Fast linear actuator for a linear surge valve

[karimwassef]

I originally posted in kcress's thread, but I think I need to start a dedicated one

I'm considering a simple linear actuator for my surge release/plug.

There is a bulkhead at the bottom of my surge tank and I will make a drain plug that matches it. The linear actuator sits on top of the resevoir and actuates up and down to plug or unplug the drain. It's a 2"/sec and the total stroke is 2".

Here is the vendor and datasheet:
http://www.actuatorzone.com/actuato...2-33-2-inch-stroke-33-lbs-force-actuator.aspx
http://www.actuatorzone.com/images/pdf/High_Speed_Actuator_PA-15.pdf

<a href="http://s1062.beta.photobucket.com/user/karimwassef/library/" target="_blank"><img src="http://i1062.photobucket.com/albums/t496/karimwassef/PA15.jpg" border="0" alt="Photobucket"/></a>

There are 3 versions and they are preset. The rate / current draw for each is a function of load. At 30lbs, the 2" stroke would take under 1 second and consume about 9A at 12V for that event. The same for the reverse with switched polarity.

The actuator is connected with a PVC pipe to the plug.

<a href="http://s1062.beta.photobucket.com/user/karimwassef/library/" target="_blank"><img src="http://i1062.photobucket.com/albums/t496/karimwassef/surge2-1.jpg" border="0" alt="Photobucket"/></a>

I still don't have a clear concept of how to make the plug (or borrow from an existing plumbing part).

This won't allow for a 100% watertight plug, but should be good enough for my purposes. Concerns:

Pressure (30lbs of force enough for a 13" water level over the bulkhead?)
Seal (will 30lbs of force be sufficient to form the seal?)
Reliability (fatigue, wear from repetitive use of 3-5 up and down cycles a minute - continuously)
Housing options (salt spray, creep)
Misalignment over time
Better seal / plug options?
Seal / plug degradation over time (seal material?)
Power consumption and thermal wear.
Noise due to actuator
Noise due to resevoir water flow (vortex, bubbles) vs. actuated valve approach.
Potential use at larger pipe sizes (3"?) for larger surges

 

[karimwassef]

Here is the seal I am considering adapting

<a href="http://s1062.beta.photobucket.com/user/karimwassef/library/" target="_blank"><img src="http://i1062.photobucket.com/albums/t496/karimwassef/flush.jpg" border="0" alt="Photobucket"/></a>
American Standard Champion 4 Flush Valve Assembly

it comes with the added side benefit of an overflow pipe eliminating the dedicated pipe in my original design.

http://www.homedepot.com/webapp/wcs...H=REC-_-product-4-_-100033648-_-203359924-_-N

 

[karimwassef]

No one with experience using linear actuators?

 

[kcress]

You may find that flush valve to be a problem. I have NEVER been able to get them to close silently. The water rushing past them sucks them shut with a massive bang. You can alleviate that some by having that overflow reach clear air unhindered. Of course that results in a massive bubble storm. Normally those self shut after all the water is nearly gone so the flow is down to nothing.

 

[kcress]

You saw my response in "Strange One"? Any response can be in this thread.

 

[_shorty_]

The linear actuator idea is interesting ...

You may find that flush valve to be a problem. I have NEVER been able to get them to close silently. The water rushing past them sucks them shut with a massive bang. You can alleviate that some by having that overflow reach clear air unhindered. Of course that results in a massive bubble storm. Normally those self shut after all the water is nearly gone so the flow is down to nothing.

kcress - in response to the slamming shut - i understand in most applications, what you're saying - but what about if it's rigidly attached to stem of the actuator? I guess I'd have to see the actuator in action... if it fails in extended position - you probably face that same slapping shut issue with most stoppers...

might be able to use a softer foam that only stops most of the flow, and as water level and pressure increases it pushes down until an upper rubber stopper as mentioned makes a full seal.

Or, maybe actuating horizontally, somehow?

Off topic - You can find 120V - 1/2" gravity feed solinoids all day long for really cheap. I've been considering plumbing up several in parallel, using a float switch to actuate. I bought one to test and have an old float switch off a failed sump pump - but haven't started testing yet. I don't know how loud it is going to be when it 'CLICKS' open, though.

 

[karimwassef]

so you would use 5 x 1/2" solenoids to plump into a 2" pipe with a manifold?

which solenoids?
reef safe?
what would the cost be?
what would the power consumption be?

In terms of slamming shut, there should be 6" of water over the stopper but I'll have to test the actuator to tell. Given that I have 30lbs of force to work with, maybe I'll use a spring on the actuator shaft to keep the water from slamming the stopper down.

