please evaluate system idea 1

[flyte]

We apply adhesive to our product from pressure pots. Currently, when the pressure pot is nearly empty, prduction is stopped so more adhesive can be pumped into the pressure pot.

My proposed system would connect a pump to the glue pot. The pots are pressurized to about 60psi. The pump would supply glue at about 90psi. A float would shut off a valve in the supply line to the pump. The pump would then deadhead and shut-off. A relief valve would allow exess pressure to escape from the pressure pot.

Do you think this system will work?

 

[TISM]

Sounds OK in principle but things to watch for in practice include:
fouling of the float by the glue in the pot,
increased glue flowrate during pumping due to higher backpressure (90 cf 60) across the discharge nozzle
control wiring access (wrt sealing against pressure)

Good Luck!

 

[ChasBean1]

I don't like floats & glue. Try a bladder-type expansion tank with a pressure switch that operates a peristaltic feed pump...

 

[BobPE]

ChasBean1 makes a good point with the float...I have done a similar project like this flyte for an insulation company that was putting aluminum foil onto compressed insulation boards. As I recall, the glue was shear sensitive...this had a lot to do with the pump selection and not using recirculation...The design also had heat control on the piping system to maintain glue temp and density. It had a purge system for down time. It was a few years ago, but it is still working to my knowledge...

BobPE

 

[pjsbeau]

I agree, sensing glue level in the pressurized pot is the major problem. I'd mount the pot on a load cell or weigh scale. Very clean -- nothing gets fouled by the glue.


Here's a trick we've used refiling an operating pressure dispense vessel without additional pumps. Configure a site glass using two three-way diverter valves. The common legs of the diverter valves connect to the site glass. The three ways are pneumatically tied together and operate simultaneously. In the Normal position the site glass is connected to the PV. In the actuated position the bottom for the site glass connects to the supply while the top vents to atmosphere (or returns to the supply drum). The site glass fills with liquid from the supply and when the system switches back to the Normal position gravity balances the liquid level between the PV and the site glass. This process repeats frequently maintaining a nearly constant level in the dispense PV with no noticeable dispense pressure fluctuations or flow rate changes at the nozzle.

Hope this helps --

 

[DLANDISSR]

flyte:
Another idea:
Add another pressure pot and switch between them. While using one pot another could be filled. Use a three way valve between them and the use point.

One problem with pumping into a pressure pot may be the change in pressure. If the pressure changes the flow will change. If you use a pump and pump into the pressure pot the pressure in the pot should be controlled so there is a minimum variation. As previouisly suggested a bladder tank may provide enough extra air capacity to that the volume of adhesive added will not change the pressure very much.
A persistaulic pump as suggested or a diaphragm pump may be suitable if sheer in the adhesive is a problem, if not, a gear pump would be a good choice.

 

[Paperpete]

I have hard knox experience and have gone thru the process of evolution in this area. Let's first look at what you want to accomplish. I would assume that your primary concern is to maintain a constant pressure to your process. Probably your actual flow is relativly low (less then or close to 1gpm). If the visc. is high then you will get a seroius pressure drop so the key is to find a happy medium in pie size. Small enough to prevent gunk buildup but large enough to not have an astronomical drop in pressure. If your glue usage is very konstant during operation then I would recomend that you use a prog. cavity (I have had good luck with Moyno but you could use a peristaltic as well)pump to pump to a tank with an air bladder. Forget the pressure relief valve it will just gunk up and besides that the spring will wear, instead put a smaller recirc line back to your glue tank with a manual valve. Buy a variaple freq. drive for the pump and an I/P for the air bladder side of the pot. Many VFDs have a built in PID loop and can accept the 4-20mA signal from the I/P and will be able to control the pressure very accurate. You have to make sure that you always have a small flow from the recirc line so the pipes do not gunk up (it's all about gunk). When the demand varies greatly (several 100%) then I have used a control valve in place of the above mentioned handvalve. The control valve should be on its own slow moving loop with the pump freq. as an imput and the valve position as an output. This way the pump will always run at a reasonable speed.