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Thread: Liquid Overfeed Systems
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24-03-2006, 11:58 AM #1
Liquid Overfeed Systems
I recently investigated a large liquid overfeed system (ammonia). The system was using multiple refrigerant pumps piped in parallel.
Each refrigerant pump was installed with a separate suction line and suction service valve dropping down from the vessel. The pump discharge pipes were installed into a common main pipe for the liquid supply to the evaporators.
What has your experience been with systems like this?
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24-03-2006, 02:10 PM #2
Re: Liquid Overfeed Systems
I look after some systems in which the pumps are installed in this way, one vessel with two pumps, common discharge,
i only usually run one pump and keep one as stand by, i do have cavitation problems on occasion with one system and have tried everything we could think of but i think it's a design issue, also found that one of the two pumps on this plant in question seems to deliver a more stable pressure and doesnt cavitate as much as the other, even after changing the pump & motor for a spare one we still have the same issues?
i believe it may be to do with the way the vessel is designed/piped. the suction lines of the pumps are at different ends of the vessel as to are the wet return and the compressor suction, the pump situated under the wet return end of the vessel is the one we have problems with.
I'm also aware of another site within our company that has the same set up but with three pumps, it was designed to have two pumps running and one stand by but they have never been able to run two pumps due to cavitation problems.
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Re: Liquid Overfeed Systems
with non returnvalves on the discharge it works like a charm.
Also, if three pipes are connected to a circular vessel, you need a vortex stopper inside the vessel so you dont get cavitation.
What kinda pump is it?
on our systems you have to manualy start and stop the pumps. On systems with two or more pumps we have diff.pressostats to start the pumps in sequence.
but on the majority of the systems we use our KS-E5 ( kvaerner pump), and usually one is enough to supply 8-12 vertical platefrezers with a stable pressure of 2 bar.Last edited by Tycho; 24-03-2006 at 04:54 PM.
-Cheers-
Tycho
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24-03-2006, 02:55 PM #4
Re: Liquid Overfeed Systems
Try to contact pump suplier to find out what he recomends and how he advice to install the pumps.
R enato
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24-03-2006, 06:07 PM #5
Re: Liquid Overfeed Systems
Originally Posted by US Iceman
Most now recognise pumps need 3" or even 4" suction lines and take as direct a route as possible. If the evaps have no load, and so reduced liquid feeding in, pumps can start to cavitate in low pressure \ off-load conditions. If the design is wrong, you can suffer no end of problems and it is costly to fix.
Quite common on large industrial plants, and have come across up to 3 pumps feeding in, but most use 2 with one as stand-by.
Steve
Steve
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24-03-2006, 06:18 PM #6
Re: Liquid Overfeed Systems
Hi guys,
I wanted to see what sort of problems the rest of you have seen or had.
Originally Posted by ecclesk
...the pump situated under the wet return end of the vessel is the one we have problems with
If liquid has bubbles in it the density of the liquid is decreased slightly. This reduces the static head on the pump suction. Any decrease in static head is a decrease in net positive suction head for the pump.
A pump curve will provide the minimum Net Positive Suction Head Required (NPSHR) that is needed at some flow condition. If the Net Positive Suction Head Available (NPSHA) is less than the requirement of the pump (NPSHR), the pump will cavitate.
One of the trouble areas is solving for the correct NPSHA and making sure the pump operating point does not change.
...it was designed to have two pumps running and one stand by but they have never been able to run two pumps due to cavitation problems
Check the motor amps to see if they are the same or different. Also compare the running amps to the motor nameplate full load amps.
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24-03-2006, 06:27 PM #7
Re: Liquid Overfeed Systems
Originally Posted by Tycho
http://www.cornellpump.com/industria...eticHansen.pdf
...you need a vortex stopper inside the vessel so you don't get cavitation
The vortex eliminators do provide a very much needed operational requirement.
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24-03-2006, 06:38 PM #8
Re: Liquid Overfeed Systems
Originally Posted by SteveDixey
I also believe it is important to have about 6-10 pipe diameters down stream of the angle valve to allow the liquid to straighten out before it enters the pump suction.