 

[_shorty_]

so you would use 5 x 1/2" solenoids to plump into a 2" pipe with a manifold?

which solenoids?
reef safe?
what would the cost be?
what would the power consumption be?

In terms of slamming shut, there should be 6" of water over the stopper but I'll have to test the actuator to tell. Given that I have 30lbs of force to work with, maybe I'll use a spring on the actuator shaft to keep the water from slamming the stopper down.

no idea on power consumption... but I don't assume very much. But yea - if I were going to do a 2" pipe - probably do like 6 for a 2" line. They are about $12 each. Less expensive and pretty instentanious compared to most valves I've seen for this purpose.

Here's a link:

http://www.ebay.com/itm/1-2-Gravity-Feed-Electric-Solenoid-Valve-DDB-CD-120VAC-/300584760678?pt=LH_DefaultDomain_0&hash=item45fc3f7566

Before I spend any more on it - and after I did a little testing - I was going to get some feedback from the forums. I belive they do have a stainless spring - so that might be an issue over time?

 

[Meshmez]

sorry if this is a stupid question, but why not set up a siphon type system with no valve?

It looks like you are planning on having this above your tank? and then pumping water into it? what if the pump fails but you keep dumping water?

I have seen surge systems that slowly fill the tub, and the drain has a "durso" looking "U" on the top of it with no vent. the tub fills slower than the full siphon, so it slowly fills until the water level reaches the top of the U and fills it, starting a siphon, which quickly dumps a certain amount of water until the siphon breaks, and then waits for the pump to refill and start over.

again sorry if i missed something, or if this is an unusable approach.

 

[_shorty_]

sorry if this is a stupid question, but why not set up a siphon type system with no valve?

It looks like you are planning on having this above your tank? and then pumping water into it? what if the pump fails but you keep dumping water?

I have seen surge systems that slowly fill the tub, and the drain has a "durso" looking "U" on the top of it with no vent. the tub fills slower than the full siphon, so it slowly fills until the water level reaches the top of the U and fills it, starting a siphon, which quickly dumps a certain amount of water until the siphon breaks, and then waits for the pump to refill and start over.

again sorry if i missed something, or if this is an unusable approach.

not a stupid question... I believe we're all talking about the same type of fill method - pumping into above DT 'box' - with safety overflows... The point in question for most surge box designs is HOW to deliver the water to the DT for that actual surge effect. Most DIY setups - like the U shape pipe/syphon (i think the carlson?) - and the toilet flush valves introduce a lot of air bubbles into the tank with your surge. Which in and of itself is not necessarily bad - but many people get tired of quickly due to asthetics and salt creap. The idea of say using a solinoid or linear actuator - is based on keeping air out of your lines - preventing those air bubbles. The linear actuator, or actuated valve, or solinoid valve are ways of potentially doing that.

 

[kcress]

Couple of answers.

Shorty, there is no way to use any kind of rigid "actuator" that will avoid the slam. The forces are so great that the float will distort if it has to. Even if it was made of steel at the last instant it would yank all the play out of the system and distort the structure holding up the actuator - to slam.

As for a bunch of valves to a manifold:

Unless they're ball valves or butterfly valves forget it. You wouldn't need 5 or 6 into a 2" pipe, you'd need 20 or 30. Is that realistic? No.

Unless you maybe did something like machined a structure that would allow one actuator to turn the 20 handles of cheap ball valves at the same time. Of course, is that easier than a 3 or 4" butterfly off epay?

If you can tolerate some bubbles and I like them and have zero issues with them coating the glass etc etc. you can use a Carlson in a novel way...

Set it up as usual but in the top of the loop put in a TEE. In the TEE you install a small solenoid valve. When you open that valve the siphon stops instantly. This allows you to have any size surges you want. Just vent the siphon at different times. This also kills the "Big Suck" at the natural end of a standard cycle. The only moving part is operating in air.

 

[_shorty_]

Nice! Thanks, bro. I'll play with that idea.

 

[karimwassef]

I'm going for a bubble free and quiet surge. There is no way to achieve this without an actuated valve. With a linear actuator, the unknown is the rate of acceleration when it closes and that's a question of damping vs. the force applied. Not trivial, but should be a workable problem.

It sounds like the fundamental idea of a linear actuator works. A cone plug would be one solution to the loud slam, but they're not cheap.

 

[kcress]

50 bucks.... Or do you want to try things for weeks?

 

[karimwassef]

I need 3 ... LOL

 

[kcress]

Ugh.

