Originally Posted by kb3lms
Since I've worked in analytical chemistry labs, I have experience with peristaltic pumps.
From Wikipedia: A peristaltic pump is a type of positive displacement pump used for pumping a variety of fluids. The fluid is contained within a flexible tube fitted inside a circular pump casing (though linear peristaltic pumps have been made). A rotor with a number of "rollers", "shoes", "wipers", or "lobes" attached to the external circumference of the rotor compresses the flexible tube. As the rotor turns, the part of tube under compression is pinched closed (or "occludes") thus forcing the fluid to be pumped to move through the tube. Additionally, as the tube opens to its natural state after the passing of the cam ("restitution" or "resilience") fluid flow is induced to the pump. This process is called peristalsis and is used in many biological systems such as the gastrointestinal tract. Typically, there will be two or more rollers, or wipers, occluding the tube, trapping between them a body of fluid. The body of fluid is then transported, at ambient pressure, toward the pump outlet. Peristaltic pumps may run continuously, or they may be indexed through partial revolutions to deliver smaller amounts of fluid.
They have a nice animation the Wikipedia page in case you are a visual person... http://en.wikipedia.org/wiki/Peristaltic_pump
I think peristaltic pumps work better for this type of application, especially for flows in the 1 ml or so per minute range compared to syringe pumps. The stepper motor in a syringe pump is not running continuously, so it's constantly squirting out little bits of fluid, like a discrete automotive fuel injection system (not a CIS system) or like a ink jet printer. Little drops, not continously, over time. Also, a peristaltic pump is not limited by the size of the syringe. (Although you can replace the syringe in a syringe pump to get volumes larger than what 1 syringe can hold.)
A peristaltic pump has a motor that runs in a much smoother fashion, and it is constantly pushing liquid out. You control the flow in a peristaltic pump by varying the motor speed and the diameter of the pump tubing. You can get a pretty wide range of flow from a peristatlic pump depending on the setup, from 0.001 ml/minute to hundreds of mls per minute. It just depends on the model of pump, the speed, and the tubing size.
Here's some photos of the set-ups I had been working on a couple years ago:
First Photo -
This set-up for a single channel pump. The stirplate has a built-in heater, and there is a temp controller (reading 41C mounted onto a ring stand that attaches to the back of the hot plate. Also attached to the ring stand, is a clamp that hold a stainless tube that I have a thinner teflon tube inserted through and then the bottom end goes into the solution in the beaker.
That teflon tube is connected to a silicone peristaltic pump tube by merely inserting the teflon tube into the silicone pump tube. The other end of the silicone pump tube goes into the graduated cylinder which is holding the silver nitrate solution.
The 3rd thing in the beaker is a kitchen temp meter (the one with the right-angel bend at the top) and you can see it reads 40C on its display.
I use a large, X-shaped, teflon-coated stirbar to get as much turbulance and mixing as posible.
Second photo -
Here's a close-up of the beaker and pump. You can see the end of the teflon tube that goes through the stainless tube. The stainless tube is just to hold the thin trflon tube. (I think the teflon is 24 or 28 ga. I have some that goes down to 36 ga. but I never tried it.) Since the teflon tube that thin is not stiff at all, it needed something for support. I had the stainless tube sitting around, so I used that. Otherwise, I would have taken some glass tubing and used it. I preferred the stainless as I didn't have to worry about breaking it!
You can see the teflon coming down from the end of the stainless tube (off frame to the top) and into the polyvinylchloride peristaltic pump tube, which is a larger diameter. The little teflon tube is just butt-connected to the larger pump tubing merely by pressing it into the pump tube. If the difference in size between the two tubes is too great to do this, an intermediate size of pump tube can be used to go between the bigger and smaller tubes. No fittings are required using this technique.
You can see the little lever on the pump platten that is used to apply pressure to the tube to firmly bring it into contact with the pump rollers. This pump has 8 rollers, which will give a smoother flow than a pump that uses say 2 rollers.
Below - The tip of the dual solution nozzle. The tubing is 24 or 28 ga teflon tubing. One of the tubes is inserted into a long stainless tube for rigidity, the second teflon tube is strung on the outside of the stainless tube. They are held in place with short sections of PVC tubing, a smaller one to keep the teflon tube that's inside the stainless from pulling up into the stainless tube, and a larger one around the stainless tube and the second teflon tube.
