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lraja
18-10-2006, 09:11 AM
Hi guys

For an ammonia recirculation system, what is the best type of pump to feed evaporators when considering reliability and maintenance; sealless canned motor pumps such as Teikoku or open drive pumps such as Cornell; I believe your experiences could tell us the pros and cons

raja

NH3LVR
18-10-2006, 11:25 PM
Iraja;
I cannot say anything about Teikou as my Employer has never used them.
We have installed a few of the Hansen Hermetic Pumps and have had no trouble with them. We put in two in 1999 and they are still working well. I believe they have changed suppliers since then. I am sure many folks here can help you with the good and bad points of Hermetics.
I am aware of at least one Hermetic whose bearings can be damaged by loss of liquid or possibly cavitation. I believe this is common to all of this style. Again more experienced people here can guide you.
What I am familiar with is Cornell. I have worked with them for many years and had good success. Like all Pumps you need to have good suction line sizing. But they do handle occasional cavitation well.
Seals last 2 to 3 years on average and are not usually a problem. Replacement is simple after you have done a few.We are experiencing a seal problem in one plant now, but are still trying to work that out. When we do I will post the solution. (One seal was defective, the other had a lubrication problem)
The only common problem we have had with Cornell is if the oil reservoirs are overfilled. This can damage the pump seal or the reservoir seals. This is usually a mater of education.
A good seal will only needed to be filled once or twice a month.
Of course ALL systems should have two pumps installed.
Will look forward to the input from others on Hermetics.

US Iceman
19-10-2006, 02:11 AM
I'm going to try this again. I had a nice reply all done this morning and when I tried to post it I received some screwy error message and lost the whole thing.:mad:

My experience with the different styles of pumps has been fairly good.

You basically have two issues; seals and no seals.

I don't encounter very many problems with the seals. If the pumps are selected and serviced properly my experience has been seal failures are rare.

We have seals on the ammonia compressors and those typically last for a long time and I can't imagine why the pump seals would not either.;)

The hermetic pumps of course do not have seals, but they have carbon bushings that support the rotor . If the bushings get worn out due to dirt/grit or other debris, the rotor can start to rub on the canned stator and eventually wear through the can.

When this happens the typical leak path is the electrical box on the motors. So yes, these do not have seals, but it does not mean they are not leak-free. At least in my opinion.

I have probably seen more Cornell pumps and prefer them over the hermetic variety.

I really think the biggest problem is not what style of pump to use, but to make sure you select and install whatever pump you do use correctly.:D

The main problem is ensuring you have sufficient NPSH on the suction side of the pump and also have the pump selected on the left side of the pump curve instead of the middle or right side. Strange things happen in these areas.:rolleyes:

Samarjit Sen
16-11-2006, 08:05 AM
Could you please provide me with the website of some of the liquid overfeed pump manufacturers so that I may contact them for my requirement.

Thank you

lraja
16-11-2006, 09:15 AM
try the web site of the Cornell pupms mnufacturer

US Iceman
16-11-2006, 04:00 PM
Here some links for you to review. If others know of additional pump links, please go ahead an post them here.

Cornell Pump (Open Drive & Hermetic)
http://www.cornellpump.com/industrial/ref.asp

Teikoku/ChemPump (hermetic)
http://www.chempump.com/search_application/refrigeration/index.html

Witt Pump (hermetic)
http://www.parker.com/RS/rswnwittpump.html

Tycho
16-11-2006, 06:55 PM
http://www.mmctendos.no/cgi-bin/webadm.cgi?gid=2104&c=1115

I like this one, no problems running dry, very low liquid head required... only downside is the weight, when every once in a while you have to lug it out from under the liquid separator and carry it up three flights of stairs :)

There is also an exchange program on these pumps. if it needs service, you get a overhauled pump shipped to your location, all you need to do is replace the old one and ship it back to the workshop.

stan1488
16-11-2006, 08:17 PM
hansens and phillips both have useful info as well regards stan