other parameters. 

 

According to the Kinetic Molecular Theory (KMT) of gases, temperature is proportional to the average kinetic energy of a given sample of gas. This can be expressed as: 

Equation (1) relates the actual experimental behavior of gases while equation (2) relates the results of experimental analysis using KMT. Studying equations (1) and (2), we can see how pressure, temperature, and volume are inter-related during leak testing. This means that changes in temperature, test part volume, and number of moles of a gas can affect the part’s pressure during leak testing. 

Effect of temperature changes on the test part’s pressure

When the temperature of air increases, the average kinetic energy and velocity of the particles increases. This is expressed in the equation (2) above. These particles now have a greater velocity, and they hit the walls of the part with greater force. The pressure exerted by these particles is in essence the force exerted per unit area of the walls of the part. So the pressure increases with an increase in temperature. Pressure is directly related to the temperature when the volume of the container and number of moles of gas are constant. 

 

Effect of volume changes on the test part’s pressure

When the test part is pressurized, the walls of the part undergo expansion. This causes a change in volume of the part. When the part expands and its volume increases, the pressure inside drops. This happens because the increase in volume increases the area of the walls. So the force per unit areas (pressure) drops because the force is constant. At constant temperature, the particles have the same average kinetic energy (or velocity) and they exert the same force on the walls. With an increase in area, the overall pressure (force per unit area) drops. Similarly, a decrease in volume causes an increase in pressure if the temperature and number of moles are constant. 

  

Effect of number of moles on the test part’s pressure

An increase in the number of moles of the gas increases the pressure inside the part when the temperature and volume are kept constant. Pressure is generated inside the part when the particles exert force on the walls of the part. With an increase in the number of particles (number of moles) increases, this exerted force per unit area (pressure) also increases. 

 

Accounting for the leak rates caused by pressure changes

In order for detecting the leak rates correctly, the fluctuations in pressure caused by the factors explained above should be allowed to settle. Oftentimes, this is not the case and in practice, leak testing is carried out without a proper fill and settle time. In order to account for these pressure changes, an adequate relation is needed that accounts for the pressure losses. 

 

Deriving the relation of pressure loss to leak rate 

Using the ideal gas law, a suitable relation can be derived that allows determination of leak rates through pressure loss in the part. A leak rate can be seen as the volume of gas that escapes through the part per second. This relation can then later be modified to account for the effects of changes in pressure, temperature, volume, and number of moles.

 

From the ideal gas law, the number of moles in the test part can be expressed by: 

If,

NL = Number of moles of gas lost

P = PATM = Atmospheric pressure

V = L.R = Leak rate or volume of gas escaping per second

Then equation (3) becomes: 

Therefore, the remaining number of moles NR will be:

Using ideal gas law, at a constant temperature, the remaining pressure after time (t) can be given by:

Putting the value of NR from equation (5) in equation (6) and solving for PR, we get:

Solving for leak rate (L.R) yields:

Modified equation for accommodating the pressure losses. Equation (7) gives the relation for calculating leak rates when the test volume, temperature and PATM are considered constants. As described above, the actual leak rates (or pressure changes) are affected by changes in volume, and/or temperature. 
To accommodate these pressure changes, a master part or ‘non-leak part’ is put under test. Despite no real leakage, some pressure change occurs in this non-leak part because of the reasons described above. This pressure loss is called the ‘zero offset’ factor. Equation (7) can then be modified after considering the ‘zero offset’ factor. The modified equation can be used to determine leak rates in test parts. The zero offset factor or the pressure loss of the non-leak part is subtracted from the pressure change of the test part in consideration. By doing this, the pressure changes due to temperature and volume are accommodated for and correct leak rates can be determined. The modified equation is:

Where,

L.R (t)       Leak rate (scc/s)

t                 Time (sec)

ΔP test          Pressure loss in the test part during the test (psi)

ΔP non-leak    Pressure loss in the non-leak part (psi)

              Volume (cubic cm)

 

Process repeatability

If the difference between ΔP test and ΔP non-leak is not great enough, the repeatability of the process will be compromised by environmental factors influencing the part under test. The selection of Fill and Settle times during the test will directly affect the test outcome. The greatest contributor to successful outcomes will be from the Fill step. Parts that have more compliance (capability to experience expansion) will need to reach a point of equilibrium. At higher test pressures, a longer fill step will allow the thermodynamic process also to reach equilibrium. Reducing or nullifying these two factors will cause a greater difference in the ΔP, thus improving the test.

