Tank Mixer Area

[Electriman]

Recently I have faced a problem around mixers. I have a fixed roof storage tank. Based on the standard API 500 the area around vents and hatches are C1D1. But no where in the standard talks about mixers or agitators. Does anybody have an idea what I should consider the area around storage tank mixers?

Thanks

 

[iceworm]

Recently I have faced a problem around mixers. I have a fixed roof storage tank. Based on the standard API 500 the area around vents and hatches are C1D1. But no where in the standard talks about mixers or agitators. Does anybody have an idea what I should consider the area around storage tank mixers?

Motor operated paddle mixer stuck through the side of a tank wall? Usually about waist high?

If so: What would be your concern? Tank product leaking past the shaft seal to outside the tank.

ice

 

[Electriman]

Motor operated paddle mixer stuck through the side of a tank wall? Usually about waist high?

If so: What would be your concern? Tank product leaking past the shaft seal to outside the tank.

ice

In my case the mixers are roof mounted. Would you consider it Class 1 Dev. 2 (C1D2) or Class 1 Dev. 1 (C1D1). I am thinking that since it is similar to Hatch it should be C1D1. What do you think?

 

[rbalex]

In my case the mixers are roof mounted. Would you consider it Class 1 Dev. 2 (C1D2) or Class 1 Dev. 1 (C1D1). I am thinking that since it is similar to Hatch it should be C1D1. What do you think?

Actually API 500 is API Recommended Practice 500. From the opening statement in Section 1.1.1: "... This publication is only a guide and requires the application of sound engineering judgment."NFPA 497 says essentially the same thing in Section 1.2.2: "This recommended practice is intended as a guide and should be applied with sound engineering judgment." I think you did just that ("I am thinking that since it is similar to [a] Hatch it should be CID1.")

For all practical purposes most (although not all) classification standards are recommended practices subject to "sound engineering judgment." See a representative list in the FPN/INs in Section 500.4(B).

 

[iceworm]

In my case the mixers are roof mounted. Would you consider it Class 1 Dev. 2 (C1D2) or Class 1 Dev. 1 (C1D1). I am thinking that since it is similar to Hatch it should be C1D1. What do you think?

I certainly wouldn't disagree with Bob. However, how is the mixer similar to a hatch? A hatch has a flip up cover with the interior open to the tank product. Is the mixer open to the tank interior? Or, does the shaft have a seal separating the inside from the outside?

ice

 

[rbalex]

I certainly wouldn't disagree with Bob. However, how is the mixer similar to a hatch? A hatch has a flip up cover with the interior open to the tank product. Is the mixer open to the tank interior? Or, does the shaft have a seal separating the inside from the outside?

ice

I suspect it is because the mixer can be pulled while the overall system is still operational. Assuming the mixer is single-phase, other than a few seals, it probably won't make a significant difference to the installation.

 

[Electriman]

That is exactly what I think. Sealing can leak like flange seal.

 

[iceworm]

That is exactly what I think. Sealing can leak like flange seal.

Again, I'm not disagreeing with requiring the equipment to be CID1. I just don't understand the thought process.

How can the seal leak? It is in the top of the tank. Is there fluid against the seal? Are these little tanks (like 3'Dia, 5'high), full of product and under pressure?

I suspect it is because the mixer can be pulled while the overall system is still operational. Assuming the mixer is single-phase, other than a few seals, it probably won't make a significant difference to the installation.

If one is pulling the mixer, it is electrically isolated, what difference would CID1 equipment make?

Maybe I have a different picture that the installation. The mixers I deal with are in atmospheric vented, petroleum distilate tanks, maybe 100' Dia and 40' high. The mixers are 3ph, 30hp - 60hp, TEFC motors suitable for a CID2 area - inside the tankfarm berm.

If your mixer motors are 1ph, likely you would get XP, just because of the internal arcing contacts

So far, I haven't heard anything that makes the mixer area CID1. It feels like there is a rest of the story

ice

 

[rbalex]

...

If one is pulling the mixer, it is electrically isolated, what difference would CID1 equipment make?

...

