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4.2.18

4.2.18. Installing Corrugated Stainless Steel Tubing .

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4.2.18

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  1. 4.2.18 Installing Corrugated Stainless Steel Tubing Corrugated stainless steel tubing (CSST) offers a flexible method for vapor distribution system line installation using minimum connections in the system. CSST may be used in 2-pound or half-pound distribution systems in a variety of distribution line layouts. Installation of CSST is made easier during the “framing” stage of new construction. Proper CSST installation requires knowledge of manufacturer installation instructions and strict compliance with recommended connection and protection methods. • In this module you will learn to identify: • Code requirements for CSST installations • Distribution line layouts commonly used with CSST • Procedures for installing CSST

  2. NFPA 54 2002 Code Requirements for CSST Installations 5.6.3.4 Corrugated Stainless Steel. Corrugated stainless steel tubing shall be tested and listed in compliance with the construction, installation, and performance requirements of ANSI LC 1/CSA 6.26, Fuel Gas Piping Systems Using Corrugated Stainless Steel Tubing. 5.6.5 Workmanship and Defects. Gas pipe, tubing, and fittings shall be clear and free from cutting burrs and defects in structure or threading and shall be thoroughly brushed, and chip and scale blown. Defects in pipe, tubing, and fittings shall not be repaired. Defective pipe, tubing, and fittings shall be replaced. 7.1.1.1 Prior to acceptance and initial operation, all piping installations shall be inspected and pressure tested to determine that the materials, design, fabrication, and installation practices comply with the requirements of this code. 7.1.1.3 Where repairs or additions are made following the pressure test, the affected piping shall be tested. Minor repairs and additions are not required to be pressure tested provided that the work is inspected and connections are tested with a non-corrosive leak-detecting fluid or other leak-detecting methods approved by the authority having jurisdiction.

  3. Code Requirements for CSST Installations 7.1.1.4 Where new branches are installed from the point of delivery to new appliance(s), only the newly installed branch(es) shall be required to be pressure tested. Connections between the new piping and the existing piping shall be tested with a non-corrosive leak-detecting fluid or approved leak-detecting methods. 8.5.7 Sediment Trap. Where a sediment trap is not incorporated as a part of the gas utilization equipment, a sediment trap shall be installed as close to the inlet of the equipment as practicable at the time of equipment installation. The sediment trap shall be either a tee fitting with a capped nipple in the bottom outlet or other device recognized as an effective sediment trap. Figure 1. Sediment Trap (as shown in Figure 8.5.7 in NFPA 54, 2002 edition)

  4. Line Layouts Commonly Used with CSST Corrugated stainless steel tubing can be used in 2-psi and ½-psi systems supplying 10 to 14 inches water column inlet pressure to gas appliances as specified by the appliance manufacturer. A wide variety of distribution line layouts are used, depending on the minimum gas input pressures and volumes (Btuh) specified by the gas appliance manufacturer, and the building design requirements. Installation of CSST must be as shown in construction drawings and must be coordinated with the customer’s building contractors and other trades involved in new construction or remodeling projects. This requires careful planning, communication with the builder, and timely conformance to an established construction schedule, making adjustments as required. Examples of commonly used CSST layouts are illustrated in Figure 2.

  5. Line Layouts Commonly Used with CSST Figure 2. Common Distribution System Designs Using CSST

  6. Line Layouts Commonly Used with CSST Figure 2. Common Distribution System Designs Using CSST

  7. Line Layouts Commonly Used with CSST Figure 2. Common Distribution System Designs Using CSST

  8. Line Layouts Commonly Used with CSST Figure 2. Common Distribution System Designs Using CSST

  9. Line Layouts Commonly Used with CSST Where construction plans call for installation of CSST in a plastic pipe chase in the building slab, connected partitions, or to outside appliances, the chases must be properly placed and anchored during the framing of foundation forms, and inspected immediately before concrete is poured. CSST used in new construction must be installed during the framing of the building, preferable before insulation is installed. In all cases the CSST and its appliance fitting must be installed before partition drywall or plaster lathing is installed. Each run of CSST must be of the correct size as set out in the project drawings and specifications to ensure that gas appliances are supplied sufficient gas volumes and input pressures as specified on gas appliance input ratings plates. NFPA 54 requires that the allowable pressure drop for the distribution system when all appliances are operating at full capacity must not result in insufficient gas pressure and volume input for any gas appliance in the system as specified by its manufacturer. This code requirement means that the installer must be sure that CSST and any connected piping is properly sized for the length of run to the appliance(s) it serves.