If the evaps have no load, and so reduced liquid feeding in, pumps can start to cavitate in low pressure \ off-load conditions. If the design is wrong, you can suffer no end of problems and it is costly to fix.
This system had four pumps in parallel. All pumps were running at 3550 RPM also!
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Re: Liquid Overfeed Systems
Now that is the oddest looking pump I've ever seen
Here's how we do it
Also note the gas trap on the suction line.
The pump we use is the same one as in the drawing, One of the engineers that worked with us before have one running a water fountain in his garden
Originally Posted by US Iceman-Cheers-
Tycho
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24-03-2006, 09:40 PM #10
Re: Liquid Overfeed Systems
Beauty is in the eye of the person looking.
The pump link I posted shows the pumps that are similar to most of those used here in the US.
Some people build their packages very similar to what you show Tycho. Others will use two independent pump suction lines instead of the one large drop leg with the pump suctions connected to it.
Why does the piping for the gas trap in the pump suction line only project a short distance into the vessel?
Do you actually run the liquid level this low in the vessel?
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Re: Liquid Overfeed Systems
I'd say that our pump looks like a Rolls Royce, next to a Yugo if it was placed side by side with the one you showed
It's only projecting (poking ) a short way into the vessel, so that if the customer choose to run with a minimum liquid level it wont work as an injector (speed of liquid passing the gas trap sucking gas into the pump).
"drop leg" is that what you call the the thing sticking out from under the tank? here in Norway we call it "udder" like the ones you have on cows
No, we dont run with that low liquid level, it's usually a few inches higher
seriously, the number on the drawing is the minimum liquid head needed for the pump to maintain it's pressure.
the good thing about having the drop leg is that with this kind of pump you can maintain a liquid head with a minimum of Kg's of refrigerant instead of having to keep a ton of extra refrigerant in the seperator, you can do it with a 100kg instead.
On our Spray chillers, all of the charge is in the drop leg of the chiller, nothing up in the shell.
we used to be world-wide when we were a part of Kvaerner, but now we are somewhat limited to Norway, Denmark, Sweden, UK, Scottland, Iceland and Faroe Islands.
(Btw, if any of you UK engineers are situated close to Peterhead, and know your way around RSW, we might be interested in a service partner over there... If I get my way, you will be taken to Norway for education on our plants )
do you mean that they use two separate suction lines on each side of the vessel, instead of the central drop leg?
we use the drop leg on all our pump systems, no exceptions.
We used to have a department in Seattle 5 years or so back... are you saying they failed in converting the U.S to our ways?
We now co-operate with Highland refrigeration (I seem to remember they are in Seattle also)Last edited by Tycho; 24-03-2006 at 10:13 PM.
-Cheers-
Tycho
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24-03-2006, 10:18 PM #12
Re: Liquid Overfeed Systems
I'd say that our pump looks like a Rolls Royce, next to a Yugo if it was placed side by side with the one you showed
the good thing about having the drop leg is that with this kind of pump you can maintain a liquid head with a minimum of Kg's of refrigerant instead of having to keep a ton of extra refrigerant in the seperator, you can do it with a 100kg instead.
do you mean that the use two separate suction lines on each side of the vessel, instead of the central drop leg?
are you saying they failed in converting the U.S to our ways?
There has not been much research on these vessels since Prof. Lorentzen wrote some articles back in the 60's and 70's. I am still trying to find some copies of these.
Do you know anyone who may have some English copies of his work?
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24-03-2006, 10:22 PM #13
Re: Liquid Overfeed Systems
Tycho, what is the name of the company you work for? I work for the largest and best refrigeration company in the world and am based in Peterhead, Scotland. I persume you are looking for someone to do service work on the pelagic vessels based across here with their RSW plants.
