seal, valve tests pass, not compression, what does this mean

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Waters 717 plus LC autosampler

I finally got the seal adjustment to work out and tested the valves with pressures of 4000 +. The valve tests, as outlined by the Waters 717 Plus manual, passed. Valve test page 157 http://www.meadowshplc.com/pdfs/717plus.pdf

However, for test number four where the needle is in the seal, and valves 2 and 3 are open while 1 is closed (1-injection, 2-syringe, 3-waste) and pressure is ramped to 4500 psi, I noticed that while the pump pressure/system pressure didn't degrade, the pressure indicated by the tranducer on the other hand (as indicated on the autosampler display) increased from a negative value all the way up to 1000 psi. Now since injection valve was closed, this seems to indicate that some flow from the pump is entering through the seals and increasing the pressure on the transducer.

In addition to this the compression test did not pass "compressibility exceeds limit". I set the pressure parameter at 30 psi and then at 350 psi and on both instances the test did not pass.

I also set the system pressure at 1000 psi via methanol flow in normal mode and messed with the valves motion page a bit, I moved the injector between the different positions and observed no leaks (except when the injector was in the sample vial position). I did this because the seal calibration test numbers seemed a bit skewy

up seal-350
dow seal-70
seal width-20

So apparently it's sealing in liquid pretty well when the pump is on but not when the syringe is applying pressure on it by moving. I did an injection accuracy test with four injections of 30 uL and it's pulling in about half of the expected amount.

Anyways, does everyone here agree that the most likely issue here is a worn seal? Any other suggestions as to what I should investigate? Why is it sealing in the flow but not when the syringe is applied to the seal? Thanks to bulldog and nkg for their assistance so far.
need a new syringe (or at least the teflon plunger tip)... Watch it do the compression test, you'll see the syringe suck in air and/or let liquid run down the plunger if I'm right.
Thanks,
DR
Image
first:
why do you start a new thread for every new question, when it's still related to the same object? This makes the follow up of the preceeding information and answers from other users difficult. Please stick within one thread until the problem has been solved or really changed to something completely different. Thx


Was your MeOH well degassed or He sparged before compr. check?
Was the system/injector well purged before the compr. check? Do 2-3 purge cycles before the compr. check
Does the compr. check fail repeatedly?
If there is some air bubble traped within the syringe, do a manual purge
->How does the plunger move? easily or strongly? (the latter would be better)

Always have the pump running at 1 ml/min and a column installed when performing a "purge" and/or "compression check"

Have you also changed the syringe?
->it could also be worn syringe/plunger-tip.
(just realize that DR was already faster...)

How did you do the inj accuracy test?
->use 6x50µL of deionized water, the weight drawn should then be within 294-306 mg

->What was the starting of the problem?
I thought you've already replaced the seal pak? if not, maybe it's in fact a worn seal? But you're saying that all valve and seal test would have passed...? :?
Hollow wrote:
first:
why do you start a new thread for every new question, when it's still related to the same object? This makes the follow up of the preceeding information and answers from other users difficult. Please stick within one thread until the problem has been solved or really changed to something completely different. Thx

will do from now on. As far as the "why" for posting a new thread....the essence of the topic or conundrum has changed, which may draw in different people who associate their expertise with the new question as opposed to the old one.

Was your MeOH well degassed or He sparged before compr. check?

yes

Was the system/injector well purged before the compr. check? Do 2-3 purge cycles before the compr. check

yes, did two purges before the compression check, the system was purged also.

Does the compr. check fail repeatedly?

not immediately, but it takes a good 5-10 minutes before the "compressibility exceeds limit" message pops up. It doesn't really explain why otherwise.

If there is some air bubble traped within the syringe, do a manual purge

There were no observable air bubbles inside the syringe.
->How does the plunger move? easily or strongly? (the latter would be better)

It moves steadily and slowly, which I'm guessing is what you mean by "strongly".
Always have the pump running at 1 ml/min and a column installed when performing a "purge" and/or "compression check"

a column was installed and it was running at 0.85 mL/min methanol, will try it at 1 ml/min water.
Have you also changed the syringe?
->it could also be worn syringe/plunger-tip.
(just realize that DR was already faster...)

don't have additional syringes in stock as of the moment, but it's been less than 8 months, if my recollection serves me correctly, since we changed out the syringe.
How did you do the inj accuracy test?
->use 6x50µL of deionized water, the weight drawn should then be within 294-306 mg

did mine with methanol, 4x30 uL, will try your version.
->What was the starting of the problem?
I thought you've already replaced the seal pak? if not, maybe it's in fact a worn seal? But you're saying that all valve and seal test would have passed...? :?


