Coldstore Relief Ports [Archive] - Refrigeration-Engineer.com forums

taz24

23-10-2007, 12:12 AM

Thanks for that guys, but I'm still a little in the dark as I don't know why a depression within a freezer would be bad,...is it less air flow and therefore less heat exchange or what?

Thanks
Expat (we may make a fridgey of me yet)

I've seen coldroom panels blown out because of excess pressure inside the coldroom caused by defrost and a sealed room.
The pressure relief allows the equalization of the pressure.

I have never known a room to implode due to lack of pressure.
In my oppinion this is not as common or as much a risk as the excess pressure.

Cheers taz

Sergei

23-10-2007, 03:08 AM

I've seen coldroom panels blown out because of excess pressure inside the coldroom caused by defrost and a sealed room.
The pressure relief allows the equalization of the pressure.

I have never known a room to implode due to lack of pressure.
In my oppinion this is not as common or as much a risk as the excess pressure.

Cheers taz
What is the size of this room?

smpsmp45

23-10-2007, 07:03 AM

In the Blast freezers we ha installed the wall panels collapsed due to malfunction of the relief ports.
it is very important to put these.

old gas bottle

23-10-2007, 09:05 AM

we allways fit them next to the door [hanging flap type]or on the roof above or ajacent to the door,[larger rooms]. just for the last post,when you open and shut a freezer door there is a big pressure differance and theese valves allow it to ballance out,if you do not fit them air will get in where it can,ie gaps in pannels,door seals,pipe holes,drains, etc,in some cases i have seen the walls pulled inwards[distorsion].

think its safe to say if you fit one near each door on a large store you will be o/k.but obviousley a calc is in order.

Sergei

24-10-2007, 03:52 AM

Can anybody give the size of damaged rooms? Most likely these rooms for commercial refrigeration but not for industrial refrigeration.

samiam

24-10-2007, 02:21 PM

Hi all,

Also have a look at the Fermod website for the pressure relief valve models.

Regards,

old gas bottle

25-10-2007, 08:38 AM

last one was a 5mtr x 5mtr x two storey freezer 6mtr high, loosened all the wall panels into the floor,told the customer it has to come down before it does it on its own.!!

TXiceman

25-10-2007, 08:25 PM

If the air in the freezer collapses, you form a lower pressure inside than you do outside. This results in a pressure being exerted on the freezer walls or panels. If the pressure difference is great enough, you can get wall panel to buckle.

Ken

smpsmp45

26-10-2007, 07:49 AM

We have also come to a conclusion that the rate of moisture abosrption in the freezer is also an important factor. If the vacumm is created fast enough, the walls still collpase. That we have observed that if the moisture content is high enough & if the freezer starts & condesnes that air, still the relief valves fail short of proper air intake & still it creates huge pr differential between inside / outside.

taz24

27-10-2007, 02:38 AM

What is the size of this room?

Hello Sergei.

I have seen rooms as small as 5mtr by 6 mtr by 3 mtr have the wall panels seperated from the roof.

I have seen 3 or 4 large cold romms about the size of tennis courts with the wall pannels pushed out.

Finaly I have seen an industrial cold store about the size of a football pitch with a fork truck size hole init from one careless drivers speeding:eek:.

All the best.

taz.

Sergei

28-10-2007, 05:16 PM

This is issue for commercial(walk-in) freezers, because the doors can be tight. Industrial(drive-in) freezers don't this problem.

taz24

29-10-2007, 02:37 AM

This is issue for commercial(walk-in) freezers, because the doors can be tight. Industrial(drive-in) freezers don't this problem.

I would agree.
Also the volume of the room makes a difference the smaller the room, less volume.

taz.

smpsmp45

29-10-2007, 06:44 AM

cold store collapse- the ceiling panels caved in. THe reason being thee are 12 fans of the evaporators & all start together. After cycling the fans, the pressures were OK.

smpsmp45

14-11-2007, 11:28 AM

Based on our recent experience & lots of data finding, we have compiled a small explaination on this point. May be it is interesting.

