entire joint surface is bright and clean. Brazing flux shall not be used.
Surplus brazing material shall be removed at all joints. Steel tubing
joints shall be made in accordance with the manufacturer's recommendations.
Joints in steel tubing shall be painted with the same material as the
baked-on coating within 8 hours after joints are made. Tubing shall be
protected against oxidation during brazing by continuous purging of the
inside of the piping using nitrogen. Piping shall be supported prior to
brazing and not be sprung or forced.
3.1.3.3
Welded Connections
Welded joints in steel refrigerant piping shall be fusion-welded. Branch
connections shall be made with welding tees or forged welding branch
outlets. Pipe shall be thoroughly cleaned of all scale and foreign matter
before the piping is assembled. During welding the pipe and fittings shall
be filled with an inert gas, such as nitrogen, to prevent the formation of
scale. Beveling, alignment, heat treatment, and inspection of weld shall
conform to ASME B31.1. Weld defects shall be removed and rewelded at no
additional cost to the Government. Electrodes shall be stored and dried in
accordance with AWS D1.1/D1.1M or as recommended by the manufacturer.
Electrodes that have been wetted or that have lost any of their coating
shall not be used.
3.1.3.4
Flared Connections
When flared connections are used, a suitable lubricant shall be used
between the back of the flare and the nut in order to avoid tearing the
flare while tightening the nut.
3.1.3.5
Flanged Connections
When steel refrigerant piping is used, union or flange joints shall be
provided in each line immediately preceding the connection to each piece of
equipment requiring maintenance, such as compressors, coils, chillers,
control valves, and other similar items. Flanged joints shall be assembled
square end tight with matched flanges, gaskets, and bolts. Gaskets shall
be suitable for use with the refrigerants to be handled.
3.1.4
Valves
3.1.4.1
General
Refrigerant stop valves shall be installed on each side of each piece of
equipment such as compressors condensers, evaporators, receivers, and other
similar items in multiple-unit installation, to provide partial system
isolation as required for maintenance or repair. Stop valves shall be
installed with stems horizontal unless otherwise indicated. Ball valves
shall be installed with stems positioned to facilitate operation and
maintenance. Isolating valves for pressure gauges and switches shall be
external to thermal insulation. Safety switches shall not be fitted with
isolation valves. Filter dryers having access ports may be considered a
point of isolation. Purge valves shall be provided at all points of
systems where accumulated noncondensible gases would prevent proper system
operation. Valves shall be furnished to match line size, unless otherwise
indicated or approved.
3.1.4.2
Expansion Valves
Expansion valves shall be installed with the thermostatic expansion valve
SECTION 15182
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