General Specifications for NRG COMPANY, INCORPORATED Helical Skimmers Part 1 - General 1.1 Scope of Work   Under this item, the Contractor shall furnish and install complete the helical scum collector equipment as manufactured by NRG Company, Incorporated or approved equal for use in ___ tank(s) measuring ________ wide. The installation shall be as shown on the drawings and in substantial compliance with these specifications. 1.2 Design Criteria   SSystem design shall be based on dry tank conditions and the following:     1. Bearing Friction - 0.05 per set of bearings. 2. Dry friction, AGMA SERVICE FACTOR- 1.5 3. Shaft Deflection - less than 0.250" inches per SHAFT LENGTH. 4. Conveyor Speed - 5 rpm (average)       _______ Mechanisms _____L x _______W x ______ SWD     6. Design flow: _____ AVE ______ Peak Part 2 - Products 2.1 Helical Skum Skimmer   The helical scum skimmer shall consist of a 18" diameter stainless steel skimmer blade welded and supported to an extra heavy stainless steel pipe of sufficient diameter to permit not more than 1/4" deflection due to bending. The helical skimmer blade shall be a minimum of 1/4" thick and shall be equipped with adjustable neoprene wipers, bolted to the skimmer with stainless steel hardware. Blades to be supported by welded rod spokes where necessary to maintain deflection. 2.2 Bearings   All bearings shall be split, peak cap, babbitted, alignable, and water lubricated. Bearing housing material shall be cast iron and shall be split for ease of assembly and disassembly. Bearings shall attach to the wall on non-drive side with two one inch diameter anchor bolts. Drive side bearings shall be supported by 1" diameter studs welded to an adjustable, 3/8" thick steel bearing plate. The bearing plate shall be fixed to the wall with four 3/4" diameter anchor bolts. All bearings shall be equipped with grease fittings for lubrication when the tanks are dewatered. 2.3 Drive Unit A. Drive unit shall consist of an electric motor and speed reducer mounted on a common baseplate. Drives shall be configured as is shown on the plans and indicated herein. Drive units shall be sized for continuous 24 hour operation, AGMA rated, with a service factor of 1.5. The Reducer shall be sized for the required service and shall be of the helical, or worm gear type. Reducer shall be totally enclosed, running in oil, with anti-friction bearings throughout. B. The Motor shall be totally enclosed, fan cooled, three phase, 60 Hz., 208-230/460 volt, 1.15 service factor chemical duty style motors. The motor shall be connected to the reducer by means of a flexible coupling and shall be sized to transmit the torque required. The motor shall be an inverter type motor to allow for variable speed operation. C. The Drive Shaft shall contain key ways with fitted keys which are properly sized. The Drive Sprocket shall consist of a UHMW or Nylon sprocket tooth section bolted to a oil filled nylon shear pin hub fitted with steel shear pins sized to protect against overload. D. The Driven Sprocket shall consist of an all UHMW or Nylon sprocket tooth section mounted on a cast iron or nylon hub. The Driven Sprocket shall have 30 teeth with a minimum pitch diameter of 24.96". The sprocket shall be of the split hub design and shall be offset to allow for full tank width skimming. E. The chain tightener shall consist of an Oil Filled Nylon slotted bracket with 8" adjustment and non-metallic shaft with a H78 UHMW 8T idler sprocket. The sprocket shall be secured by means of a non-metallic set collar. Bracket shall mount on an adjustable mounting angle. 2.4 Drive Chain   Drive Chain shall be non-metallic NH78, 2.609" pitch, glass-reinforced nylon as supplied by NRG Company, Inc. The chain shall have a rated working load of at least 1750 #. The connecting pin shall be 7/16" diameter stainless steel with 1/8" diameter cross pin of stainless steel.