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joanna
27-02-2013, 04:31 PM
Hello everyone.
There is an unexplained phenomena when we test the R22 screw ethylene glycol unit.I use howden compressor.The unit include a dry economizer.We put an fiter and a non-returen valve on the return line from economizer to the compressor(the non-return valve is near the compressor).But the temerature before the filter and after the filter is abnormal,almost it has 50 ℉ temperasure rise .We dismantal the filter,and it is not blocked.
:confused:

Rob White
27-02-2013, 04:41 PM
.

The obvious problem with any temp difference over a filter is a
pressure difference. If the temp changes then the pressure does
also.

I have no explanation why it would rise though.
Are you sure you mean rise? Measure the temp into the filter and then
out of the filter and let us know the actual measurements.

Regards

Rob

.

sterl
28-02-2013, 09:16 PM
Rise? As in outlet temperature Higher?

Check valve not closing and side port pressure too high.
What form the oil cooler on this arrangement?

cricri
28-02-2013, 10:47 PM
Hi Joanna,
the high temperature is probably caused by an oil flow back from compressor to the non return valve. either there is a very low flow of gas from the eco or the eco suction line is oversized.
you didn't forget a plug in the suction port?
what is the type of compressor (WRV, XRV....) and running coditions?

joanna
03-03-2013, 04:21 PM
The oil cooler is thermosyphon.We put a thermostaic valve on outlet of the oil cooler.the oil temperature is stable.
The compressor is howden WRV.the evaporation temperature is 14℉ and the condensing temperature is 91.4℉ .
The economizer is plate-type heat exchanger.
We dismantal the filter and it is not blocked.and the stop check valve is ok.and the thermo-static expansion valvle is appropriate.
I don't know why the temperature rise near the filter.

RANGER1
03-03-2013, 09:36 PM
Can only suggest not constant flow through cooling circuit of economizer.
Assume pipeed in copper so it will chill down very quickly, where larger strainer components would not.

Do you have a constant feed in main liquid line through a modulating valve? Or is it just on/off when required?

Magoo
04-03-2013, 01:24 AM
A low micron mesh in Y strainer will create a pressure drop and temperature change, try a larger micron grade mesh in strainer and compare the difference, or even take strainer cartridge out and compare difference. Generally Y strainers are for liquids so when applied to vapours, careful selection of micron rating is required.

joanna
04-03-2013, 04:47 PM
We take out the strainer catridge out , the temperature is still rise like before.
The liquid line to the economizer is on the middle of the main liquid line.And the stop valve stem is upward.Is the main liquid line full of liquid or it has some vapor in it. Does the stop valve should be installed horizontally?

Tycho
04-03-2013, 06:20 PM
is the economizer "active" as long as the compressor is running, or does it open when the compressor is at full capacity?

Seems like you have a higher pressure at the superfeed port than the economizer can deliver, the abnormal heat may just be heat "crawling" along the pipe from the compressor.

try activating the economizer when the compressor is at a part load and see if it helps?

I have had a similar problem with XRV compressors, when we use Liquid refrigerant injection for oil cooling (NH3), it won't start feeding before I have 19-20 degrees condensing pressure.

Tycho
04-03-2013, 06:23 PM
also, what type of WRV is it exactly?

and suction/discharge pressure?

I can run it through the calculation software tomorrow at work and see what pressure there will be at the superfeed port.

Magoo
05-03-2013, 01:40 AM
Looking at the pic the Y strainer is installed back to front. Creating a high pressure drop with or without cartridge fitted. The take off for econo liquid is not good, a Y take off and extension into main liquid off the bottom of main would help ensure continuous liquid feed to econo

joanna
05-03-2013, 03:06 PM
Thank you all!
The compressor is howden WRVi255/1.3,the evaporating/condensing temperature is -10/+33℃.The strainer in the picture show before is on the liquid inlet line of the economizer.The next picture maybe looks more clear.

Tycho
05-03-2013, 04:57 PM
I ran it through the calculating software and came up with 5.5 bar at the superfeed port.
The pressure you had noted in the pdf file (5.79bar), is that an actual reading?

is it possible to measure the pressure before the expansion valve?

all I can figure right now is that either the liquid pressure before the TEX is to low, or the non return valve is stuck or the spring is to strong for the small pressure difference

Magoo
06-03-2013, 02:37 AM
The Y strainer looks extremely small for vapour duty, check manufacturers rated Kw duty as a vapour strainer, the units I use are twice the physical size, lower PD. Is the stop valve after the strainer a combo stop/check

Tycho
12-03-2013, 09:28 PM
Wondering how this turned out

Fred Mataro
13-03-2013, 05:50 AM
Hi all,

We had this similar case just recently and it was even worse, the insulation on the pipe from the control Danfoss PM3 valve to the compressor economizer port had some sort of chemical reaction and burnt!! We think that the pipe temperature has been rising due to prolonged vacuum. The root-cause was due to the malfunctioning pilot valve (LP) which made the valve at closed position in a very long time although the solenoid valve was operating. The unit running on full-load all the time so the economizer port of the compressor is open. This is a Frick ammonia screw compressor.

Hope this will help.

Fred

Josip
15-05-2013, 07:49 AM
Hi, joanna :)


Hello everyone.
There is an unexplained phenomena when we test the R22 screw ethylene glycol unit.I use howden compressor.The unit include a dry economizer.We put an fiter and a non-returen valve on the return line from economizer to the compressor(the non-return valve is near the compressor).But the temerature before the filter and after the filter is abnormal,almost it has 50 ℉ temperasure rise .We dismantal the filter,and it is not blocked.
:confused:


Seems, you have a problem with NRV (non-return valve) and oil is flooding back to eco pipe. If that one is a flap type it is very important position and place where is installed.


Best regards, Josip :)

sgull
20-05-2013, 05:26 PM
Hi.
Since this is a WRVi compressor the VI is manually adjustable.
You should verify that this is set correctly as an incorrect setting can cause an increased pressure at the economiser port.
With the conditions you mention above the VI should be 3.2
To set this stop the compressor, turn VI adjusting screw clockwise until it locks, then turn anti clockwise 7 turns.
Regards
Denis