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Issues with Plate Freezers HELP :) :)
Hi, I am currently trying to fix up a plant that has had issues for a long period of time
my plate freezers are not performing as you would expect, I do not have allot of experience with plate freezers and not sure of there operating parameters so im going to give you what I know and hope the brains trust may be able to shed some light :)
suction is running at 75 KPA
liquid temp entering plates is -20c
suction temp leaving plates is -37c
liquid pump pressure is 250 kpa
I don't understand why my liquid temp entering is only -20c considering the low suction pressure thought it would relate more to what the PT chart states
and 17K TD on a plate freezer? would have thought this to be closer to 2K TD?
thanks in advance for your help if you need any more data I will be happy to provide if I can get it.
I am a bit at a loss here with how it should be running compared to how it actually is
thanks
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Re: Issues with Plate Freezers HELP :) :)
So Matt assume plant is ammonia?
if so 75 kpa is -21deg C.
How do you get -37 leaving plates?
Are you pressure readings accurate?
What are reg valve settings on each plate.
Do you have a suction riser out of plates, how high does it have to go into wet return header?
What is pressure at plates & same time in plant room compressor suction?
Let us know what you can
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Re: Issues with Plate Freezers HELP :) :)
Hi, yes the plant is ammonia
75KPA on the PT chart is -39.7
this is the suction pressure in my LP pot
-37c is the temp of my suction line leaving the plate ( Flooded plate via ammonia pump)
-21 is the temp of my liquid line from my LP pot to the inlet of my plate
yes the readings are accurate
the reg valve I have no idear
there is a suction and liquid header feeding the plate stack
the suction ( wet suction ) line is about 10m long back to the LP pot and the plates are higher then the plant room wet suction dose not travel up hill
I have no where to get a suction pressure reading at the plate, I was hoping/assuming it should be the same as my suction pressure in my LP pot?
thanks
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Re: Issues with Plate Freezers HELP :) :)
Sorry mate, don't mean to be to blunt but 75 kpa = -22 deg C
0 kpa ammonia boils at -33-34 deg C
Your temp readings don't make sense either, how are you reading then & have you another way of verifying them.
Liquid pump pressure could be right but also needs to be verified.
Once we clear up the readings we can go from there.
It appears the 75 kpa suction could be the problem as plates normally run a bit colder than -20 deg C
What type of product you are freezing & how it is packed example cardboard boxes etc.
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Re: Issues with Plate Freezers HELP :) :)
when using pressure, sure to state if it is "absolute" or "gauge"
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Re: Issues with Plate Freezers HELP :) :)
Where did Matt get this PT chart from, if it's in absolute or has he incorrect selection on Danfoss app.
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Re: Issues with Plate Freezers HELP :) :)
Hi,
seems this is absolute pressure
75 kPa = 0,75 bar = -39,5*C according to Danfoss Ref. slider for Android ... KoolApp v. 2.0.5
or Solkane www.solkane.com
anyhow, it will be nice to get some schematic diagram of that plant ...
Best regards, Josip :)
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Re: Issues with Plate Freezers HELP :) :)
75KPA give quite difference of boil temperature of ammonia if 75 KPA means 75 kPa Absolute pressure or means kPa over atmosphere pressure ( ie. gauge pressure)
'K' in KPA is also wrongly written ie. upper-cases 'K' is reserved for 'Kelvin' and 'kilo' written with lower cases 'k' ie. kPa for 'kiloPascal'
And for readers situation, if wrongly written upper cases 'K' for 'kilo', cannot after this be sure if later upper cases 'PA' is mean upper cases version shortening 'PASCAL' or means 'Pascal Absolute' but if written as kPA can give hint is value means kiloPascal Absolute ie. knowing kiloPascal normaly is written 'kPa' and small 'k' before validate is writers knowing differences between upper and lower cases letter significance.
Difference between lower and upper cases letter can be very important (and can make serious error) in engineering notation and in any doubt for itself with notation time or for future reader on publication, is better written in clear text if possible (ie doubtful KPA unit notation is better written as 'kiloPascal Absolute' or 'kPa Absolute')
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Re: Issues with Plate Freezers HELP :) :)
If pumped supply liquid is at -20' C , that is good as it gets. Plant room capacity undersized or not operating at full potential.
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Re: Issues with Plate Freezers HELP :) :)
Hi, thanks for the reply's
I always use absolute as my system runs in a vacuum
there is no soft copy of the plant schematic I will try find a a1 scanner so I can post the schematic
my temp readings I got by strapping a thermocouple to the pipework, pressures are from gauges
the meat is entering at +35c and leaving not cold enough over a 16 hr period and packed in a cardboard boxes
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Re: Issues with Plate Freezers HELP :) :)
is someone able to tell me the process to commission a plate freezer ?
and over feed rates ?
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Re: Issues with Plate Freezers HELP :) :)
check your hot gas valve, is not passing into the liquid feed!
