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Why would a mag drive be impractical for non corrosive applications?

Why would a mag drive be impractical for non corrosive applications?

Why would a mag drive be impractical for non corrosive applications?

(OP)
Every time I see a mag drive pump advertised it’s a lined casing specific for corrosive applications. From what I understand mag drive pumps have a much, much higher mean time between failure vs centrifugal. Sure if it runs dry it’s disastrous and it’s not conducive to slurries, but if I have a pump that runs continuously throughout the year and I want to increase the mean time between repair why wouldn’t I go with a mag drive?

This is a treated process water pump. I figure if we installed duplex filters for random crap and installed a mag drive in place of a goulds we wouldn’t have to worry about random seal leaks that take us down. This isn’t a super high horsepower pump, and it’d be a costly investment, but being able to avoid any potential downtime more than makes up for it.

I guess the other plan would be to hard pipe the bypass we need to do when we take this down for maintenance. What does everyone think on this? Thanks!

RE: Why would a mag drive be impractical for non corrosive applications?

There are mag drive pumps that can be run dry.

Mechanic seal pumps are no less sensitive to dry running.

Mag drive pumps are a great longer lasting option provided your fluid doesn't have a lot of magnetic particles in it.

Mag drive doesn't have a big presence in high power applications. I feel that while mag drive may double the cost of your pump you're talking hundreds of dollars and that is insignificant in the overall project cost.

RE: Why would a mag drive be impractical for non corrosive applications?

I depends on the styles of seals that you run.
If you are currently running very complex seal patterns than a mag drive might simplify your life enough to justify it.
They are a different animal so be careful where you use them.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

RE: Why would a mag drive be impractical for non corrosive applications?

Goulds has mag drives also so it isn't a mag vs Goulds thing really. Even if going mag, I'd still give Goulds a shot at it. A min flow spill back can help with that run dry concern. Only real drawback to your application, besides the initial outlay, would be the efficiency losses so maybe run that power consumption calc if your HP is up there since it sounds like it runs 24/7.

RE: Why would a mag drive be impractical for non corrosive applications?

Mag drive pumps are like the devil you dont know - find out first what you dont know yet. You most certainly wont hear of failures talking to vendors. Also trace components (whether intermittent or continuous) in this treated water may make a meal out of this "corrosion resistant" liner.

RE: Why would a mag drive be impractical for non corrosive applications?

The reason mag drives would not normally be chosen is because the primary aim when building plants is CAPEX.

Unless the client is very firm and has a lot of sway, OPEX costs, costs of shutdowns or stoppages etc, rarely enter the decision making process.

The MTBF is one way of assessing the issue, but if this particular unit was seen as critical then often its easier and cheaper to install a spare to prevent shutdowns and downtime on the plant.

This is something different which is a RAM study and could highlight certain areas where use of a MAG drive could be seen as cost effective.

But its not without pain as well. There are losses in the drive and the internal sealing sometimes leaks. This guy has had a lot of issues https://www.eng-tips.com/viewthread.cfm?qid=490736

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

RE: Why would a mag drive be impractical for non corrosive applications?

Keep in mind there is a difference between magnetic drive pumps and canned motor pumps. The magnetic drive pumps have a coupling mechanism that is connected to a regular motor, while the canned motor pump contains the windings within the secondary containment shell and drives the pump shaft magnetic poles directly.

Also, magnetic drive pumps are offered in ANSI configurations with PTFE-lined internals for corrosive applications. However, there are just plain metallic magnetic drive pumps for normal process fluids.

As long as the hydrodynamic bearing is running (can request ceramic for dry running situations), the pump should be okay excluding other upset conditions like overloaded torque on startup. The motor can burn up if not properly monitored.

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