Kind Regards
Chopper
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Re: Liquid Overfeed Systems
Neener neener, your pump sucks neener neener
personal preference? we dont go that way when it comes to the construction of the plant, Kvaerner had some pretty good engineers (the office kind, and the working kind) and they came up with some pretty good solutions back in the days, so we have stuck with them and we have some pretty sturdy plants, not saying they are the best, but they are way up there *floats away on a white sky*
Oh, we'll whip you into submission soon enough
*Whip crack*
(if you need a place to host the pictures, let me know)
We do struggle with (working)engineers having different minds abround the regulating, alarm and warning settings on our PLC load control system
I'll talk to a guy who knows a guy who is a friend with someone who has heard of a guy that has a friend who knows someone who once heard of someone who had seen some of Lorentzen's work in English somewhere
Kidding, I'll shoot a mail to the Lorentzen foundation and hear if they have anything, or know about any of his work in English
Originally Posted by US Iceman-Cheers-
Tycho
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Re: Liquid Overfeed Systems
Originally Posted by Chopper
You mean you work for the largest company... yes?
I work for MMC Kulde (translates to MMC Refrigeration), we are the continuation of Kvarener Kulde, or Kvaerner Fish Process Technology (KFPT), our sister company MMC Tendos (translates to MMC Tendos ) delivers vacuumpumps and vacuum systems for unloading fish from pelagic vessels.
we have an engineer heading over there on monday or tuesday to do some service on a vessel.
Seen this one before:
http://www.pbase.com/kimmo98/image/49607781
************Edit**************
Called him, he's going to Fraserbourgh, Fraserburoh or something like that (sorry, but the rough ending is hard on us lesser ones )
He didnt know yet if it was monday or tuesday, but I can hook you up if you want...Last edited by Tycho; 24-03-2006 at 11:16 PM.
-Cheers-
Tycho
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24-03-2006, 11:19 PM #16
Re: Liquid Overfeed Systems
I know it very well, It normally fishes out of Fraserburgh.
Did it not burst the cooler? I thought it was an optimar install.
Do you have many systems across here?
Coincidently its York i work for and we have a just recently opened a new branch in the area.
Regards
Chopper
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Re: Liquid Overfeed Systems
Originally Posted by Chopper
First of all, the cooler did not burst.. very important
What happened was that the company that produce the coolers for us didnt roll (extrude? you know, when you put the pipe in the cooler and use a special tool to widen the pipe so it is "widened" to fit the hole in the endplate) all the pipes on the cooler, my guess is the cooler was made on a monday or a friday
They use a Loctite compound on the pipes before they roll them, but seeing as they didnt roll all the pipes, the loctite hardened and kept it tight for a while, but with the water on one side and ammonia on the other side it wore off and the cooler started leaking. Nothing wrong with the cooler apart from that.
Yes, it was an Optimar install, we used to be called "Optimar Kulde" we seem to be changing name so often, so when anyone asks anyone of us engineers out on site about the name we usually give a reply along the lines of "Yeah, we got to be known out in the market, so we decided to change names... You know, so people wouldnt recognice us"
We have a few over there, but as you work for York... a certain place will freeze solid before our higher up's will allow you to know anything about our systems :/' as we are competing with York in our area,
By the way, did you know that the branch in our district (Aalesund) doest work overtime? dig that, I clocked in 600 hours of overtime last year and all of their 6 engineers clocked in maybe 100 togetherLast edited by Tycho; 24-03-2006 at 11:42 PM.
-Cheers-
Tycho
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Re: Liquid Overfeed Systems
I'll just throw in one that show's our work site
MMC Kulde is situated in the building infront of the wheelhouse, while Optimar, the company that makes factory processing equipment is in the larger buildings to the right.
http://www.pbase.com/kimmo98/image/49607769
(you can click the link called "ships" in the top left to get to a gallery showing some of the ships we service)-Cheers-
Tycho
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25-03-2006, 12:13 AM #19
Re: Liquid Overfeed Systems
For years all the vessels were kitted out with teknotherm chillers but the norm appears to either York or Optimar these days. Service on these systems is very minimal at the moment due to cut backs on fishing quotas and the chillers only clocking up 2'000 running hours per year! Alot of plant but not a good turn around o service work.
My previous employer used to be Teknotherms prefered contractor for warranty and service work on their installations. Wasnt too impressed!
If you are looking for a contractor to carry out such work across here i can give you a list of reputable contractors and there contact numbers if it would be of intrest.
Beautiful place Norway, was across working last summer up in Kristinsund on a dive support vessel. Scotland has some cracking veiws but Norways got some breath taking veiws, especially of the women. Beers too expensive though!!!
