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mattmechanic
23-08-2014, 12:39 AM
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

RANGER1
23-08-2014, 02:21 AM
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

mattmechanic
23-08-2014, 05:02 AM
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

RANGER1
23-08-2014, 07:16 AM
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.

mad fridgie
23-08-2014, 08:36 AM
when using pressure, sure to state if it is "absolute" or "gauge"

RANGER1
23-08-2014, 08:46 AM
Where did Matt get this PT chart from, if it's in absolute or has he incorrect selection on Danfoss app.

Josip
23-08-2014, 01:09 PM
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
(http://www.solkane.com)
anyhow, it will be nice to get some schematic diagram of that plant ...

Best regards, Josip :)

xxargs
23-08-2014, 01:55 PM
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')

Magoo
24-08-2014, 12:38 AM
If pumped supply liquid is at -20' C , that is good as it gets. Plant room capacity undersized or not operating at full potential.

mattmechanic
24-08-2014, 11:09 AM
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

mattmechanic
24-08-2014, 11:12 AM
is someone able to tell me the process to commission a plate freezer ?
and over feed rates ?

mad fridgie
24-08-2014, 11:25 AM
check your hot gas valve, is not passing into the liquid feed!

mattmechanic
24-08-2014, 11:38 AM
the plates do not have a defrost system the room gets turned of once every 6 months and thawed out

mattmechanic
24-08-2014, 11:39 AM
however there is a hot gas defrost on another blower on the same system would this have any effect? I will test it tomorrow

RANGER1
24-08-2014, 11:43 AM
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

RANGER1
24-08-2014, 11:47 AM
Circulation rates high in plate possibly 20 to 1

mattmechanic
24-08-2014, 11:54 AM
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

RANGER1
24-08-2014, 12:24 PM
Extra reg valve unusual, can you explain plant

mattmechanic
24-08-2014, 01:49 PM
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

xxargs
24-08-2014, 02:34 PM
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

RANGER1
24-08-2014, 09:26 PM
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

Magoo
25-08-2014, 04:49 AM
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.

RANGER1
25-08-2014, 07:56 AM
16 hrs freeze time can only be achieved with chilled meat.

mattmechanic
25-08-2014, 09:07 AM
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 1173211733117341173511736

mattmechanic
25-08-2014, 09:13 AM
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!

11737

kiwi
25-08-2014, 10:13 AM
@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.

mattmechanic
25-08-2014, 10:52 AM
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

Nh34life
26-08-2014, 12:01 AM
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.

Magoo
26-08-2014, 01:03 AM
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

Magoo
26-08-2014, 02:53 AM
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.

mad fridgie
26-08-2014, 03:12 AM
oil logged!

mattmechanic
26-08-2014, 07:33 AM
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

mad fridgie
26-08-2014, 08:02 AM
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.

mattmechanic
26-08-2014, 10:28 AM
well this gets done every 6 months wen the plates are defrosted

kiwi
26-08-2014, 10:34 AM
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.

mad fridgie
26-08-2014, 11:32 AM
well this gets done every 6 months wen the plates are defrosted
so how much oil do manage to get out?

mattmechanic
26-08-2014, 01:05 PM
none really

mattmechanic
31-08-2014, 09:37 AM
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..

Magoo
01-09-2014, 05:22 AM
Hi Matt.
can you elaborate on the actual resole. PD is a good bloke.

mattmechanic
02-09-2014, 12:48 PM
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

sandybapat
03-09-2014, 06:41 AM
Mat

Liquid feed temperature -21 C and wet return -39 C. One reason for this disparity may be the location of temperature sensor at in feed and evaporator starving of liquid. I mean there is less feeding to evaporator and the liquid line contains lot of flash gas and the sensor is on the top surface of horizontal pipe which senses gas temperature (12 O clock position) The temperature sensor should be at 4 O clock position and it should be covered with insulation material.

Magoo
03-09-2014, 08:10 AM
Hi Matt
thanks for come back and issues found, you will have your hands full clearing contaminants and keeping plant operational in effect. The auto purger will clean up system to a point. Draining oil and crap is important for long term reliability.
You would have to be seriously disappointed with system issues and controls problems that created the situation you inherited.
magoo

mattmechanic
19-09-2014, 12:06 PM
hey all ok so I have been very busy but a little update
I discovered the wrong oil has been used in the system also and only has a pour point of -33 ...
ran the system at -20 over the weekend and got 35odd liters of oil out of my pot, the pot was full of bloody oil
so still got a bit more work to do here then get the right oil in the system...
any hoo that has made a difference, I have been purging air every day and again made massive difference
re commissioned plates and replaced dodgy valves, drained a heep of old oil and dead ammonia from around the system...
cant wait till my new water purger gets hooked up...
basically re commissioning every thing now the system ****s it in... smashed my product temp target time frames less run time on compressors running 2 during production instead of 3 and 1 over the weekend,
previously they all ran
still much more work to do this was a quick update
thanks again for your help!

kiwi
09-10-2014, 12:02 AM
Great result Matt.