Note that the teflon tubes have very small opening. I have them mounted so that they are as close to each other as I can get them. They are also open perpendicular to the flow of the liquid past them to get the liquid to shear off the tip of the nozzles so the solutions get dispirsed into the make as quickly as possible.
Below - Peristaltic pump set-up with two pump channels bring used. One for silver nitrate, the other for halide. You can see there pump nozzle in the beaker and behind it is the temp probe for the stirring hotplate. The two channels are loaded into the peristaltic pump, the close one has the platten for the pump tube tightened down so the liquid would flow, and back one has the platten loose to the pump is not flowing in that channel.
Note the hemostat is being used to pinch the back pump tube shut so it does not siphon liquid out of the beaker! To put the back pump into operation, all that needs to be done is flip the plastic lever on the platten down and to the left to tighten the platten against the pump tube and release the hemostat.
Below - The full setup in the darkroom. Red LED lights with rubylith over them just because... Laptop with rubylith of the screen - spreadsheet with all calcs and times for the make pulled up so it can bee seen and consulted during the run (and to play music - I was in there for hours...) Clipboard to make notes and record timing/addition times. Stirplate with temp controller, peristaltic pump, reagents prepped in plastic cups, darkroom timer running in 24 hr clock mode so I could easily see and record times.
Very nice Kirk. Similar to what I am now using except for the brand names on the equipment. That tubing pair being held together is pretty much what we did at EK and what I was describing above.
PE - Well I came up with the nozzle config based on our discussions, so I'm glad it is close to what you were telling me.
I forgot to mention that with the pump running at about a 1 ml/minute, it will squirt a pretty steady stream of liquid out the tip of the nozzle and across the lab bench due to the small inside diameter of the teflon tubing! Doing that is actually a great way to see how constant the pump pressure is.
Also, I bought a lot of tubing (both teflon/ptfe and stainless) from smallparts.com. I see they are part of Amazon now...
Good to see you here again. Hope things are well with you and your family.
Yes, that squirt is quite "evil" if it gets away from you. I demo my pump on the DVD with a small tip and show how beaded drops become a rather hefty stream with just a tiny tip and the added backpressure. I wish I could put some video up on APUG, but there is no facility for it, and I don't feel like "donating" the footage to youtube.
I am working on double runs and they are not easy. I have one that runs for over 3 hours, but so far it is too messy for the average person. It would challenge a big lab I think.
Brilliant stuff; Kirk's setup is top notch.
Originally Posted by holmburgers
PE - I'm always here, just lurking mostly these days... But when I see something I can contribute to, I do.
Great stuff Kirk.
Excellent Kirk! Both you and Chris have given me some ideas. Somewhere in the basement I have a roll of Teflon tubing, maybe I can butt splice it like you did, Kirk. Hmm.
Here are a few pictures of my set up.
This is an overall view. The controls box is on the right. It has the power supply and controls for the mixer and the temp controller for the crock pot. I've left space in it to add other things if I decide to do that. I am thinking about adding a temp unit and a meter of some kind for vAg.
Here's a closer picture set up for measuring vAg. This is roughly copied from a diagram in an old thesis from RIT.
Top to bottom, the EXPO marker is the reference electrode stuck into a funnel filled with KNO3 solution. This sits on top of the salt bridge that is made from a vinyl tube connected to a pen body. The end of the pen body is plugged with a thick felt and partially filled with KNO3 solution mixed with agar. The other tube with the red lead attached is the Silver Bromide ISE. The leads go to an Extech multimeter. vAg measurement with this gear seems to work very well. The blue container at the back of the pot is for storing the kettle end of the salt bridge. The top end is covered with saran wrap when not in use. Electrodes have their own storage containers.
At left is the temp probe going to the PID temperature controller for the pot. The mixer is at right. It is a hardware store paint mixer connected to a 500 rpm geared motor. The mixer controller in the control box allows me to control the mixer speed from about 50 rpm to about 1500 rpm in 10 steps.
The red object at the bottom of the pot is a plastic lid to keep the kettle from being in contact with the pot bottom which sometimes gets pretty hot.
There is also a kitchen type thermometer like Kirk shows to monitor the kettle temperature. When connected, the syringe pump sits to the left on a brick. The tubes are clipped to the side of the kettle and enter the solution right next to the mixer.
Jason, nice setup! You got it all setup well, and I have a feeling you had a lot more cash left in your pocket than I did... Congratulations!
At present, I am working on a method to show flows to the emulsion making APUG community. Many thanks and Kudos to Hexavalent if it works! Time will tell.
Thanks Ian. PICS coming if possible.