One for the Chemists - water softening solution.

[awemawson]

I've been rejuvenating the automatic water softening / de-calcification system on my Karcher MPDS steam cleaner.

It's probably worth pointing out that this is an ex-military 'Multi-Purpose-Decontamination-System' designed to clean vehicles and personnel after battlefield nuclear weapons had been used. Not much technical information about. However this bit of the design is relatively simple. A small tank holds a reservoir of dosing liquid that is dispensed via a solenoid valve into the 'suck' orifice of a venturi thence on into the machines pipe work. Solenoid valve is worked by a timing board pulsing it every minute or so. Built into the tank are a pair of electrodes used (presumably by conductivity) to warn of an empty tank.

So far so good - the electronics of the timer have been sorted, the tank repaired but what fluid to use? Obviously it needs to shift limescale, so something like citric acid or phosphoric acid would fit the bill. Saturated solutions of citric acid are insufficiently conductive for the sensing but 40% phosphoric acid works ok.

However what is it supposed to use? I have a Nato stock number for the correct stuff but no details.

It seems that the MPDS evolved from the HDS 1000 DE and it's manual stated Karcher RM110 fluid FOR WHICH THERE IS AN MSDS SHEET 

The MSDS sheet says it contains  hydrochloric acid 1-3%  and sodium hydroxide 5-8% with a pH of 7.0-7.5

Now as far as I remember my school chemistry here we have an acid and a base being mixed producing a salt plus water with a pretty much neutral pH

so what is the resultant chemical ????

(No photographs as the forum has problems at the moment with photos!)

[philf]

Andrew,

You are spot on with salt + water.

HCl + NaOH = NaCl + H2O

But I think because the concentration of NaOH is stronger you'll end up with a mix of NaOH + NaCl. If that's the case why bother with the HCl in the first place?

It's 50 years since I did chemistry so I may be missing something.

I wanted to be a chemistry teacher until we started doing organic chemistry and I totally lost interest.

Phil.

[eskoilola]

The result is table salt.

[awemawson]

But again back to school chemistry - table salt NaCl isn't going to do much to shift calcium deposits - or am I missing something here 

[millwright]

Dendritic Dairy Salt was we used in the water softener for the steam boiler feed water at work,  Two 10,000lb an hour heavy fuel oil fired Babcock boilers 40 od yrs old and lovely and clean inside and corrosion free when opened up for the annual inspection.

John

[awemawson]

Now that's interesting

But google just tells me it's ordinary table salt in a different crystal form - those dendrites ! But makes no mention of water softening applications 

I'm aware that salt is used in the Permuit water softening process , but that is just to pluck the calcium ions off the active resin during the recharge cycle and replace them with sodium ions - I use to order it by the ton for my Launderettes, but the salt per se didn't do the softening it recharged the resin.

[millwright]

Yes Andrew You are right it re charged the resin, had to go and have a read up on the Permutit site. was thinking back and its 36 yrs ago since the boilers were cut up for scrap. but the permutit softened certainly worked well.

John

[AdeV]

Dishwashers use plain salt to soften water - as far as I know, also by ion-exchange, but AFAIK there's no resin or other component in the softening sytem - certainly nothing consumable?

[awemawson]

Ade,

Dishwashers have a small Permutit system built in, with an active resin that the salt recharges

[RussellT]

Like others I've forgotten most of the chemistry I've ever learnt, but I think so far we're all missing something.  If the HCl and NaOH were mixed in exact ratios they wouldn't make it like that - salt would be much cheaper.

I suspect there is something else going on relating to how this effects the other ions in tap water.  IIRC scale is normally Calcium Carbonate and I think there is something happening that is preventing the scale from coming out of solution.

Russell

[awemawson]

The manual that I have for this beast specifies Karcher part number 2.780-003.0 which is a 5 litre bottle of the 'Calcium Inhibitor'

Google finds this as a product (see .pdf attached) but I cant find a Material Data Safety Sheet for it.

Google also translates this into a Nato Stock Number of  6850-12-175-4344 but again I can't find any specific details of what it is.

From the .pdf it seems to be a brownish purple colour 

Anyone got contacts that can turn NSN numbers into physical reality ?

[PekkaNF]

You do have interesting stuff.

I have been wondering how these water softening stuff works. Typical to me I found that zeolite () does not work on boilers:

http://hardsoftwater.com/zeolite-process-for-water-softening/
he softening water by this process is used for laundry process and cannot be used for boiler purpose. Because this water softening system contains NaHCO3 in the water; when this water is heated, it produces CO2 which is corrosive for boilerplates.

