This Chloride PPM Business 1

[bmoorthy]

Chloride PPM restrictions in hydro test water(for example API 6D for Valves) are very common now a days:

Is the PPM restriction, the PPM of Chloride (alone with out the effect of added metal) or does it refer to full salt weight.

1) Specification: Maximum 30 Ml of chloride PPM in hydro test water.

If in 1000 Liters of Distilled and deionized water (Which has 1 million parts by volume and 1 million parts by weightt), i take out 31 grams of water and discard and add (mix) 31 grams of Salt (NaCl).

Does the above water meet the Hydro test water specification or does it not meet the requirement by 1 ppm?

2) Is there a Chloride PPM detecting portable machine, like a PMI machine or PH meter, that will give out the reading if you insert the probe into the water. (The PPm that matters)

3) If in 1000 Liter of waer i take out, 10 grams of water and add 10 grams of NaCl, then what is the PPm of Chloride in the water.

3) instead of 10 grams of NaCl, i add 10 gm KCl, what will the PPM of Chloride be

4) Instead of 10 grams of NaCl, i add, 10 grams of CaoCl2, what will the PPM of chloride be

 

[EdStainless]

There are a bunch of ways to measure Cl ions in solution. There are ion specific probes, they look and work just like pH probes. There are also chemical titration methods that are fairly easy.

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Plymouth Tube

 

[metengr]

If in 1000 Liters of Distilled and deionized water (Which has 1 million parts by volume and 1 million parts by weightt), i take out 31 grams of water and discard and add (mix) 31 grams of Salt (NaCl).

The molar weight of NaCl is 58 grams/mole

The weight of Na is 23 grams/mole
The weight of chlorine is 35 grams/mole

Assuming a 100% dissociation of salt in water

31 grams of salt * 1 mole NaCl/58 grams * 35 grams/1 mole of Cl

18.71 grams of Cl in solution


18.71 grams/1 X10⁶ grams of solution = much less than 1 ppm

actually 1.875 x 10^-5 ppm

3) If in 1000 Liter of waer i take out, 10 grams of water and add 10 grams of NaCl, then what is the PPm of Chloride in the water.

10 g NaCl * 1/58 * 35/1 = 6.03 grams of Cl

6.03 g/1x10⁶ grams = 6.03 x 10^-6 ppm

3) instead of 10 grams of NaCl, i add 10 gm KCl, what will the PPM of Chloride be

assume 100% dissociation in solution

10 grams KCl * 1/74 grams/mole KCl * 35/1 mole of Cl = 4.73 grams of Cl

4.73 grams/1 x 10⁶ grams = 4.73 x 10^-6 ppm

4) Instead of 10 grams of NaCl, i add, 10 grams of CaoCl2, what will the PPM of chloride be

10 grams of CaOCl₂

Formula weight per mole = 126 grams/mole of CaOCl₂

assume 100% dissociation in solution
10 grams CaOCL₂ * 1 mole/126 grams * 2 moles of Cl/1 mole of CaOCl₂ * 35 grams/mole of Cl = 5.55 grams of Cl


5.55 g/1x10⁶g = 5.55 x 10^-6 ppm

 

[bmoorthy]

Thanks metengr (Materials) for the calculation

18.71 grams in 1000 liters: is this not 18.71 PPM (Parts per million)

 

[metengr]

bmoorthy;
Yes, sorry about the confusing nomenclature above. If you dissolved 18.71 grams in 1,000 (or 1 Liter by volume) grams of DI water instead of 1,000,000 grams of water

18.71/1,000 = 0.01871

in parts per million

0.01871 * 1 x10⁶ = 18,710 ppm

or if you dissolve in 10,000 grams of water

18.71/10,000 = 0.001871 * 1 x10⁶ = 1871 ppm


or 18.71/100,000 = 0.0001871 * 1x10⁶ = 187.1 ppm

and as a self check

18.71/1,000,000 x 1,000,000 = 18.71 PPM

 

[mshimko]

I think it's common to express limits in terms of chloride, even though chlorides are often not the only ionic species.

Personally, I think the specs should place limits on conductivity, which will obviously measure all ionic species.

 

[moltenmetal]

mshimko: why exactly? The concern is with chloride due to the risk of SCC in the piping afterward, is it not?

 

[EngAbdelkader]

Correct me if I am wrong guys! but if I remember well the chloride is a major issue if we speak about stainless steel corrosion, isn't it?

mshimko, concerning the conductivity issue:
well there have been a couple of years now, but when I was carrying some experiment of SCC on austenitic stainless steel (AISI 316 Ti actually) for my master thesis, I used to measure the conductivity of my solution before and after the tests and it didn't help me figure out a major relation between conductivity and SCC of my probes but this was mainly to see the evolution of the conductivity of the solution and it's relation with the corrosion state of the probe (the tests were carried out until fracture actually. so called "SSRT" for slow strain rate tests) the problem is that the solution I was using was at a fixed NaCl concentration (30 g/l) so it's a bit different with the issue here and since I start working in the oil industry this issue escaped from my mind! hahaha this post just reminded me some of that.

good luck!

 

[EdStainless]

Yes, chlorides are the species of concern in SS corrosion, both pitting and SCC.
You see requirements for test water, such as for air underwater leak testing, that set limits of 4 micromhos and 1 ppm Cl. A 1 ppm solution will far exceed 4 umhos. Conductivity is easier to measure and it is a more sensitive requirement. It may cause you to treat water to remove non-harmful ions, but will keep you out of Cl trouble.

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Plymouth Tube

 

[bmoorthy]

1) Is the unit of conductivity MHOS?
2) is it the resistance that is measured or is it the conductivity that is mmeasured?
3) is 4 Micro MHOS maximum limit for conductivity?
4) Is there a standard that sets this limits for Air Under Water testing for SS/DSS/SDSS tubes?
6) Should one implement these limits on Inconel and incoloy and 6 Mo items (I am to understand that thesea are less prone to Cl attack)


7) Is it 4 Microomhos OR 1 PPM Cl

or is it 4 micromhos and 1 ppm Cl.

This is because, statements after that 9in the previsous reply from EdStainless) indicates that if a solution exhibits 4 micromhos then chlosride content limits are met.