Press Release – zHMI

Press Release – zHMI

Press Release: Zaxis has released the zHMI factory automation software that facilitates remote monitoring and configuration of Zaxis devices.

Download Press Package

SALT LAKE CITY, UT. (November 19, 2020) –The zHMI factory automation software has been developed by Zaxis to facilitate remote configuration and monitoring of Zaxis devices. zHMI software is currently available for purchase from any Zaxis sales representative.

The new Zaxis Human Machine Interface (zHMI) software can monitor up to 30 devices at once. The user-friendly interface makes operations such as start/stop or changing device parameters simple for individual devices or updating every device connected at once. The software can display live production statistics and save production history. The zHMI has a simple backup and restore function that will save important device settings.

Full remote control of Zaxis devices means no more in-person monitoring on the production floor. No more gowning-up in a clean room just to check progress or update a parameter. Many production lines today have large screens around the factory for simple production monitoring, the zHMI is perfect for this application.

The zHMI factory automation software is currently compatible with PC computers. Simply plug Zaxis devices into a wireless router and get full remote monitoring and control.

Download Press Package

Determine a Leak Rate – Live Discussion

Determine a Leak Rate – Live Discussion

Determine a Leak Rate – Live Discussion

What is a Leak Standard?

A leak standard is a calibrated, simulated leak that can be used in circuit with the part under test. A leak standard can be used during test setup to help you determine the parameters for your leak test. It can also be used to challenge your system by comparing multiple leak systems to each other.

The Ideal Gas Law & Leak Testing Video

During leak testing, changes in pressure can occur due to changes in temperature, volume, and number of moles of the gas.

Ideal Gas Law & Its Effects on Leak Testing

Pressure, volume, moles, and temperature During leak testing, changes in pressure in the test part are of primary interest. When a test part is filled with air (or any other gas), it initially expands inside the part to occupy its volume. When the part finally reaches...

Press Release – zHMI

Press Release: Zaxis has released the zHMI factory automation software that facilitates remote monitoring and configuration of Zaxis devices. Download Press Package SALT LAKE CITY, UT. (November 19, 2020) –The zHMI factory automation software has been developed by...

Determine a Leak Rate – Live Discussion

Determine a Leak Rate - Live DiscussionA leak standard is a calibrated, simulated leak that can be used in circuit with the part under test. A leak standard can be used during test setup to help you determine the parameters for your leak test. It can also be used to...

Configure a Leak Tester

Contact us today to find the right solution for your needs.

Leak Testing for Cellular Manufacturing

Leak Testing for Cellular Manufacturing

Cellular manufacturing is a lean manufacturing model. The goal of cell manufacturing is to save time and space on the assembly floor by grouping machines together by the specific task they accomplish. These grouped machines, or “cells” are then lined up in the form of an assembly line. The Zaxis PD has been specifically designed to fit in a manufacturing cell.

Lean manufacturing is a methodology developed by Toyota and defined by James Womack and Daniel T. Jones in 1996 in their book Lean Thinking: Banish Waste and Create Wealth in Your Corporation. Womack and Jones define lean manufacturing as any system that follows the following standards; “Precisely specify value by specific product, identify the value stream for each product, make value flow without interruptions, let customer pull value from the producer, and pursue perfection.” (Lean Thinking p10)

Using the lean methodology, the concept of cell manufacturing was created to streamline assembly line flow. As seen in figure 8-4 from The Toyota Way, a common cellular manufacturing format is a U-shape which promotes good communication between workers. In a fully automated assembly line, the U-shape can make monitoring the entire line easy.

When integrating a leak tester into a cell-based manufacturing format, the most common issues are size and information displays. Large testers take up valuable space and often need to be moved away from the line and connected to products via long hoses. This adds excessive volume to the leak test effecting test accuracy. Some smaller testers can be placed right on the assembly line as close to the products as possible but many of these testers have had their displays removed to save space.

This figure from The Toyota Way shows the design of a U-shaped cell, graphing the paths of two employees through it. (https://commons.wikimedia.org/wiki/File:Figure_8-4_from_The_Toyota_Way.png)

The Zaxis PD was designed to be perfectly integrated into manufacturing cells. With the size of a 6” cube, the Zaxis PD is compact enough to fit right on the assembly line close to the product. This consolidates the UTT (Unite Under Test) keeping test accuracy high. In spite of the small size a clear LCD color touchscreen is integrated directly into the Zaxis PD. The integrated touchscreen enables at-a-glance leak test monitoring on the production floor.

