# Title 40

## SECTION 1065.644

### 1065.644 Vacuum-decay leak rate.

§ 1065.644 Vacuum-decay leak rate.This section describes how to calculate the leak rate of a
vacuum-decay leak verification, which is described in §
1065.345(e). Use the following equation to calculate the leak rate
*n* leak, and compare it to the criterion specified in §
1065.345(e):

*V*vac = geometric volume of the vacuum-side of the sampling system.

*R*= molar gas constant.

*p*2 = vacuum-side absolute pressure at time

*t*2.

*T*2 = vacuum-side absolute temperature at time

*t*2.

*p*1 = vacuum-side absolute pressure at time

*t*1.

*T*1 = vacuum-side absolute temperature at time

*t*1.

*t*2 = time at completion of vacuum-decay leak verification test.

*t*1 = time at start of vacuum-decay leak verification test. Example:

*V*vac = 2.0000 L = 0.00200 m 3

*R*= 8.314472 J/(mol · K) = 8.314472 (m 2 · kg)/(s 2 · mol · K)

*p*2 = 50.600 kPa = 50600 Pa = 50600 kg/(m · s 2)

*T*2 = 293.15 K

*p*1 = 25.300 kPa = 25300 Pa = 25300 kg/(m · s 2)

*T*1 = 293.15 K

*t*2 = 10:57:35 a.m.

*t*1 = 10:56:25 a.m. [79 FR 23795, Apr. 28, 2014]