PENERIMAAN MAHASISWA BARU D1 AMC//CMA (P3TIK) UNTUK BEASISWA ANGKATAN KE-15 (2012/2013)

Materi Safety  : HOT WORK PERMIT


KATA KUNCI
• Flammable gas monitoring
• Tank Isolation
• Hot work permits, procedures, and sign-offs

Contoh kasus kecelakaan kerja :

Flammable Vapor Explosion
Welding on Tank Containing Vinyl Fluoride (1 Killed, 1 injured)
November 9, 2010
Di Perusahaan DuPont de Nemours & Co Inc., Buffalo, New York

RINGKASAN  KRONOLOGIS KECELAKAAN

This case study examines a November 9, 2010,
explosion at an E.I. duPont de Nemours and Co.
Inc., Yerkes chemical plant in Buffalo, New York
when a contract welder and foreman were repairing
the agitator support atop an atmospheric storage
tank containing flammable vinyl fluoride. The
welder died instantly from blunt force trauma,
and the foreman received first-degree burns and
minor injuries. The explosion blew most of the
top off the tank. The top and agitator assembly
hung over the side of the tank supported only
by a 2-foot section of the top (cover photo). The
explosion caused minor overpressure damage in
the tank farm area and the adjacent production
building.
The U.S. Chemical Safety Board (CSB) determined
that flammable vinyl fluoride (VF) vapor
from interconnected, in-service process tanks flowed undetected into the tank and ignited
when the welder was repairing the agitator support assembly. In February 2010, the CSB
issued a “Hot Work Safety Bulletin” that summarized 11 similar fatal incidents. Like the
incidents described in the bulletin, this was another example of improperly monitored hot
work activities involving flammable conditions inside a container.

KEY FINDINGS
1. DuPont PHAs made the incorrect assumption that VF in the Tedlar process could not
reach flammable levels in the slurry tanks.
2. DuPont restarted the unit after incorrectly concluding that the defective seal loop did
not increase the risk of VF vapor transfer into tank 2. Flammable VF vapor flowed
directly from the flash tank into tank 2.
3. DuPont did not properly isolate and lockout tank 1 from in-service tanks 2 and 3 prior
to authorizing hot work on tank 1. Consequently, flammable VF vapor passed directly
from tank 2 into tank 1 through the overflow line and accumulated to a concentration
above the lower explosive limit.
4. The DuPont hot work permit procedure did not require testing the atmosphere inside
tank 1 for flammable vapor even though the work required welding directly to the tank
top.
5. The individuals who signed off on the hot work permit were not knowledgeable in the
operations and hazards of the Tedlar process.
6. The repair work created multiple ignition sources. Welding directly to the tank top
increased the metal temperature inside the tank significantly above the VF vapor autoignition
temperature. Welding and grinding generated hot sparks, which likely ignited the
flammable vapor.
7. OSHA’s hot work standard does not specifically require gas monitoring inside containers
intended for hot work even though it is recommended by industry safe practice
guidelines.

LESSONS LEARNED
1. Welding to the outside surface of a tank or container generates heat and sparks near the
weld area. The extreme temperatures and sparks will likely ignite flammable materials
present inside the equipment.
2. Before starting hot work activities, all process connections on tanks and similar containers
should be completely isolated by closing valves, installing blanks, and disconnecting
pipes to ensure that all possible and known sources of flammable materials
cannot enter the container at any time.
3. The atmosphere inside any container previously containing flammables, regardless of
size, should be tested before authorizing any hot work involving grinding, cutting, or
welding on the outside surface and the atmosphere must be continuously monitored
during the work.

Laporan lengkapnya dapat dilihat pada link berikut ini :
Chemical Safety Board Site