NAMTS INSIDE ELECTRICAL REPAIR TECHNICIAN V-662-4650 PROCESS ... - Valkyrie

NAMTS INSIDE ELECTRICAL REPAIR TECHNICIAN PROCESS 192.01

INFORMATION SHEET 192.01-2 BALANCING

V-662-4650 Sheet 1 of 26

A. INTRODUCTION

This lesson is an introduction to balancing electric motors and electric motor components. Knowledge of these skills and procedures is required to ensure proper maintenance and longevity of electric motors used in systems onboard Navy ships. Each term and definition is utilized throughout the training material.

B. REFERENCE

1. Naval Sea Systems Command (NAVSEA) 0900-LP-060-2020, Vol 2, Vibration Analysis & Rotor Balance

C. INFORMATION

1. Introduction.

a. This lesson is an introduction to balancing electric motors and electric motor components. Knowledge of these skills and procedures is required to ensure proper maintenance and longevity of electric motors used in systems onboard Navy ships. Each term and definition is utilized throughout the training material.

2. Safety precautions.

a. Specific warnings, cautions and notes regarding the system and equipment appear throughout the technical manuals following paragraph headings and immediately preceding the text to which they apply.

1) Warning - Used to draw special attention to potential hazardous situations which if not avoided could result in minor personal injury, serious injury, or death.

2) Caution - Used to draw special attention to anything that could damage equipment or cause the loss of data and includes what could happen if the caution is ignored.

3) Note - Used to highlight essential procedure(s) by visually distinguishing it from the rest of the text and can contain any type of information except safety information.

3. Unbalance types.

a. Static.

1) Simplest type of unbalance.

2) If the mass of the wheel is unevenly distributed about the rotational axis of the shaft, the center of gravity of the wheel does not lie on the rotational axis.

FOR TRAINING USE ONLY

NAMTS INSIDE ELECTRICAL REPAIR TECHNICIAN PROCESS 192.01

V-662-4650 Sheet 2 of 26

3) The wheel, when placed on knife edges, will rotate until the heavy spot comes to rest vertically below the rotational axis, as shown in Figure 192.01-2.1.

Figure 192.01-2.1: Static Unbalance

4) This type of unbalance is known as static unbalance and can be corrected by placing an appropriate weight 180? opposite the heavy spots, or by removing weight at the heavy spot.

b. Dynamic. 1) Dynamic unbalance concerns parts in motion, as shown in Figure 192.01-2.2.

Figure 192.01-2.2: Dynamic Unbalance FOR TRAINING USE ONLY

NAMTS INSIDE ELECTRICAL REPAIR TECHNICIAN PROCESS 192.01

V-662-4650 Sheet 3 of 26

2) The solid rotor is unbalanced at both ends; in this case (pure unbalance), the heavy spots are 180? opposite each other.

3) This shaft, when placed on knife edges, will not rotate; therefore, a dynamic method must be employed to detect this type of unbalance.

4) When the rotor is turned, it will try to rotate about a line drawn through the unbalance weights, generating forces at the bearings.

5) This type of unbalance can only be corrected by applying two correction weights to the rotor.

6) The weights must be placed at each end of the rotor, 180? opposite the respective heavy spots.

7) A single weight, no matter where it is placed, can never correct the "unbalanced couple" of forces or the "moment" acting on the rotor.

8) For this reason, dynamic unbalance is often called "two-plane" or "moment" unbalance.

4. In-place balancing considerations.

a. Advantage of in-place balancing.

1) Any rotating mass will have some amount of unbalance, which can cause bearing wear and undesirable vibrations.

2) A rotor may be balanced as a unit in a balance machine, but when it is run in its own bearings and perhaps coupled to another element, a degree of unbalance is likely to be present.

3) Balancing in-place can minimize this apparent unbalance, resulting in improved reliability as well as reducing rotational frequency components.

b. Types of balancing - May be classed as single-plane and multiplane.

1) Single-plane balancing.

a) Refers to corrections being made in only one plane of a rotating element.

b) This type is applicable in cases where the rotating element is basically a disk, such as a fan, and all the unbalance is concentrated in the plane of the disk.

2) Multiplane balancing.

a) Refers to corrections being made in more than one plane.

b) This type is applicable to cases when balancing motors, turbines, etc.

3) For both types of balancing, the number of measurement locations must be equal to or greater than the number of planes used.

c. Helpful information.

1) The procedures below are primarily for use with units requiring corrections in two planes.

FOR TRAINING USE ONLY

NAMTS INSIDE ELECTRICAL REPAIR TECHNICIAN PROCESS 192.01

V-662-4650 Sheet 4 of 26

2) Single-plane iterative balancing (balancing each end of the unit alternately) or the preferred two-plane balancing may be used.

3) Single-plane iterative balancing, in most cases, requires additional time and effort because of the cross effects between two planes. For example, balancing in one plane to eliminate vibration, as measured at one location without consideration of cross-effects, can result in an increase in the vibration, as measured at other locations.

4) Two-plane balancing has the advantage that the cross-effects between the planes are measured and considered when determining the balanced solution. Hence, a finer balance is achieved with a minimum expenditure of time and effort.

d. Problem areas in balancing.

1) Improper transducer attachment.

2) Faulty transducer.

3) Faulty instrumentation.

4) Accidental shifting of photocell reference.

5) Electrical ground loops.

6) Failure to wait for operating conditions (speed, load, etc.) to stabilize.

7) Failure to re-establish precise operating conditions for each run.

8) Background vibrations.

9) Errors in plotting data.

5. Balancing instrumentation.

a. Basic balancing instrumentation systems should consist of four items:

1) Transducer system.

2) Signal conditioner.

3) Selective frequency analyzer.

4) Phase measurement system.

b. Vibration measuring equipment:

1) Not normally classed as balancing equipment, unless it is capable of measuring both vibration amplitudes and changes in vibration phase angles.

2) It must include the means for filtering the rotational frequency component out of the overall vibration signal.

c. Two portable balancing systems that are available and used for in-place dynamic balancing of rotating parts in their own bearings are:

1) General Radio Portable Balancing System.

FOR TRAINING USE ONLY

NAMTS INSIDE ELECTRICAL REPAIR TECHNICIAN PROCESS 192.01

V-662-4650 Sheet 5 of 26

a) This balancing system must be calibrated before being used following procedures provided in NAVSEA 0900-LP-060-2020, Vol 2, Chapter 6, Section 5, or in Chapter 4, Sections 1, 2, or 3, as applicable to the low-noise amplifier being used.

b) The General Radio Portable Balancing System assets and their corresponding descriptions are as shown in Table 192.01-2.1 and Figure 192.01-2.3 through Figure 192.01-2.9.

Table 192.01-2.1: General Radio Portable Balancing System Assets FOR TRAINING USE ONLY

 ................
................

In order to avoid copyright disputes, this page is only a partial summary.

Google Online Preview   Download