High pressure cut off switch?

[Tweegs]

Anyone use a high pressure shut off switch (say 250 PSI) on their R.O.?

Would like to shut the system down before I start popping connectors, membrane housings or having a pressure relief valve hosing down the R.O. room.

(You know how it gets in the shack…you get busy quenching a burning pan, putting out the pant leg that caught fire, cussing out a persnickety vacuum pump…often all at the same time…it’s not hard to imagine forgetting to check a pressure gauge)

Trouble is it’s hard to find a switch able to handle that amount of pressure, at a reasonable price anyway.
Gotta be a more cost effective way to handle an over pressure situation automatically.

Was thinking of putting a pressure regulator downstream of the needle valve. Tee off between the valve and regulator to a low pressure switch. Should the pressure between the valve and regulator exceed X psi, open the contacts and shut her down.

Not sure if that would work, hydrodynamics isn’t a particularly strong suit (though I can admit to extensive knowledge of what happens when you slip on a rock whilst river fishing).

What are you guys doing?
Got a better idea?

[ennismaple]

Trust me - if you blow a hose or a compression fitting breaks and the hose flies off the membrane the RO shuts off pretty fast!

I'm not the one to ask how to do a high pressure shutoff (I'm an RO user with enough maintenance knowledge to be dangerous) but 250 psi sounds low to shut it off. Ours runs at 400 psi all the time.

[maple flats]

Mine is only rated for 300 max. I understand if the clamps and hoses were different, it could be higher. My housings are SS but the clamps holding the top on is in 2 halves, I think there are other clamps able to contain 400 or maybe even 500 PSI.

[BreezyHill]

Mine is setup with a small copper line going to an adjustable dual limit switch. I can set a low pressure and a high pressure setting. This protects the pumps from running dry and high pressure issue.

To protect against a hose failure you want a low pressure sensor. HIgh is for a membrane plugging, incorrect plumbing, or an over speed of the pump issue.

This type of switching makes my unit so I can thru it in auto and the unit will shut down if a parameter is reached. There are also alarm lights that let you know what happened and they work all the time. There also is an alarm that sounds in auto mode but should be on a switch to run in none auto for when you are in the room and doing other stuff. Real PITA to have the unit shut down due to a bubble in the line when you change tanks or if the membrane is starting to plug up and you could have walked over and just changed to the permeate tank to flush or opened a raw sap tank to flush them clean. But No...I have to restart and work the pressure up again while flushing it and then change back. That's a waste of 10 minutes or so.

The more valves and alarms and lights the easier it is to run and the more you can do will the unit is watching itself.

Ben

[Tweegs]

Breezy,

That’s my intent, to let the thing watch itself.

The wife and I run this little operation on our own. Since she is retired and I am not, she often fires up the evaporator in the morning and runs until I get home from work. She then gets a break while I run solo.

That in mind, the system needs to be easy enough for her to use and require little operator input.
My current plan is to run a pair of XLE-4040’s in series with a straight shot from the holding tank to the head tank…no recirculation. With any amount of luck at all, I’m hoping we can get from 2% to at least 6% in one pass and keep up with the evaporator (roughly 40 GPH) using a 275 GPH @225psi Procon pump backed by a 1 HP motor.

System start up needs to be less than complicated.
Momentary switch bypasses a contactor and provides power to the supply pump.
When the low pressure cut off is satisfied those contacts close providing power to the high pressure pump and latches the contactor through the high pressure cut off contacts.
In this way either a low pressure or high pressure scenario de-energizes the contactor and shuts the system down. It also prevents the high pressure pump from starting up dry and prevents both pumps from starting simultaneously, which minimizes inrush current. At least that’s the hypothesis.

11814
(Sorry for the small schematic, can't figure out how to make it larger, just click on it :lol:)

So, for start-up, she’d need to open the needle valve, turn on the master switch, hold the momentary switch until both pumps fire up, then adjust the needle valve to operating pressure. I think that’s about as easy as it gets.

It wouldn’t be much trouble to modify the circuit to use a single high/low pressure switch, the problem is finding a switch to purchase and finding a place in the system where I should monitor the high pressure side.

[BreezyHill]

Tweegs, Sounds great but if I could make a suggestion or two:

I would set the high pressure just prior to your brane inlet with a tee to a smaller line to the pressure switch(s). This should give the most consistent reading.

