suction accumulator control

[samiam]

A industrial refrigeration design of mine utilses ammonia, screw compressors, evaporators, thermosyphon oil cooling, PHE and evaporative condersers.

A ND100mm diameter pipe leads from the liquide receiver to the suction accumulator.

A modulating liquid level regulator, servo controlled, danfoss PMFL125 was specified as the controlling for liquid injection into the suction accumulator.

My questions:
a) Could an electronic expansion valve (possible and AKVA20) of adequate size be utilised instead of the PMFL125?
b) Would control be better utlising an eletronic expansion valves?
c) What other forms of control are commonly utilised?

Kind regards

[US Iceman]

Welcome to the RE forums. It's nice to see another ammonia person on the site.

I'm not familiar with the two controls you mentioned and would have to investigate them.

Modulating control for liquid feed to a vessel for level control is the best method I believe as it does a better job of controlling the vessel pressure by reducing the pressure spikes.

The only two other methods I have seen commonly seen are:

low side float valves
or a solenoid valve controlled by a level switch and a hand expansion valve

[samiam]

This is an excellent forum. (I took a while to figure out how to post a message).

I am fairly new to industrial refrigeration - less than 2 years and do not have a good feel for the systems yet.

Thus I thought of geeting feedback of these two valves and experience in field. The main reason for selecting the modulating liquid level regulator (danfoss PMFL125) was to reduce the spikes.
The only question now remain is - is the AKVA20 better...

Back to the catalogues for me.

[US Iceman]

Back to the catalogues for me.


Don't give up yet.:eek:

Some of the other ammonia people here may have some good comments!

[BESC5240]

Hi Samiam,

I don't know if you know this book:

http://www.ra.danfoss.com/TechnicalInfo/Literature/Manuals/01/PA000C102_DILA_version.pdf

It also gives some examples on LP Liquid Level Regulation. (PMFL, AKVA, solenoid+regulating valve, motorised valve, ...); see page 31 and following.

There is no clear answer to which is 'the best' way. A lot of this comes down to habbits.

The valve itself is not the most important, but the combination of it with a mesuring/regulating device is. It's important to get a 'well tuned' combination. And this is possible with several combinations.
Best regards.

[US Iceman]

Hi BESC5240,

Thank you for posting the link to the book. This looks very interesting!

Best regards,
US Iceman

[samiam]

Hi,

Thanks for the advice - I relooked at the problem and completed the suction accumulator control including the electronic signal interface with the transmitter, etc. This helped.


Thanks again for the fedback and the link.