Defrost horizontal plate freezers

[Sandro Baptista]

Hi Guys,

What's your advices about having or not having defrost on the horizontal plate freezers. If not defrost isn't there the danger of damage the hydraulic jackets?

Can you please comment your experience on the field?

BR

[charlie n]

Plate freezers should be defrosted daily. Hot gas goes in at the top of the liquid header. Defrost relief should be connected to the bottom of the suction header.

[Sandro Baptista]

Charlie n,

But even for the horizontal plate freezer do you see as very necessary/important?

[Tycho]

Charlie n,

But even for the horizontal plate freezer do you see as very necessary/important?

depending on the ice build up on the freezer, the amounts of defrosts could be discussed.

if it's a ammonia system you need to have a hotgas defrost system in case you get oil build up in the lower plates.

[charlie n]

If you are freezing a finished product, the requirement for a smooth, consistent product means the plates have to be defrosted. Tycho also has a good point. Defrosting pushes the oil out of the bottom plates if the piping is correct.

[lowcool]

no ice build up = more heat transfer

[Sandro Baptista]

Defrosting pushes the oil out of the bottom plates if the piping is correct.

Don't see a problem. On the next cycle on the first minutes the high load transfer will cause a high NH3 vapour mass flow resulting on the oil carry out of the plate freezer.

[Tycho]

Don't see a problem. On the next cycle on the first minutes the high load transfer will cause a high NH3 vapour mass flow resulting on the oil carry out of the plate freezer.

If you say so :)

[Sandro Baptista]

If you say so :)
Don't you agree.

Despite the statement above this thread was the purpose to know your experience about using or not using the defrost to "save" the hydraulic mecanical parts. As for the vertical plate freezers I see that is extremally necessity on using the defrost so we can get out the product from between the plates.

[Tycho]

Don't you agree.

Despite the statement above this thread was the purpose to know your experience about using or not using the defrost to "save" the hydraulic mecanical parts. As for the vertical plate freezers I see that is extremally necessity on using the defrost so we can get out the product from between the plates.

I was saying that in my experience, if you do not defrost a horizontal platefreezer at all, you WILL get a buildup of oil in the lower plates and get bad performance.

the hydraulic system will probably not suffer, but you could cause damage to the plates of you load trays into a freezer when the plates are still covered in ice.

On ships that freeze catering (horizontal freezers) some defrost by eye, meaning they defrost when the ice is starting to build up, and some defrost every time they open the freezer, but on these ships it's mostly still *****.

On a land factory where we do service the on site technician says that they have to defrost every two to three cycle because of oil build up in the lower plates.

remember that most horizontal freezers (at least all MMC/ kvaerner kulde freezers) have a downpipe in the liquid collector pipe, this is there for the single reason to make sure that the lower plates are emptied and that oil will leave the freezer when the flow is reversed during defrost.

You say that oil will leave the freezer when you start a new freezing cycle with "warm" product, but remember that oil will gather in the bottom on an ammonia system, and as the freezer has been shut off for 10-15 minutes while frozen product is added and fresh product is added, the freezer is still full of -40/-20C liquid standing still, oil will have time to sink to the bottom, and once the 0.5mm nozzle on the liquid side of the plate is clogged with -40C oil it's not gonna let any liquid through, and the addition of more cold liquid will only help to make sure that that nozzle will stay plugged and you will not get any freezing on that plate.

In vertical freezers you need defrost to loosen the product from the plate since the product is in direct contact with the plates and will stick. Once again, the hydraulic system is strong enough to damage the freezer if it is operated without first defrosting.


On many ships with vertical freezers, we see that the operators open the hydraulic and then open the hotgas so they can take a smoke and coffee when it defrosts, when they hear a loud bang as the plates let go of the product after defrosting half the plates they are ready.

This seriously damages the platefreezer over time and in the end, the whole thing will be so warped that the bottoms will fall sideways and get wedged under the plates so that next time they lift it, they lift the whole plate package, and it will also curve the front of the freezer, so that the blocks in the middle of the freezer are longer than the blocks on the ends, this again causes problem in packaging when the blocks won't fit in the cartons.


How's that for a discussion?

Hope it made sense :D

[Sandro Baptista]

You say that oil will leave the freezer when you start a new freezing cycle with "warm" product, but remember that oil will gather in the bottom on an ammonia system, and as the freezer has been shut off for 10-15 minutes while frozen product is added and fresh product is added, the freezer is still full of -40/-20C liquid standing still, oil will have time to sink to the bottom, and once the 0.5mm nozzle on the liquid side of the plate is clogged with -40C oil it's not gonna let any liquid through, and the addition of more cold liquid will only help to make sure that that nozzle will stay plugged and you will not get any freezing on that plate.
Hope it made sense :D

The statement above it could be true as you say depending of the pipe/manifold at outlet of the plate freezer.
This is a good discussion