The other suggestion would be to have valves setup so you can batch circulate the concentrate to get your sugar level higher yet, prior to boiling. Since the unit can monitor itself then the lady of the sugar house can fire it up when a batch tank is full. With a low level float in the tank the RO can be switched to another tank for batching, using electric valves to change tanks.

The money you save, by going to 12% from 6% sugar, will pay for electric valves by fuel saved and time spent boiling.

Let the RO be the workhorse it is capable of being by batching rather than single pass. Send the concentrate to the evaporator/head tank as needed and keep on batching until it is done and another batch can be processed.

[Tweegs]

Thanks Breezy,

Sorry for the delayed reply, rough week at work.

Found a high pressure switch from Square D, runs about $60. It trips at 250 ps,i which is a little lower than I wanted, but I can work with it. (Cheapest I could find that would handle 275 ran over a grand)

Planned on using a 270 GPH procon for the high pressure pump. That should put 4.5 GPM across the membranes. Concentrate flow, then, should be way faster than my evaporator (on a good day, 40 GPH).

I’ll take your advice and wire in a recirc valve. Besides pushing the concentrate higher, it will likely save a few headaches in managing the head tank level.

[Flat Lander Sugaring]

at 300 psi the tops will blow off and bend all the 1/2 stainless steel output piping and tweek the 3/4 a little, not saying I have experiance at this and by the way my HP pump didnt shut off if I hadnt been standing there it would have emptied my holding tank.
This coming year I'm going to have a HP shut off switch hooked though my VFD

[Tweegs]

That’s exactly what I’m trying to prevent.

This is the switch I will be using:
http://www.zoro.com/square-d-pressure-switch-dpst-130175psi-14fnps-9013ghg5j61/i/G2248757/

I have a slight hiccup in the design though.

If I read this thing correctly, it has a range of 32-250 psi. It also has a differential of 24-45 psi.
So if it is set to trip at 250 psi, that means that the contacts won’t close until it sees a minimum of 205 psi.

With the needle valve full open I don’t think that the system will develop 205 psi.

If this is indeed the case, I’m going to have to rethink my strategy for a simple start-up. Holding a momentary switch and adjusting a needle valve at the same time won’t make the wife happy.

[maple flats]

It may be like a well pump switch in design, to start up at zero, then shut off at 250, then when it gets down to 205 it restarts. That is not how my high pressure switch on my RO works. That starts at zero and if the max. set pressure is hit, it shuts off. Then I need to restart it and address the pressure before it gets to my set max. (300 PSI). The pressure switch is not an automatic reset, it sounds like what you found IS automatic reset. In RO use I don't think an auto reset is what you really want. If the max. is hit, you need to adjust the restriction valve to lower the pressure, not just cycle on and off then on again.
If nothing else, starting under a 205 PSI load will be hard on your electric bill. You'd get a start up surge in electric with every new start and they may not be very far apart. I never paid attention to my pressure rate of drop when I shut it down, but my guess is that it would be a rather short time frame, this would not be like a well pump where you have an air filled bladder and the water in the tank must be used enough to lower the pressure enough to start the pump again. You would have no bumper and the flow would be constant, the time would be very short.

[BreezyHill]

The way my system is set up is there is a switch to select manual or automatic run for the RO.
Manual the light will signal a fault and the unit will still run.

Automatic a green light lights and the system is on auto pilot. If there is a fault the two contactors for the pumps are deenergized and the unit shuts down.
An alarm can sound if it is turned on.

I will be adding an alarm to the unit to sound in manual mode if there is a fault for next season.

When the unit is adjusted and good to run then I just go on auto pilot and go about my tasks.

On manual I am adjusting the valves or when changing from one tank to another in case there is an air bubble in the lines and pressure drops for a second.

On mine the high pressure and low pressure are in one sensor/switch and both are adjustable. High is 500 psi and low is 100 as I recall.


Red and green lights are easiest to explain. Red is a fault and green she is good to go on her own.

KISS...Keep it Simple Silly.

You do all the hard work behind the design and the front of the panel needs to be simple. Directions on operation in a book on the unit with a light for easy reading.

Do not have her or even you needing to hold a button other than to start a motor. Hard to do two things at one time and in a sugar house there is always things that need to be done.

11823 Sorry best pic I could find and I have to lay low for a bit...Lyme got in my knee and tendons...sucks like hell. Doc wants me in a knee immobilizer for 6 wks...cant drive truck and tractors with one of them on! Not happening...12 pills a day is bad enough. She had no sense of humor...but she did let me have my pants back. LOL

[maple flats]

On mine, when I'm not going to be checking it every time I fire the arch, I set the pressure a little lower, like at about 260 rather than 275. If I'm recirculating I set it down at about 225-230. Then if the pressure climbs and hits 300 it shuts off.