Every detail of the Zaxis PD was fashioned for ease of use in a cell manufacturing environment.

  • Wall mounting plates for easy instillation
  • Integrated leak standard port and with dedicated valve
  • Onboard processing
  • USB port for simple data collection
  • Automatic pressure control that allows multiple tests to run at varying pressures
  • Bottom mounted connectors to minimize internal test volume and simplify connectivity

 

Visit our downloads page for more information and to download the Zaxis PD data sheet.

Click here to request a quote or call us at +1-801-264-1000.  

Leak Testing Sealed Components – Live Discussion

Leak Testing Sealed Components – Live Discussion

Leak Testing Sealed Components – Live Discussion

Drawer Fixtures

Specially designed for chamber tests, the Zaxis drawer fixtures come in a variety of sizes to fit your application.

The Ideal Gas Law & Leak Testing Video

During leak testing, changes in pressure can occur due to changes in temperature, volume, and number of moles of the gas.

Ideal Gas Law & Its Effects on Leak Testing

Pressure, volume, moles, and temperature During leak testing, changes in pressure in the test part are of primary interest. When a test part is filled with air (or any other gas), it initially expands inside the part to occupy its volume. When the part finally reaches...

Press Release – zHMI

Press Release: Zaxis has released the zHMI factory automation software that facilitates remote monitoring and configuration of Zaxis devices. Download Press Package SALT LAKE CITY, UT. (November 19, 2020) –The zHMI factory automation software has been developed by...

Determine a Leak Rate – Live Discussion

Determine a Leak Rate - Live DiscussionA leak standard is a calibrated, simulated leak that can be used in circuit with the part under test. A leak standard can be used during test setup to help you determine the parameters for your leak test. It can also be used to...

Configure a Leak Tester

Contact us today to find the right solution for your needs.

Leak Testing in Manufacturing – Live Discussion

Leak Testing in Manufacturing – Live Discussion

Leak Testing in Manufacturing – Live Discussion

Leak Testers

The modular design of Zaxis leak testers enables us to meet the demands of a wide variety of applications.

The Ideal Gas Law & Leak Testing Video

During leak testing, changes in pressure can occur due to changes in temperature, volume, and number of moles of the gas.

Ideal Gas Law & Its Effects on Leak Testing

Pressure, volume, moles, and temperature During leak testing, changes in pressure in the test part are of primary interest. When a test part is filled with air (or any other gas), it initially expands inside the part to occupy its volume. When the part finally reaches...

Press Release – zHMI

Press Release: Zaxis has released the zHMI factory automation software that facilitates remote monitoring and configuration of Zaxis devices. Download Press Package SALT LAKE CITY, UT. (November 19, 2020) –The zHMI factory automation software has been developed by...

Determine a Leak Rate – Live Discussion

Determine a Leak Rate - Live DiscussionA leak standard is a calibrated, simulated leak that can be used in circuit with the part under test. A leak standard can be used during test setup to help you determine the parameters for your leak test. It can also be used to...

Configure a Leak Tester

Contact us today to find the right solution for your needs.

Dispensing Buffers for Covid Testing

Dispensing Buffers for Covid Testing

Dispensing Buffers For Covid Testing

eVmP

Rotating and Reciprocating Valve-Less Ceramic Piston Design with Electronic Variability and Positive Displacement.

Press Release – zHMI

Press Release: Zaxis has released the zHMI factory automation software that facilitates remote monitoring and configuration of Zaxis devices. Download Press Package SALT LAKE CITY, UT. (November 19, 2020) –The zHMI factory automation software has been developed by...

Dispensing Buffers for Covid Testing

If you guys are in that stage of making some sort of vials that you’re filling testing kits for reagents, or whatever the case may be, we have a solution to help you fill your vials quick and very accurately, and keep your production rate as fast as possible.

Electronic Variable Metering Pump Introduction

Electronic Variable Metering Pump IntroductionRotating and Reciprocating Valve-Less Ceramic Piston Design with Electronic Variability and Positive Displacement.Contact us today to find the right solution for your needs. Electronic Variable Metering Pump Introduction...

Soft Gel Capsule Dispensing

Softgel manufacturing requires precise dispensing with excellent accuracy and repeatability. For example, Active Pharmaceutical Ingredients or APIs require the utmost precision so the dosage to consumers is not only safe but effective. In addition to stringent quality...