Actinide

14-11-2007, 12:00 PM

I remember my Uni teacher talking about relief vents for freezer rooms. If you do not use these the exerted pressure on the outer sides of the walls can equate to the weight of a meduim sized car sitting on the roof of the freezer room!

Grizzly

15-11-2007, 07:36 PM

Hi Guys. PRESSURE EQUALISATION VALVE
You need them because of the pressure temperature relationship.
When the temperature within the cold room drops so does the pressure. Ask any Enginneer who services butchers cold rooms. They will of at sometime had the situation where " The door won't open" (the vaccum inside is keeping the door shut.) Because the heater element on the PRESSURE EQUALISATION VALVE has failed and the flaps have frose shut.
DO NOT underestimate the power developed if the presures are not equalised. I have seen very large cold store walls that have moved due to this problem!
Cheers Steve.

Josip

18-11-2007, 03:25 PM

Hi, Sergei :)

This is issue for commercial(walk-in) freezers, because the doors can be tight. Industrial(drive-in) freezers don't this problem.

O, yes...I am sorry cannot upload a photo of collapsed ceiling in one huge cold room due to missing pressure regulating valves....Came there later when they almost repair all damage...the reason was someone forget to leave the cold room doors open during pulling down...funny...but very expensive..

Just try to think about the Force (under pressure-vacuum) when you close the door (A=1 m2)of your kitchen freezer (V=150-500 lit) and try to open it again few seconds later :eek:...and the force in one cold room for ice-cream (-28C) size of 32,3m x 22,7m x 10,6 m (LxWxH) = almost 8300 m3....

I will not dare to not install those valves....

Best regards, Josip :)

Sergei

18-11-2007, 11:54 PM

Hi, Sergei :)

O, yes...I am sorry cannot upload a photo of collapsed ceiling in one huge cold room due to missing pressure regulating valves....Came there later when they almost repair all damage...the reason was someone forget to leave the cold room doors open during pulling down...funny...but very expensive..

Just try to think about the Force (under pressure-vacuum) when you close the door (A=1 m2)of your kitchen freezer (V=150-500 lit) and try to open it again few seconds later :eek:...and the force in one cold room for ice-cream (-28C) size of 32,3m x 22,7m x 10,6 m (LxWxH) = almost 8300 m3....

I will not dare to not install those valves....

Best regards, Josip :)
Hi, Josip.
I'm curious to see the doors of this cold room. It is a dream to have industrial cold room doors so tight as kitchen freezer door.

Sergei

NH3LVR

19-11-2007, 01:17 AM

I have the solution to the problem. No relief ports are needed.
I will send you a couple of our forklift drivers. They will have all your doors "vented" in a matter of days.:)

taz24

19-11-2007, 11:29 AM

I have the solution to the problem. No relief ports are needed.
I will send you a couple of our forklift drivers. They will have all your doors "vented" in a matter of days.:)

LOL

We must work at the same place.

taz

Except at the place I'm on about the vents are Fork truck size.

smpsmp45

21-11-2007, 11:01 AM

Even I have few photographs which had the ceiling issues. Even the suspension arrangement too was bent by almost 25mm or so.

One has to see that to believe it.

But Again the file is too big to be uploaded.

Josip

22-11-2007, 08:39 PM

Hi, smpsmp45 :)

Even I have few photographs which had the ceiling issues. Even the suspension arrangement too was bent by almost 25mm or so.

One has to see that to believe it.

But Again the file is too big to be uploaded.

You can split your file and upload within 2-3 posts, no problem, photos you can resize down to 100kb..jpg, gif, etc and upload 5 photos in one post;)

Best regards, Josip :)

Josip

22-11-2007, 10:02 PM

Hi, Sergei :)

Hi, Josip.
I'm curious to see the doors of this cold room. It is a dream to have industrial cold room doors so tight as kitchen freezer door.

