Motor vibration analysis

Sometime it is experienced high vibration levels. The cause may be an electromagnetic or mechanical imbalance, loose components, rubbing parts, bearing failure, or resonance.

When a problem occurs, it is critical to quickly identify the source of the trouble and take corrective action. Using techniques we can save money and downtime.

Vibration levels shown in the Table below are considered excessive. If you find these levels during inspection, quickly resolve the situation for motor reliability.

Shaft vibration vs. housing vibration

The necessity of obtaining housing vibration data vs. shaft vibration data depends on the problem. It is often desirable to obtain both, especially on a machine with sleeve bearings. If the problem originates in the housing or motor frame, it can be analyzed by vibration meter or vibration analyzer. follow OEM guideline or manual for vertical , horizontal or axial measurement.

Troubleshooting procedure

·         Ensure that all the bolts are tight.

·         Ensure that any part of the system (such as the junction box top cover or piping) is not vibrating excessively.

·         Ensure that the foundation or the motor frame is not vibrating at a higher level (more than 25%) than the motor. If so, there could be a weak motor base.

·         Are any parts of the motor or shaft loose?

·         Ensure that fan blades are not eroded or broken off?

·         If the above items are satisfactory, but vibration remains high, perform a thorough vibration analysis.

You can diagnose a vibration problem in two steps. First, obtain vibration data, but remember factors like noise, combined signals, and amplitude modulation can influence the data. Obtain vibration measurements with the motor operating under the following conditions:

·         Loaded, coupled, full voltage, all conditions stabilized. The first measurements you take should represent the machine under normal operation and may indicate the tests you should perform next.

·         Unloaded, coupled, full voltage. This condition removes some, but not all, load-related vibration.

·         Unloaded, uncoupled, full voltage. This condition removes all effects of the coupling and mechanical load driven by the motor. It isolates the motor/base system from the measurement.

analyze as under -

Acceptance of vibration levels during plant operations :

Motor vibration analysis

Type 1	-	Small industrial machines, e.g electric motors below 15 kW
Type 2	-	Medium size electric motors, 15-75 KW without special foundations.
Type 3	-	Large motors or machines consisting largely of rotating masses, mounted on rigid foundations having high rigidity in the direction of measurement.
Type 4	-	Type 3 but without rigidity in the direction of measurement.

transformer oil filtration format

Sara Construction & Engineer

Site: Bral engineering company, Ghaziabad

Transformer oil filtration report

Job Ref: --------------------------

Report No  ………………                                                                    Date:……………………..

Transformer no-……………              …………… Substation no- ………………………………..

Oil Capacity …………….Transformer KVA …… ……Voltage……..        ..Sr. no …………

BDV in KV (before staring of filtration)…………

Filtration m/c capacity: ………..L/M, temperature setting: …………deg.C,                     

IR value HT side with 2500V megger…….M-ohm

Reading :

Sr	Date	Time	Oil temperature	Pressure (hg)	Heater current	BDV	Remarks
1
2
3
4
5

If any ……………….

Transformer is reedy for charge or not………………….

Supervisor----------                                                                                 Operator sign ------------

IR Value:

Transformer charge date and time----------------------------

Remarks …………………………………….

Engineer sign -----------

Earthing or grounding of armoured Cables for PA system

Armouring represents a mechanical protection of the cable but can also be used for shielding. Potential equalization via the armouring cannot be recommended but should be measured or dimensioned in each particular case and belongs to the responsibility of the customer.

If the armouring is used as electrical shielding, the shielding should be grounded at one side only to protect against ground returns and equalizing currents, i.e. the armouring should end insulated in a plastic gland.

PA system manufacturer does not recommend the armouring's grounding at both sides. This would be allowed only within a PA area and could cause interferences of the communication quality

If special metal armoured glands are used, the following parameters always have to be indicated when selecting the glands:

·         Outside cable diameter

·         Outside diameter of the armouring

·         Desired type of thread

·         Ambient conditions (range of temperatures, IP protection degree)

·         Industrial or Ex version (Ex-d, Ex-e)

·         Sealing: - only outside sheath - only inside sheath - outside and inside sheath - outside sheath and lead cover

·         Armouring type and wire strength

earthing of PA system cable

Types of armouring are available:

        Steel tape armouring (DSTA)

        Single wire armouring (SWA)

        Wire braid armouring (wire braid)

        Aluminium tape armouring (AWA + ASA)

Note: t bulky glands might perhaps allow only one entry at each side of the housing as the distance between the glands is predefined by the prepared thread inset plate.

Cabling