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Re: Liquid Overfeed Systems
Teknotherm seems to be a swear word among 95% off fishingboats around here, I find it odd, as I know the people working there and they are competent people, but as soon as I enter a vessel that has had teknotherm onboard I'll be going "whoooah, it cant be that bad... NOOOooo, they didnt... really, they did that? no way... you were there yourself? and they said that?" I dont know what the deal is, but around here teknotherm is pretty much the devil...
good for us, but bad for them, it's kinda sad tho, as the people working for them are good guys and they know what they are doing.
But teknotherm, in my eyes, are stuck in the last century with their equipment... it's obsolete, end of story.
As R.J Mitchell said "It is not good enough to follow conventional methods of design. It is essential to invent and involve new methods and new ideas."
The service on our plants would be limited to the occasional solenoid calling it a day, but every now and again a relay in the controlcabinet going tits up and it would be nice to have someone over there be able to drop by and take a look at it.
If you have numbers and contact adresses for local companies that you feel are competent, it would be great if you could shoot them over, as the only ones we work with in GB is KER refrigeration in Ireland (and it seems like we only work with them, so they can get discounts on our spare parts )
Beautiful country my arse
This is me driving home from work last week... I'll agree with the beer price tho... costs an arm and a leg to get drunk in Norway and you'll have to sign you firstborne over to the government.. and I''m not kidding
Originally Posted by ChopperLast edited by Tycho; 25-03-2006 at 01:13 AM.
-Cheers-
Tycho
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25-03-2006, 02:36 AM #21
Re: Liquid Overfeed Systems
Originally Posted by Tycho
Oh, we'll whip you into submission soon enough
Control logic and safety and alarm points are always a fun discussion topic. Everyone has an idea for the best way. Myself, I like two layers of controls (at least). One layer is a fail-safe when all else goes balls up. The second layer is the upper-most layer for all of the automatic controls, PLC, computers, etc.
An example would be a mechanical float switch for a high level shutdown, while a capacitance probe can be used for normal operations and safeties. If one fails, the other is sure to catch it.
I do appreciate you inquiring about the Lorentzen papers. He wrote about some of the most interesting topics and was always based on solid evidence. Unfortunately, I suspect most of it has been forgotten by most.
Oh, by the way... The picture you took is very cloudy and out of focus.
And what is this talk about beautiful women??? You didn't answer that one.
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25-03-2006, 02:41 AM #22
Re: Liquid Overfeed Systems
Tycho,
Do have any information you can share about the spray chillers? I think these are very interesting, but this is one item I have limited experience with.
I understand the principles and the benefits but have not been able to find any technical information related to design aspects.
Thanks,
US Iceman
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25-03-2006, 09:35 AM #23
Re: Liquid Overfeed Systems
Originally Posted by US Iceman
In their news section.
Also their way of piping the pumps is the way to go. 6" drop leg turning thru 90 deg and then reducing uinto the pump, minimum drop leg lenght is about 1m I think.
Kind Regards. Andy
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25-03-2006, 04:57 PM #24
Re: Liquid Overfeed Systems
Thanks Andy. I reviewed the website, but it appeared they only listed a picture of a chiller without much additional information.
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25-03-2006, 07:26 PM #25
Re: Liquid Overfeed Systems
If you click on this line in the downloads section,
"installation manual GP" it is a pdf file, and look at pages 23 and 24.
Steve
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25-03-2006, 08:54 PM #26
Re: Liquid Overfeed Systems
Hi US Iceman, I have a 500 ton per hour surge drum that has 3 Douglas 4A pumps freeding a Freezer that needs 400 tons of Ammonia per hour in the 7 evaporators. The pump main is 6" about 230 ft. in lenght with a working pressure of .5 Bar,with a wet return of
10" the same lenght that feeds back in at each end of the surge drum. It was about 2 days untill we got it right on each coil, but now works well at -38oC on the coils and -42oC off the surge drun to the compressors.
