Type III — Low-PressureQuestion 183 of 240

Before opening a low-pressure chiller to replace a failed tube bundle, the technician must:

a.Pressurize the shell to 20 psig
b.Add nitrogen and leave the refrigerant in place
c.Recover the charge to 25 mm Hg absolute
d.Vent the charge slowly to the roof

Explanation

The refrigerant must be recovered to 25 mm Hg absolute before the machine is opened for major service such as a tube-bundle replacement. Venting is illegal, and pressurizing above 10 psig risks the rupture disk. Only after proper recovery may the low-pressure shell be opened.

Law Reference: 40 CFR §82.156

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