Sergei

What Grizzly wrote is true, but overpressure pressure is able to open the doors or to distort the walls/panels too ;)

They will of at sometime had the situation where " The door won't open" (the vaccum inside is keeping the door shut.)

It is not the question about tightness, no need to dream about, but some of them are gas tight for example ULO cold stores;), it is more about temperature and pressure change...

....for example having cold room doors at size 2,5 x 3,2 m (8 m^2) open with automatic close from 0-120 sec or manual close....try to imagine how many cubic meters of warmer and humid air will get in during that time rising the pressure....then we close the doors and start to freeze water vapour causing air pressure fall....

defrosting....freezing...cause pressure change....

...., but pressure changes we can have and we have due to weather change causing change of atmospheric pressure...eg.storms

Temperature change of 1 degree Celsius can cause approximately pressure change of 40 mm WC (water column) 40 kg/m^2....what is evenly distributed load of 29 metric tons :eek: on the cold room ceiling from my previous post...

....seems, it is not so bad idea to install pressure relief valves....

for more info about doors, please, see here...

http://www.ems-isolier2.de/gb/download/schiebetueren.asp

Best regards, Josip :)

Sergei

23-11-2007, 05:52 PM

This is only question of doors tightness. I agree that possibility of vacuum in refrigeration room exist, but only if the doors are tight. I think that these ports should be installed for walk-in freezers, but for industrial cold rooms(drive-in) impossible to get doors tightness.

Grizzly

23-11-2007, 10:04 PM

Industrial Cold Store Doors are airtight. IF NOT the warm higher pressure air from outside. Flowing into the cold store chamber condensates and freezes, causeing the door to be sealed against the door jamb
(frame in common english). ( There are also periferal heaters within the frame and embedded into the floor)
Obviously most of the doors do not remain perfectly sealed. Especially as previously mentioned, when they have been hit by a fork truck or 2.
The average UK Cold Store is 600,000 to 1,000,000 Cubic feet PLUS. with an average of 3 to 4 doors.
With -18c the required minimum chambers are kept at anything between -25c to -20c ( -13 to -4f ) so there is a thermal buffer. 1, I used to look after had a chamber at -29c ( -20.2f ).
So even during the winter months were we average say 8c there is a difference of 30c ( -22f).
Therefore the pressures pushing in ie. Forces pushing the door shut can be quite large. Not forgetting as originally mentioned the walls themselves!
The temperature differances between inside a store chamber and outside can be huge.
A moist product can have its weight reduced
dramatically through being stored for long enough.
Sometimes consignments are reduced by TONS.
ANYWAY THATS ANOTHER STORY.
remember leaking doors are money being thrown away.
Cheers Grizzly
Sorry for the rant guys but the doors are kept as airtight as possible. The primary concern is to limit heat introduction into the store. Also on larger stores the reason there is not normally an issue is because of the volumes / area 's involved and the constant operational traffic
equalises out the pressures faster than large pressure differentials can be achieved.
But as I have tried to explain there is huge potetial for problems if the need for pressure relief valves is not considered.

gwapa

30-11-2007, 11:16 PM

Hi Every body
It is clear when we have a closed volume and we lower the internal temperature then the presure will also lower

Pv=RT
PV=mRT
P=(R/V)mT

v=V/m
Where v is especific volume
and V is the Walkin Room

So the internal presure depend of the internal temperature and the air mase.
The air mase is a mixture of N2,02 and vapor of water . When we lower the internal temperatura and we condensate the humidity, both term of the equation m and T lower so the internal pressure will low dramaticaly. It cause an internal heavy vacuom.
That is the reason why we have to protect with safety valves the freezer. Our friend Smpsmp45 post the formula to estimate the number of valves

Now it is very import too, the location of the valves.
Some time we located the valves in a place where the outside wind velocity is high and it produce a static pressure over the valve pushing humidity inside the room and creating some frost araund the valves.

