Big bubble forming in doser to reagent tube??

[Fishbones]

As seen in attached pictures, there is a bubble forming in the tube connected to the reagent bottle, on the doser side. This bubble forms over a period of about 15 hours. It seems that the reagent is slowly flowing back into the reagent bottle.
The bubble then gets sucked into the KHD when the next measurement is made, (as can be seen in second picture) obviously resulting in wrong value.
The tube between the doser connector and the reagent bottle is 7cm long.

As it stands, I have to prime the reagent doser everyday in order to get correct measurements.

Also attached picture of my setup. Anything wrong there?

10226
10227
10228

[paulfars]

I have exactly the same problem

I thought at first it may be sucking air from the joint where the airline meets the doser, but the seals are very good.

If your theory is correct I might try lifting the reagent bottle higher. I have the same layout as you with the reagent directly below.

Very annoying.

[Fishbones]

So after having to prime the tubes again to get the BIG air bubble out, taking a measurement that was off by 0.1dKH compared to my Hanna tester ;), 16 hours later I check on the reagent tubes and this is what I see: :eek:

10242


The BIG bubble is there again and now there are micro bubbles too.

edit 12/02
Anyone else have this issue?
Is it a problem with the reagent forming micro bubbles?
Is air getting in through the doser 2.1?

No solution from support team?

The KH Director is useless to me if I have to prime tubes everyday in order to get a correct measurement. Quicker to test with Hanna :rolleyes:

[Mortie31]

Ive been having exactly the same issue, posted in R2R about it, wonder where there coming from. I even changed reagent bottle in case first one was contaminated and somehow causing bubbles to form in the liquid. I might try a check valve and see if that helps.

[paulfars]

The support team have gone very quiet about this issue .

It is affecting a lot of users.

It looks to me that the reagent is aerated , when it passes through the doser pump the micro bubbles burst and make a large bubble that slowly moves up the tube towards the KHD.

[Matthias]

Hi

we are already working on this issue, we didn't want to post before we had final results, assumptions don't help anyone.


It seems that there are micro bubbles in the reagent, our manufacturer told us that this can happen after temperature swings of the reagent.
This is very likely in the winter, between storage, transport and your home we have temperature differences of 20°C or more.


These are the planned actions:

1. reagent manufacturer tries to get rid of most of the micro bubbles with heating and shaking the warm liquid before shipping, this will reduce the air about 80%

2. we add a software feature "double-check" (can be disabled): if the KHD measures a suspicious value it does a second measurement, it is very unlikely that a bubble affects 2 measurements in a row


What can you do now?

1. keep the reagent tubes as short and as straight as possible

2. get rid of the micro bubbles: get the liquid a bit warmer than room temp., e.g. get temp. about 30°C on a heater, after that loose the air bubbles by stomping

[Mortie31]

Thanks Matthias

[Fishbones]

Thank you. I'll get stomping ASAP.

[Fishbones]

I warmed up the reagent and stomped the bottle but I still get a big bubble forming in the tube. Don´t see as many micro bubbles in the tube now but the big bubble formed over a period of about 15 hours is between 6 and 10mm.
Is it possible that air gets in through the hose connector causing the the reagent to flow back into the bottle?

[paulfars]

I still have this issue too after doing the same process as you describe. The bubble is quite large about 10mm after such a short time.

[Fishbones]

Very frustrating indeed! I have to either prime the tube every day prior to a measurement or do 3 or 4 sequential measurements in order to get the air bubble out and MAYBE get a correct reading on the 4th measurement. Besides the tremendous waste of reagent, this is not very practical and especially not reliable at all.

[Ian4302]

Has anyone found a work around because mine is doing the same

[MatthiasF]

Hello,

in order to avoid t he bubbles, ensure the vent tube is above the waste water surface
Follow this thread:
http://forum.aquariumcomputer.com/showthread.php?13280-KHD-ventilation-overflow-tube-ABOVE-water-surface!

[paulfars]

The bubbles are forming on the output of the doser that feeds the reagent tp the KHD so I can't see how the vent tube has anything to do with it.

[Fishbones]

Hi,

The vent tube is way above the waste water surface, so that's not it.

Suspecting that air is getting in through the hose connectors, I tried zip ties on the tube but that did not help.

This picture shows the air bubble formed since the last measurement taken 15 hours ago.

10352

[Matthias]

The bubbles are forming on the output of the doser that feeds the reagent tp the KHD so I can't see how the vent tube has anything to do with it.

yes, you are right, this has nothing to do with it, this is related to another problem
if the waste tube is below the water surface the KHD will suck waste water into the measurement cell

[paulfars]

So do you have any more ideas how we can stop the bubbles forming in the reagent tube?

[Matthias]

I tried zip ties on the tube but that did not help.


No, this will not help and is not necessary. The problem is not that there are leaks in the connection and air comes in that way, the problem is the dissolved air in the reagent which can form after some time bubbles.

