Liquid Ring vs. Rotary Vane vs. Dry Claw

[SandMan]

Is there anyone on the "trader" that can give me a +/- on the three different types of vacuum pumps:

Liquid Ring

Dry Claw

Rotary Vane

Looking for the simple answers....

Least maintenance, highest vacuum, quickest recovery, and best compensation for a system that develops a leak....is there any one of the above technologies that best fits all of these?

Thanks

[brookledge]

I don't have to much knowledge on dry claw but most vacuum systems started by using dairy vacuum pumps that were designed to run 15 to 18" they were rotary vane(excentric rotor with multiple vanes that slide out to form the seal with the outside housing. As it rotates it sucks in on the inlet side and blows the air traped between each vane out the outle as it rotates. Many producers have done things to try to keep them cool when running them at higher vacuums then designed for. Most rotary vane use oil to lubricate and cool the pump. They do make oil reclaimers on the outlets or some just blow the oil use into the atmosphere. These pumps create a lot of friction thus causing a lot of heat
Liquid ring the rotor makes no contact with the outer housing. When turned on the liquid creates the seal between the rotor and the housing thus creating the vacuum. You will either need to have a water supply or a tank of water. Continuos use of tank water will slowly heat the water up reducing the efficiency of it. They work better when you have a low volume fresh cold water supply. When running them at high vacuum they are better than rotary vane. You canalso get them that are set up with oil instead of water.
Roary claw. Simular to liquid ring in that no contact is made between the rotor and the outside housing. The rotor has curved ends that cup the air(thus the name claw) The pro to this is no oil or water needed to complete the seal to make it work.
Hope this helps like I said I'm not positive on the rotary claw though
I would think that if you were looking to buy a new pump, you would not want to purchase a rotary vane type anymore.
Also another thing to think about is using VSD. If you don't have three phase electricity you can get a phase invereter. With the drive unit the 3 phase motor can reduce the rpms as you reach the vacuum you have it set on. And also reduce your electrical consumption.
I have a liquid ring with a VSD. When running at full speed(1800rpm) it pulls 26 amps(220v single phase) It is programed to reduce down to 1100 rpm as the vacuum is reached. On the low speed it pulls 15 amps so it is about 10 amps less at the lower rpm while maintaining the same high vacuum level.
Also as soon as you have a leak the motor will begin to trottle up to maintain the programedvacuum. I can look at the digital display and imeatiately tell if I have a vacuum leak
Keith

[spud]

If your looking to buy a pump I would highly recommend buying a new one from a dealer. I know several people that have bought someone's used pump and every one of them has had problems with them. You will see countless ad's from people claiming they are going to expand their operation so they need a bigger pump. Although sometimes this could be true most time's they are selling the pump because it is a piece of junk. Most people are not willing to sell a (good used pump) because they want a good used pump for backup. I know when my pump gets a little older I will have it serviced by a qualified person and then keep it for backup. It is sad to see someone buy a used pump at a (great price) and then they loose thousands of dollars in production because of break downs. As the old saying goes (if you try to save a buck it will wind up costing you two).

Spud

[maplecrest]

i started with dairy pumps, when i sold the herd. worked great for years at 18 inches. when higher vac levels were wanted. i bought liquid ring pumps. water was the issue. need a good dependable source of water.but with good cold water high levels of vac are maintained. i use non toxic antifreeze loops now. that are dependable,start stop pumps a will. i use busch dry claw pump now also. that one is at sugar house. this one needs to be watched. need to give a tablespoon of atf often. the vapor in the vac air generates moisture in pump and the claws clash. add a sip of oil quiets the clash down. high levels of vac are maintained. i also replaced a 10 hp single phase liquid ring, with a 5.4 kw 3 phase with vfd busch pump that did the same work at less than half the cost. i am slowly replacing all single phase with 3 phase vfd. the electric bill is about 1/2 the cost with transducers.

[Mark]

i started with dairy pumps, when i sold the herd. worked great for years at 18 inches. when higher vac levels were wanted. i bought liquid ring pumps. water was the issue. need a good dependable source of water.but with good cold water high levels of vac are maintained. i use non toxic antifreeze loops now. that are dependable,start stop pumps a will. i use busch dry claw pump now also. that one is at sugar house. this one needs to be watched. need to give a tablespoon of atf often. the vapor in the vac air generates moisture in pump and the claws clash. add a sip of oil quiets the clash down. high levels of vac are maintained. i also replaced a 10 hp single phase liquid ring, with a 5.4 kw 3 phase with vfd busch pump that did the same work at less than half the cost. i am slowly replacing all single phase with 3 phase vfd. the electric bill is about 1/2 the cost with transducers.

I am going to a VFD also next year on my 20hp SIHI.

[gmcooper]

I have used all three types plus a piston pump and a diaphram. I have been most happy with the liquid ring pump. The claw pump worked well till a bearing went which in turn worn a shaft which rendered it useless. Claw pump did create a lot more noise and heat than liquid ring. The rotary vane pump worked up to a point if that is your only option as many are limited on vacuum level and the higher you crowd the vacuum level the more heat they create. The diaphram pump is very limited from my experiance. Pistom pump works ok for a small system up to 22" +/-. Next vacuum pumps I get will be liquid ring.

[DrTimPerkins]

In general:

Diaphragm pump - simple, liquid pump -- so don't move a lot of CFM (very leak intolerant), will generate moderate vacuum if system is very tight, low vacuum if system is leaky (or it is very warm and lots of gas coming from trees), generally cheaper, no releaser required, must drain during hard freezes, should change diaphragms every few years. Good for small producers with up to a few hundred taps who keep their tubing system very tight.

Rotary vane - simple, move a lot of CFM per HP (fairly leak tolerant), trade-off is that they can't generate as high a vacuum, generally require oil cooling, less expensive, repair/maintenance relatively easy, very noisy, can be hard starting when cold

Liquid ring - slightly more complex, moves somewhat less CFM per HP, can achieve somewhat higher vacuum (especially if dual-stage), require either oil or water (some also use antifreeze) cooling, somewhat more costly, relatively easy repair/maintenance, quieter

Rotary claw - more complex, move good CFM per HP (but not as good as rotary vane), can achieve high vacuum, no coolant necessary (air cooled), expensive to purchase, very easy maintenance (a little ATF or WD40 occasionally) --but repairs are complex, very quiet. Big thing with a rotary claw pump is that you should NEVER pull liquid through it....or its "game over". We use two moisture traps in series to prevent this from happening.

At UVM PMRC we use two Busch rotary claw pumps for our two main bush areas and two LR pumps for our research studies.