There may still be other nonrelated instrumentation (or equipment) in the envelope. Though as I mentioned earlier, it probably won't make much difference to the overall installation. Many Division 2 instruments are still rated for Division 1. A boundary seal or 2 may be involved.

Consider this: Even if there is NO electrical equipment within the classified location around either the vent or hatch, they still have Division 1 envelopes and it would make no difference to the installation at all. I can also identify some locations, such as around relief vents, that may never actually "blow" but they still have Division 1 envelopes.

 

[Electriman]

The tanks are relatively big. They can store more 100k barrels flammable liquid. The mixers are 60 hp.

 

[iceworm]

The tanks are relatively big. They can store more 100k barrels flammable liquid. The mixers are 60 hp.

So you are looking at a 120D x 40H tank. 60hp mixer, with the shaft extending 35' into the tank with maybe a 5' propeller on the end. Maybe mounted on a 6' dia coverplate. I suspect a crane is needed to pull the mixer?

Do you have to go in the tank to to remove the propeller/shaft structural to pull the mixer? Do they have to clean the tank to remove the mixer? Sounds like they might have to.

There may still be other nonrelated instrumentation (or equipment) in the envelope. Though as I mentioned earlier, it probably won't make much difference to the overall installation. Many Division 2 instruments are still rated for Division 1. A boundary seal or 2 may be involved.

Consider this: Even if there is NO electrical equipment within the classified location around either the vent or hatch, they still have Division 1 envelopes and it would make no difference to the installation at all. I can also identify some locations, such as around relief vents, that may never actually "blow" but they still have Division 1 envelopes.

For the mixer I'm seeing a a TEFC motor, likely an accelerometer for vibration pickup, I'm not seeing anything around the mixer that calls for CID1. Other stuff in the area could well change the classification - Who knows? That would be part of the rest of the story. As for vents, hatches, gage and thief holes, and pressure/vacuum reliefs, if they are not in the area of the mixer - so what.

I'm still not seeing your reasoning.

If you want it classified - then declare it classified. Nothing wrong with that.

ice

 

[rbalex]

Except for specific applications of Articles 511 to 516 and a few other standards, such as NFPA 820, classification is primarily an educated judgment. The essential concept though is classification comes first, equipment selection is second.

The specifics are important, of course. Knowing we're now dealing with 60hp would call for an explosionoproof, not just TEFC, motor in Division 1. While most explosionproof motors are basically TEFC or TENV, the cost differential for explosionproof is indeed significant. Nevertheless, since pulling the mixer is a "normal" (not necessarily common) activity, classifying the area around the opening Division 1, is still reasonable.

 

[iceworm]

Except for specific applications of Articles 511 to 516 and a few other standards, such as NFPA 820, classification is primarily an educated judgment. The essential concept though is classification comes first, equipment selection is second. ....

yes

 

[iceworm]

So you are looking at a 120D x 40H tank. 60hp mixer, with the shaft extending 35' into the tank with maybe a 5' propeller on the end. Maybe mounted on a 6' dia coverplate. I suspect a crane is needed to pull the mixer?

Do you have to go in the tank to to remove the propeller/shaft structural to pull the mixer? Do they have to clean the tank to remove the mixer? Sounds like they might have to.



For the mixer I'm seeing a a TEFC motor, likely an accelerometer for vibration pickup, I'm not seeing anything around the mixer that calls for CID1. Other stuff in the area could well change the classification - Who knows? That would be part of the rest of the story. As for vents, hatches, gage and thief holes, and pressure/vacuum reliefs, if they are not in the area of the mixer - so what.

I'm still not seeing your reasoning.

If you want it classified - then declare it classified. Nothing wrong with that.

ice

Last edited by rbalex; Today at 04:57 PM.

Perhaps you could be so kind as to tell me exactly what you edited in my post and exactly why you felt the need to edit my post.

 

[rbalex]

Perhaps you could be so kind as to tell me exactly what you edited in my post and exactly why you felt the need to edit my post.