  10. Installing CSST and Line Regulators Listed below are some factors to keep in mind when using the installation procedures described in this training module. • Precautions must be taken to ensure any exposed CSST is not damaged or abused during construction. • All tubing, fittings and hardware should be stored in a clean, dry location prior to installation. • Open ends of the tubing must be temporarily plugged (plastic capped) or taped closed prior to installation to prevent entrance of dust, dirt, or other foreign material. • The protective plastic jacketing should be kept in place as much as possible to protect the tubing from corrosive threats. Contact with chemicals containing chlorides, fluxes used to solder copper water tubing, and acid-based masonry washes, and some leak detector solutions must be followed by thoroughly rinsing the plastic covering, as prescribed by the CSST manufacturer.

  11. Installing CSST and Line Regulators Listed below are some factors to keep in mind when using the installation procedures described in this training module. • Protect tubing from contact with sharp objects. • Avoid stressing the tubing or fittings with tight bends, kinks, twists, or excessive stretching. • Tubing must be properly supported following manufacturer recommendations, with pipe straps, bands, or hangers suitable for the size and weight of the tubing. • Use of components from flexible gas piping systems, other than those specified as part of the CSST manufacturer’s system, may be prohibited and may result in poor system performance and serious bodily injury or property damage. • Two wrenches properly sized for the CSST nut and terminating fitting flats must be used when making connections to assure gas-tight seals, protect the tubing from twisting, and to avoid rounding off fitting wrench flats. • Install strike protection as recommended by the CSST manufacturer.

  12. Installing CSST and Line Regulators Always read and follow manufacturer installation instructions. If the manufacturer specifies special tools or procedures, use them as instructed. The following installation procedures are based on one CSST manufacturer’s installation recommendations.

  13. Figure 3. “Pulling” CSST From Coil Spools Installing CSST and Line Regulators Pulling and Attaching CSST Runs.Corrugated Stainless Steel Tubing is pulled through the structure similar in fashion to electrical conduit and therefore requires different handling and installation techniques than rigid pipe. CSST is typically shipped and handled in 150 and 250-foot coils, depending on the tubing diameter. CSST runs are typically located along the bottom of roof rafters or along the tops of joists in attic locations, or under or through floor joists in basement or crawl space locations. Often runs are located along the sides of the vertical members of “box” trusses, attached with pipe hangers. (Figure 4)

  14. Installing CSST and Line Regulators Figure 4a. CSST Attached to Vertical Stringers of Box Trusses

  15. Figure 4c. CSST Routed Through Drilled Holes in Floor Beam Joists Installing CSST and Line Regulators Figure 4b. CSST Routed Over Ceiling Joists

  16. Installing CSST and Line Regulators Pulls/runs are usually started at the manifold, in manifold layout systems, or at the outlet of the second-stage or 2-psi service regulator and tees to branch runs in trunk line and branch system layouts. The termination of the run is made at the appliance service connection. (Figure 5) CSST pulls should result in continuous tubing runs with a minimum of connections. Figure 5. CSST Pulls in Trunk and Branch Line Systems

  17. Installing CSST and Line Regulators Figure 5. CSST Pulls in Manifold Systems

  18. Figure 6b. Bottom and Side Attachments in Box Trusses Figure 6a. Attaching CSST to Bottom of Floor Joints in Basement Installing CSST and Line Regulators For vertical runs of CSST, manufacturers generally recommend that support be provided at every floor not to exceed 10 feet between supports. Inside hollow wall cavities vertical runs are preferred over horizontal sections. Avoiding horizontal runs through the walls will minimize the need for strike protection. Where CSST is routed under rafters or joists it is attached with appropriately sized pipe hangers or pipe strapping (Figure 6).

