Process Puzzler: Put Railcar Loading Back on Track

Readers suggest how to stop serious safety snags.

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2. Technical option: Most rail loading or unloading bays that handle flammable materials require the rail cars to be grounded prior to any work being done on them. These ground systems typically have some sort of indicator light to show the personnel in the area that the rail car is in fact grounded. It might be possible to tie such a system into your blue flag lights on a bay so that when a rail car is grounded the blue flags lights are illuminated and would let personnel know the cars are being worked on and cannot be moved. You could try to take this a step further to have the loading alarm be set up with the grounding cable so that whenever the loading arm is in position it also serves as the grounding system and notification system.

Len Riker, PSM coordinator
Penford Products Co., Cedar Rapids, Iowa


TEST FAIL-SAFE
I suggest the following: 1) all critical automatic valves that are interlocked to a shutdown system must be function-tested either during routine maintenance or by a test of the emergency shutoff system(s); 2) at minimum, a blue flag should be present on that spur with a closed lockedderailer located one railcar distance from the nearest loading spot railcar. The key should be under the control of operations personnel. The best protection is a closed locked derailer that is interlocked to the loading valves. Chlorine Institute pamphlet 57 covers safeguards that are recommended for chlorine rail car loading or unloading. Consider these safeguards for propylene loading.

Larry Sendlak, senior technical service specialist
OxyChem Basic Chemicals, Niagara Falls, N.Y.


START WITH DOUBLE-CHECKS
Unfortunately, this type of problem occurs over and over again. Operators extend their hours to make more money and fatigue takes its toll.

The best solution remains automatic fail-safe equipment. Of course, equipment only works if it's maintained. I recommend hoses with spring check valves at either end. Even these can become gummed up and leak. Perhaps a lockout/tagout procedure is the simplest approach. If the over-filled tank car was to remain hooked up to the vent then maybe the railcars could be locked in place until the last hose was closed and removed.

Hoses and their fittings are prone to leak (see "Watch Out with Piping, Valves and Hoses," www.ChemicalProcessing.com/articles/2010/012.html). The aviation industry resolved this issue decades ago with periodic testing and inspection. You may want to establish a hose maintenance program.

Another idea is to automate the valves. This would eliminate the risk of an operator getting burned by physically closing a frozen valve.

The shift change procedures should be reviewed immediately. Like in any other operation, each shift should brief the next of the status of the process. Also, supervisors should be approving any operation involving moving cars, let alone six cars at once. Strict discipline will make operators think twice before this happens again.

When we train operators to take on a hazardous operation we hold dress-rehearsals. The more dangerous the operation, the more often retraining is required. During commissioning of an acid unloading facility we drilled green operators for a week until they could do the work in their sleep, which could be the case. These operators should be retrained at least annually after this incident.

I've saved the root cause for last: over-filling. Level control seems to be precarious with tankcars. Weigh cells offer an expensive solution. Dipsticks are cheaper and could be equipped with limit switches; however, dipsticks expose the operator to risk. Over-fill protection would scotch the root cause. But, let's not substitute one danger for another.

Dirk Willard, consulting process engineer
Organic Technologies, Coshocton, Ohio


JULY'S PUZZLER
We recover ammonium sulfate from a power plant scrubber and sell it as fertilizer. Temperature control of the liquor going to the crystallizer is critical; liquor is circulated through a shell-and-tube heater (see Figure 1). Poor control causes nucleation, creating small crystals at the expense of large ones. The difference between the inlet and outlet stream temperatures must be ±1°F. Our customer originally insisted on using a controller temperature board in its central control room, which is more than 300 yards away, but now is demanding that we use K thermocouples. Will either idea work? What's the best way to get the accuracy needed?

Send us your comments, suggestions or solutions for this question by June 11, 2010. We'll include as many of them as possible in the July 2010 issue and all on CP.com. Send visuals — a sketch is fine. E-mail us at ProcessPuzzler@putman.net or mail to Process Puzzler, Chemical Processing, 555 W. Pierce Road, Suite 301, Itasca, IL 60143. Fax: (630) 467-1120. Please include your name, title, location and company affiliation in the response.

And, of course, if you have a process problem you'd like to pose to our readers, send it along and we'll be pleased to consider it for publication.
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