The original issue was low areas and reproducility in my chromatogram, about half of what I'm used to for my analyte peaks and the areas vary for the same standard. I haven't replaced my seal pack but replaced the needle. Performed the seal pack adjustment afterwards, first time doing so, and had some trouble with it, but it passed eventually thanks to members here in this forum such as yourself. Now the issue is with the compression test. The fact that the compression test does not pass along with the fact that there seems to be some liquid entering in via the seals during a valve test-when the injection valve is closed and the only way to increase transducer pressure is through the seals-seems to point to a worn out seal or a faulty injection valve, but I'm not an expert so I'll heed and follow up on your advice for the time being.

Wish I had an extra seal pack at hand and could just try replacing it.

hplctroubleshooting wrote:
As far as the "why" for posting a new thread....the essence of the topic or conundrum has changed, which may draw in different people who associate their expertise with the new question as opposed to the old one.
ok I see this point. But I guess with a "catchy" thread title, with possible "Update marks" will also attract the right people. But then they can update themself with all the history of the discussion.
That's my opinion.


not immediately, but it takes a good 5-10 minutes before the "compressibility exceeds limit" message pops up.
:shock: Did you mess up with the test criteria and limits? The test normally doesn't run this long.

a column was installed and it was running at 0.85 mL/min methanol, will try it at 1 ml/min water.
0.85 ml/min should also be fine

did mine with methanol, 4x30 uL, will try your version.
it's not "my version", it's Waters OQ-spec ;-)


The original issue was low areas and reproducility in my chromatogram, about half of what I'm used to for my analyte peaks and the areas vary for the same standard. I haven't replaced my seal pack but replaced the needle.
Performed the seal pack adjustment afterwards, first time doing so, and had some trouble with it, but it passed eventually thanks to members here in this forum such as yourself. Now the issue is with the compression test. The fact that the compression test does not pass along with the fact that there seems to be some liquid entering in via the seals during a valve test-when the injection valve is closed and the only way to increase transducer pressure is through the seals-seems to point to a worn out seal or a faulty injection valve, but I'm not an expert so I'll heed and follow up on your advice for the time being.
What I don't get right now, is how the worn seal would contribute to the low injection volumes?

By now, I guess there is something wrong with either V3 and/or with the syringe.
How do the valves inside the machine look like? Are they clean or any signs of leakage?

Maybe you might have Waters to have a look at this or ask them if there is a possibility to test for V3. It is not tested by the valve leak tests.

hplctroubleshooting wrote:
The valve tests, as outlined by the Waters 717 Plus manual, passed.
However, for test number four where the needle is in the seal, and valves 2 and 3 are open while 1 is closed (1-injection, 2-syringe, 3-waste) and pressure is ramped to 4500 psi, I noticed that while the pump pressure/system pressure didn't degrade, the pressure indicated by the tranducer on the other hand (as indicated on the autosampler display) increased from a negative value all the way up to 1000 psi. Now since injection valve was closed, this seems to indicate that some flow from the pump is entering through the seals and increasing the pressure on the transducer.

Weird. Have you seen liquid coming out from waste line (after V3)?
How could the solvent enter the loop line without decreasing the pressure on the pump's transducer? and 1000 psi are quite much...
Maybe there is also something wrong with the calibration of the AS's transducer that prevents the compr. check from passing?
(as the other tests and seal calibration worked, I guess not, but in troubleshooting never exclude something before you have it tested.)
Maybe redo also the seal pak calibration. You should get the same values (+/- 1 or 2 steps) for two consecutive tests.
see also here, very similar to yours
viewtopic.php?f=1&t=19015&p=91742#p91742
Hollow wrote:
hplctroubleshooting wrote:
As far as the "why" for posting a new thread....the essence of the topic or conundrum has changed, which may draw in different people who associate their expertise with the new question as opposed to the old one.
ok I see this point. But I guess with a "catchy" thread title, with possible "Update marks" will also attract the right people. But then they can update themself with all the history of the discussion.
That's my opinion.


not immediately, but it takes a good 5-10 minutes before the "compressibility exceeds limit" message pops up.
:shock: Did you mess up with the test criteria and limits? The test normally doesn't run this long.

a column was installed and it was running at 0.85 mL/min methanol, will try it at 1 ml/min water.
0.85 ml/min should also be fine

did mine with methanol, 4x30 uL, will try your version.
it's not "my version", it's Waters OQ-spec ;-)


The original issue was low areas and reproducility in my chromatogram, about half of what I'm used to for my analyte peaks and the areas vary for the same standard. I haven't replaced my seal pack but replaced the needle.
Performed the seal pack adjustment afterwards, first time doing so, and had some trouble with it, but it passed eventually thanks to members here in this forum such as yourself. Now the issue is with the compression test. The fact that the compression test does not pass along with the fact that there seems to be some liquid entering in via the seals during a valve test-when the injection valve is closed and the only way to increase transducer pressure is through the seals-seems to point to a worn out seal or a faulty injection valve, but I'm not an expert so I'll heed and follow up on your advice for the time being.
What I don't get right now, is how the worn seal would contribute to the low injection volumes?

