Performance characteristics of compressors

[PTControl]

Hi!

Here we are completely new. Our company specializes in the design, modernization, commissioning and optimization of control systems for industrial cooling based on PLC, HMI and SCADA Siemens manufacturing generally. We worked about 4 years in the Polish branch of the GEA Grasso. Now working with the industrial refrigeration market leaders in Poland.
We are looking for performance characteristics of commercially available ammonia screw compressors and reciprocating compressors, condensers, pumps, or ammonia. We have a lot of requests for upgrades ammonia refrigeration machinery (compressors, condensers, pumps, ammonia) due to energy consumption. From the control program is not a problem, queuing devices, the alignment of working hours, step by step at variable load for a differentiated system of compressors, condensers, pumps, or ammonia. But the program is one thing, and take full advantage of opportunities to save energy is another. And here comes the problem. To realistically and professionally calculate return on investment in the inverters are needed performance characteristics, COP, etc. Without this type of data harder to suggest anything, and mislead customers is very easy. And that's not the whole point of engineering work.

If anyone has some contact details of formal characteristics of performance, COP is that we asked.

Thank you
Regards

[RANGER1]

Hi!

Here we are completely new. Our company specializes in the design, modernization, commissioning and optimization of control systems for industrial cooling based on PLC, HMI and SCADA Siemens manufacturing generally. We worked about 4 years in the Polish branch of the GEA Grasso. Now working with the industrial refrigeration market leaders in Poland.
We are looking for performance characteristics of commercially available ammonia screw compressors and reciprocating compressors, condensers, pumps, or ammonia. We have a lot of requests for upgrades ammonia refrigeration machinery (compressors, condensers, pumps, ammonia) due to energy consumption. From the control program is not a problem, queuing devices, the alignment of working hours, step by step at variable load for a differentiated system of compressors, condensers, pumps, or ammonia. But the program is one thing, and take full advantage of opportunities to save energy is another. And here comes the problem. To realistically and professionally calculate return on investment in the inverters are needed performance characteristics, COP, etc. Without this type of data harder to suggest anything, and mislead customers is very easy. And that's not the whole point of engineering work.

If anyone has some contact details of formal characteristics of performance, COP is that we asked.

Thank you
Regards

Sounds like you need the compressor selection software.

Its certainly available, but you would have to approach the likes of Grasso,Mycom,Howden,JCI etc.
Its not something you can email to anyone that I know of.
Older machines can be an issue as well, as the programmes may not exist anymore.

[PTControl]

Thank you for your reply RAPID1.
Even necessarily have to be very accurate data. Rather, whatever the form of a chart for the various differences in the suction and discharge pressures. I assume that the system from -20 to 0'C works directly on the condenser and may differential pressure of 10 bar, and only from-20'C down using booster systems, intercooled, etc. and work to 1-1.5 bar. I know that. And the more I do not need. Programs which are probably writing a mystery, as the producer principle and characteristics of operation of variable Vi.

[PTControl]

Thank you for your reply RAPID1.


Sorry for RAPID1, RANGER1 ... :-)
I do not know how to edit your posts in this forum.

[josef]

Hi PTControl, your questions are difficult to answer, PC manufacturer for each compressor has its own logic and non-disclosure.

[Segei]

To create good PLC to control refrigeration plant, you need 2 types of knowledge.
1. Very deep knowledge of refrigeration and energy savings.
2. Knowledge of PLCs and programming.
PLC is just tool to implement better set points and operating strategies. This is how energy saved in industrial refrigeration. Engineering data about compressor performance(COP,...) you can get from compressor manufacturer.

[PTControl]

To create good PLC to control refrigeration plant, you need 2 types of knowledge.
1. Very deep knowledge of refrigeration and energy savings.
2. Knowledge of PLCs and programming.
PLC is just tool to implement better set points and operating strategies. This is how energy saved in industrial refrigeration. Engineering data about compressor performance(COP,...) you can get from compressor manufacturer.

Yes, we know. Some programmers hard to understand why they write programs. That is not just a single motors and valves, but as a whole system of any technology is like a living organism. When it comes to working in the refrigeration Grasso, and now implementing their orders, we are dealing with a really top-flight professionals. Of course we will never achieve the level of their knowledge of refrigeration, and if we get along with them and quite often they initiate changes in the control (algorithms, sequences, or stosowanycn types of regulators) is the solid foundation we have. I do not pour ammonia into the tank without compressors, we distinguish a bar from the bar, or suction on discharge :-)
Returning to the subject. We asked for such a characterization for one of the companies and for us to know the secret .... Why do we need it, why we are interested in, etc. That is why we prefer to ask the forum refrigeration of expert consultants rather than ask the manufacturer of machinery, which sees us as a competitor.
For now I see it as a useful hobby and willing to help a couple of colleagues from companies target customers.

[RANGER1]

Can you give us a few examples of something would like to check or compare.
At our work they put programmes on main server so cannot give anything to you.

Variable Vi is a tough one & maybe you would have to get into a Grasso controller to see calculations.
Sab S80 was good because it was all mechanical.

