Liquid ring pump as raw water pump, pros and cons?

[Nidza]

During the restoration/renovation planning of my boat, long time ago, my father has chosen not to use original impeller pump for Cummins V-504-M, but rather liquid ring pump Gilkes M 100/350 which was available at that time (in the '80s). Since I have continued restoration/renovation in recent years and finished it, I have decided to use that same pump, it was new, I like the principle of liquid ring very much, seems to me more reliable and less prone to mistakes which can destroy impeller in impeller pumps and so on... Very important for me was that I had the manual for the pump with the characteristic curves so I could calculate appropriate belt pulley diameter to achieve needed waterflow for the engine raw water cooling system (indirect through heat exchanger and then through wet exhausts (risers, waterlocks and tips above water line)). Anyway, I am very satisfied with the pump, it works flawlessly and waterflow is a good match for engine, luckily, with the first calculated pulley since engine temperatures are exactly where they should be according to engine manual. Flow is very steady which is in correspondence with liquid ring pump principal of operation.

Anyway, since most boats today use commonly impeller pumps, I am curious why is it so? Is there some technical reason or just better price? I know that on some older engines they were used, but not much info on the internet, so I am counting on experienced members view on this. What are technical pros and cons of using liquid ring pump as raw water pump for marine engine? Is there something that I should worry about or just service it regularly and enjoy? Beside greasing, there is not much things to do around it, except in case that it has to go to service due to leaking of some seals. Until now, 220 hours of operation, no problems.

 

[Northern Spy]

I'm not sure what you mean by liquid ring pump. I am familiar with liquid ring vacuum pumps (Nash) and liquid ring compressors (Garo), but both of these are used for moving gasses.

Do you mean centrifugal pump?

Either way, I believe the difference would be that a flexible impeller pump is a positive displacement pump which will pump a fixed amount regardless of discharge head. This ensures flow regardless of the amount of fouling in a heat exchanger. Whereas, a non-positive displacement pump will increase discharge pressure while decreasing flow if there is an increase in total discharge head.

As the pump is engine driven and has a variable speed, a vane pump, having a (nearly) linear affinity curve is fairly easy to plug into a piping circuit with an unknown or most likely non-calculated system curve.

 

[caltexflanc]

Never seen one used to pump water. They do have vanes as part of the system. Admittedly, my knowledge and experience is slight beyond them being used as a vacuum pump.

 

[sunchaser]

+1 on what Spy says.

 

[Nidza]

The principal is the same as Nash liquid ring pump (don't know the difference between compressor and vacuum pump in this case), same pump can be used for gasses or liquids because after you add enough liquid to the pump on initial start (prime it) to fill enclosure around the vanes (form that liquid ring), air between vanes and liquid is sealed, so it can make vacuum to pull the water if the pump is above waterline, or pull gas if it is used for gas. They are also used to pump flammable liquids in some cases. Since there is no physical contact between vanes and enclosure there is no damage if seacock is closed by mistake compared to impeller pumps, but since liquid or gas flow is cooling the pump, the pump can heat up in that case. Anyway, you can turn on the engine for short periods, like minutes not seconds for testing without worrying for the pump, but mind the heat for bearings, since when the water is flowing, liquid ring is always cooled/changed with new water so the pump is being cooled too.

These pumps were used with bigger engines like Cummins K series, CAT 3408, Volvo TAMD 162A,..., these pumps were manufactured by Gilkes and these engines used Gilkes M series 250/700 pumps, I do have a smaller one M series 100/350 pump. Here are some links which I have found on the net, they look all the same, just sizes are different and these bigger ones cost a lot:

AVM Diesel (F.E.) Pte Ltd

M Series Engine Cooling Pump

http://www.avmdiesel.com/previews/M Series Pump.pdf

Anyway, Gilkes still exists, but they manufacture some king size pumps today.

I am curious if anybody had experience with these pumps long term, how did they performed, were they reliable, did they make any problem on the engine cooling system and why there aren't many, if any, on the boat cooling systems today?

Water from my exhaust tips is coming very steady and constantly/uniformly, no pulsation at all, no matter how much throttle is given, although it is going through big waterlocks, but waterflow is increasing with RPMs. But, the engine does need a high amount of water at full RPM per specification (32 GPM / 2 liters/second).

Thank you in advance!

 

[CaptSteve53]

During the restoration/renovation planning of my boat, long time ago, my father has chosen not to use original impeller pump for Cummins V-504-M, but rather liquid ring pump Gilkes M 100/350 which was available at that time (in the '80s). Since I have continued restoration/renovation in recent years and finished it, I have decided to use that same pump, it was new, I like the principle of liquid ring very much, seems to me more reliable and less prone to mistakes which can destroy impeller in impeller pumps and so on... Very important for me was that I had the manual for the pump with the characteristic curves so I could calculate appropriate belt pulley diameter to achieve needed waterflow for the engine raw water cooling system (indirect through heat exchanger and then through wet exhausts (risers, waterlocks and tips above water line)). Anyway, I am very satisfied with the pump, it works flawlessly and waterflow is a good match for engine, luckily, with the first calculated pulley since engine temperatures are exactly where they should be according to engine manual. Flow is very steady which is in correspondence with liquid ring pump principal of operation.

Anyway, since most boats today use commonly impeller pumps, I am curious why is it so? Is there some technical reason or just better price? I know that on some older engines they were used, but not much info on the internet, so I am counting on experienced members view on this. What are technical pros and cons of using liquid ring pump as raw water pump for marine engine? Is there something that I should worry about or just service it regularly and enjoy? Beside greasing, there is not much things to do around it, except in case that it has to go to service due to leaking of some seals. Until now, 220 hours of operation, no problems.

