Table of Contents:
Scope of Work
An infrared survey was conducted to detect and analyze
overloaded components and poor connections in panels and
cabinets designated by the Owner, at Vitex Building, located at
155 Duryea Road, Melville, N. Y. 11747. Survey included bus bar
connections, breakers, wire terminals, power panels, lighting
panels and fuse connections.
Infrared Thermograph
Operating
Principles
Every object whose surface temperature is above absolute zero
(-273 Degrees C) radiates electromagnetic energy that is a
function of its surface temperature. The intensity of this
radiation varies along the wave lengths of the electromagnetic
spectrum from visual to the infrared ranges.
Using a highly sensitive, real time, infrared imaging system,
it is possible to observe, quantify and record the thermal
picture of the surface temperature of the object whose
temperature is between -20 Degrees C and +2000 Degrees C.
The sensitivity of the equipment is such that it is capable of
detecting temperatures between two given surfaces to an accuracy
of 0.2 degrees C at an ambient temperature of30 degrees C.
The infrared heat scanning equipment consists of an infrared
camera, with optics transparent only to infrared radiation and a
TV type display monitor. The camera converts the radiated heat
that it senses into an electrical signal. This signal is
displayed on a special display monitor as a real time heat image
of the object on which the camera is focused. The heat picture,
known as a thermogram, is composed of a gray scale with
continuous contrast ranging from black to white. Areas of higher
temperature appear lighter; areas of lower temperature appear
darker. If an object, or part of an object is warm (or hot), it
will appear bright in the heat image. If an object, or part of
an object is cool, it will appear dark in the heat image.
Intermediate shades of gray or color indicate variations
between
the extremes of temperature. It should be noted that the FUR
prism equipment used by Thermotest can be black and white or
color.
The thermal image of an object shown on the display monitor
screen can be photographed for a permanent record. This is done
using a specially adapted camera, and gives. qualitative visual
information about the surface temperature of the object.
Interpreting:
Thermograms
Thermogram is a "heat picture" of an object.
Unlike ordinary photographic equipment that responds to visible
light, the infrared camera responds only to invisible heat
radiation. The resulting image produced on the display unit
resembles the object in black
and white with shades of gray. The whiter an object appears,
the hotter it is conversely, the darker the cooler
the object is. The sensitivity of the thermograph equipment is
such that temperature difference of as little as 0.2 centigrade
is sensed.
Thermograph Inspection
of Electrical Equipment
Infrared thermography is an ideal inspection technique for
scanning electrical equipment for defective components.
Normal wear, chemical contamination, corrosion, fatigue and
faulty assembly or insulation may lower the conductivity and
raise the resistance level of the component in question. Such a
rise in component resistance will increase the amount of power
dissipated in the form of heat. This.in turn will cause
an increase in the temperature of the component.
This excessive heat, evidenced by the increased surface
temperature of the component, can be readily noted and the
temperature rise measured by the infrared system.
The increased temperature indicates a potential trouble spot
and possible future failure of the component.
The infrared inspection is carried out while the electrical
system is under load. There is,no physical contact with the
system, thus making it an excellent preventive maintenance tool,
which causes no disruption to the normal operation
routine of the facility
At the. plant and/or building, all the major electrical
equipment; such as the substation, motor control
centers, switch gear, circuit breaker panels, electric motor,
etc.;
can be readily checked for component parts which are at an
excessive temperature, thus indicating potential problems.
In power generating, transmission and distribution systems,
electrical energy is transferred from one facility to
the next through a series of mechanical interfaces
associated with connectors, insulators, switches, bushings,
fuses, etc. Each such interface represents a point where
conductivity may be reduced with a resultant temperature
increase, again pointing to a potential problem.
Routine infrared scanning of electrical components is thus a
valuable preventive maintenance tool, whereby early corrective
action may be taken preventing costly breakdowns and/or plant
hazards
Definitions
Ambient
-
Average surrounding temperature of similar items surveyed
in degrees.
This is used as a reference for calculating temperature rise
O/A
-
Surface temperature rise in degrees. i.e., over ambient.
Thermogram -
Thermal image of an object (sensed by the infTaredimaging
system)
shown on the display monitor screen. Also, a photograph of the
thermal image on the display monitor.
Recommended Priorities
Electrical Criteria: To determine the priority for
maintenance scheduling based on
temperature rise.
A
High Voltage. Power distribution equipment
Temperature Rise O/A
Remarks
0 to 18 degrees F
Corrective measures should be take at the next
maintenance period.
19 to 36 degrees F
Corrective measures required as scheduling permits.
37 to 72 degrees F
Corrective measures required ASAP depending
upon the class ofload carried and the severity of the
temperature rise in this range.
72 degrees F. and over
Corrective measures required immediatlely.
B.
Low Voltage. Distribution and control equipment.
Temperature rise O/A
Remarks:
0 to 18 degrees F
Corrective measures required at next scheduled
maintenance period or as scheduling permits, Little
probability of physical damage.
19 to 36 degrees F.
Corrective measures required on Priority
scheduling basis. Inspect for physical damage.
There is probability of damage in the component,
but not in the surrounding components.
37 to 54 degrees F
Corrective measures required ASAP. Replace
component and inspect the surrounding component
for probable damage.
54 degrees F. and over
Corrective measures required immediately.
Replace component, inspect surrounding
components. Repair while IR camera is still
available to inspect after repair, if 0/ A is over 1'20
degrees F.
NOTE: The above criteria is subjective and has been determined
by past field experience for maintenance scheduling. The
facility owner shall make the. final decision as to priorities
and order of maintenance. This should be determined by using the
degree of temperature rise and criticality of the equipment
involved
Summary of Findings:
The summaries of findings consist of the following eleven (11)
pages. Pages' one (1) through seven (7) list all the two hundred
and fifty-three (253) panels surveyed in twenty-nine (29)
locations throughout the Vitex Building.
The panels that have shown heat anomilies are shown in red
lettering, which are then detailed on pages' eight (8) through
eleven (11).
The twenty-one (21) red arrows on these pages note the panels
that had heat anomilies 'during the infrared survey performed in
July of 1997.
Note that five (5) of the red arrows (last years anomilies) are
located at anomilies found during this year's walk-through.
#26 - EPP A-L.
Same problem found at both surveys. The three distribution ~ires
are hot. Suggest further investigation at the source for
overload.
#90 - EPPB-J.
Different curcuit breakers are involved.
#125 - PP-P. Curcuit
breaker 9B continues to show the same anomilies. Curcuit Breaker
may not have been replace during previous shut-down. Suggest the
replacement of the curcuit breaker and recheck to see if this
eliminates the problem. Last year's difference in degrees F. was
14 degrees. That has increased to 25 degree's difference this
year. This indicates that the problem is worsening.
#164-F
Different curcuit breakers are involved.
#242 -Computer room AC panel on roof The fuses are noted as
being hot during both surveys. Please confirm that they have
been changed for the next survey.
Pages'eight (8) through eleven (11) detail the thirty-five (35)
anomilies found during the June 1-3 walk-through. These are
numbered to correspond with the thirty-five (35) pages of both
real time pictures along with the thermograms of each of the
anomilies.
Statistical Data:
Pictures:
