HOSE 1477109 - Caterpillar

Caterpillar Products:with Cabs AllIntroduction
Maintaining positive cab air pressure over the life of the machine helps ensure operator comfort, operator productivity, and increased cab cleanliness. Positive cab air pressure will reduce operator exposure to airborne particulates. Cab air quality can decrease over time from normal wear or physical damage.This document provides background information, measurement techniques, guidelines for inspection, and corrective action to maintain appropriate cab air pressure. These practices apply to a broad range of cabs and machines. The illustrations provided are to be used for reference regardless of machine model.Product Enhancement Description
Useful Definitions
Cab pressure is the difference in air pressure between the inside of the cab and the external environment.Cab airflow is the total airflow experienced by the operator that is ejected from the air vent louvers.Cab Fresh or ventilation airflow is the fraction of the total cab airflow that is brought in from the outside. This airflow is what creates the cab pressure.Cab return or recirculation airflow is the fraction of the total cab airflow that is pulled from the environment of the operator. The airflow is again cooled or again heated, and then again rejected from the air vent louvers.Cab pressure control principles
Illustration 1 g03172796
Positive cab pressure prevents dirt entry
The purpose of the cab pressurization system is to create a clean operating environment. This pressurization system is accomplished by preventing unwanted outside air from entering the cab through openings by creating a positive pressure inside the cab. Furthermore, the desired outside air that is drawn in to create that pressure is filtered.The amount of cab air pressure required to prevent dirt entry through openings in the cab is small. Therefore, the air pressure is typically measured in Pascal (Pa) units.
Illustration 2 g03172822
Total cab airflow is related to cab pressure since a portion of total airflow is drawn into the cab to create positive pressure, and maintain a comfortable temperature inside the cab. The total cab airflow is made up of fresh air (B) drawn into the cab heating or cooling unit from outside and recirculation air (C) drawn into heating or cooling unit from the cab environment. Refer to Illustration 2. The fresh air is drawn in by the heating and cooling system through the blower. At startup, fresh air is drawn in at an increasing rate until the cab leaks an amount of air (A) which is equal to the air being drawn in. The process occurs in a matter of seconds. Cab pressure inspection checklist
The performance of cab pressure-related components can degrade with aging, wear, exposure to extreme conditions, physical damage, and so on. Regular inspection of the cab and machine can be used to identify degradation of cab pressure-related components contributing to poor cab pressurization. The affected parts can be repaired or replaced as needed.Inspection Checklist
Measure cab Pressure
Proceed to Step 2, if cab pressure on high blower speed is below 0.05 kPa (0.01 psi).
Proceed to Step 3, if cab pressure on high blower speed is above 0.20 kPa (0.03 psi).
Low cab Pressure Inspection
Fresh air filter