Title: Unit 8 Outline
Course: HET 230 - Spring 2015 > Section: HET 230 - Spring 2015

Unit 8 Outline

Unit 8 Outline
Unit 8 Outline

Introduction:

Last week, we discussed the calculations of the fan laws and the relationships between CFM, RPM, sheave diameters, Bhp, and its association to static pressure.  A knowledgeable technician knows how to use the fan laws to their advantage when selecting the proper fan, motor and sheave sizes for system design, or for diagnostics.  The proper static pressure and volume of air being move through the duct system is important for air delivery and noise reduction.  Being able to control these is important to a technician.

This week, you will learn about pitch and datum diameters, the difference between the drive and driven, fixed and adjustable sheaves, and develop general understanding to properly aligning them, including common vocabulary terms.  In addition, you will be provided a PowerPoint a presentation, weekly study materials.  You will also participate in weekly discussions and complete all assignments and a content assessment quiz.  You will also discover the different types of belts used and their ratings, the proper calculations for sizing and ordering both belts and sheaves.  Additionally, you will learn about the different types of fan accessories commonly used for adjustment, vibration control, safety guards, airflow dampers and vanes, and the very basics of variable frequency drives.  Learning these subjects will allow you to form a solid foundation for the next week’s session, Identifying Fan Problems & Maintenance.

Objectives:

On completion of this week’s assignments, the student should be able to:

- understand the difference between a Direct Drive and a V-belt Drive
- describe the difference between a Drive and a Driven sheave
- describe the terms of the components which make up a belt drive/driven system
- describe the terms “Inertia” and “Torque” and their effects of rotating and twisting motion
- describe what a Key or Keyway is used for; and what a Bushing is, and its purpose
- describe Pitch Diameter (PD) and Datum Diameter (DD) of a sheave, and their differences
- explain the operation of a Variable Pitch Sheave verse a Fixed Sheave
- identify the difference between a Notched and a Standard V-belt, and their application
- understand how a Linked Belt can be used by a technician as a temporary fix for emergencies
- determine how to calculate number and type of a belt using service factors and Horsepower ratings, and how to properly order V-Belts for the application
- understand how to change sheaves and belts, and proper sheave alignment
- understand the classes of V-Belts by cross section, pitch length, and horsepower
- determine how to obtain the proper belt length using equations for old and new Pitch Diameter (PD) and Center-to-center dimensions (CD)
- understand the safety procedures for changing belts and sheaves
- describe the various fan accessories used with different fan and motor configurations
- describe the use of Vibration Dampening, Isolation Blocks and Springs
- understand the purpose of Inertia Bases
- describe the use of a flexible connector between the blower housing and the duct work
- understand the significance of Belt Guards with regards to safety
- understand the different motor mounting configurations and how to adjust belt tension
- describe the use of Air Controllers, Inlet Vanes and Outlet Dampers
- describe the  use of Variable Frequency Drives (VFD) and how they are used
- understand the use of Sound Attenuation in sound reduction within a duct

- Key Vocabulary:
Air Controllers
Belt Guard
Belt Sizes
Belt Tension
Blocking Procedures
Brake Horsepower (Bhp)
Bushing
Center-to-Center Distance (CD)
Cross Section
Datum Diameter (DD)
Direct Drive
Drive Sheave
Driven Sheave
Extracting Bolts
Fan Plenum
Flexible Connectors
Fractional Horsepower
Harmonic Distortion
Harmonic Filtering Device
Horsepower (Hp)
Hub
Inertia
Inertia Base
Inertia Block
Inlet Vane
Isolation Block
Isolation Spring
Keys
Keyways
Linked Belts
Lock-out/Tag-out Procedures
Motor Sheave
Multiple Belts
Nominal pitch length
Notched Belts
Outlet Damper
Penetrating Oil
Pitch Diameter (PD)
Pitch Length
Seismic Restraints
Sheave Alignment
Side Rails
Sound Attenuation
Tension Adjusting Bolts
Torque
V-Belt drive
Vibration Dampener
Variable Frequency Drive (VFD)
Variable Pitch Sheave
Wheel Puller