Pressure rise resulting
from hydrostatic expansion due to temperature rise of liquid
refrigerant trapped in or between closed valves shall be
addressed in accordance with Section 1112.5.1 and Section
1112.5.2. [ASHRAE 15:9.4.3]
Where trapping of liquid with subsequent
hydrostatic expansion is capable of occurring automatically
during normal operation or during standby, shipping,
or power failure, engineering controls shall be used
that are capable of preventing the pressure from exceeding
the design pressure. Acceptable engineering controls
include but are not limited to the following:
- Pressure relief device to relieve hydrostatic pressure to another part of the system.
- Reseating pressure relief valve to relieve the hydrostatic pressure to an approved treatment system. [ASHRAE 15:9.4.3.1]
Where trapping of liquid with subsequent hydrostatic
expansion is capable of occurring only during
maintenance-i.e., when personnel are performing maintenance
tasks-either engineering or administrative controls
shall be used to relieve or prevent the hydrostatic
overpressure. [ASHRAE 15:9.4.3.2]