Page 20 - MGPI_Case_Study

Figure 14. Part of the Mod B sodium hypochlorite unloading procedure (left) and sulfuric acid unloading procedure (right) (Source: MGPI).

and found that they lacked consistency. Consistency in procedures been greater than) that of the sodium hypochlorite procedure,
ensures that they are easy to follow and demands the use of, especially since sulfuric acid is classified as an “Extremely Hazardous

among other things, standard, effective formatting and page Substance” under the EPA’s Emergency Planning and Community
75
72
layout. Procedures must also be complete and accurate and Right-to-Know Act (EPCRA), while sodium hypochlorite is not.
73
include the appropriate level of detail. This is particularly true
for procedures involving critical tasks or activities. Procedures that The CSB also found that the WWTP procedures employs a much
are not followed due to obsolescence, inaccuracy, unavailability, different, more specific, approach to chemical unloading. Critical steps
74
or difficulty in implementation often present safety risks. missing in the sulfuric acid unloading procedure are included, for
example, in the WWTP’s unloading procedure for caustic, a chemical
The CSB examined the unloading procedures at Mod B for sulfuric delivered to Mod B. In terms of verifying a correct connection, the
acid and sodium hypochlorite and found an inconsistent approach. WWTP caustic unloading procedures states, “Verify the truck driver

While the sodium hypochlorite procedure included space for has his hose hooked to the correct fill line and that all connections
the operator to sign, date, and timestamp each step, the sulfuric are secured. Sign the truck driver[’]s paper work that you verif[ied]
acid procedure did not (Figure 14). Furthermore, the sodium correct connections [ . . . ] and then allow the driver to start unloading
hypochlorite procedure was more detailed and direct, especially the caustic.” Compared to the Mod B sulfuric acid procedure step
with respect to ensuring that truck driver actions aligned with for verification, this is much more specific. The procedure also calls
the procedure. For example, the sodium hypochlorite procedure for WWTP personnel to ensure the cap is locked after delivery.
states, “Have supplier slowly open vehicle transfer valve,” while While including such steps in a procedure does not guarantee

the sulfuric acid procedure does not mention the vehicle transfer that the steps will be followed, including critical verification steps
valve. The CSB notes that the rigor applied to the sulfuric acid increases the likelihood that such steps are not overlooked.
unloading procedure should have at least matched (or preferably
5.1.3.2 HARCROS
72 CCPS. Guidelines for Writing Effective Operating and Maintenance Procedures
[Online], Center for Chemical Process Safety/AIChE: New York, NY, 1996. http://app. 5.1.3.2.1 Procedures and Work Practices Not Aligned
knovel.com/hotlink/toc/id:kpGWEOMP01/guidelines-writing-effective/guidelines-
writing-effective (accessed September 20, 2007). The CSB reviewed the Harcros CTMV unloading procedure and
73 CCPS. Guidelines for Writing Effective Operating and Maintenance Procedures found that work practices did not align with the procedure in
[Online], Center for Chemical Process Safety/AIChE: New York, NY, 1996. http://app.
knovel.com/hotlink/toc/id:kpGWEOMP01/guidelines-writing-effective/guidelines- two critical ways. On the day of the incident, the truck driver
writing-effective (accessed September 20, 2007).
74 CCPS. Inherently Safer Chemical Processes--A Life Cycle Approach: 6.4 Error 75 EPCRA requires industry to report on the storage, use, and release of hazardous
Prevention [Online], Center for Chemical Process Safety/AIChE: New York, NY, 2009. substances to federal, state, and local governments. Sulfuric acid is on EPCRA’s list
http://app.knovel.com/hotlink/pdf/id:kt0068GRV3/inherently-safer-chemical/error- of Extremely Hazardous Substances, with a reportable quantity of 1,000 pounds. 40
prevention (accessed September 12, 2007). C.F.R. § 355 app. A (2017). For more information on EPCRA, see Section 5.5.2.
20 CSB MGPI Processing Case Study