Fuel Oil

[GregPLC]

Howdy everyone from the great city of Milwaukee, hope everyone is having a good week...I have an application, which I'd like to use a submersible pressure transmitter for level. I have used several submersible Wika transmitters in utility applicatons for level, and they have been working out very well.

This application is a blend of #1 and #2 fuel oil in a tank, which is pumped out to the boiler. Most of my applications aren't "hazardous", and I don't know if the submersibles I'd like to use are "legal" or a safe/good idea to use with fuel oil.

I'm looking at using the Wika IL-10. It's an intrinsically safe device, don't know if that makes it better for this application. Talking with Wika, it was what they recommend, however their recommendations are based on "yes the transmitter will hold up in fuel oil". I need to know if it's safe/legal kinda thing. As I said, we like these submersibles, and there is really no fitting on the tank for an external device.

TIA,

Greg

 

[elevmike]

What about using an ultrasonic device, with an intrisncilly safe barrier?

http://www.omega.com/toc_asp/subsectionSC.asp?subsection=K03&book=Green

http://www.omega.com/ppt/pptsc.asp?ref=LVU950&Nav=grek03

 

[rsdoran]

This is what the manual states:

• Pressure ranges from 0 … 100 mbar to 0 … 25 bar
• d -protection: EEx ia IIC T6 in compliance
with ATEX
• Applicable in all hazardous environments:
- Gases and vapour: Zone 0, Zone 1 and Zone 2
- Dusts: Zone 20, Zone 21 and Zone 22
• Vented PUR-cable
• Maximum tensile strength of the cable 1000 N
• Ingress protection IP 68 (up to 300 m immersion depth)
Optional extras:
• FEP-cable
• Additional weight
Applications
Areas of application are level measurement in hazardous
environments, e.g. in refineries, distilling equipment, painting
plants, filling equipment for combustible gases, overfilling
systems on tank vehicles, bore holes, waste water plants
(biogases from sewage), etc.

Its rated as applicable in all hazardous environments so should work in this app.

 

[GregPLC]

Thanks Ron, that's kinda what I assumed....want to make sure. Mike, we really like the submersibles, at all cost we try to keep the different types of sensors to a minimum in the utilities area...Thanks again for the input. I tried to attach the manual, but was unable to....too large.

Greg

 

[GregPLC]

Got them on order....What "book" would I have looked in to know what type of transmitter must be used in a fuel oil application? I just assumed it needed to be intrinsically safe....



Greg

 

[rsdoran]

Assess the hazardous location type/zone and match to that. Intrinsically safe is a protection concept for use in potentially explosive environments. If its flammable/explosive then its definitely a hazardous environment.

NEC Article 500 gives definitions etc of Hazardous locations and equipment/material.

 

[Ken Moore]

Be aware that if you are going to use an IS (Intrinsically safe) device, then you must use an IS barrier. There are different types of barriers, (different technology). Depending on what type/style you choose, you will need to study up on the wiring/grounding requirements.
The two types I'm familiar with use galvanic isolation, or zenner diodes. The galvanic type is the easiest to use, but cost the most.

Last time I checked (it's been a while) a dual channel zenner was around $80.00 and a dual channel galvanic was around 250.00.

The zenner technology has special grounding considerations, and must be checked/maintained, to ensure safety.

We have thousands of the zenner type installed, and have decided to go with galvanic for all future installations. Without the maintenance issues, the galvanic total cost of ownership will be less.

 

[GregPLC]

Thanks again, Ken, I'm assuming the barrier is for electrical isolation? I'm going to have to do a bit of research on this, as I said before I've never needed to use an IS device...I'll have to check into the zener and galvanic devices....Is this just for isolation to the PLC analog input card? What am I actually intending to isolate?

Thanks again,


Greg

 

[RMA]

You're isolating the hazardous area from the safe area, so that in the event of a fault, regardless of whether the fault is in the safe or in the hazardous area, it is not possible for sufficient energy to reach the hazardous area to cause a spark.

The biggest problem with the whole game is avoiding ground loops - particularly in regard to analog systems. I don't know about American regulations, but here in Germany it can somtimes be nearly impossible to comply with safety requirements and yet still achieve a star-point grounding system for your analog circuits. On the whole, the problem is not so acute with digital I/O, but you can still have probelms, particularly if all the I/O on the card uses one common power rail, but the signals are intended to go to different parts of the plant, some inside, some outside of the hazardous area.

You've got a lot of reading ahead of you, but don't worry, "with a little help from your friends", you'll get there!

 

[Ken Moore]

I prefer the P&F brand of barriers.
Here's a link to thier zenner barriers: http://www.pepperl-fuchs.com/pa/interptop/barriers/default_e.html

 

[Eric Nelson]

HERE'S another link for IS barriers. I've used thier 'SAFE-PAK' units for pressure vessel monitoring.

beerchug

-Eric

 

[GregPLC]

Thanks guys, makes sense. I think I'll go with the P&F zener barrier. It's always nice to trek down a road that's a little different than you're used to.


Greg

 

[Jeff1234]

EEx Rating

Hi Greg,
Please be very careful regarding this installation, the EEx criteria is like a mine field here in the UK. (Probably Europe in general)
Zener Barriers are cheeper but not always the best solution, process control loops cannot totally float above ground, and hence can pick up noise.
Look at the P&F Isolated Barrier, it still contains the zenner for V&I limitation but doesn't use an Intrinsically safe ground.
The galvanic seperation provides a high degree of isolation between primary and secondary and requires no ground.
They are recommended more for process control loops. (mA or mV signals)
I'd still recommend talking with an expert, as over here competence must be demonstratable in the form of experience and / or professional training.
I'm not doubting your abilities for one second, but seek further advice from someone who does this work on a regular basis.

Regards, Jeff.

 

[GregPLC]

Thanks for the valuable insight Jeff, and everyone else. The last point you made Jeff about finding an expert is the exact reason I posted the question here. As I said, I have basically zero experience with IS devices, and what regulation requires here in the states. I am in the process of getting further guidance from P&F on this....thanks for the tip on the isoloated barrier (galvanic), this is a process control loop.


Greg

 

[GregPLC]

I called P$F, they also recommended against the zener model. The "K-System" device they have is sort of an opto-isolator from what the application engineer told me. I went with the KFD2-STC4-EX1 model. I was told that ISA publishes a good article on intrinsically safe devices, the publication is: ANSI/ISA-RP12.6

Greg