boiler operating switch shall have a dust-tight sealed snap-action type.
The precision switches shall have cadmium, silver, or platinum contacts,
wiping action type, rated at 10 amperes. Electrically or pneumatically
test controls and equipment to simulate complete operational sequence.
2.8
BREECHING
Connect breeching to [the] [each] boiler and to intermediate heat recovery
equipment as required. Structural materials shall comply with the
applicable sections of the AISC 335, "Structural Steel Buildings Allowable
Stress Design and Plastic Design." Shop connections shall be welded
gas-tight. Field connections may be welded or bolted as required for
joining breeching to equipment. Hot dipped galvanized bolts and lock
washers shall be supplied for all bolted connections, shall not be less than
10 mm 3/8 inch diameter and spaced not more than 76 mm 3 inches apart.
Furnish bolted joints with 3.20 mm 1/8 inchthick non-asbestos gaskets.
Breeching plate shall be not less than 10 gage (3.40 mm) (0.1345 inch) in
thickness. Welding shall conform to AWS Z49.1 and AWS D1.1/D1.1M.
Breeching system shall provide for maximum expansion and contraction.
Expansion joints shall be of the guided, flexible-crease type with flexible
element of not less than 16 gage (1.50 mm) (0.0598 inch) thick stainless
steel. Provide access doors constructed of cast iron or reinforced steel
plate with gaskets and positive closing latches of sufficient number to
ensure a gas-tight seal. Clean breeching of rust and scale after
fabrication. Insulation and covering for breeching shall be as specified
in [Section 15080 THERMAL INSULATION FOR MECHANICAL SYSTEMS].
2.8.1
Round Breeching
Construct round breeching 305 mm 12 inches in diameter and smaller of not
less than No. 10 gage (3.40 mm) (0.1345 inch) steel with longitudinal
groove type seam. Joints between lengths of breeching shall be of the tight
slip fit type with not less than 100 mm 4 inchengagement. Construct round
breeching over 305 mm 12 inches in diameter of not less than No. 10 gage
(3.40 mm) (0.1345 inch) steel with welded seams and joints. Construct
round breeching over 457 mm 18 inches in diameter of not less than No. 10
gage (3.40 mm) (0.1345 inch) tank steel with seams and joints welded.
2.8.2
Expansion Joints
2.8.2.1
Metallic Breeching Expansion Joints
Provide factory fabricated metallic breeching expansion joints [where
indicated]. Expansion joints shall be guided metal bellows type capable of
a minimum of [_____] mm inches of axial travel. Form metal bellows from
not less than 1.60 mm 1/16 inch thick type 321 stainless steel plate.
Cover plates shall be not less than 3.20 mm 1/8 inch thick steel plate.
2.8.2.2
Non-Metallic Expansion Joints
Provide factory fabricated non-metallic breeching expansion joints 3.20 mm
1/8 inch minimum thickness [where indicated]. Expansion joints shall be
constructed of a fluoroelastomer vulcanized to two plies of knitted wire
mesh capable of a minimum of [_____] mm inches of axial compression, [_____]
mm inches of axial extension and [_____] mm inches of lateral offset
[unless indicated otherwise]. Joints shall have a continuous operating
temperature rating of 204 degrees C 400 degrees F, with excursion design
standards up to 400 degrees C 750 degrees F. Operating pressure range
shall be minus 34 kPa (gage) 5 psig to plus 34 kPa (gage) 5 psig.
SECTION 15517N
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