  19. Installing CSST and Line Regulators Figure 7. Manufacturer Suggested USA Support Spacing

  20. Installing CSST and Line Regulators Clearance holes for routing CSST through floor joists and ceiling plates should be approximately ½ inch greater than the outside diameter of the CSST. Drilling of any structural member must be in conformance with the local building code and with the prior approval of the building contractor. Changes in the direction of CSST runs must avoid stressing, damaging, or reducing capacity of the tubing, and should comply with manufacturer recommendations. Figure 8. Manufacturer Suggested Minimum and Suggested Bend Radius for Various CSST Diameters

  21. Figure 9a. Bends in Truss Routing Figure 9b. Pulling CSST Through Ceiling Plate from Roof Rafter Location Installing CSST and Line Regulators Once the tubing has been pulled to its terminating location, typically at its connecting point to a gas appliance or a tee filling for connection of branch lines, and the tubing is secured by at required support points, the tubing should be cut for the length of its initial connection at a manifold or other starting point. The cut length should be an inch longer than its measured length, providing an allowance for a final fit-up cut.

  22. Installing CSST and Line Regulators Cutting Corrugated Stainless Steel Tubing To ensure a quality flare, all cuts should be made on a straight section of tubing. The cut should be centered between two corrugations (Figure 11). Use light roller pressure with extra rotations in one direction to leave tubing round and free of burrs. Figure 10. Cutting Straight Tubing Section Figure 11a. Figure 11b.

  23. Figure 12b. Removing Plastic Jacket Figure 12a. Cutting Plastic in Second Valley from End Installing CSST and Line Regulators

  24. Installing CSST and Line Regulators Making CSST Connections The most frequently used fitting is a male CSST to male national pipe thread (NPT) brass fitting (Figure 13). This fitting is used in manifold, single pipe coupling, and service outlet connections. Figure 13. CSST to NPT Brass Fitting

  25. Figure 14. Nut, Bushings & Brass Fitting (Brass fitting should already be installed in pipe fitting.) Installing CSST and Line Regulators This procedure is one example of how to make a CSST connection. Refer to specific manufacturer’s instructions. Manufacturers require training in the proper use of their products. Steps for making one type of CSST to brass fittings are:

  26. Figure 16a. Cut Tubing to Length Figure 16b. Remove & Slip Nut Over CSST Figure 15. Bushings Inserted— Ready for Hand-Tightening Installing CSST and Line Regulators These steps for installing the tubing and brass fitting in a manifold are illustrated in Figure 16.

  27. Figure 16c. Remove Bushings Figure 16d. Position Bushings, Locating Locking Ridge in 1st Valley Installing CSST and Line Regulators Figure 16e. Insert Bushing Into Brass Fitting and Hand-Tighten Nut Figure 16f. Using Two Wrenches, Tighten Nut Onto Brass Fitting

  28. Installing CSST and Line Regulators CSST Distribution and Appliance Connection Components Manifoldsare installed where multiple runs are made from a common location in a parallel arrangement.The installation of manifold assemblies using a pounds-to-inches regulator must be in accordance with all local codes, and the following guidelines: Figure 17. (Top) Welded Manifold (Bottom) Cast Manifold A manifold assembly utilizing a pounds-to-inches regulator shall be installed in an accessible, ventilated location so that the regulator can be inspected, maintained and serviced if repair or replacement is required. For manifold systems that use a pounds-to-inches regulator installed behind an access panel, all tubing penetrations in the cabinet should be sealed, caulked or grommet-sealed. The cabinet must be ventilated through the panel/door and not into a wall space. Open face cabinets, which communicate with the normal room environment, may be utilized without the need for ventilation or penetration sealing requirements.

  29. Installing CSST and Line Regulators Figure 18. Manifold and Regulator Installed in Garage Location

  30. Installing CSST and Line Regulators Floor flange fittingsare used to secure CSST to sub-flooring in protected gas appliance connection locations. Figure 19a. Attaching Brass Fitting To the Tubing Figure 19b. Threading the Flange onto the Brass CSST Fitting Figure 19c. Mounting Completed Floor Flange Assembly

  31. Figure 20a. Facing Plate Wall Bracket Mount Figure 20b. Spanning Wall Bracket Mount Installing CSST and Line Regulators Wall bracket mountingsprovide protected horizontal terminating gas appliance connecting points. The wall bracket mount shown in Figure 20a is secured on the face of a framing stud. Its steel plate provides strike protection. The spanning wall bracket shown in Figure 20b provides the same protective measures for one or more CSST connections.

