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usgreg
25-03-2013, 08:21 PM
Hi all, I am a service tech (I am not on site with this unit) and have inherited a howden screw serving a spiral chamber. the issue is, erratically, the oil cooling stops and the compressor shuts down on high oil temp. The oil cooling is liquid injection into screws through a solenoid valve and a TXV. I cannot get either to fail. It happens about once or twice a month. It has a new frick Quantom controller and oil cooling works every time I cycle it. liquid level in high pressure reciever is always stable, but a little low in my opinion (2 out of 5 sight glasses). Volume is set at 3.0. thank you for any help. I have not worked on any howdens before.

NH3LVR
25-03-2013, 11:12 PM
Welcome to the Forum US Greg!
To your problem. These kinds of problems can be annoying.
You say that the level is stable at two sight glasses. If it shuts down on oil temp we of course do not know if it was at two glasses when it shut down. A lot of things can affect the level at various times. Hot gas defrost etc. One good place to look to see if it happens is when the freezer is being defrosted. (Assuming hot gas defrost) This could affect the level and head pressure.
Head pressure can be a big issue if it is not stable. It has the same effect as low liquid level, starving the compressor of cooling liquid.
Is the cooling liquid drawn from the receiver at a lower point than the liquid supply to the rest of the plant?

usgreg
26-03-2013, 03:54 AM
I have setup logging in the Quantum controller to trend Head pressure, suction pressure, motor amps, oil temp, slide valve percentage and discharge temp., and head pressure has been steady at 115-125# through oil temp rise and shutdown within 5 minutes. only three freezer coils with hot gas defrost. spiral only runs one day a week until full production is established. There are 2 vilter 456-xl's for backup/additional load for this howden screw. oil high temp shutdown has been erratic with no appearent link to spiral operation or defrost. I have not seen specs on the receiver, but the liquid is drawn from the top of vessel and would assume the pickup point is 1.5-double the 3/4" diameter off the bottom which would be lower than the main liquid supply to the rest of the facility, which goes to the roof, and the compressor is at same level as the reciever and feed line goes overhead about 8'.

Grizzly
26-03-2013, 07:13 AM
Hi Greg.
Just out of interest, what is the oil temp cutout set to?
Also is this an aged or new problem?
Are you having the problem in winter or is the ambient irrelivant?
Grizzly

RANGER1
26-03-2013, 08:53 AM
Also what type of TX valve are you using & what is the setup you have. Can you try adding some ammonia to get a higher level?

usgreg
26-03-2013, 06:52 PM
Thank you all for your interest, The oil cutout is 180 Degrees F. when injection is working normally, it runs 120-130 F. setpoint is at 120 F. when injection is not working, it rises to cutout temp within 4-8 minutes. I have had this customer for about 2 months and this used (mfd.1998, ran 3 years, sat for 9 years) screw was installed here, 6 months ago. I checked alarm log to find high oil temp failure around once a month regardless of outdoor ambiant. The TXV is a sporlan, with the sensing bulb in the discharge pipe well. and the discharge temps are in the same range as the oil temps. I have thought about adding ammonia to raise the level of reciever, and the customer also wants me to replace the solenid valve and the TXV. Though I do not like to "change parts" the process of elimination has it's economic value when you cannot catch a failure.

RANGER1
26-03-2013, 08:31 PM
usgreg, If you do end up changing TX valve consider Hansen (Frick use them) or Danfoss ICM as you will have more precise control & monitoring capability. I have installed them with a bypass (which you leave closed), but runs off a t/stat & solenoid if you need it in case of ICM failure.Have you also been through the set up procedure for the Sporlan valve?

Magoo
26-03-2013, 08:43 PM
Hi usgreg.
Check the internal pushrod seals in sporlan TXV, some also had internal strainers at liquid entry port.

Tycho
27-03-2013, 05:59 PM
do you have any possibility to check what capacity the compressor was at when it failed?

What kind of system is this?

Any chance the customer was doing something with the system at the time of fail? maybe defrosting something, causing the condenser pressure to drop and stop the feed to the LRI?

usgreg
23-07-2013, 10:12 AM
Update. Sorry for delay in responding. Customer insisted on replacing TXV. I did so, with a Parker. And as I suspected, I now have a good used TXV. I then caught the receiver low at one time, and convinced owner to add ammonia. unit has not failed since then. Thank you all for your interest.

Josip
23-07-2013, 05:00 PM
Hi, usgreg :)


Update. Sorry for delay in responding. Customer insisted on replacing TXV. I did so, with a Parker. And as I suspected, I now have a good used TXV. I then caught the receiver low at one time, and convinced owner to add ammonia. unit has not failed since then. Thank you all for your interest.

nice, problem solved ....

.... just one off topic notice ...

.... seems that all around the world customers need a very long time (in this case almost 4 months) to start to believe in our suggestion-judgement to spend some money for spare parts to have a trouble free running plant ....

sometimes just incredible ...:eek:

Best regards, Josip :)