So I would like to hear from you your expirience in the location of this safety valves
Regards
Gwapa

smpsmp45

01-12-2007, 06:23 AM

Incidently the doors on the cold stores were from EMS!!!.

I shall try & split the Photos in small size & try & poet them up.

yes the location is very important. The valves should not be fitted in the air path as otherwise, the valves shall be forced open due to the air pressure. So also they should not be in the suction path of the fans. That also makes them open inwords causing considerable leaks into the cold store. So also they should be located preferably in the ante room wherein no ambient air is taken inside incase the valves operate.

We have as a precaution started putting up an indicator in series with the heater on the valve. So that one knows that heater is operating.

Peter_1

01-12-2007, 09:15 AM

smpsmp45

01-12-2007, 03:44 PM

Dear Peter_1,

Megaupload has no uploading available from India for timebeing as it has exhausted its limits.!!!

gwapa

01-12-2007, 04:59 PM

smpsmp45
I think it is not a good idea to install the safety valves in the wall between the freezer and ante room
I prefer select a wall to the outside o maybe the roof panels

Sergei

03-12-2007, 01:08 AM

smpsmp45, otherwise via megaupload.com.

Sergei, a well service door is always gas-tight.
Why can an industrial freezer-door not be gas-tight?
I don't see the difference with a commercial freezer.

If not ,you will see a lot of snow forming on the ceiling above your door. This snow falls down on the entrance in front of the door and the reach-trucks will melt this due to the high weight. So this will become an ice-rink instead of a freezer.
Commercial freezers have swinging doors, industrial freezers have sliding doors. I didn't see gas-tight sliding doors. It is something new about snow melting inside the freezer by lift trucks. Where did you see this?

Josip

03-12-2007, 09:31 PM

Hi, Sergei :)

Commercial freezers have swinging doors, industrial freezers have sliding doors. I didn't see gas-tight sliding doors. It is something new about snow melting inside the freezer by lift trucks. Where did you see this?

Maybe you did not see, but I was supervisor engineer during installation a lot of gas-tight freezer sliding doors. Seems some other members can say that too....

Gas-tight :confused: I do not understand what is gas-tight for you...here we are speaking about very small pressure difference and very very small leaking but practically those doors are gas tight but not tight like car tire...

For example: speaking about vacuuming of system can be the same... we all know that absolute vacuum we can not reach at refrigeration plants...thus vacuuming is useless because it is not an absolute vacuum:confused:

Regarding Regelation please see links..
http://www.newton.dep.anl.gov/askasci/gen99/gen99523.htm
http://en.wikipedia.org/wiki/Regelation
http://www.tiscali.co.uk/reference/encyclopaedia/hutchinson/m0016641.html

Best regards, Josip :)

Sergei

04-12-2007, 06:23 PM

Hi, Sergei :)

Maybe you did not see, but I was supervisor engineer during installation a lot of gas-tight freezer sliding doors. Seems some other members can say that too....

Gas-tight :confused: I do not understand what is gas-tight for you...here we are speaking about very small pressure difference and very very small leaking but practically those doors are gas tight but not tight like car tire...

For example: speaking about vacuuming of system can be the same... we all now that absolute vacuum we can not reach at refrigeration plants...thus vacuuming is useless becuse it is not an absolute vacuum:confused:

Regarding Regelation please see links..
http://www.newton.dep.anl.gov/askasci/gen99/gen99523.htm
http://en.wikipedia.org/wiki/Regelation
http://www.tiscali.co.uk/reference/encyclopaedia/hutchinson/m0016641.html

