9 CFR § 590.540 - Spray process drying facilities.
(a) Driers shall be of a continuous discharge type and so constructed and equipped to prevent an excess accumulation of powder in the drier, bags, and powder conveyors.
(b) Driers shall be of approved construction and materials, with welded seams, and the surfaces shall be smooth to allow for thorough cleaning.
(c) Driers shall be equipped with approved air intake filters.
(d) Air shall be drawn into the drier from sources free from foul odors, dust, and dirt.
(e) Indirect heat or the use of an approved premixing device or other approved devices for securing complete combustion in direct-fired units is required. A premix-type burner, if used, shall be equipped with approved air filters at blower intake.
(f) High-pressure pump heads and lines shall be of stainless steel construction or equivalent which will allow for thorough cleaning.
(g) Preheating units, if used, shall be of stainless steel construction, or equivalent which will allow thorough cleaning.
(h) Powder conveying equipment shall be so constructed as will facilitate thorough cleaning.
(i) Sifters shall be constructed of an approved metal or metal lined interior. The sifting screens and frames shall be of an approved metal construction. Sifters shall be so constructed that accumulations of large particles or lumps of dried eggs can be removed continuously while the sifters are in operation.