So, because I am noob - I google:
http://www.nationwideboiler.com/boiler-blog/the-water-softener-what-why-and-how.html
The Chemical Process – Ion Exchange
The Cleaning Process – Regeneration

So, I know that this might be usefull and very similar that has been discussed before. One more serach..
http://www.waterprofessionals.com/learning-center/softening/
Getting closer isn't it?

And one link further - bottom of the page:
http://www.waterprofessionals.com/learning-center/ion-exchange/

Do we have a winner? Or we are not in Kansas anymore?

Regeneration

The "reactivation" process is called regeneration and is carried out using a strong acid for the cation (as a source of hydronium ions) and liquid caustic (sodium hydroxide) as a source of hydroxyl ions for the anion. Resin is regenerated on site using hydrochloric or sulfuric acid and sodium hydroxide (caustic) to regenerate the cation and anion respectively. Controls cause the resin to backwash and then draw a set amount of regenerant chemical for a specified period of time and at a specified flowrate, followed by a slow and fast rinse. In the case of mixed bed resin, a controlled backwash causes the resin to separate and two manifolds function to direct acid to the cation and caustic to the anion.

So, How is the plumbing and is there a holding vessel that softens the water + pluming to regenerate it?

Pekka

[awemawson]

No, the feed water is only 'treated' by dosing with this mystery liquid.

Cold water passes through a venturi that draws the liquid into the stream (as long as the release valve is opened by the electronic timer) and then travels on into the coils of the diesel powered burner, emerging at a controlled temperature which can exceed 100 deg C. It has a 'dry steam' facility whereby the water flow is halved and steam at 140-150 deg C emerges ready to take your skin off 

[awemawson]

Link to my original post on this device with pictures:

https://madmodder.net/index.php/topic,11079.0.html

[RotarySMP]

My understanding (which is not very robust) of an Ion exchanger, is that it will have two chambers. In the first, the cathion exchanger the HCi is added, so the disassociated H+ ions replace the Ca+ ions which then fall out. In the second chamber, the anion exchanger, the NaOH is added, with the disassociated Hydroxide ions binding with the carbonates.   

Of course it could be completely different.
Mark

[awemawson]

But Mark this unit has nothing like that - just the mystery liquid injected into the water stream.


I just remembered that the entire water system in our holiday cottages has a ' Combimate' softening system where all the water passes though a chamber containing spheres of 'Combiphos' which gradually dissolve and have to be replaced - looking at my bottle of spare spheres lead me to the manufacturers web site:

http://www.combimate.co.uk/what-is-combiphos.html

So here is another total loss (ie cannot be regenerated) water softening system (*) that is perhaps in some way similar to the Karcher one 


(* strictly speaking it's NOT softening the water but preventing the calcium being deposited )

[bertie_bassett]

 we have a total loss calgon dosing system at one of our treatment works which might be similar?

the 'calgon' comes in 25kg bags in a granular form and is dissolved in a tank then dosed directly into the drinking water to soften it and help keep the filters clean.

not sure what the chemical composition is but it cant be anything too fancy as its going in the drinking water

[awemawson]

Ho ho Bertie - send me a sack 

I found this interesting paper on the Southern Water web site:

[bertie_bassett]

ill see what i can do ;) i had asumed it was a salt based system but will have to get hold of the msds to check

[charadam]

Andrew,

Happy New Year!

Try a search as National Stock No, rather than NATO and you get this:

https://www.nsncenter.com/NSN/6850-12-175-4344

It used to be my life's bane trying to equate across the pond.

[awemawson]

Well amazingly some RM110 Karcher water softener fluid has turned up on eBay. This is the stuff recommended for the MPDS precursor the  HDS 1000 DE

I shall order some and try it for conductivity


https://www.ebay.co.uk/itm/KARCHER-Water-Softener-RM-110-For-HDS-Hot-Pressure-Washer-6295625-6-295-625-0/192429550659?hash=item2ccdb1ec43:g:CYQAAOSwLF1X2Se4

[PekkaNF]

That's interesting...it says no phosphates...and the stuff I keep on bumping on this total loss system is hexametaphosphate. Like here:
https://www.plumbingsupply.com/scale-inhibitor.html


And  where it leads me:

pH control

Another vital parameter in water treatment is controlling the pH of the water. Due to their buffer (pH regulating) capacity, orthophosphates and purified phosphoric acid can keep the pH level of the water as constant as possible.
Corrosion inhibition

Phosphates are used to reduce corrosion in water mains. This may be either anodic corrosion or cathodic corrosion.