[Tweegs]

The wife likes thing simple, so do I for that matter.

The electrical circuit is designed to shut the system down if either an over or under pressure situation occurs (de-energizes the contactor which removes power from the system). In this way, cycling of pump power via the pressure switch isn’t a concern.

The fly in the ointment is if the contacts of the pressure switch are closed initially (at 0 psi), I’ve got a problem. My intent was to allow the system to build low pressure through the supply pump before energizing the high pressure pump. This would prevent the high pressure pump from firing up dry and reduce the inrush current by having only one motor start at a time. It can still be done, just going to require a little more thought.


Sucks about the knee thing Breezy.
I call my Doc “The Vampire”. He wants at least a gallon of blood every time I go in. But at least I’m mobile, if not light headed, when I leave. Then there’s that whole conversation about the pants, followed by a quick snap of a glove…shudder to think. At least you got yours back. Me and the vamp have an understanding. I don’t get mine back until I submit, and that usually involves a couple of laps around the clinic and at least once around the parking lot, complete with staffers, restraints and a left tackle named Mona, the blood draw-er. It’s a silly game, but one he feels necessary to play.

Anyway, lay low and heal up. I can help keep you entertained bouncing questions back and forth in the meantime.

[BreezyHill]

Hahaha, My pumps run off of a relay and quite often the low pressure will run for a bit when changing filters, first firing up, flushing lines after an off season, etc.

You cant beat simplicity. I hate it when the wife or the boys call when they cant get the tanker truck to prime. They have all done it and know how. Problem is there are so many valves that you can get confused if you second guess yourself. * valves that need to be changed at one time or another. At one time they all had colored tape and went thru the rainbow. First time we needed to use it I was one the road in another truck and the oldest, wife and youngest and their girlfriends couldn't get it figured out; so they texted me and then after a five page text I get "Got it, valve to the suction line was closed not open."

I am headed down to get you a pic of the front & side of mine. Simple mess of valves and light.

1182411825

Every collection tank has a supply and return valve Evap tank has a valve on the concentrate line. Every valve has name in perm ink. Black vavle is to the drain. Large lower three lines are supply lines. Adding a supply line for a wash tank to mike things easier next season.

[maple flats]

Breezy, your attachments come up as "invalid attachment"

[BreezyHill]

11826

11827

Well lets try this. They show on the preview section?

PC gremlins I guess. lol

[maple flats]

That's better, now they show up.

[bowhunter]

Not sure exactly what you're trying to do, but I think you're making it way too complicated. Here are some pressure switches ($45) that should work for your application (http://www.dwyer-inst.com/Product/Pressure/SinglePressure/Switches/SeriesA1PS-A1VS#ordering). Here's what I would do. Have a separate on/off or start switch/stop switch for each pump. Put a low pressure switch (set for 30-40 psig) on the filter outlet. Put a high pressure switch on the ProCon pump outlet. Mount it close to the pump because that is the highest pressure in the system. Wire the high pressure pump motor with both pressure switches in the circuit in series. These switches have a normally open and normally closed set of contacts so you can use one to shut the pressure pump down on low suction pressure and one to shut it down on high discharge pressure. I haven't used these particular switches, but they're made by a good company. Each which has an adjustable range that you can set for whatever pressure you like within the range for the switch with just a thumb screw.

With this set up the pressure pump and the RO system are protected from high pressure and the pressure pump is protected from no suction pressure so you don't run it dry. You don't need any relays etc. The switches are capable of handling the full pump current. You just start the low pressure pump first then turn on the high pressure pump.

[Tweegs]

In essence, Bowhunter, that is exactly what I am doing, with one exception.

If the system can sense 30+ psi on the low pressure side at start up, then it can turn on the high pressure pump by itself through the contacts of the low pressure switch. This would eliminate the need for a high pressure pump on/off switch, which also eliminates the potential for a rookie mistake and a high dollar fix.

The problem was, as Maple Flats pointed out, that a standard low pressure switch (like the Square D) will have its contacts closed at 0 psi, I needed them open at 0 psi for the system to operate as I had intended.

I’ve taken a quick look at the switches you linked to and knee jerk says those are what I need for the low pressure side. I’m trying to dig a little deeper on the specs to be sure…Thanks for that!