By now, I guess there is something wrong with either V3 and/or with the syringe.
How do the valves inside the machine look like? Are they clean or any signs of leakage?

Maybe you might have Waters to have a look at this or ask them if there is a possibility to test for V3. It is not tested by the valve leak tests.




-For the compression test, a purge was part of the step, I guess that's why it took so long.

-I figure that when the sample is being drawn, if there isn't a good seal, the drawing of the sample wouldn't be as efficient.

-The valves seem fine, but I'll test them again today.

-There supposedly is a test for valve 3 in the waters manual, page 157, the fourth test from the top. edit: nevermind, it's not really test for valve 3 but rather a test for "needle port too high in seal".

Thanks for your help, will be trying out your suggestions either today or tommorrow.
hplctroubleshooting wrote:

-I figure that when the sample is being drawn, if there isn't a good seal, the drawing of the sample wouldn't be as efficient.
there is only one opening of the needle at this is in your sample. The seals just seal the flow path to the column. It's like a cross-road.
But if V3 doesn't seal properly, there will no vacuum and to few sample would be taken up...


-The valves seem fine, but I'll test them again today.
if we suspect V3, there is no need to re-do it, cause it's not beeing tested.

-There supposedly is a test for valve 3 in the waters manual, page 157, the fourth test from the top. edit: nevermind, it's not really test for valve 3 but rather a test for "needle port too high in seal".
That's what I've realized too. There is no test for V3, but there is a section for the Waters service people for special valve tests (page155).
Maybe you can get them to assist you on the phone?


Thanks for your help, will be trying out your suggestions either today or tommorrow.


experimental idea:
maybe you can build yourself some diagnostic setup for V3.
I'm thinking of kind a translucent peace of tubing attached to the waste line of V3. Then immerse this into some (coloured) liquid.
Then watch if liquid will be drawn into this tubing just the same time when your sample is taken up. If so, your V3 is faulty.
Depending on your tubing, test with large sample volumes, so not to oversee effect.


I don't believe this would realy help, but:
if there is "only" some dirt/buffer crystals within V3, try to thoroughly flush the waste line with 100% water, and maybe consecutevly even with IPA or mixtures of it, then back to MeOH.
I don't speak of only "purge inj", but configure the valves manually like during the purge cycle (V3 open, V2 open(?), V1 open, column/restrictor installed) and set a flow of about 1 ml/min and let it flow for some time (don't exceed 1000psi)
Repeat some purge cycles and then compr. check
...depending on your time vs. money budget...
Hollow wrote:
hplctroubleshooting wrote:

-I figure that when the sample is being drawn, if there isn't a good seal, the drawing of the sample wouldn't be as efficient.
there is only one opening of the needle at this is in your sample. The seals just seal the flow path to the column. It's like a cross-road.
But if V3 doesn't seal properly, there will no vacuum and to few sample would be taken up...


-The valves seem fine, but I'll test them again today.
if we suspect V3, there is no need to re-do it, cause it's not beeing tested.

-There supposedly is a test for valve 3 in the waters manual, page 157, the fourth test from the top. edit: nevermind, it's not really test for valve 3 but rather a test for "needle port too high in seal".
That's what I've realized too. There is no test for V3, but there is a section for the Waters service people for special valve tests (page155).
Maybe you can get them to assist you on the phone?


Thanks for your help, will be trying out your suggestions either today or tommorrow.


experimental idea:
maybe you can build yourself some diagnostic setup for V3.
I'm thinking of kind a translucent peace of tubing attached to the waste line of V3. Then immerse this into some (coloured) liquid.
Then watch if liquid will be drawn into this tubing just the same time when your sample is taken up. If so, your V3 is faulty.
Depending on your tubing, test with large sample volumes, so not to oversee effect.