Best regards, Josip :)
Hi, Josip.
I think that we have 2 types of door tightness. Pressure tight and draft tight. To damage the freezer, door should be pressure tight.
1. Home fridge. Door should have good alignment with the frame. Door tightness can be checked by opening and closing this door quickly. Slight vacuum should be created in the fridge. This vacuum will be braked in few second by air from defrost water drain. Vacuum won't be created if door misaligned. Door closer(magnet) isn't strong and any pressure inside the fridge will be released through drain or door seal.
2. Walk in freezer. Door gasket is thick to compensate any misalignment, closer is strong and it can keep the door tight under certain pressure inside the freezer. This door can be pressure tight. Freezer walls can be damaged if defrost water drain is frozen or plugged.
3. Industrial freezer(sliding doors). These doors are draft tight to prevent free air movement in and out of the freezer. These doors aren't pressure tight. To be pressure tight, they should have device(closer) to push them to the frame and to the floor. Theoretically it can be done, but not practically, because these are high traffic doors(unlike fridge door and walk in freezer door). Industrial doors, usually have just rubber strips for draft tightness.

Josip

04-12-2007, 11:50 PM

Hi, Sergei :)

Hi, Josip.
I think that we have 2 types of door tightness. Pressure tight and draft tight. To damage the freezer, door should be pressure tight.
1. Home fridge. Door should have good alignment with the frame. Door tightness can be checked by opening and closing this door quickly. Slight vacuum should be created in the fridge. This vacuum will be braked in few second by air from defrost water drain. Vacuum won't be created if door misaligned. Door closer(magnet) isn't strong and any pressure inside the fridge will be released through drain or door seal.
agree...

2. Walk in freezer. Door gasket is thick to compensate any misalignment, closer is strong and it can keep the door tight under certain pressure inside the freezer. This door can be pressure tight. Freezer walls can be damaged if defrost water drain is frozen or plugged.
agree...

3. Industrial freezer(sliding doors). These doors are draft tight to prevent free air movement in and out of the freezer. These doors aren't pressure tight. To be pressure tight, they should have device(closer) to push them to the frame and to the floor.
agree and not agree...and they have device (eccentric rollers to push them to the frame and weight to pull them to the floor...

Theoretically it can be done, but not practically, because these are high traffic doors(unlike fridge door and walk in freezer door). Industrial doors, usually have just rubber strips for draft tightness.
...double rubber strips all around and frame heater/s to avoid formation of ice due to small air leak...

Let's return to beginning....why and how many pressure equalizing valves to install on industrial drive in freezer rooms... equalizing

As per my knowledge and experience during time people have faced some problems with collapsed cold room walls/ceiling....they start to investigate why...found out that is due pressure reduce caused by low temperature....what to do ...doors should be tight as much as possible ...still with some air leak but negligible and for that reason they start to install pressure equalizing valves to avoid further damages... (leak of air through door sealing rubber was not enough to equalize air pressure;)) furthermore the doors are on external side of the room thus created vacuum pull them close to the frame reducing small air leak practically to zero...

You may not agree with me, but as I said before I would not dare to not install those valves to industrial drive in freezer room...never;), that could be too expensive...

Best regards, Josip :)

smpsmp45

05-12-2007, 11:04 AM

Dear gwapa,

Can you pl. explain why you prefer them to be put in the ceiling???

smpsmp45

05-12-2007, 11:25 AM

Pl. check these photos from top of the ceiling.

Even the top skin is damaged.

http://upload.imgspot.com/u/07/338/01/P1010944.JPG
http://upload.imgspot.com/u/07/338/01/P1010949.JPG

Grizzly

05-12-2007, 06:45 PM

SMPSMP45.
Great pictures. Not so easy to repair those panels eh!
I was at a chill room (-5.5c) today and the pressure relief valve was sited below 1 of 2 evaporators.
This room is maintained at -5.5c and the vent opens into a production area with a room temperature in the high 20's.
Guess what? This evap keeps freezing up, do I know why? And can i HELP?
At the moment I have set the defrost interval at 5hrs and a duration of 45min.
Hopefully this will be often enough to combat the volume of hot moist air being introduced?
Time will tell!
Cheers Grizzlyhttp://www.refrigeration-engineer.com/forums/images/icons/icon14.gif

Sergei

05-12-2007, 07:14 PM

Hi, Sergei :)

agree...

agree...

agree and not agree...and they have device (eccentric rollers to push them to the frame and weight to pull them to the floor...