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Re: Issues with Plate Freezers HELP :) :)
the plates do not have a defrost system the room gets turned of once every 6 months and thawed out
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Re: Issues with Plate Freezers HELP :) :)
however there is a hot gas defrost on another blower on the same system would this have any effect? I will test it tomorrow
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Re: Issues with Plate Freezers HELP :) :)
Quote:
Originally Posted by
mattmechanic
Hi, thanks for the reply's
I always use absolute as my system runs in a vacuum
there is no soft copy of the plant schematic I will try find a a1 scanner so I can post the schematic
my temp readings I got by strapping a thermocouple to the pipework, pressures are from gauges
the meat is entering at +35c and leaving not cold enough over a 16 hr period and packed in a cardboard boxes
Never heard anyone reading pressure like that, better off just talking saturated suction temp if anything.
So Matt, temp of liquid entering plates is -21 C! How can that be.
Accumulator with -39C liquid ammonia, liquid pump, 10 metre run liquid is then -21
Freeze time to short, need probably 24 hrs with meat that
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Re: Issues with Plate Freezers HELP :) :)
Circulation rates high in plate possibly 20 to 1
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Re: Issues with Plate Freezers HELP :) :)
I don't have a gauge port to fit gauges to so I strapped a temp probe to the pipe work and measured it,
I don't understand why I have -39 suction temp in my liquid pot and only -21c at the liquid entering the plate
I have no idea why this is happening it makes no sence to me
all valves are Hanson, now here is something you may be able to explain to me after the supply solenoid there is cone valve that is a No 7 this is fully open from that it feeds a header then there is a refrigerant flow valve that is open 2 turns there is 15 outlets/plates on the header all have the flow valves set to 2 turns.
why is there a cone valve on the supply to the header then another flow valve at each plate and do they do 2 different jobs?
for example cone is for expiation and flow valve of header is for balancing of the plates in the stack?
in the original paperwork I found that the freezing cycle was originally designed for 16 hrs
thanks
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Re: Issues with Plate Freezers HELP :) :)
Extra reg valve unusual, can you explain plant
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Re: Issues with Plate Freezers HELP :) :)
hi, what plant detail would you require?
I will try and do it tomorrow however there is about 500mm of ice around the pumps....
at the end of 16hrs should be -12
the LLSV is simply turned on/off via a switch at the plate stack by the operator not via the PLC ( I know very primitive )
I will start checking all strainers soon its on my list to do, the maintenance manager there told me they haven't been done since he started 4 odd years ago..
there is no strainers upstream of the LLSV until you return to your LP POT
on a side note I also found the recirculation rate of the plate is apparently suppose to be 8:1, please excuse me for being so new to this type of system but I have no idea how to measure/check/set this
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Re: Issues with Plate Freezers HELP :) :)
Are cardboxes different now compare from beginning (single wall to double wall card for example)? this can affect cooling speed of meat depend of higher isolation.
pressure 75 kPa absolute give boil temperature of -39 degree C, so is seems same as your accumulator temperature
for -21 degree C vapour pressure should be 181 kPa Abs so question is if you have restriction/valve between inlet to plate and platers inside pipework with over than 1 Bar pressure drop and question, actual working pressure in pipework?
have you measure surface temperaturer on plate ? - this should give idea if plate work around -21 degree C temperature and restriction for vapour is near end of plate or if work around -39 degree C, restriction is beginning of pipework
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Re: Issues with Plate Freezers HELP :) :)
Quote:
Originally Posted by
mattmechanic
hi, what plant detail would you require?
I will try and do it tomorrow however there is about 500mm of ice around the pumps....
at the end of 16hrs should be -12
the LLSV is simply turned on/off via a switch at the plate stack by the operator not via the PLC ( I know very primitive )
I will start checking all strainers soon its on my list to do, the maintenance manager there told me they haven't been done since he started 4 odd years ago..
there is no strainers upstream of the LLSV until you return to your LP POT
on a side note I also found the recirculation rate of the plate is apparently suppose to be 8:1, please excuse me for being so new to this type of system but I have no idea how to measure/check/set this
You have to understand we cannot see our plant so anything asked for could help solve problem
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Re: Issues with Plate Freezers HELP :) :)
Hi Matt.
Back to my original comment, you are supplying plates with -20' C liquid, should be in range of - 40' C. What make of plates are these, some have distribution orifices in each plate, to get even distribution.
Oil logging is another problem with plates, particularly if no hot gas, and that is definitely unusual.
What are your plant room conditions, mainly SST ? Do you know the over feed rates design.?
Would suggest that plant be re-commissioned and start from scratch.
magoo.
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Re: Issues with Plate Freezers HELP :) :)
16 hrs freeze time can only be achieved with chilled meat.
