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Electric Trim Heater for Ethylene

01/18/2017 8:54 PM

As part of a new installation, we will be using ethylene cylinders contained in a flammable gas cabinet. I noticed today there is an electric "trim heater" outside this cabinet. This is presumably because someone thinks that expanding ethylene could go "cryo" under certain conditions. As the end user, and under my standard operating conditions, I don't think this is necessary.

Cylinder P ~2200 max

Regulator outlet P 1000 max

Flow rate 7 L/min max by flow controller

Reactor P ~600 P max "hot" (after loading Et=)

They plan to hard wire this heater next week, not sure it is intrinsically safe either. I'm going to tell then not to do it unless I hear experienced arguments from you guys.

Thanks.

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#1

Re: Electric trim Heater for ethylene

01/18/2017 10:33 PM

Trusting the advice of an anonymous online forum is a bit risky, don't you think? Especially where safety is concerned? I mean, you've really no idea of our qualifications. You can still ask of course, and you may receive excellent advice, or excellent-sounding crap advice which you follow and then a week later we read all about it in the Houston Chronicle.

Where safety issues are concerned, I would seek out the advice of known professionals whose credentials can be verified, quite honestly. Shouldn't you? Seriously, wouldn't this be the better approach than asking a bunch of complete strangers whom you don't know from Adam's housecat?

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#4
In reply to #1

Re: Electric trim Heater for ethylene

01/19/2017 3:25 PM

Trusting the advice of an anonymous online forum is a bit risky, don't you think?

I don't trust anyone absolutely.

Especially where safety is concerned?

Especially

I mean, you've really no idea of our qualifications. You can still ask of course, and you may receive excellent advice, or excellent-sounding crap advice which you follow and then a week later we read all about it in the Houston Chronicle.

I would have to decide between excellent and put me in the Chronicle advice.

(I had in fact already decided I am not going to be in the Chronicle)

Where safety issues are concerned, I would seek out the advice of known professionals whose credentials can be verified, quite honestly. Shouldn't you?

Yes. Did. And have you ever heard of a credentialed professional making a deadly decision?

Seriously, wouldn't this be the better approach than asking a bunch of complete strangers whom you don't know from Adam's housecat?

Did it. Done. Thanks.

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#2

Re: Electric trim Heater for ethylene

01/18/2017 11:24 PM

Andrew Westman is right. You may get some opinions here, but nothing that should be considered an "expert" assessment of your specific situation.

If your equipment supplier, or facility safety officer can't give you a written recommendation, then you will be accepting liability for the installation in the event of an injury or fire.

Your insurance carrier will have a definite opinion about this installation, especially if something goes wrong.

If in doubt, hire an expert who will stand behind their recommendation.

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#5
In reply to #2

Re: Electric trim Heater for ethylene

01/19/2017 3:27 PM

Congratulations on swapping good answers with Andrew.

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#8
In reply to #5

Re: Electric trim Heater for ethylene

01/19/2017 3:29 PM

I think Adam's housecat probably has more common sense than whoever advised to install this ridiculous heater. It is really intrinsically safe? How? Are there other electrical controls nearby that could make contact with vapor in a flammable context?

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#15
In reply to #8

Re: Electric trim Heater for ethylene

01/20/2017 8:28 AM

<...It is really intrinsically safe?...>

See #3⇓.

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#6
In reply to #2

Re: Electric trim Heater for ethylene

01/19/2017 3:27 PM

They already did hire an expert that told them to install the trim heater.

Let them blow the place up first, then we can figure this out.

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#7
In reply to #6

Re: Electric trim Heater for ethylene

01/19/2017 3:29 PM

Let them blow the place up first, then we can figure this out.

That advice would be unacceptable even if I didn't have to be there.

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#10
In reply to #7

Re: Electric trim Heater for ethylene

01/19/2017 3:33 PM

Well, if they have no common sense, we have increase the surplus intelligence of the planet almost instantly.

I have no use for complete dumb butts.

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#16
In reply to #6

Re: Electric trim Heater for ethylene

01/20/2017 8:30 AM

<...expert...>

"X is an unknown quantity. Spurt is a drip under pressure" - Anon.

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#3

Re: Electric trim Heater for ethylene

01/19/2017 3:04 AM

Heaters cannot be <...intrinsically safe...>, or EEx i, under the definition of the term. However, it might be "flameproof" to EEx d, and without knowing the model number it cannot be checked from here.

Ethylene boils at -104degC at atmospheric pressure. Without defining the units of pressure <...Cylinder P ~2200 max...> in the original post, the forum waits in wonder.

Has anyone at the facility asked the question "why", and received a satisfactory answer? It sounds not.

If in doubt, consult a qualified Process Engineer.

"What you don't have, cannot leak." - with apologies to the late Dr. Trevor Kletz, acknowledged worldwide as a process safety guru.

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#9
In reply to #3

Re: Electric trim Heater for ethylene

01/19/2017 3:32 PM

Do you happen to have the autoignition temperature of ethylene on the tip of your tongue? Is it

Autoignition
temperature

542.8 °C (1,009.0 °

as stated in the Wikipedia article?

Small voltage sparks, and arcs from bad contacts, or even lighting fixtures, can easily ignite this.

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#17
In reply to #9

Re: Electric trim Heater for ethylene

01/20/2017 8:32 AM

That's why there are pan-Europe standards for the installation and use of electrical equipment in potentially explosive atmospheres.

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#11
In reply to #3

Re: Electric trim Heater for ethylene

01/19/2017 3:34 PM

Without defining the units of pressure <...Cylinder P ~2200 max...> in the original post, the forum waits in wonder.

For that I must apologize. Should have read Cylinder P ~1200 psig max.

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#12

Re: Electric Trim Heater for Ethylene

01/19/2017 3:38 PM

Sorry folks. Identified and solved. I thought it might inspire some lively conversation on strange experiences with the Joule Thompson effect.

Now back into exile I go.

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#13
In reply to #12

Re: Electric Trim Heater for Ethylene

01/19/2017 3:46 PM

Nah, it is OK, surely when a bottle is under heavy flow, it could produce liquidus level in the bottom. This heater is supposed to counter the effect, but does it introduce more problem than it solves? What about just moving warm air past this cabinet (or through it).

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#14
In reply to #13

Re: Electric Trim Heater for Ethylene

01/20/2017 8:26 AM

That would be a far better idea than installing an electric heater: simply duct-in warm air from somewhere else.

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#19
In reply to #14

Re: Electric Trim Heater for Ethylene

01/20/2017 11:48 AM

Yeah, thanks for my good answer on that. Don't worry, I won't hold my breath.

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#18

Re: Electric Trim Heater for Ethylene

01/20/2017 11:31 AM

Who designed the system? They should have some sort of documentation stating design conditions and process parameters, which would include inlet and outlet conditions at the heater. Is the installation permitted, inspected or certified? What is the ethylene used for?

Curious minds just want to know.

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#20

Re: Electric Trim Heater for Ethylene

01/20/2017 1:19 PM

you need the heater. Assuming PSI. at that flow rate the expansion of the gas will pull a lot of heat out of the cylinder causing it to cool and quite possibly freeze. you did not mention if anything else is being used to heat the gas after it expands from pressure drop.

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#21
In reply to #20

Re: Electric Trim Heater for Ethylene

01/20/2017 1:51 PM

In such a case, just putting some electric heater near the enclosure is not going to get the job done. He will need direct heat transfer.

The best way to do this is with heated metal-metal contact with the container. There are numerous ways to do this, some safer than others. Depending on the container metal, then we could even say that induction heating might work.

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