Great problem........

[nike123]

Whenever HE inlet ref. temp. reached at 3 deg. C.

If your HE has Δt of 0K or 1K as measured and stated in your data than freezing fault mean that your set point is set to low or you have some changes in water flow during operation that can lead to high Δt. Or you have faulty temperature sensors.

Also, alarm of 3°C should be triggered by water outlet temperature.

According to our previous discussion I think that main problem there is incorrect water flow which probably varies as other circuits on that network closes or opens for regulation and by that action changes balance of flows. That can be connected with reading of evaporation temperature at 9:10, 10:30, 11:30. So you should first ensure steady and corect water flow at that chiller. Where did you measuring water outlet temperature. Is that measured at common pipe of other chillers, or at evaporator outlet?

Next what can be read from your data is that you still have lack of any subcooling. Ether it is short of refrigerant, incorrect or contaminated refrigerant or your air flow is incorrect or your heat exchanger need cleaning.
So you should measure airflow, clean condenser and recover portion of refrigerant in drum and check its correct PT ratio.

Also, according to your data, you have negative approach at condenser in amount which is possible only when there is no saturated refrigerant there.
If there is no liquid refrigerant at enter of EEV than there is no liquid refrigerant that evaporate and that is why other data looks like that in your table.

No subcooling at condenser outlet
No subcooling at EEV inlet
Low amperage
High evaporator approach
Negative condenser approach (no saturation)

[moideen]

everybody confirm that PHE is in trouble.so better to overhaul or replace PHE.please go to this link.you can down load PHE maintenance manual
http://www.schaufcompany.com/v3/owner/alfalaval.htmlmoideen-dubai

[Bashir01219]

Sir,
Thanks, we will do what you suggest.
We measured chilled water temperature just after the HE, actually we provide two temperature gauges in the chilled water inlet & outlet, and we calibrate it several times with the testo apparatus. And we can check it through inlet outlet sensors.

[Bashir01219]

Thanks Sir,
@moideen
It will help us lot.

Thanking You,
Bashir

[eghbali]

It explained that the density of subcooling on refrigeration for correctly making the expansion valve is necessary saturation temperature of 15 degrees Fahrenheit above the temperature cycle is good.
Better characteristics for proper charging system is suctionsuperheat saturation temperature above 10 degrees Fahrenheit is good.If this rate is higher undercharge system. If this amount was less overcharge system</SPAN>

[nike123]

It explained that the density of subcooling on refrigeration for correctly making the expansion valve is necessary saturation temperature of 15 degrees Fahrenheit above the temperature cycle is good.
Better characteristics for proper charging system is suctionsuperheat saturation temperature above 10 degrees Fahrenheit is good.If this rate is higher undercharge system. If this amount was less overcharge system</SPAN>

To use superheat or subcooling as indication of charge depend on used metering device. Since here is EEV which maintin programed superheat, correct is charging by subcooling.

[Bachuss]

Have you checked that the evaporator is clean and clear on the water wide, in many places even supposedly clean water can leave scale which creates a restriction in the water lines and insulation from the refrigerant both of which will stop your water from chilling.

[Bachuss]

To use superheat or subcooling as indication of charge depend on used metering device. Since here is EEV which maintin programed superheat, correct is charging by subcooling.

Personally I don't think you can use only sub cooling or super heat to charge a system, you should also be watching the motor running amps of the compressor and your sight glass.

[Bachuss]

Sometime I can no believe my luck! Wherever I go, whatever I see, I always found problems………..
Pressure drop across Evaporator 1.2 bar,
Read properly before answer.

No offence intended but is hard to read properly when English is so obviously not your first language.

[Bashir01219]

No offence intended but is hard to read properly when English is so obviously not your first language.

What does it mean?
Maybe I just miss a "T", no=not; when you are busy this might happen.

[Bashir01219]

Have you checked that the evaporator is clean and clear on the water wide, in many places even supposedly clean water can leave scale which creates a restriction in the water lines and insulation from the refrigerant both of which will stop your water from chilling.

