Pipe and Pipe fittings in HVAC

11. Pipe and Pipe fittings in HVAC

11.1   Refrigerant System Piping

Pipe material selection shall be as per Table IV.

Table IV – Pipe Material

11.2   Fittings Materials

11.2.1 Fittings materials shall be as per Table V based on application.

Table V – Fitting Materials

• • • Long radius elbows shall be used for refrigerant piping. Reducing fittings or reducing couplings shall be used for changes in pipe sizes. Fitting reducers shall not be used.

• • • Factory fabricated butt weld fittings shall be used for welded steel pipe. Elbows shall be long radius.

11.2.2  Unions (steel pipe)

1. 1. • Size 2 inch and under shall be Class 150 per ASME B16.39.
      • Size 2½” and over shall be Class 150 weld neck flanges per ASME B16.5 with 1/16 inch performed synthetic rubber bonded asbestos ring gaskets.
      • c. Where dissimilar piping materials are connected, threaded dielectric unions on shall be used on piping 2” and under. Dielectric flange kits on pipe shall be used on piping 2” and larger.

11.3   Quality Assurance

11.3.1  Welding procedures and personnel shall be qualified in accordance with the ASME BPVC, Section IX.

11.3.2  Hydronic materials, products and installation shall comply with ASME B31.9. Safety valves and pressure vessels shall bear the appropriate ASME label.

11.3.3  Refrigerant piping installation shall comply with ASHRAE 15.

11.3.4  Refrigerant piping shall comply with ASME B31.5.

11.3.5  Refrigerant products shall comply with UL 207 or UL 429.

11.4   Flushing Chilled Water Pipe

11.4.1  Pipe runs and joints shall be visually inspected for proper installation and continuity.

11.4.2  The following shall be blocked off, disconnected, or removed from the piping system to be cleaned:

1. 1. • Filters and screens
      • Exposed instruments, gauges, and cylinder
      • Orifice plates
      • Relief valves, control valves, and plug cocks
      • Expansion joints
      • Vessels and exchangers g.    Mechanical equipment
      • Items with restricted flow passages or inaccessible areas where sediment could collect shall be given special consideration in preparing the flushing procedure.

11.4.3  Where flushing water is re-circulated and not wasted to sewers, temporary strainers or baskets shall be installed at sumps, tanks, and other accessible areas where extraneous material flushed from the piping system can be collected and removed.

11.4.4  To prevent contamination of instruments, instrumentation lines shall be disconnected during the flushing operation. These lines shall be cleaned separately by blowing out with air or flushing with water. Instrumentation lines shall be reconnected after completion of the cleaning operation.

1. 1. • Fresh, clean water shall be used as the flushing and cleaning agent with the following criteria: Water containing less than 35 ppm chloride shall be used.

11.4.5  For each applicable line size, minimum acceptable flushing velocities shall be proposed for approval. Pipelines shall be flushed at velocities as close as possible to their design flow rates. Where possible, piping systems shall be sectionalized to help achieve this velocity.

1. 1. • Degree of Cleaning: Loose, non-adherent material that could break away during operation of the equipment shall be removed.
      • Inspection Procedure: Flushing operations shall continue until extraneous material is no longer observed.
      • c. Post-Cleaning Procedure: Upon completion of flushing, equipment and piping shall be returned to their pre-flush condition.

11.4.6  Connection

1. 1. 1. Refrigerant piping joints shall be brazed with 35% maximum silver solder. Tubing and fittings shall be cleaned before brazing. After brazing, joints shall be wiped clean. Certified brazers shall perform brazing.
      2. Welding thread-o-lets shall be used for pressure gage and flow switch tapping.
      3. c. Screwed joints shall be with made with full cut standard taper pipe threads with red lead and linseed oil or other approved non-toxic joint compound applied to male threads only.
      4. Connections to equipment shall be made using unions or flanges. Unions shall not be used on refrigerant piping.
      5. Equipment furnished with flat faced flanges shall have connection made with matching weld neck flat faced flange. Gasket shall be a full faced gasket. Reducing flanges shall not be used.
      6. f. Route and Grades:
      7. Piping shall be routed in an orderly manner and proper grades shall be maintained. Piping shall be installed to conserve headroom and minimize interference. Exposed piping shall be run parallel to walls. Piping shall be grouped whenever practical at common elevations. Concealed pipes shall be installed close to building structure to keep furring to a minimum.
      8. Water piping below the roof line shall be sloped 25 mm per 12 m towards low points to permit complete draining at low points and venting at high points.
      9. i. Low points shall be equipped with 3/4” drain valve and hose nipples. Collecting chambers and high capacity float operated automatic air vents shall be provided at high points.
      10. Reductions in horizontal water pipes shall be made with eccentric reducers installed to provide drainage and ventin Reductions in vertical water pipes shall be made using concentric reducers.
      11. Horizontal drainage piping shall be graded 6 mm per 0.305 m minimum.
      12. Piping shall be installed to allow for expansion and contraction without stressing pipe or equipment connection.
      13. Clearance shall be provided for installation of insulation and for access to valves, air vents, drains, and unions.