I don't believe this would realy help, but:
if there is "only" some dirt/buffer crystals within V3, try to thoroughly flush the waste line with 100% water, and maybe consecutevly even with IPA or mixtures of it, then back to MeOH.
I don't speak of only "purge inj", but configure the valves manually like during the purge cycle (V3 open, V2 open(?), V1 open, column/restrictor installed) and set a flow of about 1 ml/min and let it flow for some time (don't exceed 1000psi)
Repeat some purge cycles and then compr. check
...depending on your time vs. money budget...


well, in summary for today....and needless to say I am very confused and frustrated right now

1)I repeated all of the valve tests, the tests for the needle position relative to the injector seal (whether it was too high or too low so as to cause a leak), valve 2 and valve 1 checked out just fine. In that respect, I take back my emphasis on the seals, it doesn't seem to be an issue at this point.

2)repeated the compression test but this time noted a bubble after changing the compression parameters so that the syringe draws a lot of sample. I got excited over this and changed out the syringe, but unfortunately I wasn't able to get the syringe filled even manually drawing the syringe in and out while purging the autosampler. So, I got desparate, and perhaps a bit on the ridiculous side, and actually filled the syringe itself with some methanol, attached it to the autosampler, and then injected it into the system while it was purging so that all of the gaps could be filled so that I could draw some sample with the syringe and actually have it filled.

But overall the compression test never passed. And I could never get the system to draw some sample in the vial via a needle.

I tried to close V3, open V2, close V1 and try drawing some sample manually with the syringe, but for some strange reason my waters 717 plus autosampler wouldn't allow me (on the valve motion page-where you can adjust the valves one by one manually) to to have V2 open while V3 was closed, via any order in which it was applied i.e. opening V3, opening V2, then closing V3.

In any case, the compressibility test doesn't pass, even if I change out the syringe. At this point your assertions about having to focus on V3 seem valid. I may try out your test using some indicators tommorrow. At this moment, I can't think of anything else other then V3, I've purged the sample many times and it didn't change anything.

We've got a Waters guy coming soon, better that I tell him to bring with him a V3-waste valve.
hplctroubleshooting wrote:

We've got a Waters guy coming soon, better that I tell him to bring with him a V3-waste valve.

sounds like a good decision.

please respond what was it finally
Hollow wrote:
hplctroubleshooting wrote:

We've got a Waters guy coming soon, better that I tell him to bring with him a V3-waste valve.

sounds like a good decision.

please respond what was it finally


well, Waters came today, he replaced the seal pack and v3 amongst other things. Did a compresssion test and it did not pass. So he plugged up the outlet of the v3 valve during the compression test and it still did not pass and saw bubbles in the syringe even after syringe replacement and purging. It turns out that valve 2 wasn't plugged in properly, we plugged it in good and the compression test passed.

Two things here that concern me.

1)Really have no explanation for why a non-functional v2 (syringe valve) would draw air bubbles, assuming everything else was working properly. Perhaps its internal components were in an awkward position and some how this caused cavitation when mobile phase was passing via the valve.

2)The valve test for 2 actually passed when I did it two days ago. So maybe a it was plugged in a way that caused some parts of the valve to function and other parts to not function.

After the compression test passed, we did an injection accuracy test. It didn't pass, in fact, we found substantial amounts of liquid on the caps of the vials. This would seem to indicate an issue with valve 1-injection valve-or the seals, but the seal pack adjustment passed, via better numbers btw (dc-90, up-320, sw-78), once that v2 was plugged in better, the seal pack passed easily. I tested out valve 1 just a few days ago and the valve test passed, in addition to this I observed the needle manually in the vial position, which of course had liquid coming out of it, and then closed the injection valve, after which the flow ceased.

First thing I'm going to do tommorrow is to observe the needle in the vial position and then shut off the injection valve with the flow on to see if liquid comes out, perhaps the seal calibration needs to be redone. Perhaps the needle is sticking too far out when it's supposed to be in the seal itself.

It's been quite confusing, a lesson that there's plenty of things in life that simply escape our awareness.
thank you for the feedback.
It's interessting to see that somethimes things aren't that simple as thought...

(I guess once more "1:0" for good old Mr. Murphy... ;-) )
Hollow wrote:
thank you for the feedback.
It's interessting to see that somethimes things aren't that simple as thought...

(I guess once more "1:0" for good old Mr. Murphy... ;-) )


Water technican said he replaced valve 1 and valve 2 (injection and syringe valves), apparently that fixed the problem because the areas are normal again. I tested both of these valves and they seemed fine so I'm wondering if he's telling me the truth about what's going on. Anyways, thanks again for your help, it was quite the learning experience.
I HV unique sort of issue it surpasses compression test but leaving few drops on vial probably needle wash solution the values of seal Pak r within limits as described.It performs n passes V1 n V2 tests
Can somebody give guideline
Thanx
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