[Pete Bisila]

Update on the pit fire issue. Has anyone else experienced a pit fire attributed to static discharge in the pit? If so, how did you determine the cause and what did you do about it? As rare as it may be, we feel it is quite likely that one of our problematic pumps may indeed be starting fires due to static charge off the lubricating flow. (Unless someone else can postulate an ignition source that occurs within 45-60 minutes of the installation and start up of a brand new pump???) There is a fair amount of literature avaialble referring to the potential to build a charge, but I have yet to see it be associated with the pumps. Anybody?…..Hello, hello, hellooooooo……….

[Pete Bisila]

SRE- Thanks for the response and welcome to Sulfur Unit! The steam jacketing as you mention is a good place to start troubleshooting. I would like to install wireless trap monitors on my sulfur equipment to detect an immediate loss of trap function rather than having to wait until I have a problem. Unfortuntately, our infrastructure isn’t ready for wireless yet.

The eductors we use are fully steam jacketed, as is the inlet and outlet piping. This leads me to believe the fouling is actually in the eductor nozzle rather than the piping. We still use 70# saturated (or super saturated at times) steam for the motive force. I’ve heard from wiser sources that medium (~150#) pressure superheated steam is recommended for eductors.

One interesting thing our operators discovered was what they call a “Turbo Boost” of the eductor. When performance drops, they would turn off the motive steam for a minute or so and then quickly crank it all the way open. This would help restore some of the lost eductive flow.

Thanks

Pete

[Pete Bisila]

General rules I have heard for run down lines:
1) Treat them like sewer lines, everything should flow downhill to the pit.
2) Install a cleanout/ rodding port at every change of direction. Make sure you can access all directions of the line. Minimize the number of turns in the rundown piping

We had one sulfur plant with the sulfur condensor drains on the bottom of the condensor and a horizontal rundown line coming out of a jackete pot under the condensor. The sulfur had to make two right angle turns to get into the rundown line. Worst of it was we had no way to rod directly through the two 90 degree bends. We hot tapped a new outlet into the condensor cover plate on the run and installed a new rundown line on the worst of the condensors and then replaced the rest of the cover plates with new nozzles at the next TA. Problem solved.

[Pete Bisila]

SRS- thanks for the encouragement.  I would be more discouraged if no one was looking at these posts, but since they are, I wish they would offer their advice or ask a question for discussion. I would like to know what are the barriers keeping people from sharing their knowledge and experience. Is it an information security thing/company policy, a lack of interest, not the right participants, etc?
 
I didn’t make it to the conference this year.  Are there any reports on how it went? Plusses/Minuses?

[Pete Bisila]

Surfer-thanks for the input.  We’re finding that the high speed (3600rpm) pumps associated with the higher head requirements of the process change have some reliability issues.  From our work it appears to be related to loss of lubrication in the upper intermediate bearing.  Others are reporting shaft stability/ excessive vibration problems as well. The cure appears to be the same with a design change to the bearings and clearances.  We have a plan forward, but are still in the testing stage so I can’t confirm that the problem is solved.
If your problems appeared and then seemingly went away, I would not be surprised if you find them return.  We have managed to run the pumps for a little over 12 months with no issues, and then suddenly have a rash of events, with no apparent changes in the system.  I suspect sulfurcrete/solids lodged in the upper bearing clearances tends to starve the bearing, forcing the lubricant out the lower ports. 
Do you have cast iron/steel bushings or the carbon filled/graphite bushings?

[Pete Bisila]

Material chemical analysis showed the fouling to be mostly iron, sulfur, silica, alumina and sodium. 

[Pete Bisila]

Thanks for the reply, SRS. From what we are hearing anyway, it appears to be quite rare to foul a waste heat boiler in a sulfur plant. I guess that makes us ‘special’, and not in a good way.  It could be a collection of debris left behind at startup from the refractory repair in which case we hope to not see that again for twenty plus years.  My fear is that it is somehow coming from the process under the right combination of flame temp in the furnace and composition of the acid gases.  There is a large body of literature around the formation of fly ash and coal slag in coal-fired boilers that relate flame temp and mineral content of the coal to fouling potential.  We have all the mineral components of fly ash in our refractory and in deposits found in the acid gas lines and amine systems.  What we don’t know is how they get there and why haven’t we had problems in the past.

