Different types of vacuum?

[DLogan]

Can anyone explain to me in regular terms the difference between how a lobe blower such as a Roots Blower and a vane pump works? We are in the sewer cleaning business and have a Vactor and a CleanEarth truck with blowers, but just bought a straight vacuum truck to venture into the septic tank business. It too has a blower on it (came from a company that used it primarily for industrial pumping) but i was told that it would not work for septic tanks and that a vane pump is better? Any insight is appreciated thanks! Darren

[VacuumEngineer]

Well to answer the first part - basically a lobe blower uses 2 rotors that rotate together at high speed to create the vacuum and vane pump uses - well - vanes that rotate around inside of a housing creating a seal gap that does the job. A vane pump burns oil, a blower uses oil to lube gears but does not burn it.

For septic - vacuum is vacuum. It doesnt matter if you have a blower that produces 27" with 200CFM flow or a vane pump that produces 27" with 200CFM flow.

Blower advantages include sustaining high vacuum for unlimited periods of time without over heating. Blowers do not burn oil and have no emissions other than heat. Disadvantages include cost and if they crash, theyre usually not repairable.

Vane pump advantages include cheap start up cost and ability to repair easily. Disadvantages include use of oil requiring you to refill the reservoir. The oil is exhausted to atmosphere. Heat during high vacuum levels could get out of hand if run for extended periods of time.

Make sense?

[Hibon]

In addition to the comments from VacuumEngineer, I have received the following from owners and operators:

The vane pumps offer a lower initial investment, but are much more expensive to maintain. I have been told that the vanes need to be replaced annually at a cost of about $1000. As the vanes wear, your performance decreases. I have also heard that they are loud and messy.

The pd pump is much more reliable, typically lasting 10+ years with little maintenance. Unfortunately, they require a larger initial investment. The pd pump is usually smaller and lighter for the same performance, but require a good filtration system and a set of silencers.

Usually the flow rate determines the equipment. If the flow rate is low enough, the vane pump is the best solution. As the flow rate requirement rises (600cfm @ 18" Hg), the vane pump and pd pump performances will overlap. I think most would agree that once you get into the overlap scenario, the pd pump is the best solution.

[VacuumEngineer]

Just an additional comment on Vane cost. Ive seen vanes last 2-3 years in a pump with proper maintenance. Typically Vanes can anywhere from 50 - 200 bucks each depending on the pump size.

[jason]

The vanes in my Masport are six years old. I guess I need to change them soon.

[Trent]

Only if it is losing performance. If it is working up to specs, leave them.

[KPToilets]

Just replaced my vanes in my pump after 10 years and over 2 million gallons, they had about ¼” wore off, and where in good shape, but I had the pump apart so I put the new one in. I bought replacement vanes 10 years ago when the pump was new for $38 each (my pump takes 3)

I have never had a blower, but cheap to buy, easy to repair, rotary vane pump are hard to beat.

[Jim]

Only if it is losing performance. If it is working up to specs, leave them.

Typically if your vanes are worn beyond ¼” they should be replaced.

It’s my understanding and belief…that vanes are self-adjusting as the wear.
With this understanding…take a pump with many miles & years with excessive vane wear!
By simply replacing vanes don’t expect all new vacuum.
Because vanes are self-adjusting, including badly worn vanes.

[Trent]

Typically if your vanes are worn beyond ¼” they should be replaced.

Why? Just curious.

[jason]

I think I will take my pump apart before the spring rush just to to see how they look. I do wash the pump with diesel fuel to make sure it is clean. I have a newer Jurop pump on a small tank. Do all Jurop pumps pump slow or do I just have a bad one?

[Jim]

Good question! Not really sure…the ¼” measure is given by most pump manufactures.

The rotor is off set inside the pump housing, near the ceiling.
As the rotor spins the vanes slide out and sweep the housing walls, and are naturally returned as the rotor revolves around.

During this process of rotation the greatest distance of vane slide is at the 6:00 position.

I once thought if a vane were extremely worn it might completely fall out of it slot at the 6 position.
I don’t think that’s the case though.
I have seen vanes that were extremely worn, that had a crease on one side. I felt it was formed from lack of support in the rotor slot. I believed the vanes began to cock & canter, and that would eventually lead to a fracture or broken vane.

[Trent]

I think I will take my pump apart before the spring rush just to to see how they look. I do wash the pump with diesel fuel to make sure it is clean. I have a newer Jurop pump on a small tank. Do all Jurop pumps pump slow or do I just have a bad one?

Pumping slow is a relative term. You would need to know what the specs on the pump are (how much cfm it moves) and the size of your tank to figure out if it is pumping slow or not. I'd check with a manufacturer or Jurop themselves to see if they think it is working up to snuff or not. You will also want to time how long it takes to pump a tank. A tank that is mostly water will be the best to judge by.

[KPToilets]

My Jurop is a pn58 and work very well for a small septic pumper, on yours, you might replace the vacuum relief valve, the vanes, and check for vacuum leaks. I just did this on mine and it perk up. Also check your oil make sure it’s the right type, and weight.