...double rubber strips all around and frame heater/s to avoid formation of ice due to small air leak...

Let's return to beginning....why and how many pressure equalizing valves to install on industrial drive in freezer rooms... equalizing

As per my knowledge and experience during time people have faced some problems with collapsed cold room walls/ceiling....they start to investigate why...found out that is due pressure reduce caused by low temperature....what to do ...doors should be tight as much as possible ...still with some air leak but negligible and for that reason they start to install pressure equalizing valves to avoid further damages... (leak of air through door sealing rubber was not enough to equalize air pressure;)) furthermore the doors are on external side of the room thus created vacuum pull them close to the frame reducing small air leak practically to zero...

You may not agree with me, but as I said before I would not dare to not install those valves to industrial drive in freezer room...never;), that could be too expensive...

Best regards, Josip :)
Hi, Josip.
Two have a vacuum in the freezer we need 2 events at the same time:
1. Freezer doors should be pressure tight.
2. Defrost water drain should be plugged.
It is hard to believe that big industrial doors can be pressure tight. What about the drains? Why they are plugged?
Probably, the reason of collapsed panels is rapid cooling of new building. Warm building should be cooled gradually(a few deg. per day), otherwise inner part will shrink too fast and can damage outer part other building.

smpsmp45

06-12-2007, 07:59 AM

Dear Grizzly,

If the Relief valve is in the suction path of the evaporator fans- & that is so. Your problems shall never end. The valve shall keep sending air from outside & the freezing shall never stop. Remove the valves immediately then only the things can improve.

Josip

06-12-2007, 09:26 AM

Hi, smpsmp45 :)

Pl. check these photos from top of the ceiling.

Even the top skin is damaged.

http://upload.imgspot.com/u/07/338/01/P1010944.JPG
http://upload.imgspot.com/u/07/338/01/P1010949.JPG

Sorry about your troubles...not nice...a lot of works for repairing...

Just curious....is this Allana in New Mumbai?;)

Best regards, Josip :)

gwapa

07-12-2007, 02:40 AM

Dear SMPSMP45
First of all nice photos

To located the pressure equalizing valves I would said that we have to check where there is a spot inside the freezer where the internal air velocity is perpendicular to the wall panels .Is is normally in the oposite wall where the evaporator are.
Some times when we install the equalizing valves in the side wall ,the internal air velocity create a ventury efect getting in water humitity which condensate forming a ball of frost
At the air return the static presure is the lowest so it will increase the humity coming in and frost formation in the evaporator

smpsmp45

07-12-2007, 04:44 AM

Dear Josip,

I am curious to know more about you!!!!! You know lot of things about India. You work with Carsten????? Yes the Photos are related to Allana.

Josip

07-12-2007, 09:04 PM

Hi, smpsmp45:)

Dear Josip,

I am curious to know more about you!!!!! You know lot of things about India. You work with Carsten????? Yes the Photos are related to Allana.

No problem;), tell me what you want to know?

Yes, I was in India and I am in touch with some very nice people there:D

I was walking on those panels...maybe we met each other...I am using my real name here....but some use to call me Joseph:)

Working with Carsten too, from time to time ;) I'm freelance....

Best regards, Josip :)

Peter_1

07-12-2007, 10:49 PM

Josip, Smpsmp45....what a small world, what a coincidence.
This emphasizes once again the power of this forum which goes over boundaries, ethnic, political and religion diversities.

Both already some time here and just no realizing that you perhaps met each other already.

A fine story.

Next time Josip, take a big fat marker pen and wrote on the roof - nobody sees this- your name and date.
Like My dad and later I did when we poured concrete, my fathers name and/or mine was always in the concrete as long as the concrete remained on its place.
Like my name in some switch-cupboard behind the panel or on the back of it.

Did a little search http://www.allana.com/products.html

Like the story of Kilroy http://en.wikipedia.org/wiki/Kilroy_was_here