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14

Instruction Guide

Replacing the NPD Bead

 

Turning On the Bead

Now that the bead is installed, it is turned off but warm, with 
gases sweeping any evaporating moisture off of the bead and 
out of the detector. Next you will adjust the bead voltage to 
achieve the desired response using either the Adjust Offset 
process (recommended for the 7890A GC with firmware A.01.09 
or greater) or manually.

Set the Initial Bead Voltage to a Safe Value

Before you turn on the bead for the first time, manually set its 
voltage to a safe value so that the new bead is not destroyed. 

1

Make sure 

Adjust Offset

 is turned 

Off

.

2

After the temperature stabilizes at setpoint, set the initial 
Bead Voltage, depending on bead type:

•

Blos bead: 0.0 V to 0.5 V

•

Ceramic bead (white or black): 0.0 V to 2.0 V

To Use the Adjust Offset Process to Set Bead Voltage

If you choose to use the GC Adjust Offset process, do the 
following:

1

Set the offset. 

•

Blos bead: 20 pA

•

Ceramic bead (white or black): 30 pA

2

If your GC has an 

Equilibration time

, set it to 0.0.

3

If using an Agilent data system, start the online session for 
the instrument. 

For 7890A users: If you changed the bead type, you will need 
to resolve the current method to match the new bead type.

4

When the GC becomes Ready, start 

Adjust Offset

.

NPD Bead Replacement.book  Page 14  Monday, October 13, 2008  2:32 PM

Содержание 6890 Series

Страница 1: ...Agilent Technologies Replacing the NPD Bead Instruction Guide NPD Bead Replacement book Page 1 Monday October 13 2008 2 32 PM ...

Страница 2: ...bility and fitness for a par ticular purpose Agilent shall not be liable for errors or for incidental or consequential damages in connec tion with the furnishing use or per formance of this document or of any information contained herein Should Agilent and the user have a separate written agreement with warranty terms covering the material in this document that conflict with these terms the warran...

Страница 3: ... detector NPD Before following this procedure refer to the safety information on the inside front cover and in your GC user information Parts list 1 NPD bead assembly ceramic or Blos Cap for the bead Test chromatogram NOTE If you used Blos beads before 2008 you may notice that the current bead has a slightly different shape and color This is normal NPD Bead Replacement book Page 3 Monday October 1...

Страница 4: ...make sure the firmware version is A 01 09 or higher If using a 6890 Series GC make sure the firmware version is A 03 05 or higher If using a Blos bead on a 6890 Series GC make sure the firmware version is A 03 08 or higher Firmware versions earlier than A 03 08 will immediately destroy a Blos bead if you use the Adjust Offset feature Figure 1 Blos bead assembly NPD Bead Replacement book Page 4 Mon...

Страница 5: ...ose the GC parameters screen of the data system Upload the revised setting then save the method and shut down the instrument session 3 Set Adjust Offset to Off 4 Cool the detector to 60 C or lower Leave all gas flows on To cool the detector faster raise the GC detector cover and open the hinged NPD cover CAUTION The bead is delicate Be careful not to break or crack the bead When performing mainten...

Страница 6: ...tilation slots For models with the hinge bracket The hinge is a metal bracket attached to the oven top Pull the clip at its top toward you to release the hinge pin Push the pin to the left to release the cover Raise the cover and remove it Remove the top electronics cover Push the clips underneath the cover shown in Figure 3 toward the center to disengage them Figure 2 Lifting the electronics top ...

Страница 7: ... Instruction Guide 7 Other models Push the clips underneath the cover toward the center to disengage them Figure 3 Removing the top electronic cover 6890 Clips NPD Bead Replacement book Page 7 Monday October 13 2008 2 32 PM ...

Страница 8: ...ctor parts NOTE The illustrations below show a ceramic bead Blos bead installation is the same WARNING Be careful The oven or detector fittings may be hot enough to cause burns CAUTION Wear clean lint free gloves to prevent contamination of parts with dirt and skin oils NPD Bead Replacement book Page 8 Monday October 13 2008 2 32 PM ...

Страница 9: ...on Guide 9 2 Twist the ring to disconnect the bead assembly cable Push and twist the lock so that the button slides up in the groove then pull the cable ends apart 1 2 3 NPD Bead Replacement book Page 9 Monday October 13 2008 2 32 PM ...

Страница 10: ... the collector 5 Remove the protective cap covering the new bead Bead assembly NOTE For a new Blos bead the bead should be centered as shown in Figure 1 If you notice that the bead assembly does not appear like the assembly shown in Figure 1 carefully center the bead Be sure to not contaminate the bead during this process NPD Bead Replacement book Page 10 Monday October 13 2008 2 32 PM ...

Страница 11: ...e bead on the sides of the lid or collector 7 Replace the screws Finger tighten the first screw tighten the remaining screws normally and then completely tighten the first screw Do not overtighten the screws 8 Carefully bend the bead assembly cable 90 NPD Bead Replacement book Page 11 Monday October 13 2008 2 32 PM ...

Страница 12: ...Set the bead type Review the Maximum Bead Voltage setting and adjust if necessary Review the Dry Bead and Auto Adjust Bead settings 12 Restore normal NPD operating gas flows 13 With all gases on heat the detector to 150 C and hold for about 15 minutes then increase the temperature to 250 C and hold for 15 minutes 14 Increase the temperature to operating value 310 to 320 C recommended Allow 15 minu...

Страница 13: ...a Display the detector output b Verify that the output leakage current is stable and 2 0 pA If 2 0 pA verify bead installation and recheck If still high replace the ceramic insulators inspect replace the collector NPD Bead Replacement book Page 13 Monday October 13 2008 2 32 PM ...

Страница 14: ...yed 1 Make sure Adjust Offset is turned Off 2 After the temperature stabilizes at setpoint set the initial Bead Voltage depending on bead type Blos bead 0 0 V to 0 5 V Ceramic bead white or black 0 0 V to 2 0 V To Use the Adjust Offset Process to Set Bead Voltage If you choose to use the GC Adjust Offset process do the following 1 Set the offset Blos bead 20 pA Ceramic bead white or black 30 pA 2 ...

Страница 15: ...0 05 to 0 1 V until reaching the desired offset With a clean environment clean gas supplies and low bleed column a typical offset may decrease 6 12 pA during a 24 hour period Blos Beads A new Blos bead typically ignites between 0 5 and 1 1 V A Blos bead typically requires a lower offset than the white and black beads to achieve a similar response A new Blos bead shows an increase in baseline durin...

Страница 16: ...Black A new ceramic bead typically ignites between 2 8 to 3 2 V Recommended flow settings starting values Capillary makeup flow N2 5 to 10 mL min He 5 mL min Hydrogen flow 2 to 5 mL min Air flow 60 mL min NPD Bead Replacement book Page 16 Monday October 13 2008 2 32 PM ...

Страница 17: ... the three T 20 Torx screws The installation of traps is recommended for the detector hydrogen air and make up gas A moisture trap followed by chemical traps is highly recommended pA Leakage Current System status Comment 0 3 0 9 CLEAN 1 0 Dirty Decrease in sample response 10 Very dirty Almost no sample response Cause is usually contaminated ceramic insulators on the collector usually the upper ins...

Страница 18: ...Agilent Technologies Agilent Technologies Inc Printed in USA October 2008 G3430 90037 NPD Bead Replacement book Page 18 Monday October 13 2008 2 32 PM ...

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