RETA Breeze Jul-Aug 2025

150-ppm during a leak incident.

INSPECTION, TESTING AND MAINTENANCE

Testing emergency ventilation fans—as outlined in Table 12.1 “ Emergency Ventila tion Systems Inspection, Testing and Maintenance Tasks ” of the ANSI/IIAR 6—can detect or predict future problems. Table 12.1-c recommends detecting vibration, as excessive vibration will affect performance. It is difficult to assess whether a fan excessively vibrates, however, maintenance technicians can at least check to see if some type of vibration isolation mounts were employed in installation. Vibration isolation may have been specified by the consulting engineer, but that does not guarantee the mechanical contractor installed them. Vibration isolation mounts can be added. Also, roof curb openings can be lined with a rubber neoprene seal that acts as a buffer between the curb and the fan it supports. A good maintenance check that is not in the ANSI/IIAR 2 or ANSI/IIAR 6 guidelines is to use an amp draw meter to measure the amps a motor draws during startup and runtime. If the motor does not draw the specified amps within a predetermined amp range in the control system, it will activate an alarm. Amp draw meters are excellent for troubleshooting a failed start, stalled motor and other issues. If there is a belt problem, the motor will run without resistance and less amp draw, which the amp meter would detect. An amp meter and a control system with alarm points can save a lot of troubleshooting time and detect issues in real time. Aside from the expected operating hum of a fan motor, any noise as per Table 12.1-d can also detect current or future problems. If it makes an atypical noise, there is probably something wrong. For example, if an emergency fan squeals during start up, that is a simple diagnosis of a loose fan belt. Older fans might not have spark proof blades, because it was not a building code years ago. Recent ANSI/IIAR 2-2021 guidelines dictate a fan construction “so that two ferrous parts can’t rub or strike and create a spark.” Therefore, broken fan blade replacement should use aluminum or other spark-proof materials to eliminate potential sparks. For similar reasons, fan

A sample rooftop exhaust fan.

motors should be totally enclosed so that potential arching is not exposed to leaked airborne flammables. It is vital when changing fan blade materials that facilities procedures are followed. Changes in pitch can have an effect on the ventilation system ratings. Many facilities have management of change procedures for the use of non-OEM parts, or parts affecting the design specifications. Other testing should ensure the machinery room operating pressure is negative. If there is a gas leak, the room pressure should not be under positive pressure which would push the contaminant to other areas of the cold storage warehouse/ production facility versus outdoors. Emergency fans that are not operating to specifications can affect room pressuriza tion. While it may sound trivial, keeping the machinery room entry door closed is also critical for room pressurization. Keeping doors closed allows the exhaust fan(s) to sweep the room without leaving airborne contamination dead spots. Therefore, doors must remain shut and display signage indicating it. ANSI/IIAR 2-2021 mandates a negative pressurization that does not exceed 0.25/ in. wc. Today’s trends point toward using mechanically controlled/operated louvers. This supplants the old school strategy of supply fans calibrated to supply slightly less CFMs than the exhaust fan. Instead, the exhaust fan pulls outdoor air through the louver(s) and simultaneously dilutes machinery room airborne contaminants and exhausts them during emergencies. Louvers need inspection for operation, if

Bearing manufacturers recommend rotating the shaft periodically for it to rest in a new position. Inspecting bearings is difficult since most are in a sealed housing. However, following ANSI/IIAR 6 guidelines of testing emergency fans semi-annually for proper operation should be able to detect faulty bearings or fan belts. Unusual sounds or vibrations could indicate bearing deterioration. The fan motor can also suffer the same outcome from inactivity. An armature resting in the same spot on the motor needs rotation periodically to proactively stop any corrosion formation. All these potential issues can affect emergency fan performance which the ANSI/IIAR 2-2021 mandates at least 30 air changes/hr; and a discharge velocity of 2,500 ft/min. This rate is designed to evacuate the machinery room if and when airborne ammonia concentrations reach

RETA.com 27