Entrainment stacks need to work in the outdoor environment in which they are installed. As crosswinds accelerate, it is important for public safety that stacks maintain designed dilution ratios. Plasticair has now fully addressed dilution and crosswinds.
Our originally designed uni-passage SKYPLUME G1 has wind deflection characteristics inherent to the design on two sides. Our further developed SKYPLUME G2, has greatly enhanced this design feature by adding wind deflection panels. This is very important and ensures that dilution ratios are constant up to 41 MPH with a nozzle velocity of two times crosswind speed.



• Our nozzle is a constant velocity nozzle, meaning that the area is constant from inlet to outlet which translates to virtually no pressure loss. Although this is not a factor dealing with entrainment, it is very beneficial to the whole system as it will result in lower electrical horse power requirements and lower sound output, all this while maintaining a minimum 205% dilution ratio up to 27-34 MPH and resisting downwash within the windband.

• The SKYPLUME G2 is constructed of solid UV stabilized FRP and can structurally withstand winds up to 125 MPH.

• SKYPLUME G2-MFS High Plume Dilution Systems


• General

Fans and stacks shall be designed for maximum efficiency. Fans shall have a sharply rising pressure characteristic extending through the operating range and continuing to rise well beyond the efficiency peak to assure quiet and stable operation under all conditions. Horsepower characteristics shall be truly self-limiting and shall reach a peak in the normal selection area.

Acceptable Manufacturers: Plasticair Inc.

• Air Performance — Performance ratings shall conform to AMCA Standard 205 (fan efficiency grade), 211 (air performance) and 311 (sound performance). Fans shall be tested in accordance with ANSI/AMCA Standard 210 (air performance) and 300 (sound performance) in an AMCA accredited laboratory. Fans shall be licensed to bear the AMCA certified ratings seal for both sound and air, and fan efficiency grade (FEG). Sound certification shall apply to both inlet and outlet sound power levels.

• Fan Outlet Nozzle and Windband
Material of construction will be UV stabilized solid FRP and the manufacturer will provide a 20 year warranty against equipment failure due to rust. The nozzle windband assembly will be structurally designed to withstand 150 MPH winds. Design calculations will be presented to the specifying Engineer for review and approval. FRP construction will be Derakane 510-C and will have a 0-25 flame spread. The Stack assembly will comply with the requirements of ANSI Z9.5.
The nozzle assembly will be designed to induce outside air by a venturi effect and also entrain air to provide dilution ratios that are not less than 192% and average 205% throughout crosswind speeds up to 41 MPH. For safety reasons, the stack will also be designed and thoroughly tested to resist downwash within the wind band caused by crosswind pressure/vortices up to 41 MPH as a design standard. Stack design shall be stable enough to accommodate internal downwash protection against any wind speed using a nozzle velocity that is two times cross wind speed. Stack scaled design must undergo physical wind tunnel testing to the following criteria:
1) Testing to confirm dilution results from crosswind effect from any position 360 degrees around the stack and three speeds up to 20 MPH.
2) Chemical concentration testing with a minimum of 65 pitot tube sampling points evenly distributed in a radial direction located level with the stacks physical highest point. Parts per million input vs. parts per million output will be used to determine dilution ratio. For large sizes, a minimum of 79 pitot tube sampling points per square foot are required.
3) Tested with at least 2 pitot tube sampling points located at base of windband for monitoring down wash against crosswinds up to 20 MPH. At least one pitot tube will be placed down stream of the crosswind.
4) Corresponding velocity testing with a minimum of 65 pitot tube sampling points

5) All wind tunnel testing completed as listed above, stamped by a reputable third party Fluid Dynamics Consulting Engineering Firm.

• Housing —

Housings shall be cylindrical and welded steel throughout. Inlets shall be fully streamlined. Housings shall be suitably braced to prevent vibration or pulsation. Totally enclosed belt guard shall enclose motor sheave and V-belt drives. Punched inlet and outlet flanges shall be equipped for duct mounting. Extended lube lines shall be provided for ease of lubrication. Model QSL shall include bolted access door for inspection and maintenance of wheel.


Fan wheels shall have die-formed hollow airfoil blades designed for maximum efficiency, and quiet and stable operation. Blades shall be continuously welded to the back plate and wheel cone. Wheels shall be statically and dynamically balanced and the complete fan assembly including motor and drive shall be test balanced at or near the operating speed at the factory prior to shipment.

• Shaft —

Shafts shall be AISI 1040 or 1045 hot rolled steel, accurately turned, ground, polished, and ring gauged for accuracy. Shafts shall be sized for the first critical speed of at least 1.43 times the maximum speed.

• Bearings —

Bearings shall be heavy duty, grease lubricated, anti-friction ball or roller, self-aligning, pillow block type and selected for a minimum L-10 life of 40,000 hours at the maximum fan RPM. Bearings shall be equipped with extended lubrication lines with grease fittings outside of the fan housing.

• Drive —

Motor sheaves shall be cast iron, variable pitch on applications 10 HP and smaller, and fixed pitch on 15 HP and larger.

• Inlet Vanes —

Inlet vanes, where specified, shall be of the nested design. Inlet vanes shall be designed for economical, stable, and efficient air volume control at partial load conditions.

• Finish and Coating —

The entire fan assembly, excluding the shaft, shall be thoroughly degreased and deburred before application of a rust-preventative primer. After the fan is completely assembled, a finish coat of paint shall be applied to the entire assembly. The fan shaft shall be coated with a petroleum-based rust protectant. Aluminum components shall be unpainted.

• Factory Run Test —

All fans with motors and drives mounted by Twin City Fan & Blower shall be completely assembled and test run as a unit at the specified operating speed prior to shipment. Each wheel shall be statically and dynamically balanced in accordance with ANSI/AMCA 204-96 “Balance Quality and Vibration Levels for Fans” to Fan Application Category BV-3, Balance Quality Grade G6.3. Balance readings shall be taken by electronic type equipment in the axial, vertical, and horizontal directions on each of the bearings. Records shall be maintained and a written copy shall be available upon request.

• Plenum

The materials of construction will be as per the attached schedule. Dampers, controls and other options will be as detailed in the schedule.

• Warranty

The supplier shall warrant that all system components shall be free from defects in materials and workmanship for a period of 15 months from date shipped or 12 months from equipment start up, whichever occurs first. Extended warranty on induction stack shall be honored to 25 years from date of purchase.