Metered Dispensing

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Dispensing Buffers For Covid Testing, Video Transcript

Hello. Welcome to the Zaxis video blog. Today we’re going to talk about filling up vials for Covid testing kits. We’ve had a lot of customers who were either already making some sort of kit or now are making some sort of Covid testing kit, so we’re getting a lot of pump applications for this. The majority are running somewhere between 1 and 3 ml shots. To represent, basically what the vials look like [I have] this little syringe. But somewhere between 1 to 3 ml is typically the dispense [volume] of the buffer solution that is carrying the dna, saliva, whatever they’re using for the kit.

With our pumps, you have a 1% or better accuracy with less than half a percent repeatability after that. So when you’re pumping a real expensive fluid, like those buffers tend to be, the accuracy is very important. Not only can you do it accurate[ly] but you can do it very fast. A lot of our customers are currently shooting, i’ll use this as a vial, they’re filling up a small vial to go in the kits. Right now you may be doing one every seven/eight seconds, whatever the case may be. As your production grows and you can find ways to speed that up.

We can hold that same accuracy with our pumps, to go up to maybe doing one a second one every two seconds. We’re doing quite a few 8-up projects right now where we are filling multiple vials at a time as they’re coming down the assembly line. Some have a real small end you’re shooting into. Some have a larger funnel type. That’s all going to play with different nozzles and tubing that we’ll use in order to shoot it in and not make a mess.

If you guys are in that stage of making some sort of vials that you’re filling testing kits for reagents, or whatever the case may be, we have a solution to help you fill your vials quick and very accurately, and keep your production rate as fast as possible.

Thanks for tuning in and we’ll come at you next week with another video from Zaxis.

ISO 10555 Correlation to a Pressure Decay Test

ISO 10555 Correlation to a Pressure Decay Test

ISO 10555 Correlation to a Pressure Decay Test

Air to Liquid Correlation

Often a process or product has an ISO or similar standard for leak testing.  The following describes how a customer took the ISO 10555 leak test and correlated it to a pressure decay leak test using an Isaac HD pressure decay test.

The ISO 10555 process states that a product can leak no more than one falling drop of water in less than 30 seconds when pressurized to 3 ATM of liquid pressure.  The following describes the tests that were performed to correlate this to a nondestructive pressure decay test.

A group of parts were gathered that had been determined to be leak free.  Some of the parts were sent out to a company to have holes drilled through them in varying diameters.  The part was a catheter and the hole was drilled through the catheter hub directly into the eventual fluid path of the catheter.  The holes varied in size from 1 to 20 micron in diameter.  The parts were then taken and tested with air.  The customer wanted to use 15 PSI of air pressure as their test medium.  The laser drilled catheters were first put on a flow meter to determine the amount of flow through the hole.  Once a flow had been recorded the parts were put on an Isaac HD pressure decay tester to measure the amount of decay that they generated.  The pressure decay test was repeated four times with a one minute interval between tests.  Once this data had been recorded the parts were tested with water.  The parts were pressurized with water to 3 ATM and monitored for water drops forming.  Each part was timed and the timer stopped once the drop formed and fell off of the part.  The following chart shows the air flow, diameter and time for the drop to fall.  The study determined that for a drop to fall the hole size had to be 10 micron and the air flow at 15 PSI was greater than 2 SCCM.  A leak standard of 2 SCCM at 15 PSI was then created to be used for test development.

Configure a Leak Tester

Contact us today to find the right solution for your needs.

Issac HD

The Isaac HD packs industry-leading capabilities into a small package. Isaac HD is an out of the box solution for your leak testing needs.

The Ideal Gas Law & Leak Testing Video

During leak testing, changes in pressure can occur due to changes in temperature, volume, and number of moles of the gas.

Leak Testing Sealed Components – Live Discussion

Leak Testing Sealed Components - Live DiscussionSpecially designed for chamber tests, the Zaxis drawer fixtures come in a variety of sizes to fit your application.Contact us today to find the right solution for your needs.

Dispensing Buffers for Covid Testing

If you guys are in that stage of making some sort of vials that you’re filling testing kits for reagents, or whatever the case may be, we have a solution to help you fill your vials quick and very accurately, and keep your production rate as fast as possible.

ISO 10555 Correlation to a Pressure Decay Test

ISO 10555 Correlation to a Pressure Decay TestAir to Liquid Correlation Often a process or product has an ISO or similar standard for leak testing.  The following describes how a customer took the ISO 10555 leak test and correlated it to a pressure decay leak test...

Configure a Leak Tester

Contact us today to find the right solution for your needs.