For the high pressure switch, having the contacts closed at 0 psi is preferable.

But yes, both high and low pressure switches in series to latch the main power contactor. (See the schematic I attached in an earlier post).

[mellondome]

You don't want an autostart on the high pressure side. This could lead to membrane failure as you apply pressure to the membrane while there is air in it. it can also cause it to keep running or cycle on and off when you run out of sap or have restricted sap flow.

[Tweegs]

The high pressure switch arrived last night (/hattip Breezy) and the low pressure option Bowhunter linked to will work (A1PS-34).

Mellondome,
With the way the system is wired, it is not possible for the pumps to cycle on and off. Should either of the pressure switches trip, it requires manual intervention to restart the system.
If the system shuts down, one couldn’t help but to have a look-see as to why.

My wife does have a degree in Aerospace Engineering (yep, she really is a rocket scientist) so I wouldn’t expect to come home and find her repeatedly starting the R.O. Now coming home to find the snow melted within a 10 foot radius of the shack because she’s cussing a blue streak and an auxiliary pump is deployed to fill the head tank…well, that’s within the realm of possibilities. It’s not uncommon to find her patching up a piece of shoddy work on my part, neither.

I’m aware of hydraulic shock to the membranes, and since you brought it up, let me make sure I’ve got my head around this right.

XLE-4040’s are designed to work at 150 psi.
The supply pump (at least the one I’ve chosen) will run at 65 psi max.

If we assume that sap at 65 psi will make it past an idle high pressure pump and given that the high pressure tubing is ½” (the same size as the ports on the membrane housings), then the only significant source of restriction, and thus pressure on the system, comes from the needle valve.

If the needle valve is fully open at system start up, pressure on the membranes will be well below the operating level of the membranes resulting in little, if any, permeate flow. This means there will be air in the permeate cavity without the addition of the high pressure pump.

It is my understanding that the needle valve should be closed slowly, over a 20 minute period, until operating pressure is achieved. This prevents hydraulic shock to the membranes.

If all of the above is true, then why would an auto start on the high pressure pump be inadvisable?

This is how I understand things anyway, please correct any mistakes I’ve made.

[BreezyHill]

As I recall you were looking at a procon or this style pump. I think you are going to have an issue getting past the pump on low pressure. I have limited experience with these but the one I say apart was a small nonmetal rotor on a SS shaft. Not sure you well you will get sap buy this pump with out it spinning or causing the motor to spin.

On my unit the supply pump fires to purge the system of air and not cavitate the piston pump.

I will email you a copy of what dow sent me on the xle. Very wide range of working pressure. If I recall correctly, 100 psi was a normal pressure all the way to 500psi.

I ran at 450 last season when I got back late and tanks were full of sap and it was going to run all night long. Youngest fired the RO at 2:30 after school and I got back around 5. He was keeping up with the flow but that was all at 200 psi. in 15 minutes we were at 450 and more than doubled the permeate out flow.

Friend has a DIY RO with 2 xles and a procon single pump and loves it and can do what I can with a 5 hp pump and a 3/4 hp supply pump. He wants to increase his pump flow to maximize the branes.

My experience is that the unit trips off for a reason. To just restart automatically could create an issue. I would love to install a delay on make timer for our unit...$14 for the timer; but some times it takes 2 minutes to get the air out of the system and others it takes 5-6. I guess I could set the timer to the max of 8 minutes and just let it go and manually start it earlier.

One could have a series of valves with bypass electric valves to have an automatic pressure ramp. 4 steps with 4 delay on make timers to close a bypass valve and jump the pressure up in 20-30 psi steps. Pricey at first but it could pay for it self over time with a labor savings.

Ben

[Tweegs]

I ordered a procon pump yesterday (105E240F31BA170). That’s a 240 GPH @ 275 psi SS pump. Found it on E-bay for $99. Old stock but new in the box. Couldn’t pass it up. I’m going to put a 1 HP motor behind it, supply pump will be ¾ HP, both wired 220V.

I’ve got a spreadsheet going of what I bought from where and how much. I’ll post that once everything is up and running. Target is to come in around $1,500 for the whole shootin’ match.

I’m in no hurry right now, still waiting to get some concrete work done in the shack. Having trouble getting folks to give a call back, I guess they aren’t hungry enough yet and don’t want to take a “little” job, that or they’re overbooked. Regardless, it gives me time to ask questions and shop around a bit, better chance to stay within budget.