Results 1 to 18 of 18
-
29-01-2007, 10:33 PM #1
Frick Quantum LX Compressor control panel: Capacity Control Screen
Hi All
I have been looking at Frick Quantum LX compressor control panel's operation service manual. In its Capacity control Screen description, they have the following parameters:
Setpoint : 20 PSIG (just example numbers used in manual)
HIGH LOW
Proportional Band: 15 PSIG 15 PSIG
Dead Band : 0.5 PSIG 0.5 PSIG
Cycle Time : 3 SEC 3 SEC
Channel: Suction Pressure
According to the description of each field and the numbers they used, i am a little confused here. Do these numbers mean as follows:
if my sp is at 20 PSI then the dead band high would be set at 20+0.5 = 20.5 PSIG and the Proportional band high would be set at 20.5+15 = 35.5 PSIG (set above the dead band high). Also if lets say my suction pressure actual reading is 40 PSI (assume) which would be beyond my proportional band high value(35.5) , i have to energize my load solenoid all the time. Also what does that cyle time mean?
After reading the description on their service manual, i am really confused how actually loading and unloading works in their control panels. If someone can explain to me within the context of the numbers they have used in their service manual, i will really appreciate it. Here is the their service manual number S90-022 O
It didn't let me post the link to above manual, but if you google the above number, you will be able to find that manual.
Thanks in advance
-
29-01-2007, 11:51 PM #2
Re: Frick Quantum LX Compressor control panel: Capacity Control Screen
Hi Screw Geek,
I'm not an expert on these controls but have had a quick look at the manual, link here...
http://www.frickcold.com/documents/library/1275.pdf
Looking at page 11 the unload description seems to go like this, I think
If the master compressor’s Suction Pressure is above
the Capacity Control setpoint, the master calculates
the increase in capacity that is required. The
calculation is as follows:
Difference = Suction Pressure – (Capacity
Control Setpoint + Upper Dead Band)
Using your figures...
Difference = 40psi - (20psi + 0.5psi)
= 40 - 20.5
= 19.5
Diff is greater than Upper Band
If the Difference is less than the Upper Proportional
Band:Capacity Change = (Difference / Upper
Proportional Band) * Upper Cycle Time
Therefore
Change = (19.5 / 15 ) * 3secs
= 3.9
If the Difference is greater than the Upper
Proportional Band:
Capacity Change = Upper Cycle Time
= 3secs
And it appears that depending on the exact model being used the Capacity Change is added to the compressor(s) loading or a direct Load Pulse is given.
I hope this helps a little.
Brian - Newton Abbot, Devon, UK
Retired March 2015
-
30-01-2007, 12:02 AM #3
Re: Frick Quantum LX Compressor control panel: Capacity Control Screen
Thanks
Also if u have some time and if u take a look on page 24 of this manual, they talked abt a Cyle Time. Do they mean to capture a suction value for the calculations after every cyle time is complete? that's the confusing part. If you guys can elaborate this, it helps a lot.
Regards
-
30-01-2007, 12:07 AM #4
Re: Frick Quantum LX Compressor control panel: Capacity Control Screen
Let me try. Frick panels are a bit complicated in comparison to some.
Forgive me if I do not get this exactly, as I have not worked on a Quantum in a while.
Dead band is a range during which the compressor will not load or unload. if set at 0.5 it will not load or unload the compressor unless suction pressure goes above or below the suction setpoint by this much.
Cycle time is the amount of time that the load/unload solenoids are energized within the Proportional Band.
Proportional band is the area in which the panel sends short pulses to the solenoids. Outside the proportional band the solenoids are energized all the time, until the suction moves within the proportional band. It serves to keep the suction pressure stable, rater than rapid unneeded loading/unloading.
Clear as mud?
This is the link. There are a couple of other manuals on the panels in there you might want to look at as well.
http://www.frickcold.com/documents/library/1275.pdf
-
30-01-2007, 01:36 PM #5
Re: Frick Quantum LX Compressor control panel: Capacity Control Screen
Hi, Screw_geek
According to your values:
SP=20 psig
NZ= 0.5 psig 0.5 psig
PB= 15 psig 15 psig
Cycle time 3 sec 3 sec
Seems you can set you NZ as you like around SP and the same is for PB. Time to engage solenoids you can also change up maybe from 0.5 sec up to 3 sec both for up and down.