But we found out that the impact of some air is not as large as you may think. Keep in mind that a measurement process needs about 2-3ml, and then compare how much volume this bubble has, this is a fraction.
According to the feedback we got so far it seems not a general problem, it seems the results are still very good.

Anyway, to get the best results: the less air in the reagent the better.

How?
a) get rid of the micro bubbles - see above, worked here
b) increase the measurements per day, so the "bubbles" have not much time to grow

[Matthias]

Very frustrating indeed! I have to either prime the tube every day prior to a measurement or do 3 or 4 sequential measurements in order to get the air bubble out and MAYBE get a correct reading on the 4th measurement. Besides the tremendous waste of reagent, this is not very practical and especially not reliable at all.

we need to become a bit more concrete here now

about what differences from measurement to measurement are we talking here?

how many measurements do you take per day?

[Fishbones]

we need to become a bit more concrete here now

about what differences from measurement to measurement are we talking here?

how many measurements do you take per day?

I take 1 measurement per day. I prime the tube every time there are bubbles in it so I can't tell you the differences from measurement to measurement, day to day, but the only time I let the bubble go it gave a result of 12.4dKH from my usual 7-8dKH. I'll stop priming the tubes now and see how it goes.
Taking more measurements a day could help I guess but at the moment I don't need to as I have few SPS and I would only be wasting reagent. (Shipping of the reagent to my location is expensive :( ie, €28,91)
Thanks for the suggestions. Hopefully the air bubbles will all make their way out one day so I can get consistent values.

Cheers.

[Matthias]

Thanks for details, helps to see clearer.
So yes I agree, the deviation (> 10) comes from the bubble.

Any chance you could use a thinner tube (e.g. ID = 2mm)? This will still fit on the doser fitting.

Still try to get rid of the air in the reagent - make it a bit warm (e.g. 30 - 40°C), shake it carefully

[Marc Vargas]

I to am having bubbles form in the tube supplying the KH director. Is it possible the reagent is reacting with the tubing supplied with the director?

i purchased a clear dosing container specifically for the reagent and the bubbles are only forming in the tubing supplied with the director

[PIWAWT]

Info from the German forum
A silicone hose with a thicker wall, or ptfe hoses solved the problem. obviously, "normal" silicone hoses are not diffusion-proof enough.

regards Pit

[pedromrg]

Info from the German forum
A silicone hose with a thicker wall, or ptfe hoses solved the problem. obviously, "normal" silicone hoses are not diffusion-proof enough.

regards Pit

ptfe hose ? is that aquarium co2 hose ?

[Mortie31]

I’ve just ordered this...
https://www.amazon.co.uk/Meters-Teflon-Filament-Printer-Rostock/dp/B018EC80V6/ref=sr_1_7/260-5693994-5704758?ie=UTF8&qid=1521923271&sr=8-7&keywords=ptfe+teflon+tube

[Gael]

Thanks for details, helps to see clearer.
Any chance you could use a thinner tube (e.g. ID = 2mm)? This will still fit on the doser fitting.


Info from the German forum
A silicone hose with a thicker wall
regards Pit
I have silicone tube with 2mm inner and 5mm outer and same problem...
Also even if this would solve the problem (which is not the case), nothing could be done with the hose in the head of the dosing pump and the hose inside the KH Director.
it is hopeless...

10521

[paulfars]

Same here. I used thick wall silicone airline and have also heated the reagent to 40c and given it a shake. The problem remains the same.

[Fishbones]

OK, so the 2mm ID silicone tube and heating the reagent does not solve the air bubbles forming. Are we looking at a design problem here? How do we solve this?


I’ve just ordered this...
https://www.amazon.co.uk/Meters-Teflon-Filament-Printer-Rostock/dp/B018EC80V6/ref=sr_1_7/260-5693994-5704758?ie=UTF8&qid=1521923271&sr=8-7&keywords=ptfe+teflon+tube

Lets hope Mortie31 has positive feedback soon then GHL can send out PTFE tubes to all.

[paulfars]

Does GHL have any solution to the bubble problem yet?

This has been a issue since the start of KHD.

It would be nice to have some updates so at least we know that it is still being looked into.

[pedromrg]

I think I found the right tube... but I need one more week of testing but haven't seen a bubble for 1week and a half.

Pedro

[Mortie31]

The Teflon tubing wasn’t suitable, too rigid, I have now gone for 7mm o.d. And 4mm I.d. Silicon tube and the bubbles are forming far less, and so far I’ve had no bad readings in the last 10 days. Is does seem to be the thicker wall that as previously suggested may reduce/ stop the bubbles

[paulfars]

I think I found the right tube... but I need one more week of testing but haven't seen a bubble for 1week and a half.

Pedro

Could you send me a link for the tube you are using?

[paulfars]

GHL Still silent. ???

[Gael]

GHL Still silent. ???

Matthias is at Reef-A-Palooza Orlando

(Last Activity on this forum: 24.03.2018 11:47)

[paulfars]

Well I hope he's having a really great time !!

Im sure he has a his laptop with him

[pedromrg]

Could you send me a link for the tube you are using?