( Got called to a Ashworth Inc. freezer today it had Frigoscandia on the door but the plate inside said Ashworth Inc. USA, Mini gryo belt freezer as the belt had stoped. found it had come over the top of the drum. Not bad it was made in 1972. The freezers we get now are the Frigoscandia Gryocompact units self-stacking belt, We had the first one in the UK 3 years of over time untill it was right and lots of nights out with the Frigo boss men.( Good old days)
all the best Arthur.
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25-03-2006, 11:42 PM #27
Re: Liquid Overfeed Systems
Originally Posted by SteveDixey
I would assume the pump suction design is similar for both liquid overfeed or spray chillers. The inside of the spray chiller is what I'm interested in.
Thanks Steve.
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25-03-2006, 11:46 PM #28
Re: Liquid Overfeed Systems
Originally Posted by aawood1
It does not really surprise me that it took this long. These adjustments can really eat up time.
What type of methods did you use for the hand expansion valve adjustments?Last edited by US Iceman; 25-03-2006 at 11:52 PM. Reason: editing
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26-03-2006, 02:22 PM #29
Re: Liquid Overfeed Systems
Yes it was time taken to adjust the hand expansion valves. When the freezer was moved we had 18 probe pockets welded in to the coil infeed and return pipe work and the liquid line header and wet return header, all feeding back to one digital thermometer. Then with some good luck it all started to get a good balance over the coils. Down side was the main contractor did not work out the right Ammonia charge for the new pipe work, Had to charge 5 Tons of Ammonia into the old and new system, 4 Tons more that they worked out. I have adjusted the liquid feed pressure down on the RS A4A pressure regulators on each pump to .5 Bar from 1 Bar.
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26-03-2006, 06:18 PM #30
Re: Liquid Overfeed Systems
Originally Posted by aawood1
If I am following your description then these regulators are for the minimum flow pressure control?
The four extra Tons of ammonia is a fairly big mistake. Any ideas on how they were this far off of the system charge?Last edited by US Iceman; 26-03-2006 at 06:26 PM. Reason: added text
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26-03-2006, 07:38 PM #31
Re: Liquid Overfeed Systems
Hi Iceman, The RS valves are fitted next to the pumps before the right angle non-return/ stop valves where the 3 pumps connect into the liquid line. As for the Ammonia charge they said it was the fact that the main system was low to start with. But if you take 50 ft of 10" pipe that makes up the wet return header on the freezer and the coils that have about 1/4 a ton of Ammonia in each one with the 25 ft. up lift onto the roof. (They did not have to put the cost of charging into the cost of moveing the freezer it made the bill look good. The job was put out with us doing all the pump outs and venting of the pipe work and the pressure testing/ recharging of the plant.) What would say.
Arthur.
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26-03-2006, 07:38 PM #32
Re: Liquid Overfeed Systems
Here are some pictures from one system.
One picture is of the low-pressure receiver and pump looking down the engine room.
The other picture shows a single pump installed before insulation was applied.
I apologize for the small pictures, but the file size was too large to post directly. They were printed into a PDF to get the file size down to the limit allowed by the RE site.Last edited by US Iceman; 26-03-2006 at 07:39 PM. Reason: text editing
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26-03-2006, 07:53 PM #33
Re: Liquid Overfeed Systems
Hi Arthur,
The RS valves are fitted next to the pumps before the right angle non-return/ stop valves where the 3 pumps connect into the liquid line.
As for the Ammonia charge they said it was the fact that the main system was low to start with.
They did not have to put the cost of charging into the cost of moving the freezer it made the bill look good. The job was put out with us doing all the pump outs and venting of the pipe work and the pressure testing/ recharging of the plant. What would say.
I think it is a good idea for the facility people to do the pump outs and venting since they probably know more about the system though.Last edited by US Iceman; 26-03-2006 at 07:55 PM. Reason: editing of quotes
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27-03-2006, 04:51 PM #34
Re: Liquid Overfeed Systems
Hi Iceman, Yes the pressure valves return into the surge drum at just over the liquid high level control about 1/3 up at one end. The Freezer was made by Hardy Lucas of the USA and is about 30Ft wide 50 Ft long and 30Ft high with a 6Ft 6ins wide belt.
