I have written about this hazard numerous times as it is the leading cause of flash fires within process vessels, but during a recent Combustible Dust project, I noticed that the 2017 edition of NFPA 654 has some new and specific requirements for this activity. I had always used NFPA 77 as my RAGAGEP for this activity, but now NFPA – 654 Standard for the Prevention of Fire and Dust Explosions from the Manufacturing, Processing, and Handling of Combustible Particulate Solids is a bit more specific in that it mentions the worker doing the addition(s) be donned in Flame Retardant Clothing meeting NFPA 2113…
9.3.7* Manual additions of solids through an open port or a manway into a vessel containing ammable atmospheres shall be permitted to be done in 50 lb (25 kg) batches or smaller, provided the requirements of 9.3.7.1 through 9.3.7.7 are satisfied:
(emphasis by me)
9.3.7.1* Conductive or static-dissipative components of the container shall be grounded.
9.3.7.2 Direct emptying of powders from nonconductive plastic bags into a vessel that contains a flammable atmosphere shall be strictly prohibited.
9.3.7.3 The use of nonconductive liners in grounded conductive or static-dissipative outer packaging shall be permitted, provided that the liner thickness is less than 0.08 in. (2 mm) and the liner cannot become detached during emptying.
9.3.7.4* Loading chutes, receiving vessels, and auxiliary devices used for addition of bulk material shall be conductive and grounded.
9.3.7.5* Personnel in the vicinity of openings of vessels that contain ammable atmospheres shall be grounded.
9.3.7.6 Operators shall wear flame-resistant garments as specied in NFPA 2113 and any other personal protective equipment (PPE) required for protection against flash fire hazards during charging operations.
9.3.7.7* A documented risk assessment acceptable to the AHJ shall be conducted to determine additional engineering and administrative controls necessary to protect against ignition of the ammable atmosphere.