Sounds like you have one of those discontinued Wearever Chicken Buckets, which work pretty good if you know how to use it. Here's a link that discusses its use: http://kfc.forumup.co.uk/about279-kfc.html
I'm struggling somewhat on how to answer this. For commercial equipment users, there's most often no problem. They have their timers and/or "beepers" and temp gauges on their professional equipment. For home users, their equipment does not come with timers or "beepers." Can the home user make "pressure fried" chicken as good as the pros? Yes, but it takes experience and a lot of "trial and error."
First, its best to get a "pressure fryer" as opposed to a pressure cooker (am not certain if that's the cooker referred to here). Unfortunately they usually cost considerably more than the average pressure cooker. But it isn't as simple as that as even with a pressure fryer, there are generally 3 results: undercooked, gooey coated fried chicken, perfect pressure fried chicken, and burnt or overcooked fried chicken. Trial, error, timing, etc. is essential here and I can't begin to describe all the variables. But one determined to do so can and will make great pressure fried chicken at home.
Can the common pressure cooker accomplish this also? Answer, yes and no. There are many websites that I don't have at my fingertips right now that say if done right, pressure cookers can do the same as so called pressure fryers. I generally agree but with one caveat: it has to be a good, well constructive pressure cooker and not one of the 29.95 specials. So generally (but not always) a higher priced pressure cooker is needed. And oil temperature has to be carefully measured -- not getting higher than 350 to 370 degrees F for the first basic fry (for the first minute or two uncovered). Then temp should be slightly lowered when covered and cooker watched constantly (no running off to the bathroom or TV). Timing here is critical and . . . only trial and error (and sometimes a lot of waste when not done well) can teach one how to do it best.
But this is a very involved and deep subject not capable of a quick advisory note like this.
I am unfamiliar with any combo pressure cooker/canner and would be hard pressed to say that model would be all right for pressure frying. It does look like a very sophisticated one, tho, with multiple clamp downs, steam gauge, automatic overpressure release, ability to set pressure at 5 psi, 10 psi, or 15 psi. For pressure frying chicken, one would use the lowest pressure level of 5 psi. I might be game to try it if I had it. But at 21 - 1/2 quarts, that one seems to be extremely large size rivaling many professional pressure fryers. Mine is a 10 quart size and that's pretty big for home use.
Check out the Pro Selection group out of Texas at http://www.pro-selections.com/ . Beside their pressure fryer models, they are a good source of information on the subject. Plus you might want to consider buying the Pressure Magic Video from them for only 4.95. While it says its for use with Pressure Magic cookers only, I think it would have general application and would be helpful to see their tips and procedure.
And remember with pressure frying, one uses much, much less oil (generally peanut) than one would for regular deep frying. But the 21 -1/2 quart model would seem to need an awful lot of oil. And I don't think the "dispersement" measure that you mentioned for oil applies to a pressure fryer. I seem to recall that the heated oil covers no more than 1/4th (or even much less) up the side of the cooker. Under low pressure, the oil level rises all around the chicken in the cooker. Good luck with whatever you do.
BTB - Thank you so much in helping me to educate myself on pressure canners/cookers. I checked out the site you suggested but they had pretty much regular pressure cookers or professional chicken fryers, which is way out of my league. I decided to buy the All Amerian 10 1/2 quart pressure canner/cooker because it looks to be very hardy and locks down easily and tightly without a gasket. I will try frying chicken in it when I work up the nerve after studying the dos and don'ts in the manual. I did sent an e-mail to them asking if this could be done but have receieved no answer and probably won't receive one. I bought it on Amazon.com much cheaper than from their own web site and the one I ordered is brand new. Thanks again.
BTB answered the way I would have - except I would like to add that a cheap metal pressure cooker at high pressure is much more likely to explode than a pressure fryer made of heavy duty metal. If it does explode the 360 degree oil would kill you or at the very least severely disfigure you as opposed to boiling water that would burn you but could be easily wiped off before it burned you badly. Oil is like napalm... burns right through you. If you must use a pressure cooker to fry foods do so without your clothes on and have a bathtub nearby filled with ice water that you can jump into the moment anything goes wrong... cooling the oil is tantamount to saving your life.
Thank you for the helpful information. The pressure canner/cooker I am talking about has no rubber gasket in it. It is a metal on metal pressure cooker, it is made by All American Canners or something like that. I realize it would be by trial and error and the oil would have to be measured kind of by the dispersment method (chicken covered by water, removed, measure the amount of water, replace with oil) but I would be willing to try as long as I know the cooker wouldn't explode
I thank you so much for your help and your concern. I promise that I will be extremely careful when using this pressure canner. I do have gloves that can withstand high heat (from when I bought my rotiserie, to take it out of the machine) and I will use them when opening the cooker. Do you mind if I let you know how I make out. I also realize what you say about the dispersment method should not be used. Forgot that oil does boil up pretty much since I almost had a disaster a couple of years ago with a frying pan that had too much oil in it an almost went over into the fire. Fortunately, I was able to move it with no repercussions. I really can't stress too much how you have helped me.