[Pete Bisila]

Thanks- it’s nice to know I’m not the only one stubbing my toe on the yellow brick road, or banging my head against a yellow brick wall.  We use MEA in 10-18% strength.  I’m not talking HSS but rather elemental sodium as measured in an amine test.  I don’t know what form it is taking in the amine.  My concern/wonderment is the potential for sodium to be carried out of the amine with the acid gas.  Does anyone know of a transport mechanism for sodium or sodium hydroxide to leave the liquid stream and go out with the vapor stream?

[Pete Bisila]

The skin effect tracing looks like some cool stuff, and beats standard electric tracing all hollow.  I see is has a rating up to 50W/ft on 5000Volts.  How does that compare to steam jacket or controtrace heat inputs?  Does anyone out there have this installed on a sulfur run down line?  Are there any safety concerns or special marking on the line to identify the tracing?  Just curious. Thanks

[Pete Bisila]

Speaking of new sulfur run down lines, what is considered the current best practice for long sulfur transport lines? Controtrace vs steam jacketed? How long of a run between steam supply and trap? Wireless/continuous condition monitors on steam traps? How often are the traps checked for proper operation? 

[Pete Bisila]

“Questions – are all your problems you described in your prior notes caused by your original pump or the new one? Or both? Were modifications made by your reliability group or the vendor?

If possible, bring the vendor out to the field and have them check it out.”
 
We are having the most problems with a pair of our new pumps, and vitually no problems with the pair of original pumps with faster motors.  We have a third set of new pumps that are in between. All three sets are slightly different.
We started with the factory clearances in 2005 and immediately had problems with the pumps tripping out and locking up.  Our reliability group recommended opening up the clearances on the pumps and installing trap bypasses, and that has worked for the third set of pumps.  We had the vice president of engineering from the manufacturer onsite to look at the setup and talk about the pumps.  They didn’t have much to offer in the way of solutions. 

[Pete Bisila]

I can certainly understand your frustration.  Both functions are a necessary and important part of running a safe and reliable refinery.  High quality operator rounds are necessary to detect deviations in the operation and make corrections before things get out of hand.  Maintenance needs good review of their work permits to ensure the risks and operating conditions are properly addressed.  We have struggled with this as well. What seems to work is having a well managed work process where the crafts stick to a schedule that has been communicated to the operators.  We publish a weekly schedule and a daily schedule, and require higher level approval (Shift manager) to deviate from the approved daily schedule.  Operations generally has a list of jobs that maintenance will be coming to get permits for such that the night shift can get the equipment ready and locked out.  During shutdowns, it also helps to have designated permit writers to funnel all the work permits through so they aren’t being distracted from operating the unit.  There are times when the craftspeople have to sit and wait for their permits until an operator is available to review the job with them.
I suggest you share your concerns with your unit manager to see if you can find a compromise to avoid shortcutting rounds or rushing through permit writing.

[Pete Bisila]

I am curious to see the response to this question.  I would think that direct injection of steam versus the reboiling of stripped sour water from within the tower would add water to the system, which is trying to process a waste stream, sour water.  We are usually maxed out on sour water stripping capacity, so increasing the volume of water to be processed is a step in the wrong direction.  We did consider going to live steam addition when we fouled a reboiler, but I don’t think we ever installed it. 

[Pete Bisila]

SRS- just another point of interest that adds to our confusion.  We have two separate sulfur pits with the same length and style of pump, but different discharge pipe size and different numbers of intermediate bearings.  We have one set of pumps that were originally designed for 1800rpm operation that we installed 3600rpm motors on to increase the discharge head with a 2X3″ jacketed discharge line. We have another set of pumps the exact same length, but with 3X4″ jacketed piping, designed for 3600rpm with 3600rpm motors on them.  The key difference between them is the number of intermediate bearings on the pump shaft.  The original 1800rpm pumps have one less intermediate bearing than the 3600rpm pumps.  We are having a lot of problems with the pumps designed for 3600rpm and virtually no problems with the ones converted from 1800 to 3600.  We believe the problems are related to the lubrication of the pump, but haven’t figured out how to completely resolve the problem yet. 

[Pete Bisila]

“Was the waste heat steam generator cooled down evenly, with blowing down the system well to get all the sludge out? It doesn’t take much scale to compromise the heat transfer ability of the system. ”
 
We cool down evenly, but I’m not so sure about any blowdowns.  We have room for improvement (to say the least) in our management of non fired steam generators in our facility.

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