Chemical Injection Pump design (needle) 1

[MonicaLee]

Objective: redesign existing pilot adjusting needle to regulate pressure. The timer cap that controls the needle:

http://www.williamspumps.com/corp/details/0,,CLI1_DIV26_ETI3168,00.html

I would like to know the following if you have had the experiences in this kind of pump design:

1. How many type of needle (pin) designs to control the pressure with a timer cap? (As much I know, there would be "slope" needle (no seals o-ring required, but you have to tight very hard to seal), and "dent" needle (seal teflon o-ring is required, but teflon will cracks over repetitive dent contact)

2. If it is the slope type, how do I calculate the needle (pin) slope, thread versus, pressure regulators, and timer cap (turning knob) relationship? Does anyone has some formula or calculating methods to share?

3. Which design is the most efficient as far as pin design?

Thank you so much so much for anyone who has any idea what I am talking about.

 

[pennpoint]

MonicaLee
Seems to me you should be addressing your questions to the valve manufacture, because your questions are absolutly design and application specific.
By "slope type" do you mean "taper".
Still, someone here on this forum will attempt to answer your questions as best they can, far better than my post anyway.

Good Luck

pennpoint

 

[MonicaLee]

Pennpoint,

I am just asking for the people who specifically has experience in design with this type before. But you know what, thank you anyway. I am still looking for Chemical Injection Pump experienced designer. If you or anyone can help me, please reply here.

 

[Scipio]

First, the page you're referencing doesn't have the 'timer cap' needle valve I think you're referring to. It only shows a micrometer stroke length adjuster for the pump plunger. I think you're referring to the MKVII type oscillating controller, which is one of a few different controllers Williams makes for these pneumatic metering pumps, and uses a needle valve to throttle the air/gas flow to the pneumatic cylinder, increasing or decreasing the stroking rate. Are you referring to regulating the air/gas supply pressure (which would result in a very coarse adjustment in the maximum pump discharge pressure) or regulating the pump discharge pressure?

 

[MonicaLee]

I am trying to redesign the PILOT ADJUSTING NEEDLE.

CURRENT DESIGN: Needle (pin) has a dent cut to allow air (increasing/decreasing the stroking rate) by adjustment of thread from the timer cap. This needle is regulating air supply pressure to eventually inject chemicals mixing at desired stroking rate. We are currently using Teflon O-Ring, with the V-Cut dent, the dent is causing residual stress to Teflon (hard material) to wear out and crack. e.g.

http://www.morganproducts.com/

IMPROVED DESIGN: Needle to resign instead of V-Cut dent to regulate air, Taper Needle without V-Cut is introduced. I like to copy the Williams design concept to use Taper Needle and redesign seat to match with new design. Please share your experience with calculation of pressure/stroke rate/tolerances required to support design. I am very interested to know any bright ideas to assist us improving our products. I can even hire you as a consultant if you come up with something brilliant.

I really need some basic calculation like what is the maximum/minimum air flow through opening, stroke rate, etc...Any calculations pertaining to this design would be helpful since I have to show back up calculations. I look forward to hear from you all and appreciate deeply your valuable time for reading this post.

 

[MonicaLee]

Can anyone assist me in this topic? I am sure someone out there dealed with chemical injection pumps before. Please help!!!

 

[MonicaLee]

Scipio,
Are you referring to regulating the air/gas supply pressure (which would result in a very coarse adjustment in the maximum pump discharge pressure) or regulating the pump discharge pressure?

Yes I am.

What formula should I use to calculate? Do you have any suggestion? Thank you very much in advance.

 

[Scipio]

Well, I can't be of any help designing a needle valve pressure regulator, you're looking for a valve designer, not a pump designer. One thing I can tell you though, that needle that you're referring to has nothing to do with regulating the air supply pressure. It adjusts flowrate, nothing more.

 

[MonicaLee]

Scipio,

Thanks for your tip, I will use design concept of needle valve design. I just need to find out the taper degree for the needle and seat design. At least from your help, now I can figure out the design concept. Thanks.