[PTControl]

Ok.
For example. The customer has a screw compressor, a fairly old SAB202SM. Together with our partner from all the upgraded engine cooling using PLC and SCADA. For this machine we set in the SQL database performance record of 1 minute, the same for status (off, ready, Time Lock, increase delay, work, no condenser, etc.). When you export to excel for 1 month of service came to us that the status representing the work machine worked an average yield of about 25%, but by about 20% of the time was above 90%, so this power range is needed. With regard to the suction and discharge temperature was a medium-5'C / 28'C. A simple characterization of the site:

http://www.forummleczarskie.pl/RAPORTY/118/1/optymalizacja-ekonomiczna-procesow-chlodniczych/

comes to us that the performance (question of whether the slider position is that whatever is presented on the chart) 25% of motive power we have about 47%. A simple calculation gives us less than 50% efficiency. The question of whether my reasoning is ok for a simple determination of efficiency. And whether such data will help determine the recovery time from the application of the inverter to the machine - I assume bearing replacement.

thx

[Segei]

As far as I understand, you are programmer. We are refrigeration guys. Sometimes it is difficult to understand your terminology.
Example. "recovery time". What does it mean? "I assume bearing replacement". Why do you replace bearings?

[PTControl]

Yes, I know. Sometimes Google Translator works miracles to what was we want to say. And unfortunately, especially for terminology other than I know without this tool for sure I would not to an agreement.

Example. "recovery time". What does it mean?

Exactly What I meant when you start to make money on investments. He bought an inverter, exchanged in the motor bearings (for isolated). He gave the such it 15 000 euros. After approximately four years, investments turned to him. He gave money and cost savings under this heading are for the earn money.

"I assume bearing replacement." Why do you replace bearings?

As in the old motors bearings are not isolated and the the motor with inverter very often you would need to be replaced. From what I associate the the usual Bearing replacement is the cost of 1500 euros, the same, but isolated the cost of 4,000 euros.

[Segei]

In our world "recovery time" is return on investments or simple pay back. This is PP on page 3 of your link.
Regarding motor bearings. I would prefer to replace the motor. To make sure that it will not burn out next year after bearings replacement.
You try to optimize issue of part load operation of screw compressor. This is small part of energy saving process. Information about part load operation you can get only from compressor manufacturer. However, to get real life potential energy savings you should determine real life part load of this compressor. Is it going to be 20% or 30% or 45%? You can put some sensors and monitor plant operation or you should take real life assumptions.

[PTControl]

PP. You can see very I concentrated on the trend efficiency and left the contents ... :-)
Regarding motor bearings. Total there I have no experiences, I associate that in the Grasso is always bearings with these motors is always gave.
As for the optimization of work compressors. How to measure the actual load in kW pump system with a load of, air coolers, or tunnels. We do not have the flow of ammonia, we have a differential pressure ammonia pump or the suction temperature of the air coolers. Nothing more. As a measure to actually calculate the load?

Regards

[Segei]

To measure flow you need flow meters for every suction temperature. I saw many plants, but I don't know any that have flow meter. However, another approach can be used. To optimize operation, we should run plant at optimum set points. Only one question. Where is optimum? Usually(but not always) the higher suction pressure the better. During winter operation condensing pressure should be as low as possible. During summer operation condensing pressure should be optimum. Hot gas defrosting can be optimized as well.

[PTControl]

The question of the flowmeter was obviously rhetorical ... :-)
If you do not inverters for motor cooling devices, it is really the most savings applies to the algorithm of the system compressor as a whole (single-step, parallel), and air coolers team as a whole (the differential regulation is not the only condition for start / stop). But it's hard to assess the results.
And here is the problem. You may be considered reasonable for the month, quarter, or year. And this time, the client may have different occupancy of production, or distribution. Another may be the external conditions. Others may also be people, and for example, often go for a cigarette and did not close the freezer door.
So the easiest way to explain the change of control of compressors - instead of the slider to adjust the inverter, as having the characteristics of the COP is difficult to determine if a customer loses every day. Because it's what we wrote above applies only to the algorithm that is difficult to verify. Customers even for software service does not quite see the sense to pay - I can not see it ... :-) Pipes can be seen, the inverter is hanging on the wall - you can pay for it. The program does not necessarily ... :-) A little water must elapse before this change, at least in my country.

PS. That is why we are looking for partners outside Polish borders. But this is a subject for another story. And it is not the subject of this post ... :-)

[Segei]

I'm not sure about algorithm you are talking about. Usually, it is pretty simple for screw compressors. Every suction pressure level should have compressors operating at 100% and one compressor as trimming one to change the capacity based on load fluctuation.
Regarding to energy savings verification. Usually, we try to improve efficiency or energy use per unit of refrigeration E=P/RE. P is power or energy use. RE is refrigeration capacity. We can't measure RE, because we don't have flow meters. The only way to verify energy savings by keeping RE constant. However, you can't do that for long period of time. Usually, we run plant at constant load for 1 hour and measure the energy use. Than 0.5 hour transition period. Than 1 hour operation at new set points and measure the energy use. Than compare before and after. However, refrigeration load should be steady.