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06-12-2024, 16:10
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#16
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Registered User
Join Date: Oct 2007
Location: Hollywood, Fl.
Boat: FP Athena 38' Poerava
Posts: 4,028
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Re: What is Spectra SC-1, really?
Just wanted to jump in and say that PG-50 should be exclusively used for storage. I now look at SC-1 and sodium metabisulfite as an emergency storage agent. It's far easier to store to be sure, but there are issues with any powdered storage solution. If you unfortunately have to fly home in an emergency or such certainly store your system with what you have. But PG-50 is by far the more preferred even at the equator. The anti-freezing capabilities are not what we are after though it's good in the cold climes. But it is more for the protection of the entire system. When I first started building watermakers membranes were far, far more expensive than they are now. The thought back then for all watermaker companies was to protect that expensive membrane. You will find on older watermakers that they are loaded up with multiple pre-filters because of that thought. Normally SC-1 is good to store your "Membranes" up to six months when you must flush it out and re-pickle the system again. PG-50 will store your system for two years. I've unpickled systems stored over five years this way and they work as well as when they shut down. But the main advantage to PG-50 is the protective qualities when it comes to the rest of your system. Most watermakers have far more expensive parts than the membrane/s. A SS feed pump alone can be the cost of three or four new membranes. If you have ever felt PG it's like soapy dish detergent. This protects far better SS corrosion, all the soft parts, O-rings, shuttles, seals, etc. Storing the membrane is just a nice side benefit these days.
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07-12-2024, 00:49
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#17
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Registered User
Join Date: Dec 2024
Posts: 8
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Re: What is Spectra SC-1, really?
Hello Tellie,
By "PG-50", do you mean PG diluted at 50% in freshwater ?
By the way, I have opend another thread about the maximum reasonable recovery rate that a 2540 can withstand. I'm building a watermaker and would really appreciate your thoughts on this topic.
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07-12-2024, 01:03
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#18
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Senior Cruiser

Join Date: Sep 2014
Location: puget sound washington
Boat: 1968 Islander bahama 24 hull 182, 1963 columbia 29 defender. hull # 60
Posts: 13,095
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Re: What is Spectra SC-1, really?
Quote:
Originally Posted by Fredrikx
Hello Tellie,
By "PG-50", do you mean PG diluted at 50% in freshwater ?
By the way, I have opend another thread about the maximum reasonable recovery rate that a 2540 can withstand. I'm building a watermaker and would really appreciate your thoughts on this topic.
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No pg -50 means it protects to -50 °F as antifreeze.
Use full strength for longevity of pickling.
__________________
Non illigitamus carborundum
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07-12-2024, 01:16
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#19
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Registered User
Join Date: Dec 2024
Posts: 8
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Re: What is Spectra SC-1, really?
Thank you newhaul,
Regarding the curve of freezing point and concentration, this means that PG-50 is mix of 55% PG with 45% water.
http://novatrix.free.fr/images/preservation/Image30.jpg
In Europe at least, it's cheaper to buy 99% pure PG and do the mix with water.
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07-12-2024, 03:46
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#20
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Senior Cruiser

Join Date: Mar 2003
Location: Thunder Bay, Ontario - 48-29N x 89-20W
Boat: (Cruiser Living On Dirt)
Posts: 51,805
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Re: What is Spectra SC-1, really?
Quote:
Originally Posted by newhaul
No pg -50 means it protects to -50 °F as antifreeze.
Use full strength for longevity of pickling.
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I think we should let Tellie specify what he means, by PG-50.
However, I think that “PG-50" might refer to a solution of 50% propylene glycol [C3H8O2] by Volume, plus 50% De-ionized Water, which gives freeze protection down to about -28°F to -30°F.
Freeze protection to about -50°F would require about a 57%PG solution.
__________________
Gord May
"If you didn't have the time or money to do it right in the first place, when will you get the time/$ to fix it?"
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07-12-2024, 05:01
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#21
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Registered User
Join Date: Oct 2007
Location: Hollywood, Fl.
Boat: FP Athena 38' Poerava
Posts: 4,028
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Re: What is Spectra SC-1, really?
Quote:
Originally Posted by GordMay
I think we should let Tellie specify what he means, by PG-50.
However, I think that “PG-50" might refer to a solution of 50% propylene glycol [C3H8O2] by Volume, plus 50% De-ionized Water, which gives freeze protection down to about -28°F to -30°F.
Freeze protection to about -50°F would require about a 57%PG solution.
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Gord, as usual, is amazingly correct.
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07-12-2024, 06:07
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#22
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Senior Cruiser

