Page 15 - MGPI_Case_Study

unlocked the sulfuric acid dust cap for the delivery. The sodium fill line before they
hypochlorite dust cap was unable to be locked because it was made a connection.
Work with motor
missing a split ring on one lever. Without the split ring on one Since both fill lines
carriers to select
of the cam levers, it was impossible to secure the dust cap on the had the same diameter
hose couplings and
fill line with the padlock and orientation, the
51
Physically isolating (Figures 5 and 7). driver could connect fill line connections
The CSB was unable
the sulfuric acid hose
or using distance to determine why the to the incorrect, but with uniquely
to separate fill sodium hypochlorite unlocked, sodium shaped and color-
lines can lower the dust cap was missing a hypochlorite fill line. coded fittings for

risk of incorrect split ring nor how long each chemical or
connections during it was left unsecured Chemical process class of chemicals
plants and chemical
bulk unloading on the fill line prior distributors can
to the incident. It
operations is possible that the reduce the likelihood of an incorrect connection by designing

sodium hypochlorite and selecting equipment so that connections or manual
dust cap was not secured by the driver of the last sodium configurations of components are difficult or impossible to
52
hypochlorite delivery nine days prior, and this went unnoticed perform in error. This includes designing fill lines so that
by MGPI. Mod B operators reported that the split rings a particular hose can be connected only to a fitting mated to
experienced chemical corrosion and this could have caused receive it. The use of uniquely sized or shaped hose couplings
the split ring to deteriorate and fall off the dust cap. Though and fill line connectors is another example of a passive control
not causal, the CSB observed that the acetic anhydride dust that eliminates or reduces the possibility of connecting the
cap was also missing a split ring on one lever. On the acetic wrong hose and inadvertently transferring material (Figure 10).
anhydride dust cap, a chain was attached to a split ring on only

one cam lever and wrapped around the empty lever, giving it In reviewing the range of fitting diameters offered by various
the appearance of being secured on the fill line (Figure 6). hose manufacturers, the CSB found that the size and orientation
of the fill lines used at Mod B are consistent with common

MGPI started using dust caps to prevent product contamination industry practice. Based on information from the chemical
or tampering issues on all receiving lines in response to a 2010 distribution industry, 2- and 3-inch round hose couplings and
food safety inspection. Though the practice of locking dust caps fill line receivers are most common for this type of service.
is not a specific requirement for process safety or environmental Though the identical size of the fill lines allows facilities to

reasons, when executed properly, it was the only physical barrier receive chemicals from multiple distributors, it also provides
preventing drivers from incorrectly connecting to the wrong fill the opportunity for a wrong connection. Since the incident,
line. MGPI had no design or engineering controls preventing Harcros has worked with MGPI to select uniquely shaped
the driver from making an incorrect connection. At the time of transfer equipment for sulfuric acid to make it impossible for
the incident, the Mod B fill lines were similar in appearance and drivers to connect another delivery hose to that line (Section
identically sized. Because operators had a practice of keeping 9.0). Facilities that receive multiple chemicals should work with
the fill lines locked with dust caps when not in use, drivers distributors to determine what size and shape hose couplings
typically relied on operators to unlock the dust cap for the correct are feasible and modify unloading equipment accordingly.

51 Through mechanical functionality testing of the as-found sodium hypochlorite dust 52 CCPS. Inherently Safer Chemical Processes-- A Life Cycle Approach: 4.5.10 Limitation
cap and single split ring, the CSB determined there was no other way to lock the dust of Available Energy 2nd ed.; [Online], Center for Chemical Process Safety/AIChE New
cap on the fill line using only the padlock and one split ring (e.g., by inserting the York, NY, 2009. http://app.knovel.com/hotlink/pdf/id:kt0068GQQ3/inherently-safer-
padlock through the lever that was missing the split ring). chemical/limitation-available (accessed September 12, 2017).
CSB MGPI Processing Case Study 15