Help with KHD readings

[Aaronsreef]

Hi all,
I'm struggling to get the khd the read constantly or correctly

I've measured and double checked the lengths I've calibrated the dosing heads with digital scales I've calibrated the probe at 25°
All of the above seems fine and is correct I believe
I don't have any air in any of the dosing lines the pH probe is new in August and I've even brought a cheap one from amazon just to check and they both seem fine
I'm not sure what else to do
Any help would be appreciated


13095

[Vinny]

What settings did you enter into the dosing pumps?
Speed? Flow rate?

What number did you enter into the KHD water sample volume?
Are you in front of the device during a measurement? Do the pumps spin normally during each measurement?

The KHD probe cannot be replaced with an ordinary pH probe, they are not the same.
What fluids are you calibrating the probe with?

[Aaronsreef]

Settings for dosing pumps are

Pump1 water sample speed 3, 38ml/m
Pump 2 reagent speed 0, 4.1ml/m
Pump 3 waste speed 3, 34.2ml/m

Sample line is 135.9cm, 11.9 for dosing head tube, 16 for connecting the doser to khd, and 108 for tube from sump to doser. No water filter is attached and the sample tube volume is 17ml

I have sat in front and pumps all spin normally

I am using the GHL probe just tried a different one to see if it'd make any difference.
Am using GHL calibration fluids 4 and 7

[Vinny]

Those numbers look OK.

Any reason why you are not using the water sample filter?
Without a filter installed, one cannot rule out the possibility of sediment getting into the sample which is therefore skewing the end results.

The widely fluctuating numbers is a general indicator of air bubbles or foreign matter getting caught in the water sample.

[Aaronsreef]

The filters I have don't fit onto 4mm ID hose, they are GHL ones but can't get the line over the barb.

Is there a way to clean out the measuring housing inside the KHD , the bit the pH probe sits in ?
I've done flushes but maybe you know of a way of a more deep clean,
You may also know how to fit the pre filters on 4mm hose

[Vinny]

Stock GHL tubing will fit over the GHL filter. It will fit very snug, but it will fit.
Dipping the end of the tube in hot water will give it enough flex to connect the filter.

You can press "Flush measurement cell" a few times to clean out the tubes and cell. Don't forget to vent the internal reagent tube before you run a new test after those flushes.

[Aaronsreef]

Should the filter be fitted to the line from the sump to the doser or fitted on the line from doser to khd?

[Vinny]

As per the filter manual, from sump to doser.

[Aaronsreef]

OK I'll fit one now and flush the cell a few times

[Aaronsreef]

Im getting air bubbles from the filter into the khd line now

[Aaronsreef]

My pH probe seems to be a bit slow in recognising the change, I keep getting error titration takes to long, I've just watched the pH reading and it goes up while the reagent is being added and then after a few seconds starts to decrease

[Vinny]

How old is the probe?
If it's showing slower reaction than what you remember seeing before, it's probably time to re-calibrate.

[Aaronsreef]

I brought the unit second hand, and am told the probe was new in August.
I've calibrated the probe several times at the correct temperature but am getting titration takes too long error.
The pH reading goes up before it starts to come down
I've checked the calibration of the dosing heads and have tried a new bottle of reagent but still no luck.
Can I use my p4 probe to test if that works ?

[Vinny]

It is possible the probe has reached end of life and will need replacing. Being that this was a second hand unit, there's no telling how long it sat in the box before being put to use. This also plays a role in the longevity of the KHD probe.

No, a traditional pH probe cannot be used because they are not the same. KHD probe is modified for horizontal use and made specifically for the KHD.

[Aaronsreef]

Will order a new probe, unfortunately its going to take about 10 days to arrive

[Aaronsreef]

Unfortunately my probe has been returned the GHL due to some issue with the contents of other items in the box

Can I use my P4 probe and stand the KHD up so the probe would be in vertically?

I could so with eliminating the probe being at fault so I can work on resolving the issues

[Vinny]

The KHD must lay horizontally with the probe also laying in the same way. The pH probe from the P4 is NOT the same kind used by the KHD and would therefore not be a suitable alternative.

[Aaronsreef]

OK, just trying to find a way of testing without a new probe as I don't know how long it'll now take.

Should the measurement cell hold water in once the test has been completed? Until the next test is due ? I haven't used it for a awhile and have taken the probe out and the cell is dry leaving the probe to of been dry for days also

[Vinny]

The probe should be stored in water if it won't be used for more than 2 days. Otherwise it has a chance of drying out completely if it sits inside an inactive KHD measurement cell.