Schematics of a high pressure water switch

[Asymptotic]

Just curious about these sizes. At one lab that I worked at, the last RO element filterd down to 2 micrometers.

Do you mean 2 nanometers? From what I've been reading, the final carbon block filter feeding RO membrane cartridges in these home RO systems is often rated 0.5 or 1 micron.

I've been trying to understand RO filter membrane specifications, but with mixed results. I had been expecting in part something similar to how other filters are rated, a combination of nominal and absolute micron sizes (for example, 50 micron nominal/20 micron absolute), or a filtering effectiveness and pore size (95% capture at 1 micron), but these types of values aren't provided in any of the manufacturer specs sheets I've read so far.

For instance, the spec sheet for the Pentair TLS series gives them a flow rate in liters/day at a 98% rejection rate for NaCl at both 500 ppm and 1000 ppm salt concentrations, at 65 PSI inlet pressure, at 25°C. Specs for Dow Filmtec elements are much the same, although theirs is for 250 ppm softened water, and include graphs showing the effects of pressure (at constant temperature) and temperature (at constant pressure) on permeate flow rate. Neither mentions pore size.

From what I've gathered, such elements come in two basic types - CTA (cellulose acetate) and TFC (polyamide-based thin film composite). CTA is more tolerant to oxidizers such as chlorine, but more prone to organic fouling, have a smaller pH range (4 to 8), and a salt rejection of only 93%. TFC elements operate over a pH range of 4 to 11 at a 98% rejection rate, but even small concentrations of chlorine (0.1 ppm max) cause premature failure.

Everything I've seen so far regarding particle size through an RO element has been on the "hand wavy" side, with claims ranging from 0.004 micron to 0.0001 micron (although 0.001` micron appears to be cited more than the others). This ought to be small enough to block disease viruses, but none of the elements I've investigated are certified to guarantee 100% elimination.

Nothing so far indicates whether some percentage of the smaller viruses can pass through an intact membrane, although mention was made that downstream UV disinfection is required to allow for small tears and general degradation of the RO film.

The questions move on to "how effective is UV in reducing infectivity?", and "what UV flux is required?".

Take the Norwalk norovirus. It is 27 nm in diameter, so it ought not pass through an intact 1 nm RO membrane. Provided that it does, will a 30 millijoule/cm² rated UV disinfector inactivate it?

Near as I can determine, it's a definite maybe. From https://www.waterpathogens.org/book/norovirus-and-other-caliciviruses

A few studies have investigated the effect of ultraviolet irradiation on noroviruses but, since no cultivation method is available, only MNV data are available so far, which showed no evidence of resistance higher than other (cultivable) enteric viruses (Lee and Ko, 2013). It is noteworthy that PCR data may overestimate the persistence of noroviruses after inactivation by UV (Rönnqvist, 2014); norovirus genome reduced only 0.62 log10 at 300mJ/cm2 by low-pressure mercury-vapor UV lamp, whereas MNV infectivity reduced 5 log10 at 90mJ/cm2.​

I'd be interested in learning a virologist's take on the matter were one to weigh in ...

 

[dlgoff]

Do you mean 2 nanometers? From what I've been reading, the final carbon block filter feeding RO membrane cartridges in these home RO systems is often rated 0.5 or 1 micron.

No. It was 2 millimeter = 2 microns. I guess demand rate specs. limits just how small you can go?

 

[dlgoff]

(although 0.001` micron appears to be cited more than the others)

I had no idea. That's really small. They make 'em better than they use too.

 

[Tom.G]

It was 2 millimeter = 2 microns.

Due to typos or whatever, there seems a bit of confusion about what a "micron" is.
Both Google and Wikipedia claim 1micron= 1×10^-6 meter, or 1μm, or 1000ηm

 

[dlgoff]

Due to typos or whatever, there seems a bit of confusion about what a "micron" is.
Both Google and Wikipedia claim 1micron= 1×10^-6 meter, or 1μm, or 1000ηm

... the last RO element filterd down to 2 micrometers.

Yes. A typo. I meant 2 micrometers.

 

[chirhone]

Ok. I was able to let the technician remove the high-pressure switch since the UV light can't be turned on 0.5 sec before turning on the faucet (thanks to Asymptotic and others for this). Here is the external and interior diagram.

After opening the screws. We saw it was a combined Tee (?) and pressure switch (as one of you rightly guessed). Using a continuity meter, the technician determined the wire was continuous at default. When the center (at top) was pressed, it became disconnected.

 

[chirhone]

Ok. I was able to let the technician remove the high-pressure switch since the UV light can't be turned on 0.5 sec before turning on the faucet (thanks to Asymptotic and others for this). Here is the external and interior diagram.

View attachment 256415View attachment 256416

After opening the screws. We saw it was a combined Tee (?) and pressure switch (as one of you rightly guessed). Using a continuity meter, the technician determined the wire was continuous at default. When the center (at top) was pressed, it became disconnected.

This is internal of the switch component in the above picture.

It has a switch inside, when you press it, the terminals get disconnected in continuity. It is like an on and off switch. Is this the same in ordinary high pressure switch (see below)? What controls the sensitivity is the spring. When you turn the hex allen key clockwise. It makes it harder to press the button. Can anyone identify what kind of switch is the above (rectangular thing that makes a clicking sound when you press it (which disconnects the terminals continuity)?

I'm asking this because early this week when I turned the hex key fully counterclockwise. It worked half a day but afterward it no longer worked, meaning there was not enough pressure to press the switch and turn the switch off. It was on the whole week (and I didn't bother to fix it again because I wanted the UV lamp to stay on after reading Asymtotic comments of UV lamp taking 3 minutes to be optimal).