Arthur
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27-03-2006, 10:21 PM #35
Re: Liquid Overfeed Systems
On the overfeed systems you guys work on do you install the pressure control valves at the pump discharge or at the end of the liquid line (as shown in the attached drawing)?
For those of you who have done it both ways, any complaints or suggestions with either method?
I am interested in learning more about the installations you work on and the problems you frequently encounter.
Thanks,
US Iceman
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Re: Liquid Overfeed Systems
Originally Posted by US Iceman
We dont have much information about the Chillers ourselves, as it's not our product.
The design is very simple, looks alomst like a normal chiller, tho on the inside only the lower half has tubes, in the top half there are two pipes with nozzles, side by side running the length of the chiller. The two top pipes are fed by the ref.pump.
No charge in the shell, all the charge is in the dropleg.
------------------
And on the girls, I'm not sure... the wintergear makes it kinda hard to determin-Cheers-
Tycho
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28-03-2006, 07:06 PM #37
Re: Liquid Overfeed Systems
Thanks for the information Tycho. The arrangement you describe sounds very similar to the water spray headers used on evaporative condensers.
Do you know the spacing on the spray nozzles, nozzle type, and flow rate through the nozzles?
I think the idea of using the large drop leg for the pump makes a lot sense. The volume of liquid required for the chiller is fairly small and the piping circuit is really short. The amount of refrigerant in suspension could be contained within the drop leg very easily.
I'm getting a pretty good picture of these now. Thanks again.
And on the girls, I'm not sure... the wintergear makes it kinda hard to determine
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Re: Liquid Overfeed Systems
Originally Posted by US Iceman
I (My company, as far as I know) Have no information when it comes to the design features of the chillers, as I said, it's not our product we are only informed when it comes to the waterflow, cooling effect and so such.
we do all the calculation on the piping and compressor/condencer capacity needed and ship it all off to SES in Holland and they build the units for us.
By the time we touch it, it's all placed on a skid allready welded to the hull or placed on vib.dampers.
I was looking through my papers just now, but couldnt find the flow chart... from the top of my head I'm gonna say ummmm... cant remember... was gonna say 653 cubic yards an hour... but that just sounds wrong in my head
When are you 'muricans gonna submit and start using the metric system anyways?
It all goes in 10's... how hard can it be
5280 feet to a mile? I mean c'mon...
wouldnt 10 Km to a metric mile be better?
Oh and the ladies are starting to dress down in anticipation of summer... I'm still wearing my winter jacket while at work... but dang... some of those girls HAS to be freezing with their bellies uncovered like that... makes me wanna jump out of my car, run over and drape my jacket around them and go "here... come home with me"-Cheers-
Tycho
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Re: Liquid Overfeed Systems
Originally Posted by US Iceman
to paint a flow diagram:
Pump - ofv - flashgas trap (or whatever you call it) - nrv - main liquid tine - reg.valve - freezer/evaporator.
Not many problems on our installations... we also have 0.2" nozzles on each plate on our freezers. the reg valves we use to ensure a stable pump pressure to the last consumer on the liquid line.
Must say your piping looks very clean, and I envy you for gettion to work on land installations when we work on ships, the only line we refuse to yield on is the return line and every time we have shipbuilders tearing their hair out while we stand there saying "Thats the way it is"Last edited by Tycho; 22-04-2006 at 12:08 PM.
-Cheers-
Tycho
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22-04-2006, 12:18 AM #40
Re: Liquid Overfeed Systems
Originally Posted by Tycho
I will say talking to people on this forum has forced me to remember things I had forgotten.
...some of those girls HAS to be freezing with their bellies uncovered like that
the reg valves are there to ensure a stable pump pressure to the last consumer on the liquid line.
I can well imagine the issues you have to deal with on marine systems. A lot more issues to deal with than just level and stationary.
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29-04-2006, 12:03 AM #41
Re: Liquid Overfeed Systems
having built recirculator packages for many years i have found that the majority of the problems have been not following the pump company guidelines.
Pumping volatiole liquid like ammonia or ***** is easy if you have enough npsh and keep the pd down with proper inlet sizing i think Iceman was all correct in his observations
I mostly saw npsh problems causing the most difficulties.