  32. Installing CSST and Line Regulators Providing Strike Protection for Corrugated Stainless Steel Tubing Where CSST is located away from framing components and provided room to deflect away from puncture threats of short nails, wallboard screw fasteners, and similar strike hazards, no strike protection is required. However, strike protection is required where: • Tubing is concealed • Tubing is constrained (secured and prevented from moving away from potential puncture threats) • Tubing is routed within 3 inches of puncture threats

  33. Figure 21. Strike Plates (Top) Stud Spanner Plate (Middle Left) Stud, Base or Ceiling Plate (Middle Right) Header (Stringer) Plate (Bottom Right) Single Side Base or Ceiling Plate Figure 22. Corrugated Sheathing Installing CSST and Line Regulators • Strike protection is provided by two types of CSST shielding: • Carbon steel plates (Figure 21.) • Stainless steel corrugated sheathing (Figure 22.)

  34. Figure 23a. Ceiling Plate Figure 23b. Stringer Plate Installing CSST and Line Regulators Typical strike protection installations are shown in Figure 23.

  35. Installing CSST and Line Regulators Figure 23c. Ceiling Plate Figure 23d. Base Plate

  36. Figure 24a. Slipping Protective Sheathing Over CSST Figure 24b. Installed Sheathing Installing CSST and Line Regulators Protective sheathingis installed by slipping the required length of corrugated sheathing over the CSST before the sealing nut and bushing are installed. Sheathing is flexible and is used on CSST sections that are within 3 inches of potential puncture threats. (Figure 24b.) The sheathing is continued to the point at which the CSST is routed further than 3 inches away from the potential puncture site.

  37. Installing CSST and Line Regulators Note the CSST installation shown in Figure 24c in which steel piping connects the fireplace insert valve to the insert and burner assembly. CSST should not be routed into masonry fireplaces nor manufactured fireplace inserts, nor used to make direct connections to log lighters installation within a fireplace. Figure 24c. Sheathing Above Fireplace Valve (Pipe below the valve runs into fireplace.)

  38. Figure 25. In-Line CSST Coupling Methods Installing CSST and Line Regulators Repairing or Extending CSST Sections.If extending or repairing a section of CSST not located in a concealed space is necessary, manufacturer supplied brass couplings (Figure 25, left) may be used. Two CSST brass termination fittings and a pipe coupling may be used as well (Figure 25, right).

  39. Figure 26a. Pool Heater Installation Figure 26b. Buried Chase Installing CSST and Line Regulators Special Applications.CSST distribution lines are well suited for special applications such as in-slab installations and outdoor appliance connections. CSST shall not be buried in the ground without a chase nor directly embedded in concrete.

  40. Installing CSST and Line Regulators Figure 27a. In-Slab Installation to Supply and Island Appliance Location Figure 27b. Inserting Capped CSST into PVC Chase Sealing Cap

  41. Figure 28. Supported Meter Installation Installing CSST and Line Regulators The gas piping for a vapor meter "stub-out" is usually subject to local requirements such as size, location, and material type. Manufacturers recommend the use of 1/2" CSST or greater as the minimum trunk line size. Size 3/8" should not be used for trunk lines. Meters that depend on the service supply line and/or the house piping for support shall not be directly connected to the CSST. Meters that are independently supported with a bracket can be directly connected to the CSST.

  42. Installing CSST and Line Regulators Pressure Testing Newly Installed CSST Distribution LinesAfter CSST runs are routed, properly supported, connected to distribution manifold(s), and appliance connecting terminations, the outlets of each run should be capped or plugged as appropriate for pressure testing. This operation should be done after strike protection is installed but before line regulators, appliance shutoffs and appliance controls are connected to the CSST lines.

  43. NFPA 54 2002 Installing CSST and Line Regulators 7.1.4.1 Test pressure shall be measured with a manometer or with a pressure measuring device designed and calibrated to read, record, or indicate a pressure loss due to leakage during the pressure test period. The source of pressure shall be isolated before the pressure tests are made. Mechanical gauges used to measure test pressures shall have a range such that the highest end of the scale is not greater than 5 times the test pressure. 7.1.4.2 The test pressure to be used shall be no less than 1-½ times the proposed maximum working pressure, but not less than 3 psi, irrespective of design pressure. 7.1.4.3 Test duration shall be not less than ½ hour for each 500 cubic feet of pipe volume or fraction thereof. When testing a system having a volume less than 10 cubic feet or a system in a single-family dwelling, the test duration shall be a minimum of 10 minutes. The duration of the test shall not be required to exceed 24 hours.