The Gilkes M 100/350 is actually a centrifugal (self priming) pump specifically designed for engine cooling applications (Made in the UK) and has been around for years with a good reputation for reliability,

As for why most engines use rubber impeller pumps is that they are fitted directly to most engines via the gear train (so no belts to worry about-no adjustments-no breakages) and very compact in size, Lets face it if the impeller is changed every season and normal intake maintenance (required for both) there's hardly ever a situation of a failure.

Cheers Steve

 

[sunchaser]

While true that Gilkes pumps have been used on larger marine motors, the 555 is a perfect candidate for a Jabsco type pump. Celectric on this site and boat diesel is a smart 555 guy, he will likely chime in.

 

[Nidza]

Thank you Steve. I was just curious, not against rubber impeller pumps, so basically compactness could be the main reason, since both can be implemented with pulley or gear. Are you sure 100/350 is centrifugal pump (self priming is obvious)? I am confused since in original Gilkes brochure for M series says "...self priming....side channel liquid ring type", and in manual is mentioned side channel and intersection picture and diagram of pump really resembles liquid ring pump. But, I was not lazy and I have then investegated self priming centrifugal pump types and also it does resemble a bit on centrifugal pumps called regenerative pumps or centrifugal pumps with two casing chambers and open impeller. Would you know to tell me what type exactly is this pump? It is not my original brochure, but in the link I have given is really representative intersection picture of the pump:

http://www.avmdiesel.com/previews/M Series Pump.pdf

Anyway, glad to hear that they are reliable and present for years.

Thank you Sunchaser, I would be very glad to hear the pros for using rubber impeller pump on 555 from Clectric, I know he is using 555 and I have already got good infos about the engine from him in the past.

Thank you Northern Spy.

 

[C lectric]

Have some small familiarity with your pump type from work, not in your application though.
My applications were either vac. or drying positive dessicated air circulation system's.
If it works then continue to use it.
The Jabsco rubber impeller pump I have has been long term reliable. Rebuild fully every 5 years, approx 500 - 750 hrs. These pumps were setup as relatively slow turning , large for the job pumps so had long life generally. Not fool proof of course as no pump is.
The one thing I can think of that might be an advantage of the rubber impellor type is some ability to better deal with trash that gets past a strainer. But that,s a thought.

 

[FF]

The rubber pumps will prime very well on each engine start, regardless of the engine height to waterline.

 

[CaptSteve53]

Thank you Steve. I was just curious, not against rubber impeller pumps, so basically compactness could be the main reason, since both can be implemented with pulley or gear. Are you sure 100/350 is centrifugal pump (self priming is obvious)? I am confused since in original Gilkes brochure for M series says "...self priming....side channel liquid ring type", and in manual is mentioned side channel and intersection picture and diagram of pump really resembles liquid ring pump. But, I was not lazy and I have then investegated self priming centrifugal pump types and also it does resemble a bit on centrifugal pumps called regenerative pumps or centrifugal pumps with two casing chambers and open impeller. Would you know to tell me what type exactly is this pump? It is not my original brochure, but in the link I have given is really representative intersection picture of the pump:

http://www.avmdiesel.com/previews/M Series Pump.pdf

Anyway, glad to hear that they are reliable and present for years.

Thank you Sunchaser, I would be very glad to hear the pros for using rubber impeller pump on 555 from Clectric, I know he is using 555 and I have already got good infos about the engine from him in the past.

Thank you Northern Spy.

Definition of centrifugal pump:

A pump having vanes that rotate in a casing and whirl the fluid around so that it acquires sufficient momentum to discharge from the extremities into a volute casing which surrounds the impeller and in which the fluid is conducted to the discharge pipe:

Definition of a Liquid Ring Pump: A liquid ring vacuum pump has an impeller with blades attached to a center hub, located in a cylindrical body, but off-set from the center. ... When the pump starts, the impeller slings the liquid sealant by centrifugal force, to the outside walls of the body, forming a ring of liquid at the outside walls of the body.

Actually the Gilkes Series 'M' Gilmec self-priming CENTRIFUGAL pump is one of the most widely used self - priming pumps in the marine world today.(Mainly Commercial Applications how ever)from fire pumps/bilge pumps/cooling pumps etc.The Vane on the Gilkes pumps are quite unique in shape and do not look like a conventional CENTRIFUGAL pump impeller (but an impeller it is!)

The Series 'M' Gilmec pump was designed specifically for the marine market, and is not just another industrial pump adapted to meet a market where reliability is all important. These pumps are constructed in all bronze materials that has been proved over many years to be one of best to with-stand seawater erosion and corrosion.
Their shafting is made in stainless steel and runs in heavy-duty ball and roller bearings designed for a minimum life of 25,000 hours

Perhaps the" liquid ring" you are referring to, is the unique side channel primer chamber which aids in the quick self priming of the pump? as above true Liquid Ring pumps are normally used for Vacuum applications.

Cheers Steve

 

[Nidza]

Now, that is an answer Steve and I like it, thank you. Those definitions have removed any doubts about what type of pump is it. Truth, I have found centrifugal pumps with side channel for priming, so that is what Gilkes is talking about in brochure and manual, but not in details. And, yes I know it is built for the marine environment since body and impeller are built by bronze, some bearings of aluminum bronze, shaft is molybdenum stainless steel. And it is truth, impeller has odd looks compared to other centrifugal pumps. I do like those numbers that you have given

Thanks C lectric and everybody else.

Dilemma solved for me.