You must play with those values but you can try
SP=20
NZ= 0.5 psig 0.5 psig
PB= 5 psig 5 psig
time down 3 sec time up 2 sec
Once you set your NZ and PB it will come along with any SP you set.
Please take a look at attached file:
Best regards, Josip
It's impossible to make anything foolproof because fools are so ingenious...
Don't ever underestimate the power of stupid people when they are in large groups.
Please, don't teach me how to be stupid....
No job is as important as to jeopardize the safety of you or those that you work with.
-
30-01-2007, 03:58 PM #6
Re: Frick Quantum LX Compressor control panel: Capacity Control Screen
Josip;
Nice PDF. A picture can be better than a thousand words!
Did you make that up?
-
30-01-2007, 04:06 PM #7
Re: Frick Quantum LX Compressor control panel: Capacity Control Screen
Thanks a lot guys, just one final thought to discuss:
So the cycle time up means total load time for the compressor, for example If cycle time up and other parameters set as follows:
Cycle time up = 3 sec
Proportional Band = 15 Psi
NZ = 0.5 Psi
SP = 20 Psi
Actual value = 35 Psi
Then Difference = Actual Value – (SP+NZ) = 35-(20+0.5)= 14.5 Psi (for loading)
If Diff < PB Then
Capacity change = (14.5/15) x 3 = 2.89 sec
Therefore, the load solenoid will be ON for 2.89 sec and off for (3-2.89) = 0.1 sec. Is it correct? The above calculation will be valid for 3 sec. Once the 3 seconds elapsed, a new value of suction pressure will be captured and the above calculation will be generated, is it correct also? Or the above calculation will be taking place continuously until the suction pressure meets the SP. The way i understood cycle time is that,there is a cycle time up or down timer that will be resetting automatically once the .acc value becomes equal to .pre value (3 sec in this case), and from the start of the new cycle it will reevaluate the response and actual value.
Regards
-
30-01-2007, 09:01 PM #8
Re: Frick Quantum LX Compressor control panel: Capacity Control Screen
It's impossible to make anything foolproof because fools are so ingenious...
Don't ever underestimate the power of stupid people when they are in large groups.
Please, don't teach me how to be stupid....
No job is as important as to jeopardize the safety of you or those that you work with.
-
30-01-2007, 09:47 PM #9
Re: Frick Quantum LX Compressor control panel: Capacity Control Screen
Hi, Screw_geek
About this I do not know because I am not familiar with Quantum controller. My previous picture is from another controller.
For me it seems something here is missing (we call that step delay=time to measure actual set point) and then to issue another signal (to engage solenoid) which can be now to reduce the capacity.
This must be PID controller with P-proportional, I-integral and D-derivative functions with feedback signal. The algorithm is different for different controllers.
You should check that in manual for that controller
,but as per my experience you must run your plant and see what happen and for sure you must make some fine tunning either for P,I or D values. Otherwise your compressor you can set to be a "hunter". This is more like a game do not be afraid
Best regards, Josip
It's impossible to make anything foolproof because fools are so ingenious...
Don't ever underestimate the power of stupid people when they are in large groups.
Please, don't teach me how to be stupid....
No job is as important as to jeopardize the safety of you or those that you work with.
-
26-02-2007, 04:45 PM #10
Re: Frick Quantum LX Compressor control panel: Capacity Control Screen
-
27-02-2007, 12:52 PM #11
Re: Frick Quantum LX Compressor control panel: Capacity Control Screen
It's impossible to make anything foolproof because fools are so ingenious...
Don't ever underestimate the power of stupid people when they are in large groups.
Please, don't teach me how to be stupid....
No job is as important as to jeopardize the safety of you or those that you work with.
-
27-02-2007, 06:35 PM #12
Re: Frick Quantum LX Compressor control panel: Capacity Control Screen
Well what i meant to say is that, i have two discrete outputs to control: Load solenoid and unload solenoid. The method you suggested in your last msg was to develop some sort of PID controller to control loading or unloading sequence. thats why i asked this. Hope that clears......