  44. Figure 29. Line Regulator With Vent Limiter Installing CSST and Line Regulators Line Regulatorsare used in dual pressure (2-psi) distribution systems to reduce appliance inlet pressure to manifold CSST or individual appliances to approximately 11 inches water column pressure. They provide flow pressure metering and lock-up functions similar to two-stage and 2-PSI service regulators. The following guidelines for line regulator selection and installation apply: A CSST system utilizing gas pressures exceeding 1/2 PSI shall include a regulator to limit downstream appliance supply pressure to 1/2 PSI or less. The regulator shall have a lock-up feature that will limit the downstream pressure to ½ PSI.

  45. Installing CSST and Line Regulators Line Regulators To select the correct regulator for pressure regulation, the following information must be established: • Available inlet pressure range at the regulator inlet • Desired outlet pressure • Required maximum flow rate (total demand of connected appliance(s) Btuh input rating(s) • Desired inlet pressure at the gas appliance

  46. Installing CSST and Line Regulators Line Regulators The following guidelines for line regulator selection and installation apply: • The regulator shall be installed in an accessible location with an approved shut-off valve on the inlet side and a union on the outlet side so that it may be inspected, maintained and serviced if repair or replacement is required. • The regulator is suitable for multi-position mounting. When using a vent limiter however, the regulator must be mounted in a horizontal upright position. • The vent limiter is a fail-safe device that permits free air movement above the diaphragm during normal operation. In the unlikely event of a diaphragm rupture, the vent limiting orifice will limit gas escapement to 0.65 cubic feet per hour of propane vapor at 2 psi—a value below the ANSI standard of 2.5 CFH. Note: The vent limiter does not allow gas to escape to the environment during operation. • Do not leak test the vent orifice with liquid leak test solution. This action will contaminate the internal ball check mechanism or plug the breathing hole resulting in erratic regulator performance.

  47. Installing CSST and Line Regulators Line Regulators The following guidelines for line regulator selection and installation apply: • When using a vent limiter, the maximum inlet pressure is 2 psi. • When using a vent line, the line must be at least the same size as the regulator vent connection, and cannot exceed a length of 30 feet. The vent shall be designed to prevent entry of water, insects or other foreign materials that could cause blockage of the line. No vent line is required when using a regulator incorporating a vent limiter. Do not vent to appliance flue, pilot light or building exhaust system. Comply with any company-specific procedures for installing line regulators in outdoor locations and venting regulators to outdoor locations. Outdoor regulator installations and vent terminations require protective measures to prevent blockage or contamination.

  48. Figure 30. CSST Connection to Water Heater Shutoff and Sediment Trap Installing CSST and Line Regulators Making Appliance Connections.CSST may be connected directly to non-moveable appliances such as water heaters, furnaces, boilers and island cook-tops without the installation of a termination outlet or flexible appliance connector. Code requirements for sediment traps and appliance shutoff valves must be observed.

  49. NFPA 54 2002 Installing CSST and Line Regulators Electrical Bonding/Grounding. Never use CSST or system components as a grounding electrode or as the grounding path for appliances or electrical systems. 6.13.1 Each aboveground portion of a gas piping system that is likely to become energized shall be electrically continuous and bonded to an effective ground-fault current path. Gas piping shall be considered to be bonded when it is connected to gas utilization equipment that is connected to the equipment grounding conductor of the circuit supplying that equipment. 6.13.2 Gas piping shall not be used as a grounding conductor or electrode. 6.14 Electrical Circuits. Electrical circuits shall not utilize gas piping or components as conductors. 6.15.1 All electrical connections between wiring and electrically operated control devices in a piping system shall conform to the requirements of NFPA 70, National Electrical Code.

  50. Installing CSST and Line Regulators Leak Checking the Distribution System and Placing Appliances Into Service Before gas appliances are placed into operation, two requirements must be met: • A leak check of the complete vapor distribution system, including regulators and appliance control valves must be completed and documented. Leak checking procedures can be found in NFPA 54 or company-specific standard operating procedures. • Distribution lines and gas appliances must be properly purged of air as required by Chapter 7 of NFPA 54, 2002 edition, and the appliances placed into operation according to their manufacturer’s operating instructions.

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