PDA

View Full Version : Liquid Line Driers







GSUK
08-02-2012, 07:13 PM
Hi,

I'm new to this forum and I'm after some advice :)

I'm not a refrigeration engineer. However, I am responsible for ensuring the two 250kw chillers I have on site are maintained and serviced regularly. Iíve just had a service report back from the engineers and a fair bit of remedial work is required. One of the jobs is to replace the liquid line driers. So, my questions are:


Is it possible to detect when one needs replacing?


Are they essential or will chillers run ok without them?


Do they have a certain life expectancy? (both chillers are about 4 to 5 years old)



I'm basically trying to work out if they really do need replacing or if it's just a nice "tick in the box" to have them replaced.

Thanks in advance for all advice.

chemi-cool
08-02-2012, 07:55 PM
Driers are to be replaced at the minimum, once in two years, mainly as precaution, every time the system is opened, when acidity test shows acid, when it is blocked or partially blocked.

Its one of the cheaper parts in the system but very important.

You can have a system run without one but you will have to take full responsibility.

Grizzly
08-02-2012, 08:21 PM
To add to Chemi's excellent answer. I would say frequency can depend upon the chiller size and make.
On some larger systems we change the Driers every Year.
Those would be the cannister type with a removable end cover.
If you have some service records refer to them to see at what frequency they have been changed in the past.
Size and frequency of use does matter.
Grizzly

monkey spanners
08-02-2012, 08:35 PM
The third blocked drier in the vid led to a 5K compressor replacemnt, it caused the system to cycle too rapidly and the compressor suffered a lubrication failure.

http://www.youtube.com/watch?v=NcrnzxbEtSk&feature=g-upl&context=G2f0d8b4AUAAAAZAAAAA

Like a lot of things, you can either pay for it now or pay for it later!

Jon :)

Tesla
09-02-2012, 07:02 AM
It's like a car, the cheapest things to replace are oil and filters (driers in refrigeration) as prevention is better than cure, there should be records of oil sample analysis too.

Scottyice
24-03-2012, 05:07 PM
I would recommend that you change drier cores once in every two years. If there has been a problem with the unit I recommend that they are changed as good practice, and if work is due to be done on a unit then they should be replaced.

Chillers and refrigeration plants alike will run without a drier, but it's always good to have something there to remove moisture from the plant. Like it has been mentioned that would be your responsibility and not that of the refrigeration contractor

Nh34life
24-03-2012, 10:00 PM
The moisture absorbing capacity of a drier core is minuscule so changing them often will ensure your system is clean and dry, If it were my system I would install duel set so they can be changed online every 6 months or after any line opening/ compressor service, get in writing what vacuums were achieved after each service if you want to be finicky and scare your service company, this will ensure there are no quick purge short cuts, get oil samples taken regularly also, if this is done as well as other condition monitoring like VA you will save a fortune over the life of the unit ( no catastrophic failures ) this will give you excellent trending records and allow you to forsee problems and establish when issues had occured, So common with customers they will not do the $100-$500 repairs and it bites back hard however this is when the person in charge sacks the service company to cover his arse!

Peter_1
25-03-2012, 03:03 PM
I disagree with most of you.
What about a VRV/VRF which is running the whole year? When and even better, where will you replace the drier?
If the system and more specific in this case, a factory made chiller was soldered with nitrogen, was vacuumed according to the proper rules and the system was never opened, the sight glass shows a dry refrigerant, why then replace the drier?
I still have now systems running more than 30 years old which never saw a wrench and with the original drier in it.
You may not compare this with a care engine where you have internal combustion, ingress of moisture, acids, oxygen, water, excessive temperatures in some parts of he motor, ...
The chiller is working on an overpressure, so it can't never contaminate from the outside.
Make it runs fine and well tuned the whole year (clean condensers, clean evaporators, flow switch working well, superheat as low as possible and needed, safety devices checked...)
The moisture absorbing capacity of a drier is indeed not that big but we're not dealing anyhow with large quantities of water in a refrigeration system. Ever visualized boiling of water with vacuum? This goes fast, very fast. We're not talking any longer of water but about moisture.
If a drier blocks like the one in the movie of Chillerman - and especially the high quality Sporlan driers and not the KMP or Totaline drier like in the 2nd part of the Youtube movie - then this happened mostly due to impurities which were brought into the system by technicians themselves (air intruding when attaching manifolds, nitrogen trapped in the system after leak or pressure testing, LP safety devices cut off in vacuum, water in the hoses, topped off with contaminated refrigerant recovered on another site,...) Or the system ran with too high Hp pressures, lack of refrigerant,...
My device is: if it's running fine...don't touch it.

Grizzly
25-03-2012, 03:21 PM
Size and frequency of use does matter.
Grizzly

I agree Peter.
However to whoever is reporting to GSUK may have a valid reason for changing the driers as we don't know what other works have been advised.
There are certain tasks where we would recommend the changing of the liquid line filters.

So although yours is a sensible and practical argument, We are all dealing with a non fridge person.
Who is being very fair and honest.
My training has been that the need to change would depend upon the D/Temp across the filter.
I don't want to go further as we may be loading a gun for GSUK to fire at innocent engineers.

Also if we take over a troublesome or unknown chiller contract, one of the things we would recommend (especially if their are scant records) is filter and maybe even a oil change?
Further recommendations are not unknown however the state of this plant is!

Grizzly

Peter_1
25-03-2012, 03:46 PM
Grizzly, agree for 100% If we take over machines from other technicians, one of the first things we doe is taking oil sample and changing driers. Because we always suspect what others did on these machines and I don't want to take any risk that they will point to us when we have a failure after we just took over the maintenance.

aramis
25-03-2012, 03:57 PM
I agree with Peter_1 and Grizzly

You should change filter dryers if and only if:

The system manufacturer (or any other entity by contract) states a time to change filters in lieu of warranty or other contractual reason, though stupid it may seem.

If the filter dryer shows an increasing pressure drop trend.

Visible signs of temperature change within the length of the filter.

If you have any signs that the refrigerant contains water like a sight glass humidity detector changing color.

If an oil test checks for acidity.

If a megohm meter shows a decreasing trend.

If oil changes color (without a reasonable explanation).

If you have to intervene the system in anyway, like for leaks.

If the system is working OK I would’t even touch them. As for life expectancy (except for the above) I’d say the same as the least life expected for any other part of the system.

Changing for any other reason won’t solve anything and something may go wrong because of it.

Peter_1
25-03-2012, 04:02 PM
Aramis, the perfect answer :-) .