-
01-03-2007, 03:49 PM #13
Re: Frick Quantum LX Compressor control panel: Capacity Control Screen
Hi, screw_geek
No, you have your set point (pressure, temp) and you have to instruct your PLC how to reach that point, thus tell him about proportional bad, I-time meaning time to come to your set point, slower or faster response and controller will issue needed signal for loading/unloading accordingly. Derivative function we use to smooth output regulating signal.
We have to set one good proportional band not too wide nor narrow, some good sample time (means when repeat to read actual point and then issue an regulating signal up/down, usually I-time is bigger if system response is slower and vice versa, and we have derivative function to shape output signal meaning as reading/input signal is close to set point regulating/output signal will be smaller and within dead band there will be no signal.
You have nothing to control, for that you have your controller which must be programed good.
Hope this give some picture
Best regards, Josip
It's impossible to make anything foolproof because fools are so ingenious...
Don't ever underestimate the power of stupid people when they are in large groups.
Please, don't teach me how to be stupid....
No job is as important as to jeopardize the safety of you or those that you work with.
-
01-03-2007, 04:20 PM #14
Re: Frick Quantum LX Compressor control panel: Capacity Control Screen
Hi Josip
So if i have to make an analagy of your graph (a pdf document that you posted in the beginning of the thread) with the capacity control screen in frick control panel then it will be something as follows:
FRICK PANEL Graph
Proportional band = Proportional band
Cyle time = Integral time
Dead band = Neutral band
Just to let you know that compressors that i am dealing with don't have frick panel installed with them. they are purely based on a customized PLC panel, plc programming would be my job. I am just looking at different options for slide valve capacity control algorithms in different manufacturers panels.
I dont have enough information to begin programming on this part, so i am just working around different ideas or options i could possibly have.
When i looked at the firck capacity control algortihm, it looked pretty close to me what i will be doing. Since i dont have any experence with screws and with frick panel thats why i tried to explore them with the help of you guys.
frick algorithm is looking pretty simple to me ( unless something complexed going at the back end which i am not aware of).All its doing is calculating the error signal after every cycle time and based on that error signal, calculates the capacity change...hope this will give you more clear idea of what i am going after for.
Regards
Pro
-
01-03-2007, 09:17 PM #15
Re: Frick Quantum LX Compressor control panel: Capacity Control Screen
Hi, Screw_geek
You are in a deep water now
I'm not very familiar with quoted expressions and exact meanings, i.e. the same expressions can be used for different meanings
but...
Dead band is Neutral band no change in capacity no regulating signals but with minor error signal
Proportional band is an area with proportional regulating signal meaning if you are far from set point that signal will be stronger
I-time is time within we want to reach to set point what depend on system, direct or indirect cooling, etc
Cycle time or sampling time i.e. reading time for reading of real working point-set point=error signal. this time we need to get back response of system to our previously issued regulating signal, we do not have a real time response and we have to wait. This also depend on type of system.
But according to your post you are on good way
Do not worry about different algorithms, with different approaching your solution/algorithm will be different
Best regards, Josip
It's impossible to make anything foolproof because fools are so ingenious...
Don't ever underestimate the power of stupid people when they are in large groups.
Please, don't teach me how to be stupid....
No job is as important as to jeopardize the safety of you or those that you work with.
-
01-03-2007, 09:40 PM #16
-
02-03-2007, 10:23 AM #17
Re: Frick Quantum LX Compressor control panel: Capacity Control Screen
Hi, screw_geek
Hope you will not misinterpret this : you must know how your system/compressor must work to achieve what you need, then you can write down a good program.
Of course no need to repeat some mistakes and for that step you can use some other algorithms to guide you.
You can send me PM with your email address and I will send you some pdf files to get some old (but good) ideas
Best regards, Josip
It's impossible to make anything foolproof because fools are so ingenious...
Don't ever underestimate the power of stupid people when they are in large groups.
Please, don't teach me how to be stupid....
No job is as important as to jeopardize the safety of you or those that you work with.
-
15-06-2008, 06:47 AM #18
Re: Frick Quantum LX Compressor control panel: Capacity Control Screen
Has anyone known the level password for the Frick Quantum LX compressor?
The level 1;password:10
The level 2;password:20
The level 3;password:??
The level 4;password:??
Please help me, thank you!