Oil Pump in Ammonia Compressor?

[NNNNNN]

Dear All,

We are looking into purchasing 100 HP Ammonia compressor Looking between FES and Frick. (replacing an old rep. comp.)

1- I don't which is better than other FES or Frick?

2- The FES supplier offered that his compressor has an oil pump that helps especially in winter days and on power failure, as it will be not easy to start if there is no oil pump (As in the Frick Compressor) because there will be not pressure differential to be achieved with in the firsts minutes as it could take 10 to 20 minutes to build head pressure and/or drop the suction pressure when start-up the system on a cold day. There are additional valves that can be installed in the discharge line of the compressor to provide the required differential for the oil d pressure however this just moves the problem from oil pressure to oil cooling. On compressors with oil pumps, the oil pump provides the required differential and it will start and run without issue in these same conditions.”

2a- Where is the reality?

2b- If that is right why Frick did not add Oil Pump?

Thanks in advance for your help.

[brian_chapin]

I work for a company that operates FES, Frick, Vilter and M&M compressors.

I don't think #2 has ever proved true for us and we live in the NE US.

I personally think the recommended maintenance schedule on the FES's is very expensive and if you operate a PSM/RMP regulated plant then that can be a real problem.

[US Iceman]

Why don't you use a reciprocating compressor?

If you are only looking at 100 HP, a recip. will be the most economical to install and operate (as long as your compression ratio is not too great).

[Sergei]

Dear All,

We are looking into purchasing 100 HP Ammonia compressor Looking between FES and Frick. (replacing an old rep. comp.)

1- I don't which is better than other FES or Frick?

2- The FES supplier offered that his compressor has an oil pump that helps especially in winter days and on power failure, as it will be not easy to start if there is no oil pump (As in the Frick Compressor) because there will be not pressure differential to be achieved with in the firsts minutes as it could take 10 to 20 minutes to build head pressure and/or drop the suction pressure when start-up the system on a cold day. There are additional valves that can be installed in the discharge line of the compressor to provide the required differential for the oil d pressure however this just moves the problem from oil pressure to oil cooling. On compressors with oil pumps, the oil pump provides the required differential and it will start and run without issue in these same conditions.”

2a- Where is the reality?

2b- If that is right why Frick did not add Oil Pump?

Thanks in advance for your help.

Frick compressors have 3 applications of oil pumps.
1. Prelube oil pump. This pump runs at start up of the compressor.
2. Full flow cycling pump. This pump runs at start up and when pressure difference between suction and discharge is low. At high pressure difference this pump is off.
3. Full flow pump. This pump operates all the time. Usually, this is booster application.
By the way, FES has all 3 applications for different series of compressors.

[TXiceman]

Personally, on a 100 HP machine, I'd go with a slow speed recip. Keep the piston speed under 60 ft/min and it will have a long useful service lifeand cost less than the screw.

When you get into the small screws, they tend to be "throw-away" compressors.

For a good recip, look at Vilter, Mycom, or Grasso. The trick is run them slow.

Ken

[mcalko]

We run a two stage system with soc cooling.All our comp are FES made, but actual compressor is dunham/busch. We are located in Baltimore,Md and have a psm program. These compressors are 200-300 hp and are very easy to maintain and have very few problems.

[NH3LVR]

Both FES and Frick make excellent machines.
Is one better than the other? That is really hard to say.
If most of your experience is with one, that is probably what you would chose.
Salesman will make statements about the failings of the competitors machines every time they get a chance.
I find it hard to believe that you would have to wait 10 minutes building up head pressure.
As Sergei says, you can order machines configured in any way you want.
As to the recips, the controls are more easily repaired. They are reliable and Mycom and Vilter have excellent reputations.
I have done a lot of maintenance in the past on FES machines. I do not recall any excessive maintenance being called for in their schedules. Some of the things mentioned in their class b inspections did seem a bit much, but not all that bad.