Alright lets try something else. The valve you're proposing is a non-balanced valve. What that means is that it is going to be much harder in one direction than the other. Another words, it's going to tend to slam. Slamming breaks things and makes noise. Look at the butterfly above. Notice half of it is going to twist towards the water and half is going to twist away. The half that twists towards the water to open is going to try to slam shut when closing. But! The side that twists away from the water to open is going to be fighting to get closed at the end. These two opposing forces do battle and prevent the valve from slamming shut.

Whatever you end up doing you want this kind of balanced process NOT a plug going into a hole. That's completely unbalanced and always going to slam.

The flush valve you showed above? That is as unbalanced as you can get and boy do they slam. Slamming could ultimately tear the bulkhead out of the bottom of your surge tank.

Did you understand my comment about the Weber barbecue?

 

[karimwassef]

Can't find a comment referencing A Weber barbecue...

If you mean to make the plug pivot on one side to reduce the force pulling it down, I can see that and the actuator can still work with a "flapper" type.

I see this as a force balancing problem too. The force of the water suction pulling the plug down as it begins to close is like a vacuum causing the slam. Why wouldn't an equal and opposite force that is only applies when the plug is in the zone where that force is applied be the solution? A stiff spring with an initiation position to balance this force should do it and the actuator has 30lbs of force to push it closed.

The vaccum force is not infinite. It just gets ~exponentially large as the distance is reduced. This is like magnets attracted to each other. Still controllable with enough opposing force. Maybe reverse polarity hard magnets mounted in a rigid frame would act as a near field cushion in the "crash zone"

 

[_shorty_]

I can see maybe getting the spring thing functional... but I don't know about eliminating the hammer completely.

If you could somehow actuate horizontally - for example - a disk that covers your opening, that slides off and then back over... But in practice, unless you could mount vertically above, and rig up some gearing to mechanically pull your disk horizontally it probably wouldn't be worth it.

If you were going to go through that trouble of mechanics - you could probably do the same thing more easily with a rotating actuator, where the design of the disk (that plugs your pipe opening) is 4+ times larger than your pipe opening - with the hole in it being in one 'quadrant' of that disk. Where, when rotating one direction, your pipe opening is covered and when rotated back, the hole is oreinted over your pipe releasing flow. If you have multiple pipes (which it sounds like you do) - you could place them closer together and actuate all of them with the same disk and actuator (which would probably help balancing of mechanics anyway). If it worked, it'd be a much cheaper over-all solution.

I guess.. what's the problem with larger actuated valves (other than price) ? ... is it speed?

 

[kcress]

Can't find a comment referencing A Weber barbecue...

If you mean to make the plug pivot on one side to reduce the force pulling it down, I can see that and the actuator can still work with a "flapper" type.

I see this as a force balancing problem too. The force of the water suction pulling the plug down as it begins to close is like a vacuum causing the slam. Why wouldn't an equal and opposite force that is only applies when the plug is in the zone where that force is applied be the solution? A stiff spring with an initiation position to balance this force should do it and the actuator has 30lbs of force to push it closed.

The vaccum force is not infinite. It just gets ~exponentially large as the distance is reduced. This is like magnets attracted to each other. Still controllable with enough opposing force. Maybe reverse polarity hard magnets mounted in a rigid frame would act as a near field cushion in the "crash zone"

Barbecue: Let me get this straight. You went over and cross posted in my build thread and then didn't bother reading the answers??!! :debi:


As for thinking you can balance the "exponentially" increasing force with some exterior force mechanism.. No you can't. You mention a "spring". Springs are linear devices not exponential, so from the git-go that's not a matching force. On top of all that the forces will be dynamic and varying and unmatchable.

Shorty has it. Use a rotating valve, (Weber), not a hatch-type valve. Take two disks. Bolt an axle through the dead-center of them. Then make about 6 equidistant radial slots thru the bolted together pair. Now when you turn one of them the slots will cease to line up and flow will be blocked. All you'll need to do is rotate the top disk from above the water with some little gearmotor about 60 degrees to completely open or close the valve. Nothing to slam.

Shorty: Large actuated valves slam unless you do special things that prevent it but those things would be very bad in a marine environment. Unless you mean ball valves and they are difficult to drive since they get hard to turn in larger sizes. They aren't really for this type service. They're very tight so they don't leak when shut while having 100psi across them. If they were really made for our measly 1psi application and even allowed to drip when shut they'd be ideal because they're a balanced type valve and would turn with little effort.

 

[Gorgok]

I may be missing something obvious, but how do you plan to keep it free of bubbles if the line past the valve is not flooded?