Yes, we clean as described by the HE supplier, SWEP.

[Bashir01219]

To use superheat or subcooling as indication of charge depend on used metering device. Since here is EEV which maintin programed superheat, correct is charging by subcooling.

Sir,
After cleaning the HE, and adjusting the chilled water inlet and outlet flow we are getting improved result (I mentioned improve result only the basis of chilled water inlet and outlet temp. diff. previously it was 1 or 0 but now it consistently 2 or 3). We close 70% chilled water inlet line & 10% chilled water outlet line (valves r butterfly). What is the logic? If i want to set up a logic. We yet not charged the system as refrigerant is not available, it will take some time.

[nike123]

Sir,
After cleaning the HE, and adjusting the chilled water inlet and outlet flow we are getting improved result (I mentioned improve result only the basis of chilled water inlet and outlet temp. diff. previously it was 1 or 0 but now it consistently 2 or 3). We close 70% chilled water inlet line & 10% chilled water outlet line (valves r butterfly). What is the logic? If i want to set up a logic. We yet not charged the system as refrigerant is not available, it will take some time.

OK good! You need now to take whole set of measurements again. Try to provide all data as asked before. It is essential to cover all data for proper evaluation.

[nike123]

Personally I don't think you can use only sub cooling or super heat to charge a system, you should also be watching the motor running amps of the compressor and your sight glass.

Motor running amperes are dependent on mechanical state of compressor and compression ratio. With corect charge and various temperatures of evaporation and condensation (which depends on many things) you have various current reading. Therefore, current of compressor is not clear indication of correct charge, but it should be monitored in case if something other is wrong, or to be sure that you are not grossly overcharged.
Sight glass could be misleading especially with blends because they represent difference in flow resistance (therefore pressure change) and liquid refrigerant could flash in sight glass and collapse again after sight glass when flow restriction become same as before sight glass.

Proper subcooling and proper superheat along with proper air/water flows and cleanliness of heat exchangers will tell you that you have balanced and properly charged system.

[icecube51]

how has this story ended??? ore is the problem still on??

Ice

[garethjones10]

Hello

This is Gareth Jones

what type of evaporator is it? Plate heat exchanger or shell and tube?

It would appear that there is a lack of heat exchange occuring, if it is a shell and tube it is possible that the refrigerant is bypassing the evaporator via. a split end gasket, allowing low pressure liquid refrigerant through to the suction. I have had a similar problem in the past but my concern was with the low superheat. The compressor turned out to have the wrong oil, mineral instead of synthetic. This caused waxing on the evaporator tubes which reduced the heat exchange and superheat.

Gareth
CNM ONLINE

[Bashir01219]

sometnhing may happen with the page, I can not replay

[Bashir01219]

@ICE: This is really frustrating for all of us, our knowledge is limited but we tried all the possible ways. It seems that the problem with the beginning or commissioning period nearly two & half years ago (and that time I worked in another Cement plant), we did not have the commissioning report, and if we analysis last one and half year’s operation log sheet we found some interesting observation:

[Bashir01219]

We open the LC for some spare parts and offer help from local HITACHI supplier, hoping that they will fill & understand what they have done with the system two years ago!

[moideen]

At the enter of HE is liquid gas mixture after TXV and that temperature is of no use (it is not saturated temperature) because gas is not there because of evaporation but because of pressure drop at TXV.
We need liquid line temperature 15 cm before expansion valve (to see if there is pure liquid refrigerant at TXV inlet) and we need pipe temperature after HE where TXV bulb is placed (to find evaporator superheat and proper TXV operation).
Take your measurement with accurate calibrated service instrument and not with unit sensors. You could give unit sensor readings only when you check wit accurate service instrument that their readings are accurate.

Take your reading only when capacity control is at 100%

hi nike,trane RTAA,chilers have installed suction saturation thermistor after exv ,before reaching HE.
could you clear me
moideen

[nike123]

hi nike,trane RTAA,chilers have installed suction saturation thermistor after exv ,before reaching HE.
could you clear me
moideen

Maybe I am wrong in my thinking that flash gas and liquid refrigerant mixture at exit of EXV is not in saturated state. Maybe someone could clear that for both of us.