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5 Attachment(s)
Re: Issues with Plate Freezers HELP :) :)
Hi All, ok turns out I may have given you a bum steer, turns out my measuring instrument wasn't exactly accurate
today I took temps again with a fluke IR camera with temp read out.
so at the start of the day I had -28c liquid temp at my pumps and my inlet to my chiller plates and -29 at my suction header from the plates and 94 kpa absolute suction pressure at compressors
in the afternoon with the plates fully loaded I had -27c at my liquid pumps, -30 at my plate inlet -31 at my plate outlet @94kpa absolute
I have also attached some plant schematics Attachment 11732Attachment 11733Attachment 11734Attachment 11735Attachment 11736
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1 Attachment(s)
Re: Issues with Plate Freezers HELP :) :)
the plant original designee according to the limited documentation I found is product entering at +35 chilled to -12 in 16hrs
plate over feed rate is 8:1 as you can see in the above drawing, how you set this I don't know...
the plates do not have a distributor there is a 1" line from the header to the side of the plate
the plates are in a room with a de-humidifier to reduce ice build up, they get manually defrosted during shut downs every 6 months
I also checked all my hot gas defrost valves today and none are leaking through.
magoo I would love to start from scratch with the commissioning but I don't know how to set up a plate system any advice would be tops!
Attachment 11737
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Re: Issues with Plate Freezers HELP :) :)
@mattmechanic. This certainly looks like our drawings (Realcold/Milmeq). Please give me a message and I can arrange for either myself or another engineer to walk you through the problems you are experiencing. Until I know where your plant is I couldn't say too much but Im certain we can sort a solution for you. We have number of projects underway in Australia at present so will have engineers available locally.
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Re: Issues with Plate Freezers HELP :) :)
thanks kiwi, I tried to sent u a PM on here don't think it went threw mind sending me a text msg and ill call you back
cheers
0401877649
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Re: Issues with Plate Freezers HELP :) :)
Definitely look like our drawings, reg valve after the LLSV is used to balance between multiple plate packs prior to the reg valves at the plates.
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Re: Issues with Plate Freezers HELP :) :)
Quote:
Originally Posted by
mattmechanic
I don't have a gauge port to fit gauges to so I strapped a temp probe to the pipe work and measured it,
I don't understand why I have -39 suction temp in my liquid pot and only -21c at the liquid entering the plate
I have no idea why this is happening it makes no sence to me
all valves are Hanson, now here is something you may be able to explain to me after the supply solenoid there is cone valve that is a No 7 this is fully open from that it feeds a header then there is a refrigerant flow valve that is open 2 turns there is 15 outlets/plates on the header all have the flow valves set to 2 turns.
why is there a cone valve on the supply to the header then another flow valve at each plate and do they do 2 different jobs?
for example cone is for expiation and flow valve of header is for balancing of the plates in the stack?
in the original paperwork I found that the freezing cycle was originally designed for 16 hrs
thanks
The sv sounds like a Hansen pulse width valve
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Re: Issues with Plate Freezers HELP :) :)
Matt
Your temps indicated at plates, you indicate that they drop, from inlet to outlet, they should at 8:1 stay fairly constant or marginally rise. Would say that plates are starved of liquid.
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Re: Issues with Plate Freezers HELP :) :)
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Re: Issues with Plate Freezers HELP :) :)
Hi, I assume the best way to wash oil out is a full pump down then open the LLSV and this should wash the oil back to the LP pot and then get separated? I can try this..... and see what it dose
magoo how do I re-commission the plates properly I need a starting point I ges
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Re: Issues with Plate Freezers HELP :) :)
Quote:
Originally Posted by
mattmechanic
Hi, I assume the best way to wash oil out is a full pump down then open the LLSV and this should wash the oil back to the LP pot and then get separated? I can try this..... and see what it dose
magoo how do I re-commission the plates properly I need a starting point I ges
Not at those temps, you need to drain them when they are warm.
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Re: Issues with Plate Freezers HELP :) :)
well this gets done every 6 months wen the plates are defrosted
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Re: Issues with Plate Freezers HELP :) :)
Quote:
Originally Posted by
mattmechanic
thanks kiwi, I tried to sent u a PM on here don't think it went threw mind sending me a text msg and ill call you back
cheers
0401877649
Message sent mate. Try me Wednesday and we can sort it out.
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Re: Issues with Plate Freezers HELP :) :)
Quote:
Originally Posted by
mattmechanic
well this gets done every 6 months wen the plates are defrosted
so how much oil do manage to get out?
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Re: Issues with Plate Freezers HELP :) :)
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Re: Issues with Plate Freezers HELP :) :)
hey all just wanted to let you all know I got it sorted...
added up to a large number of incorrect things to give me my end result
thanks kiwi for your input and our chat on the phone..
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Re: Issues with Plate Freezers HELP :) :)
Hi Matt.
can you elaborate on the actual resole. PD is a good bloke.
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Re: Issues with Plate Freezers HELP :) :)
ok so in short here is what I found I am still working on a few items..
* back pressure regulator between IP >LP pots set incorrectly bleeding IP constantly to LP
*suction set point not low enough for system designee
*large amounts of air in system
* refrigerant flow valves set incorrectly on plate freezers
* control issues in the PLC with pumps and solenoids
*hot gas defrost suction solenoid leaking through
*condenser control in PLC incorrect
there also seems to be a ton of water in the system so getting a water/air purger fitted
so this is a basic list of stuff I found... all adding up to cause the issues I was having...
thanks again guys for your input