Join Date: Mar 2003
Location: Thunder Bay, Ontario - 48-29N x 89-20W
Boat: (Cruiser Living On Dirt)
Posts: 51,805
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Re: What is Spectra SC-1, really?
FWIW: In order to provide adequate freeze protection, the propylene glycol and water solution must maintain a freezing point of at least 5°F (3°C) below the lowest expected ambient temperature.
There are two basic protection points, for anti-freeze solutions: Freeze Protection, and Burst Protection.
The freeze point is the temperature where ice crystals begin to form in the fluid, and the fluid becomes slushy, but it does not expand.
The burst point is the temperature where the fluid will freeze solid, expand, and break pipes, or damage membranes, pumps, coils, fittings, or valves in the system.
For freeze protection, the system requires a glycol concentration that is sufficient to prevent the formation of ice crystals, at the lowest temperature the system will experience.
Freeze protection is required, when pumping, or where there is inadequate space for expansion of an ice/slush mixture, or any applications where no ice crystals can be permitted to form.
For burst protection, the glycol concentration needs to be high enough to prevent bursting or other damage to equipment, but not necessarily high enough to maintain the fluid in a pumpable state.
Burst protection is sufficient if the hydronic system will remain dormant, or inactive, when the temperature drops below freezing, and there is adequate space to accommodate the expansion of an ice/slush mixture. You may not be able to pump this slush, but your system will not burst.
__________________
Gord May
"If you didn't have the time or money to do it right in the first place, when will you get the time/$ to fix it?"
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07-12-2024, 07:07
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#23
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Senior Cruiser

Join Date: Sep 2014
Location: puget sound washington
Boat: 1968 Islander bahama 24 hull 182, 1963 columbia 29 defender. hull # 60
Posts: 13,095
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Re: What is Spectra SC-1, really?
Quote:
Originally Posted by GordMay
I think we should let Tellie specify what he means, by PG-50.
However, I think that “PG-50" might refer to a solution of 50% propylene glycol [C3H8O2] by Volume, plus 50% De-ionized Water, which gives freeze protection down to about -28°F to -30°F.
Freeze protection to about -50°F would require about a 57%PG solution.
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The protection to -50°F is literally in the description on the bottle when used without diluting
__________________
Non illigitamus carborundum
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08-12-2024, 16:42
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#24
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Registered User
Join Date: Oct 2010
Location: Corona Del Mar
Boat: Trimarans!
Posts: 302
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Re: What is Spectra SC-1, really?
Yeah, so PG is cat’s meow when it comes to storing water makers. If anyone imports a 55gal drum to Tahiti I’ll buy 2-3g, and I know people who’ll make it 10-15gal.
In the absence of that, a good locally sourced powder alternative to SC-1 would be most welcome.
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09-12-2024, 06:48
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#25
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Registered User
Join Date: Oct 2023
Posts: 292
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Re: What is Spectra SC-1, really?
Quote:
Originally Posted by earthbm
In the absence of that, a good locally sourced powder alternative to SC-1 would be most welcome.
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In the second post you were given a formula:
"From my understanding, including the SDS for SC-1 it is King Lee Technologies MEMSTOR repackaged.
The SC-1 SDS lists boric acid, and the MEMSTOR SDS lists three "trade secret" acids/salts. The largest one, at >80%, has the same health characteristics as boric acid, so that is a likely candidate. The next one, at <10% has the same health characteristics as citric acid, so another likely candidate. The last trade secret acid, at <5% has the same health characteristics as metaboric acid.
Based solely on circumstantial evidence, I would estimate that SC-1 is:
boric acid 85-90%
citric acid 5-10%
metaboric acid 1-5%"
Either you can source the above (and I'd be very surprised if you couldn't at least find boric acid), or go ask people in Tahiti what they are using in their watermakers.
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