[TXiceman]

Personally, I like to have as a minimum a part time oil pump. I have had too many machines that were hard to get on line during the winter. With a differential pressure feed machine, you have to build enough heat in the condenser system to get the discharge pressure up enough to feed the oil. A way around this is to use a discharge pressure control valve on the oil separator outlet to hold up the pressure in the compressor until you can get some load in the condenser and build pressure. If you do not have sufficient pressure in a given time period, the controls will shut you down.

I meant to say 600 FPM on the recip piston speed. And this size is definately a better choice for a properly selected recip over a small screw.

Ken

[NNNNNN]

Hello All,

First I would like to thank you for your help and reply.

The thing is we already have Vilter Rep. Old 1962 60 HP is the one we would like to replace with FES or Frick (We are selecting those because already we have another 100 HP Frick and 200 HP FES) I just want to purchase the same.

But the Problem with the Frick that we do have does not have an Oil Pump. Looking into that option I have been told as I mentioned at the begining for a comp. problem with out oil pump. as now the Rep. is starting for that we do not have problem but what about the futhure after taking away the Rep. Vilter and putting new Screw? For that I would like to know how important in the comp. with an oil pump? and what are the other options?

Thanks.

[TXiceman]

If you go with a part-time oil pump, it can come on when you first start up and make sure the compresor beairngs are lubricated until you build pressure in the oil separtator/discharge. My preference is to have at least a part-time pump.

My last choice for most systms is a differential pressure feed system...ie, no oil pump.

Ken

[US Iceman]

I vote with TXiceman. A pre-lube pump is a required item in my opinion.

You may already have some small screws, but I would seriously consider installing a recip. compressor for part-load reasons.

Part-load performance on screws just sucks, unless you use a VFD.

[hendry]

i remember there are Hall engineers amongst us. may be he has something to add because Hall has similar design in their single screw; no-pump, pre-pump, constant pump.

I think it is in the 3000, 4000, 2000 series of the comp. i also remember it has to do with part load issue ....

[Josip]

Hi, NNNNNN

Dear All,

We are looking into purchasing 100 HP Ammonia compressor Looking between FES and Frick. (replacing an old rep. comp.)

1- I don't which is better than other FES or Frick?

2- The FES supplier offered that his compressor has an oil pump that helps especially in winter days and on power failure, as it will be not easy to start if there is no oil pump (As in the Frick Compressor) because there will be not pressure differential to be achieved with in the firsts minutes as it could take 10 to 20 minutes to build head pressure and/or drop the suction pressure when start-up the system on a cold day. There are additional valves that can be installed in the discharge line of the compressor to provide the required differential for the oil d pressure however this just moves the problem from oil pressure to oil cooling. On compressors with oil pumps, the oil pump provides the required differential and it will start and run without issue in these same conditions.”

2a- Where is the reality?

2b- If that is right why Frick did not add Oil Pump?

Thanks in advance for your help.

...my vote for unit with oil pump...even if you use it only for pre-lubrication or part-time.....

...units without oil pump are cheaper to buy....but many times you have to buy a new compressor (but now with oil pump) after a while......like TXIceman said:

My last choice for most systms is a differential pressure feed system...ie, no oil pump.

valid for me too....

Stal-Astra was among the first companies manufacturing vertical screws without oil pump, but due too many problems with oil pressure/lubrication they stop to manufacture them...you need to install pressure discharge valve to arise discharge pressure during start to move oil through cold oil cooler....not easy to return a slide valve to minimum (there was not a spring to help) a lot of troubles for customers especially in winter periods...

think also about this....

You may already have some small screws, but I would seriously consider installing a recip. compressor for part-load reasons.

Part-load performance on screws just sucks, unless you use a VFD.

it is a good advice too....

Best regards, Josip

[hendry]

Hola Josip,

do enlighten me ... would the body structure's design of a screw comp may determine the need of oil pump instead of causes from part load?

as i understand, comp of different brand has different bearing design, fitness, & conditions.

please advise ... cheers

[Josip]

Hi, Hendry

Hola Josip,

do enlighten me ... would the body structure's design of a screw comp may determine the need of oil pump instead of causes from part load?

as i understand, comp of different brand has different bearing design, fitness, & conditions.

please advise ... cheers

I'm not sure shall I give you a right answer....

you are right...design of compressor will determine the need of oil pump, more to that the system on which it works (buster or high stage)....