Sure. I'm sorry it wasn't clear. I didn't change your content. But what was originally there was:




"

The tanks are relatively big. They can store more 100k barrels flammable liquid. The mixers are 60 hp.

So you are looking at a 120D x 40H tank. 60hp mixer, with the shaft extending 35' into the tank with maybe a 5' propeller on the end. Maybe mounted on a 6' dia coverplate. I suspect a crane is needed to pull the mixer?

Do you have to go in the tank to to remove the propeller/shaft structural to pull the mixer? Do they have to clean the tank to remove the mixer? Sounds like they might have to.


[quote-rbalex]There may still be other nonrelated instrumentation (or equipment) in the envelope. Though as I mentioned earlier, it probably won't make much difference to the overall installation. Many Division 2 instruments are still rated for Division 1. A boundary seal or 2 may be involved.

Consider this: Even if there is NO electrical equipment within the classified location around either the vent or hatch, they still have Division 1 envelopes and it would make no difference to the installation at all. I can also identify some locations, such as around relief vents, that may never actually "blow" but they still have Division 1 envelopes.[/quote]
For the mixer I'm seeing a a TEFC motor, likely an accelerometer for vibration pickup, I'm not seeing anything around the mixer that calls for CID1. Other stuff in the area could well change the classification - Who knows? That would be part of the rest of the story. As for vents, hatches, gage and thief holes, and pressure/vacuum reliefs, if they are not in the area of the mixer - so what.

I'm still not seeing your reasoning.

If you want it classified - then declare it classified. Nothing wrong with that.

ice


"

Where you quoted me wasn't clear. I didn't change either your content or my own, just how mine was formatted.

 

[iceworm]

Sure. I'm sorry it wasn't clear. I didn't change your content. ...

... Where you quoted me wasn't clear. I didn't change either your content or my own, just how mine was formatted.

I certainly appreciate you not changing my content or your quoted content in my post.

And, I certainly can't stop any of you with moderator super powers from messing with my posts.

However, I consider it professional courtesy to mark exactly what you changed in my post. No, not for this one. This is done.

ice

 

[ActionDave]

I certainly appreciate you not changing my content or your quoted content in my post.

And, I certainly can't stop any of you with moderator super powers from messing with my posts.

However, I consider it professional courtesy to mark exactly what you changed in my post. No, not for this one. This is done.

ice

He didn't change anything. He did you a favour and fixed a formatting error in your post. Everybody benefited. You look professional instead of coming off like a young turk posting from his smart phone we get a thread that is easier to read.

 

[rbalex]

He didn't change anything. He did you a favour and fixed a formatting error in your post. Everybody benefited. You look professional instead of coming off like a young turk posting from his smart phone we get a thread that is easier to read.

I sincerely appreciate you coming to my defense but he's right and I equally sincerely apologize to him. I originally attempted to place both versions in single post but couldn't figure out how at the time. I should have cut and pasted the original into a new post and edited it instead.

Apparently there's also a way to recover his original post in it's original location but I don't know to do that either. I should have just left it alone. It was an abuse of power.

 

[iceworm]

...I equally sincerely apologize to him. ...

sincerely accepted

... I should have cut and pasted the original into a new post and edited it instead. ... ....

Yes

... Apparently there's also a way to recover his original post in it's original location but I don't know to do that either. ....

You are one of the good guys and I sincerely recognize that.

I agonized for a couple of days trying to word this right. My intent was to remind you, "Don't do this" and not leave you feeling slapped. According to Dave I didn't get there. That was unfortunate.

Like I said - this is done. It's okay for us to move on.


Tongue in cheek note to Dave:
I afraid my phone still has buttons on it. You know, "If you need to press a '4', I have a button for that" So when I screw up the formatting it is with the best keyboard/monitor/computer/software I can afford.


ice

 

[ActionDave]

Tongue in cheek note to Dave:
I afraid my phone still has buttons on it. You know, "If you need to press a '4', I have a button for that" So when I screw up the formatting it is with the best keyboard/monitor/computer/software I can afford.


ice

I had you figured as a land line kind of guy. I do have a cell phone but it is a dumb one, my other phone has buttons on it too.