Ok, I'm testing a tube that comes with industrials detergent dosing pumps(my company sells sells this so I grab a piece of tube to test)

https://www.rehau.com/download/1465474/materialmerkblatt-rau-pe-en.pdf

The only indication I see writen on the tube is "REHAU RAU-PE"

The tube is semi-rigid but fits well in the doser and KHD so... it works for me... checked today still no bubbles.

Pedro

[Fishbones]

Thanks or the info Pedro. Could you post a pic of the setup with this tube. Thanks.

[Fishbones]

GHL Still silent. ???

And in the meantime ... this is what my measurement graph looks like due to this bubble issue.

10589

[pedromrg]

Thanks or the info Pedro. Could you post a pic of the setup with this tube. Thanks.

Here yopu go:

http://i1220.photobucket.com/albums/dd454/pmrg/KHD1_zpsxdowkofb.jpg

http://i1220.photobucket.com/albums/dd454/pmrg/KHD2_zpstec4zv9s.jpg

[paulfars]

Still waiting for a reply from GHL.......

[paulfars]

Still waiting

[unixninja]

I had a problem with the forming bubbles in the dispenser on the reagent tube. I set the tube from ADA and it helped me get rid of the bubbles.

ADA Pressure Resistance Tube
It is used for the connection between CO2 Regulator and Check Valve.
This tube is also good for connecting the joint parts. Do NOT connect it directly to the glass products.

[paulfars]

I had a problem with the forming bubbles in the dispenser on the reagent tube. I set the tube from ADA and it helped me get rid of the bubbles.

ADA Pressure Resistance Tube
It is used for the connection between CO2 Regulator and Check Valve.
This tube is also good for connecting the joint parts. Do NOT connect it directly to the glass products.

Thanks , have ordered one . I hope it helps.

Well it looks like we have been left to figure this thing out our selves .

I see the support staff are active on the other sections of this forum but don't want to add any comments about this.

Nearly 4 months now and I still can't use KHD as it was fully intended .

Im sure after this long GHL have had lots of time to look into issue and come to a conclusion . How hard can it be for the designers to look at Reagent, a bit of tube and a doser.

As you may guess GHL I am not happy. I think we have been very patient about this problem.

Please Please respond.

[Fishbones]

Very disappointed in GHL!!!
It's obvious that as there aren't many people complaining or going public about this, GHL don't care. Just keep selling ...
I have emailed support@ghl-kl.de and will start posting on facebook and forums to see if we can get a solution for this, and alerting others to this problem.
Suggestions given here by Mathias did not solve anything. Also, buying every type of tube someone here suggests to test is not what I intend to do.
What we need is a tried and tested solution from GHL.

[MatthiasF]

Matthias will return from a business trip on Monday and reply then.

[paulfars]

Still waiting a reply !!

[Matthias]

After doing a lot of testing we came to these findings:

- no bubbles which have an SIGNIFICANT impact on the KH measurement, the value stays perfectly stable in a range of about +/- 0,1
-> the small amount of bubbles which exist can be ignored and have no impact

we did these tests with
- different tube materials, incl. the tubes which are part of the KHD shipment
- with several batches of the reagent, incl. the newest batch (light blue)

yes, we are aware, that there were some bottles among the first shipments which tended more to produce small bubbles in the reagent tube
this is either solved with warming + stirring as mentioned above in this thread or after using a new bottle of reagent

we sold now > 1000 KHD and the feedback is extremely positive, I personally spoke at several shows in the last weeks with many people who use the KHD, they ALL were excited about the precision and had no issues at all
they reported they have precise KH measurements and a stable KH value in their tank they never saw before

BUT of course we take the problems some customers have very serious, and try to find a solution for everyone

maybe there are othere reasons which affect the measurment, make sure we can rule out these "common" mistakes:
- reagent tube too long and/or not straight - see manual
- vent tube dipped in the waste water - must be above - see manual
- using reagent of the first batch which may intend to create bubbles - see above
- too few measurements per day / too small sample water amount for your purpose / precision - increase

let me reply to some previous comments:


How hard can it be for the designers to look at Reagent, a bit of tube and a doser.
Very. If you can't reproduce the problems.


I have emailed support@ghl-kl.de and will start posting on facebook and forums to see if we can get a solution for this, and alerting others to this problem.
We actually don't know what this is supposed to mean. Does this mean you want to give us some pressure over social media and forums in order to get us working and reacting as you want us to?
This is not how this works. We are not starting fights over these channels. We do our job, we don't waste our time and energy in useless debates. Please follow the forum rules in the future.

bottomline:
EVERYONE who has a problem with the KHD, no matter what problem, please contact the GHL support directly, GHL is happy to assist you.
Visit our support page for contacting us.

when we found something which is in interst for ALL KHD users we will open this thread again and publish our findings

[Matthias]

addition:

although we were not able to "produce" enough bubbles in our test environment we think the above observations about different tube materials are very interesting and helpful
thank you so much for sharing your helpful thoughts and tests

we will look into this further and decide if we follow this route