.....there are some problems with oil flow (gas pulsation, loading unloading) caused by part load, but I mention that (I believe US Iceman too) for another reasons...like....

.....a single screw compressor unloaded to 25 percent of its full capacity has nearly a 50 percent increase
in specific power when compared to a reciprocating compressor.

.....screw compressors perform better than reciprocating compressors when operated near full load

.....reciprocating compressors are better suited in refrigeration systems where significant unloading/loading is required.

....from an energy standpoint, is more important to size screw compressors correctly as compared to multi cylinder reciprocating compressors.

....anyhow I can accept compressors without oil pumps, but I do not like that design at all...

Best regards, Josip

[TXiceman]

US Iceman and I both have many years of experience with both screw compressors and recips. Manufacturers that only produce screws will naturally try to push you toward what they sell. Screws are better in some and recips are better in others. Like we have already stated, a properly designed recip will provide better service here.

Ken

[US Iceman]

This may be an unpopular statement to some but...

Screws are not always the best choice for a compressor.

If the pressure ratio limit is within the acceptable range of a recip. the performance will be beneficial and probably cheaper to install and maintain.

If someone says a screw is the best selection it is because he only sells screw compressors, OR, doesn't know the difference!

[hendry]

Hi, Hendry


I'm not sure shall I give you a right answer....

sorry i did not understand this part ... others are ok & clear.

agree that some engineers [square-head] does it like what the supplier told him/her.

in most cases, i sell solutions to my clients. i give them the overall pictures of both even explain about the power issue and swicthboard designs.

i feel that should be better in refrigeration proposals.

[Josip]

Hi, Hendry

I'm not sure shall I give you a right answer....

sorry i did not understand this part ... others are ok & clear.

Due to situation that English is not my mother tongue it is very easy to miss understood question and gave completely wrong answer or at least miss the point of your question, a little....

for that reason I wrote that...seems all is ok

Best regards, Josip

[hendry]

same here Josip ...

[Macabenta]

Hi members,

Actually I have read all your comments which are all true one after the other. Before anything else I am Anthony presently working with GEA Grasso Phils. Inc, manufacturer of Grasso compressor and presently acquired FES System Inc.

Mr. NNNNNN question was regarding oil pump. All Screws or Reciprocating compressors have oil pumps. Mr. FES representative is maybe pertaining to External oil pump(with motor) rather than an internal or built-in oil pump that is directly driven by the compressor rotor.

Actually the advantage of having an external oil pump is you can run the oil pump first to your prefer time settings so that you could built an oil pressure, temperature and lubricate the whole system before starting the compressor, specially if it is winter or the compressor is shutdown for a long period. Unlike the internal/built in pump were it runs together with the rotor, so if you can't built a good oil pressure failure may occur.

[NNNNNN]

Mr. Macabenta,

I understand from you that also the frick does have internal pump.

For that it is enough to only have what they call "cold start Valve" located on the discharge.

with what ever it takes to buld the pressur does not mater while the oil inside the compressur is lubricating as it should be.

Am I right. So now we are going to circle one. to compare between the Frick and FES Ammonia Compressors?

[Macabenta]

Mr. NNNNNN

Actually both Frick and FES are good ammonia compressor, including other brands. All have advantages and disadvantages with one another. Choosing between the two will depend on what are the benefits and advantages will be in your company.

To highlight some are the following :

1. Application of the compressor to achieve beter COP.

2. Technical supports(servicing) of the supplier, closes to your plant.

3. Training and familiarity of your plant personnel for startup, maintenance, trouble shooting and repair.

4. Cost and availabity of spareparts.

5. Of course initial investments or budget of your company in accordance to the price offer of FES or FRICK representatives.

Maybe there are still other things that some guys would suggest that might be helpful in making your final decision.