Installation Guidelines

Transcription

1 Issued: 10/02 Supersedes: 7/02 Installation Guidelines Flygt PP-4600 series propeller pumps are designed for easy removal and reinstallation on a dual guide rail system. The pump is horizontally mounted to reduce hydraulic losses when pumping at very low heads through a wall or pipe run. from the free surface can become strong enough to draw air and floating debris into the pump. Vortices originating at solid surfaces can cavitate and release dissolved air into the pump. Entrained air can reduce the flow and efficiency, and it can cause vibration and noise. Flow conditions at the pump inlet are initiated in the approach-flow region. The following guidelines, which will provide good inlet conditions, are based on the assumption that the approaching flow is steady and that the velocities in the approach are less than 4.3 ft./sec. No large velocity-gradients, separated boundary-layers or obstacles that may produce rotational wakes should exist, and entrainment of air should be avoided to the extent possible. If bottom aeration devices are located near the pump, they must be located so that no air will enter the pump. This is achieved if the device is placed at a horizontal distance L (in feet), from the pump inlet: The pump lifting system requires an adequately load rated davit that can be permanently attached in a wastewater environment or can have an optional lifting bail for lifting with a grappling hook in a clear water environment. Care should be taken to make sure that the pump inlet does not sit above or near air diffusers when operating in the oxic zone of a biological treatment process. The electrical cable should be fastened to the lifting wire or a safety line to prevent entanglement of the electrical cable with the pump propeller. Ideally, the flow at the pump inlet should be uniform and steady, and it should be without swirl, vortices and entrained air: Nonuniform flow at the pump intake can reduce efficiency, cause pulsating loads on the propeller blades, and produce both noise and vibration as well. Unsteady flow can also cause fluctuating loads, noise and vibration. Swirl at the intake can change the head, flow, efficiency and power in undesirable ways. It can also augment vortices. Vortices with a coherent core can lead to noise, vibration and local cavitation. Vortices emanating L= D + (B+D) * v where D is the inlet cone diameter (in feet), B is the bottom clearance (in feet) and v is the velocity of the approaching flow (in ft/sec). The dimensions provided in this catalog are given as minimum allowable values and should not be greatly exceeded. The closeness to a wall may aid in preventing swirl. The distance to the floor is particularly important in preventing swirl. If this distance is greater than the recommended distance, the submergence should also be greater. In tanks that are shallow or have poor flow conditions, it may be impossible to provide the amount of submergence specified in the guidelines. In such cases, the low head axial flow pump can be equipped with a vortex protection shield. Such shields are designed to reduce the tendency to form vortices and swirl and to make it possible to operate with less than the prescribed submergence. The guidelines presented here can be used for typical low head axial flow pump installations as described herein. Should your conditions not correspond to those described, please contact your Flygt products distributor. They will be able to assist you in obtaining a satisfactory installation.

2 Installation Guidelines Issued: 7/02 Supersedes: 3/97

3 Installation Guidelines Issued: 4/97 Supersedes: 11/94 PP4630/ Submergence Diagrams (for pumps without vortex suppressors) Flow (gpm) PP4650/ Flow (gpm) PP4670/ Flow (gpm) *Minimum Submergence PP-4630 PP-4640 PP-4650 PP-4660 PP-4670 PP " 12" 12" 12" 16" 20" * For pumps equipped with vortex suppressors

4 Wall & Pipe Flange Mounting Issued: 11/11 Supersedes: 3/97 (NOT BY FLYGT, CUT (NOT BY FLYGT, CUT

5 Biological Nutrient Removal (BNR) Nitrification/Denitrification Process Issued: 3/97 Supersedes: 11/94