Limescale inhibition — softening agents

Hard water causes the build-up of limescale deposits in pipes, leading to a lower water flow rate and therefore higher pumping and cleaning costs.
Polyphosphates can trap calcium and magnesium. Calcium is the source of limescale formation and can dissolve the compounds formed, which prevents deposits from building up. Depending on the pH of the water, preference will be given to either SHMP (sodium hexametaphosphate) or STPP (sodium tripolyphosphate).

http://www.prayon.com/en/our-activities/products/industrial-applications/water-treatment.php

But the karcher stuff is phosphate free...There may be different chemical systems, I could ask my friend. He used to work with power plants ans he is now in a company that makes water treatment systems for ships. Scale problems with boilers should be pretty analogous to this hot water washer heater - I think.

So, is it possple that karcher pump or boiler materials don't like phosphates? That leaves two more options: Polyelectrolytes and chelatants.
http://www.chemtreat.com/solutions/scale-deposition/

Could it be one of these?


Pekka

[awemawson]

Yes Pekka, the phosphate free bit was the first thing that struck me.

I've no doubt this stuff will work in the sense that if introduced into the water it will prevent calcium deposits. What I don't know is if it's electrical conductivity will be sufficient to pass enough current between the sensor electrodes that detect an empty tank (no current flow between electrodes). The electronic valve timer module is inhibited if an empty tank is detected.

A quick test will soon show though 

These inhibitors don't remove existing calcium deposits, so I will probably set it up to recirculate a phosphoric acid solution by letting it suck it's feed water from a (plastic) bucket, and having removed the 0.6 mm nozzle from the lance let it pump back into the bucket.

[naffsharpe (Nathan)]

Andrew, have you thought of using " Bore Saver" from Geoquip in Ipswich ? We've used it for years for cleaning borehole pumps of scale. These pumps have been either landfill or domestic sites. Mike Deeds who owns Geoquip will only sell kit that works.
Nathan.

[awemawson]

I'll go do a bit of Googling 

Thanks for the link - meanwhile I've been advised that the RM 110 is 'dispatched, so I wait with bated breath

[awemawson]

So now the photo issue on the forum is solved I'm uploading a few images of what I've been up to:

Firstly the de-calcifying tank and it's odd sensor electrode set up.

The tank had a broken outlet spigot that I repaired by turning one up from plastic and super gluing it in place. Right sat the bottom of the tank are two electrodes embedded in the plastic of the tank and looking possibly to be carbon, but they are pretty well un-get-at-able 

The lid of the tank has a long plastic column pointing downwards with a spring on the bottom that shorts the electrodes (Shorted electrodes means 'tank has contents' to the electronics) This spring really confused me, as I could see no way the electrodes could be used for sensing - something MUST be missing. But no, it turns out that the spring is there for initial delivery tests to inhibit the flashing 'low fluid' light - there is a moulded set of German text on the lid that Google Translate tell me is 'remove spring on initial filling' 

So the previous discussion 'up thread' about conductive liquids may now make more sense to people ?

Well this morning the Postman brought the bottle of RM-110 de-calcifying fluid specified for the earlier version of this steam cleaner - will it's conductivity be sufficient ......... in simple term YES 

I temporarily wired the control electronics to 12v to avoid having to run the engine indoors - proved that the warning light flashed when the tank was empty and had no spring shorting the electrodes. Repeated the exercise with the lid and spring which stopped the flashing light, then removed the lid and spring (making the light flash) and poured in a tiny amount of the fluid - just enough to fill the well round the electrodes, and guess what - the flashing light was extinguished and the control valve was activated about every minute or so. All as should be.

Not surprisingly there is electrolysis going on between the sensing electrodes with bubbles (of probably hydrogen and oxygen ???) rising to the surface and indeed this may explain why one electrode is very much shorter than the other. I suppose long term it is feasible to drill out the electrodes and re-glue new ones in, and if I get to that stage their composition should become obvious

[awemawson]

While the MPDS was in the workshop I fixed castors to it's frame so more easily to be able to move it about - oddly in the front lower frame are pre-drilled holes for standard castors, but there was no provision at all  at the rear. Pipe clamps round the chassis frame proved up to the task with slight modification to the hole spacing of the castors.

I had had the pipe clamps in stock for best part of a year, as they were bought to fix  redundant fire hose reels to the framework for feed water and pressure hose. The rolling up of stiff pressure pipe at the end of a cleaning session had always been a chore as it fights back all the way !

So again - whilst in the workshop fix those reels

It proved relatively easy. The feed water which is only at water main pressure could run though the original reel rotary joint and hence be permanently fixed to the machine. However the  high pressure hose had to have quick disconnect fittings to be done / undone each session, as the high pressure and temperature would easily  spell it's doom