ACtion Magazine - July/August 2015 - (Page 24)
CAT Training @ T/CCI
By Steve Schaeber, MACS Technical Editor
here are many reasons technicians enjoy attending training
classes. Sometimes we go to learn about new trends in the industry, or to ask the experts about the most complex situations
we've come across. Still other times we're just looking for
a refresher course. While there are many instructors teaching
classes like these, it's a rare treat to get training directly from the engineers
who design and build the systems we service. That's exactly what we got
from eight of Caterpillar's climate systems engineers, who conducted
training classes at T/CCI's Climatic Wind Tunnel facility in Decatur, Illinois on May 29th, 2015.
Rotating between two separate classrooms, attendees had the opportunity to hear from four engineers in each as they presented material in their
areas of expertise.
Clutch wear caused by over cycling from low system
Cabin air quality
"We don't want accidents based on something that's preventable,"
said Daren Carr, senior design engineer specializing in cabin air quality.
Discussing CO2 levels in an operator's cabin during a typical working
shift, he pointed out, "That's why we need to bring in some outside air to
help keep CO2 down to acceptable levels."
CAT's engineering team provided exceptional training.
CO2 Concentration Levels Inside Cabs:
Compressor failure modes
Why do we need to understand failure modes? "Because after the leak,
the compressor is still the highest failure rate component in the air conditioning system," remarked Sadish Penmetsa, climate systems design engineer. "We need to understand basic failure modes on the compressor so
we can fix problems without having further damage in the system. It also
helps to know what we need to fix when we have a failure."
Sadish opened his discussion of failure modes stating, "Of these, seizures are the most common, which are often caused by leaks." He further
emphasized the importance of compressor lubrication, explaining that
when refrigerant leaks out, less oil is returned to the compressor. "We call
this Oil Circulation Ratio, or OCR." Sadish explained that having the correct amount of refrigerant and oil circulating back to the compressor is
imperative to proper operation. "OCR depends on the amount of refrigerant in the system."
Sadish described other common failure modes, such as system contamination, moisture, clutch issues, and damage resulting from improper
installation or assembly.
ACTION * July/August 2015
* Normal Cab Levels are <1,000 ppm
* 1,000 - 2,000 ppm may cause drowsiness
* 2,000 - 5,000 ppm may cause headaches, poor
concentration, and increased heart rate
* >5,000 ppm may cause loss of consciousness
* >10,000 ppm may lead to oxygen deprivation
Another area of concern for CAT is something called Respirable
Crystalline Silica (RCS). Basically, this is extremely fine particles of sand,
dirt or stone. Specifically, the issue relates to particle sizes less than 10
microns which cannot be extracted from the lungs once they're inhaled.
This dust is extremely abundant in the environments where machines typically operate, high exposure to which is linked to diseases such as Lung
Cancer, Chronic Obstructive Pulmonary Disease (COPD) and Silicosis.
While there are exposure limits set by OSHA, proper cabin air filtration
and HVAC system maintenance can go a long way in helping to control
Proper performance includes maintaining a constant source of fresh
air. CAT recommends 25cfm per person in the cab, which helps make
up what a normal person exhales. It's also important to keep the cab pres-
Table of Contents for the Digital Edition of ACtion Magazine - July/August 2015
T/CCI's Wind Tunnel: Let's Test It
CAT Training @ T/CCI
By the numbers
ACtion Magazine - July/August 2015