Major Ducting Systems

Round Ducts

Typical Dimensions of Round Ducting

1. 10 to 1 design factor for pressure service and 5 to 1 design factor for vacuum service based on 3 m lengths between stiffener rings for vacuum service.
2. Theses ratings are suitable for use up to 80°C in pressure service and ambient atmospheric temperature on vacuum service. For ratings at higher temperature, consult the manufacturer.

FRP rectangular duct is fabricated to virtually any dimension specified by the customer. Rectangular duct is generally equivalent to the thickness of round duct with a comparable cross-section area. In most cases, splitters or stiffeners may be required to reinforce rectangular duct.

Elbows

FRP elbows in diameters up to 600 mm NB are moulded in one piece with a continuous radius. This size range has a 1½ diameter centreline radius. Standard elbows over this size are produced in a three-section metered construction with any desired centreline radius. Mitred elbows can be produced with a greater number of sections when specified by the customer. All FRP elbows are produced with a smooth interior to eliminate air turbulence and assure long service life.

Transitions

FRP transitions are designed and accurately fabricated to assure tight leak-proof joints in rectangular-to-round connections. These transitions are available in standard sizes or they can be custom fabricated to meet individual customer requirements.

Reducers

FRP reducers for use between different sizes of duct are furnished with a standard taper of 2.5 (D1 - D2) and are available in either concentric or eccentric profiles.

Duct Supports and Hangers

FRP duct is typically recommended to be supported on 120º (min) saddles or hangers to avoid localised stress concentrations and point loads.

Stacks

Corrosion proof and weather proof throughout, high strength FRP stacks require minimum support because of their light weight. These stacks have no longitudinal seams and are supplied in 6m and 12m sections. Fabricated with a bell-joint or flanged ends (optional), they can be factory assembled before shipment or erected in the field without special equipment.

Branch Connections

Standard FRP branch connections are available in the 45° and 90° configurations shown below as well as in 30° connections. The stub is normally cut and bonded to the manifold or main by factory personnel, unless otherwise specified. Branch connections can be assembled in the field by RPC installation crews or by customer personnel.

Weather Caps

Maintenance-free FRP weather caps are ideal for both corrosive fume ventilating systems and for industry-wide applications involving less severe industrial fumes. Offering proven resistance to the effects of weather, including, hail and windstorms, these caps feature a special rigid construction that eliminates the need for guy-wires and other external support.

Dampers

FRP dampers provide positive system control plus maximum resistance to severe corrosive attack. These units are standard adjustable dampers complete with quadrants and locking screws. Adjustment ranges from complete shut-off to full 90° opening.

Blast Gates

Furnished for both round and square duct systems, FRP blast gates are recommended for use where relatively few adjustments are required. The gate fits snugly into the slot moulded into the FRP section. A convenient hand grip is provided to facilitate removal. Dampers are recommended where the system requires frequent adjustment.

Joining Techniques

The three joining methods most commonly employed by RPC for duct installation are described below. First, all surfaces to be joined should be completely cleaned, preferably by grinding, prior to strapping. Strapping consists of the identical resin used in the duct, combined with glass mat reinforcement. Joints are usually strapped inside and outside. Where small duct diameters prevent inside strapping, the cut end is liberally coated with identical resin before joining.

BUTT AND STRAP joints are an economical joining method used in most FRP applications. This joint is especially recommended for joining all types of ventilating components, including risers and manifolds. Two or more layers of resin-saturated mat are normally used in building the strap.

BELL AND SPIGOT joints are recommended for use in installing large-diameter round duct where positioning one duct end in the bell of the other facilitates the assembling operation. This method is commonly used on stack installations where ease of positioning eliminates "jigging", assures perfect alignment and a positive seal.

FLANGE joints are specifically recommended for use in ventilating systems where occasional disassembly and reassembly are anticipated in certain areas. Areas requiring this type of joint include cleanout openings, fan connections and similar sections where inspection or maintenance are required.

Duct Flanges

Standard FRP Flanges are produced to suit most clients' requirements and are integrally attached to the duct in the factory. Heavy duty flanges are also produced to meet special customer requirements. The only differences between standard flanges and heavy-duty flanges are in the flange thickness and weight.

Design Data

Friction Loss. The interior of FRP duct is much smoother (0.002 mm) than average sheet metal. Use of 6.0m and 12.0m sections results in minimum joints in the system.

Dynamic Loss. The relationship of dynamic loss to friction loss in FRP systems can be considered to be in the same ratio as for standard sheet metal data.

Expansion. Normally, elbows and bends in the system will be adequate to absorb expansion. To assure absorption of expansion and to dissipate vibration, flexible couplings should be used (where required).

Duct Supports and Hangers. FRP duct requires supports in the horizontal run generally on 3.0m to 6.0m centers. Stacks should be supported to the building exterior, or guyed to "deadheads" if free-standing.

Note: Round duct is more economical to produce than rectangular duct. The design engineer should specify round duct where room permits.

Installations

Materials, equipment and experienced installation crews under the supervision of competent RPC project engineers are available under contract to assure the correct installation of complex or extensive ventilation systems. Under this one-contract plan, RPC guarantees job satisfaction, workmanship and materials. FRP systems are also commonly installed by customer personnel. FRP can be drilled with ordinary carbide-tipped drills; sawed with Kett saws or sabre saws; sanded or ground with abrasive wheels. RPC project engineers are available under contact to supervise customer personnel or local contractors.

Engineering

RPC places its staff of competent engineers at your service to assist company and consulting engineers in designing complete FRP ventilating systems or individual components to meet your special needs. Thoroughly qualified in all phases of FRP construction, RPC engineers are also prepared to modify your present system to permit gradual conversion to FRP. When inquiring about RPC complete ventilating engineering service, please include the following information:-

1. Drawing of site layout.
2. List of types of reagents used and concentration.
3. Temperature limits.
4. Operating pressure/vacuum

Important Notice

The technical data furnished herein is true and accurate to the best of our knowledge; however, no guarantee of accuracy is given or implied. RPC assumes no responsibility for any loss of damage resulting from the handling or use of the products by the buyer. Seller warrants only that the products to be delivered will conform to RPC's manufacturing standards. In no event shall RPC be responsible for consequential damages of any such breach of warranty including, but not limited to, the Buyer's loss of material or profits, increased expense of operation, down-time or reconstruction of the work, and in no event shall the RPC obligation under this warranty exceed the price of the defective material.

THIS WARRANTY IS IN LIEU OF ANY OTHER WARRANTY OR OBLIGATION, EXPRESSED OR IMPLIED, AND NO LIABILITY IS ASSUMED BY THE RPC COMPANY, EXCEPT AS IS EXPRESSED STATED ABOVE.