How to Run and Interpret the Inlet Leak and Restriction Test for the Agilent 7890/8860/8890 GC Systems

Answer

This Information Applies To: Agilent 7890 A/B, 8860 and 8890 GC Systems with Split/Splitless (SSL), Multimode (MMI) or Programmable Temperature Vaporization (PTV) Inlets

Issue:

The Inlet Leak & Restriction Test is executed after every inlet maintenance procedure. It can also be run for troubleshooting purposes or as a frequent confidence check for GC performance.

Useful to

• Find and repair medium to large leaks. Useful when the inlet will not pressurize to the setpoint due to a large leak: Troubleshooting a Leak in a Split/Splitless Inlet , Inlet Pressure Shutdown / Gas Cannot Achieve Setpoint .
• Confirm that the column is not restricted and actually has carrier flow.
• Check day to day leak rate. Run every morning before running samples. Confidence check. (Can be executed as a Prerun test as part of the method.)

Steps to follow:

Caution: The accuracy of the Leak and Restriction Test is directly related to the accuracy of the column configuration and carrier gas configuration. Confirm the configuration is correct prior to performing the test!

How-to perform an Inlet Leak and Restriction test on a 7890

1. On the keypad press: [Service Mode] > Inlet Leak Check and confirm with [Enter]. (Figure 1)

2. Set a test pressure. Usually, the default 10 psi pressure is suitable for the test, but it actually depend on the column dimensions, see the following examples:

   1. For 30 m X 250 µm on GC/MS: 5–20 psi.

   2. For 30 m X 530 µM column on GC Detector: 5 to15 psi.

   3. For 30 m X 320 µM column on GC Detector: 5 to 25 psi.

   4. For 30 m X 200 µM column on GC Detector: 5 to 85 psi.

      Caution: With a GC/MS system, use a test pressure that will not result in excessive flow to the MS.

       

3. Set Warning or Fault thresholds if needed. (Figure 2) More information is available in the Troubleshooting Manual.

   1. A warning will create a "Service Due" reminder.

   2. A fault will set the GC in a "Not Ready" state.

      Caution: On a 7890 GC the leak check will always report "OK" unless a Warning or Fault Threshold was set prior.

       

4. Press [ON] to start the Leak Check.
    

Figure 1 Selecting the Leak and Restriction Test on a 7890.

Figure 2 Setting of Warning and Fault thresholds.

How-to perform a Leak and Restriction test on a 8890/8860

1. Select the automated test

   1. on the 8890 touch screen display press: Diagnostics > Inlet > Leak & Restriction Test. (Figure 3) 

   2. on the 8890 or 8860 Browser Interface (How to Use the Browser Interface for 8890 and 8860 GC Systems ): Diagnostics > Diagnostic Tests > Inlet > Leak & Restriction Test. (Figure 4)

2. Press Start Test. 

   1. The test shuts off all exits to flow in the inlet system except the column. The target flow is set as 4 ml/min ± 2 ml/min. The diagnostic measures the column flow and calculates the Leak Rate.

   2.  During the test details are displayed along with test results. (Figure 5)
        

Figure 3 Selecting Leak and Restriction Test on the 8890 GC touch screen display.	Figure 4 Selecting Leak and Restriction Test through the 8890 or 8860 Browser Interface.

Figure 5 Leak and Restriction Test page on the 8890 touch screen display.

How-to interpret the results of a Leak and Restriction Test

With the Leak and Restriction Test leaks > 2 ml/minute can be detected.

If the actual is the target ± 2 ml/minute, the test is considered passed.

• If you suspect smaller leaks, perform a Pressure Decay Test. (Troubleshooting Manuals)

If the actual is larger than the target, a leak exists in the flow path.

• To identify a leak, check possible leak sources Troubleshooting a Leak in a Split/Splitless Inlet . If available, use an electronic leak detector.

• Remove any leak sources from the previous step.  Run the Leak and Restriction test to confirm “Passed” status.

• If the leak can't be identified, contact your local Agilent Technical Support.

If the actual is less than the target, a restriction exists in the flow path.

• Check if a clean and correct liner is installed, the gold seal is not contaminated / blocked, and the column is not blocked.

• If the restriction can't be identified, contact your local Agilent Technical Support.
  
  

Actions to take on a 7890

Caution: On a 7890 GC the leak check will report "OK" unless a Warning or Fault Threshold was set prior. Check the Total Flow and Column Flow results of the test.

1. Two flow values are presented on the GC display. The approximate Leak Rate is the difference between the actual measured flow ("Total Flow") and the calculated column flow ("Col"). (Figure 6.1, Figure 6.2)

2. If the test fails, touch or tighten each of your potential leak points while watching the display. When you touch the primary leak point, the “Total Flow” will respond up or down in the display.  

3. Reset Early Maintenance Feedback counters (EMF) if applicable after change of inlet consumables. More information is available in the respective Operation Manual.

Figure 6.1 Passed Leak and Restriction Test.	Figure 6.2 Failed Leak and Restriction test.

Actions to take on a 8860/8890

The Active Monitor gives the user the ability to troubleshoot the problem live during the test.

1. If the test fails, select Active Monitor to isolate the leak(s) while the pressure is displayed. (Figure 7). Chec possible leak points while measuring the pressure on the screen.

2. Reset Early Maintenance Feedback counters (EMF) if applicable after change of inlet consumables. More information is available in the respective Operation Manual

3. If the leak can't be identified, contact your local Agilent Technical Support..

Figure 7 Active Monitor option. In this example, the failure is a leak.

Learn more about how to troubleshoot your Agilent GC System: Agilent 8890 GC with OpenLab CDS Agilent 7890 Series GC with OpenLab CDS e-learning paths available from Agilent education.