Here is some thread with that thematic:
http://www.refrigeration-engineer.co...read.php?t=888

[moideen]

We open the LC for some spare parts and offer help from local HITACHI supplier, hoping that they will fill & understand what they have done with the system two years ago!

hi bashir,why u r silent?what is the status your chiler?problem solved..............
moideen

[Bashir01219]

hi bashir,why u r silent?what is the status your chiler?problem solved..............
moideen

No, we are waiting for the spare and HITACHI local suppliers, they need some time.

[nike123]

Spare evaporator perhaps?

[icecube51]

spare complete unit (LOL)

Ice

[Bashir01219]

spare complete unit (LOL)

Ice

Hummmmmmmmmm........
Lets see what they (HITACHi) do!

[nike123]

I am sure that are so many China made chillers of better quality than Hitachi.

[dgt]

check if you dont mixed two kind of oil

[Bashir01219]

I am sure that are so many China made chillers of better quality than Hitachi.
Sir,

They provide us lots of papers and ask for data, now we are waiting, waiting, & waiting..............

@dgt: We did nothing with the compressor ever

[lma]

Hi..

I am new to the site and this is my first post. Not sure what the update is at present ... the post being close to two months now.

I have followed with interest your discussion above and I am curious to know the outcome ... and what made you believe there was a problem in the first place. You mentioned no cooling ... what was the temperature of the medium being cooled ?

What made you believe there was a problem with the chiller ?

Regards

[Bashir01219]

Thanks for your curious....
At present the unit is under servicing of Hitachi personeel, they are not only slow but also boring.
The main problem is with the evaporator, pressure difference too high........any way lets see what r they doing?

[Bachuss]

Motor running amperes are dependent on mechanical state of compressor and compression ratio. With corect charge and various temperatures of evaporation and condensation (which depends on many things) you have various current reading. Therefore, current of compressor is not clear indication of correct charge, but it should be monitored in case if something other is wrong, or to be sure that you are not grossly overcharged.
Sight glass could be misleading especially with blends because they represent difference in flow resistance (therefore pressure change) and liquid refrigerant could flash in sight glass and collapse again after sight glass when flow restriction become same as before sight glass.

Proper subcooling and proper superheat along with proper air/water flows and cleanliness of heat exchangers will tell you that you have balanced and properly charged system.

Thank you nike, as usual your posts are very informative and help me greatly in my learning.

[Bashir01219]

Dear Sir,
How r U?
After long time and collecting data they decide to clean the HE and install a flow control valve in chilled water inlet line. Now the pressure diff. between chilled water in and out is 0.5 bar which is recommended by HITACHI.
I am also attaching a data sheet with this mail (after their work).
Note: Still suppliers are working.
If possible analyze the data sheet and give your suggestion.

[nike123]

From quick look I see your evaporator dT is still small (1-2K).
Did you, or did you not confirmed correct flow of water at all times. It should be around 0,15-0,20 m^3/h per kW of chiller capacity.
Also I see high dT on condenser which mean low air circulation at condenser. Are you sure that fan is spinning in correct direction (suction from outside across fins and than at fan blades then exhaust at outside)

[Bashir01219]

Also I see high dT on condenser which mean low air circulation at condenser. Are you sure that fan is spinning in correct direction (suction from outside across fins and than at fan blades then exhaust at outside)[/QUOTE

Yes Sir your idea is correct, previously chiller unit installed in ground floor and beside the unit there was a garments, that's why condenser fines are blogged with cotton type dust, its acting like glass wool insulator inside the condenser fines. we tried to clean the fines with pressurized water and soap water but it didn't work. The cotton dust are also not visible to us or we can not open the side cover of the condenser (plate & condenser pipe lapping each other, if we want to open side cover we need to cut the condenser pipe, which is difficult and risky).

Any suggestion?

[nike123]

Only what comes to my mind is to change condenser.

[Bashir01219]

Thanks, Its the best way to overcome the problems........