In ordinary high pressure switch, only the springs controls the sensitivity and there is no switch like a light switch?

 

[Tom.G]

Can anyone identify what kind of switch is the above (rectangular thing that makes a clicking sound when you press it (which disconnects the terminals continuity)?

The technical name is "miniature snap-action switch."
Many people call it a "Microswitch", which is the name of the company that is best known for making them. There are also several other makers. Depending on exact configuration and brand, prices can range from about 1 USD to over 800 USD for one piece.

https://www.google.com/search?&q=microswitch

Cheers,
Tom

 

[Asymptotic]

In ordinary high pressure switch, only the springs controls the sensitivity and there is no switch like a light switch?

Do you have in mind a micro-miniature version of a toggle switch like those often used to turn lighting on and off? No, probably not.

Electromechanical switches come in all shapes and sizes with a wide selection of actuation methods - everything from a small snap-action switch like this example to massive ones used to isolate power transformer - but all of them boil down to a device that connects two conductors together (switch closed) and separates them (switch open).

In your case, water pressure creates force on the 'wet' side of the diaphragm, making it distend by some distance (more pressure >> more force >> a longer travel distance). The 'dry' side of the diaphragm presses against a cylindrical piece molded into a lever arm, and that lever arm comes into contact with the movable element of the snap-action switch.

The hex screw/spring adjustment puts force on the switch side of the lever arm. It is in opposition to force transferred from the diaphragm (the force created by water pressure). More spring force >> more opposition to water pressure-created force >> higher pressure switching set point.

There are hundreds of varieties of snap-action switches, but most of them share common traits. Study this table outlining of one type of pin plunger actuated switch manufactured by Microswitch, and explore what they mean by operating and release force, pre-travel, over-travel, and differential travel.

From https://sensing.honeywell.com/switches/general-purpose-basic-switches/sm-series

Once the diaphragm extends enough to make the lever arm touch the snap-action switch plunger (if indeed it is plunger actuated) it has to do so with enough force to overcome the switch's operating force, and must extend beyond the 'pre-travel' distance before the switch contact opens (or closes, as the case may be). It's up to the manufacturer of the device using the switch to prevent actuation past the over-travel distance, beyond which damage will occur.

 

[chirhone]

Do you have in mind a micro-miniature version of a toggle switch like those often used to turn lighting on and off? No, probably not.

Electromechanical switches come in all shapes and sizes with a wide selection of actuation methods - everything from a small snap-action switch like this example to massive ones used to isolate power transformer - but all of them boil down to a device that connects two conductors together (switch closed) and separates them (switch open).

In your case, water pressure creates force on the 'wet' side of the diaphragm, making it distend by some distance (more pressure >> more force >> a longer travel distance). The 'dry' side of the diaphragm presses against a cylindrical piece molded into a lever arm, and that lever arm comes into contact with the movable element of the snap-action switch.

The hex screw/spring adjustment puts force on the switch side of the lever arm. It is in opposition to force transferred from the diaphragm (the force created by water pressure). More spring force >> more opposition to water pressure-created force >> higher pressure switching set point.

There are hundreds of varieties of snap-action switches, but most of them share common traits. Study this table outlining of one type of pin plunger actuated switch manufactured by Microswitch, and explore what they mean by operating and release force, pre-travel, over-travel, and differential travel.

From https://sensing.honeywell.com/switches/general-purpose-basic-switches/sm-series

View attachment 256484

Once the diaphragm extends enough to make the lever arm touch the snap-action switch plunger (if indeed it is plunger actuated) it has to do so with enough force to overcome the switch's operating force, and must extend beyond the 'pre-travel' distance before the switch contact opens (or closes, as the case may be). It's up to the manufacturer of the device using the switch to prevent actuation past the over-travel distance, beyond which damage will occur.

View attachment 256483

This is the connector I used in place of the high pressure switch.

The UV is always on and my cousin has the same model and the lamp is still on after one year. They also let it tested with microorganisms and none (I may ask them if they test for viruses).

I want to ask something and I don't want to repeat all of the details if I started a new thread, so just want to ask this quickly.

I tried washing my eyeglasses in the reverse osmosis water purifier faucet thinking all the chlorine was filtered. I read chlorine can remove the coating in the eyeglasses.

And I noticed for the first time that I have difficulty removing the soap in my fingers using the faucet in the reverse osmosis water purifier whereas using normal water direct from the supply. It's easy to remove. Do you know what minerals can cause the difficulty of removing soap in fingers?

I noticed the same effect when staying in certain hotels.

Sorry for this bit of off-topic but I just can't start a new thread and add all the details of my reverse osmosis water purifier which you were already familiar in our days of discussions.

But to make it not so off-topic. The high pressure switch sensitivity was difficult to adjust (while still there last month). It may be because of some pressure changes in the overall system as one of you explained earlier. So if there is a more sophisticated high-pressure water switch for use in the system. Please share in mind and the electrical connections (mentioned this to make it more on topic). This is for stock knowledge although I won't add the high pressure switch for now. Thanks.

 

[dlgoff]

And I noticed for the first time that I have difficulty removing the soap in my fingers using the faucet in the reverse osmosis water purifier whereas using normal water direct from the supply. It's easy to remove. Do you know what minerals can cause the difficulty of removing soap in fingers?

bold by me

I think it's not a mineral that is causing "difficulty" but the lack of minerals. My father worked in the water business and was asked to help with getting an automatic photo film developing machine to work properly. To make a long story short, the problem; the water was so soft that there was no scurbing action to remove the films emulsion. He changed the soft rinse water to unsoftened tap water; problem solved.

 

[Dullard]

Where reverse osmosis is used at large scale, 'remineralization' is commonly practiced.