I also like the seperate suction lines in lieu of the common drop leg.
Sometimes i have found engineers overthinking the problems.
i never tried it but i want to put in some of the witt pumps simply hanging from the vessel. with the suction straight into the pump inlet. with a valve of course.
Have seen a few sketches of this but never seen it in practice.
Would really save us on installing cost. Anyone do it ?? and what problems or success have you had.
David in texas
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29-04-2006, 02:46 AM #42
Re: Liquid Overfeed Systems
Hi David,
I mostly saw npsh problems causing the most difficulties.
i never tried it but i want to put in some of the Witt pumps simply hanging from the vessel. with the suction straight into the pump inlet. with a valve of course.
If the suction valve was a globe style in the vertical suction line, I think you would loose more than you can gain because of the inherent extra length of the globe valve.
Using a high-performance butterfly valve would of course drastically reduce the equivalent pressure loss.
I should check in with him and see what the results were. Thanks for reminding me of that.
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19-06-2006, 04:36 PM #43
Re: Liquid Overfeed Systems
I installed Witt pumps type HRP 3232. They hang directly under the separator (with only a ball valve in between if you want). Works superb, easy to install, insulate and to service. As we always use one stand-by pump, the piping as shown in the attached file is standard. It clearly shows the advantages of the pump directly fit to the separator. However, only one capacity available at Witt(for now that is). Find info in the WITT HRP manual at th-witt.com.
As for the pipe inserted into the dome; as to my understanding that was invented to prevent falling oil from the separator to enter the pump, but being collected at the bottom of the dome.
We always use leg's as drawn in the attached file. Very little (never) problems with oil in the pumps.
Also standard is the use of a pressure regulator near the pump. That, with a good(!) discharge head of the pump makes it easy to set the regulating valves, and the system will be very stable. No need to go to the end of the wet return line.
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19-06-2006, 04:38 PM #44
Re: Liquid Overfeed Systems
****, forgot the drawing.
This will be better I think.
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20-06-2006, 03:14 PM #45
Re: Liquid Overfeed Systems
Very nice drawings Nico. Thank you for sharing these.
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Re: Liquid Overfeed Systems
Originally Posted by Nico
On ***** R-22 this will work fine, as the oil will gather in a "layer" around the top of the liquid head...
but on ammonia, you will have no way of draining the oil before it enters the pump and is flushed out into the system along with the liquid ammonia.
As I have shown previously in this thread.. (I know might sound like a "know it all" in showing this again... but I know it works)
(added some english text in the picture)
Notice that there is a ring around the drop leg preventing oil from draining down into the dropleg, there is a seperate dropleg for draining of oil... and as a precaution, there is an oil drain valve on the dropleg just in case
Just have to say that I'm not a big fan of having any important pipes going out of the bottom of a dropleg like that, cause any "contamination" in the plant that finds it's way to the liquid tank will go straight into the pumps.-Cheers-
Tycho
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21-06-2006, 08:49 AM #47
Re: Liquid Overfeed Systems
Generally in the large overfeed system has liquid feed pumps which supply liquid refrigerant to the evaporators.
I think your system must have multiple evaporators. I have read that your system has separate lines connected to pumps. This is not advisable.There must be a common header between vessel & pumps.I have handled very large overfeed ammonia system.If any querry pls write to me.
Thanks
AMARNATH JHA
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21-06-2006, 02:21 PM #48
Re: Liquid Overfeed Systems
Originally Posted by AMARNATH JHA
Thanks.
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22-06-2006, 03:52 PM #49
Re: Liquid Overfeed Systems
Both left and right side of the drawing are of a separator with pumps. One with horizontal and one with vertical shaft. The top is a detail of the oil dome with ammonia down pipe to the pump(s) in the middle. The system is for Ammonia indeed! As oil is more heavy than Ammonia, it will fall down to the bottom of the separator, and than sort of fall off the edge into the oil dome. Ammonia is collected just 10mm higher than the bottom of the separator. That's why the vortex breaker is so important.
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22-06-2006, 06:58 PM #50
Re: Liquid Overfeed Systems
This detail will be more clear I guess.
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