Component Related Documentation

Pressure scales are means of measuring the pressure of air. Both metric and English based systems are commonly used. Gauge pressure, pressure measured by a pressure gauge, does not take into account atmospheric pressure. Essentially, we live in an ocean of air. At sea level, a pressure gauge does not indicate atmospheric pressure which is present at approximately 14.7 psi. Thus, while the pressure gauge needle indicates 0 psig (pounds per square inch – gauge) the actual pressure is 14.7 psia (pound per square inch – absolute). In the metric scale, typically “bar” is a commonly used pressure unit; 1 bar = 1 atmosphere = 14.5 psi. Bar may be stated in either gauge or absolute values. Other scales, such as inches of water, inches of mercury, millimeters of mercury and Pascals are used to measure pressure, either positive or negative (vacuum).

Safety Related Notes

Before working on this machine, perform lockout-tagout procedures per the rules of your plant. Determine the sources of energy on this machine – electrical, pneumatic and hydraulic – and release or vent sources of stored energy – electrical capacitors, air receivers, and hydraulic accumulators. Shut off sources of power – electrical, pneumatic and hydraulic. Safely block mechanical sources of energy such as loaded springs and loaded machine members, or safely position the machine members so they are unloaded and springs are not under tension. Beware of hot hydraulic fluid and hot surfaces which can cause burns. Never “crack a hydraulic or pneumatic fitting” to check for the presence of stored energy. Hydraulic fluid injection injuries, as well as injection injuries from many other fluids, are extremely serious and must be treated immediately by medical personnel familiar with this type of injury. Loss of body parts or death may result from improperly treated fluid injection injuries! Never use your hands to feel for a hydraulic leak! Never use compressed air to blow dust off yourself or someone else – there is risk of an air injection injury. Review the schematics and think before proceeding to work on the machine to ensure you have made the machine safe to work on.