US 5,621,180 A · Capillary sampling flow controller

Abstract

A capillary sampling flow controller provides an improvement in the process of sampling or monitoring for the analysis of air and gas chemistries; a constant flow rate is used to introduce a specific volume of gas into a vessel or through a trapping media over the selected sampling period. The improvement employs calculated geometry of the capillaries employed to deliver the gas sample to the evacuated vessel. It can also include a pressure reading device installed between the vessel and the capillary, and a filter at the inlet. The length of capillary with available internal diameters is estimated mathematically and confirmed experimentally to achieve any sampling time using any size sampler. The flow rate obtained from the controller is constant over its operating range and is designed to meet a specific sampling duration to obtain long-term integrated samples. The sampling process becomes completely passive, precise, reliable and simple to operate.

Claims17

Dependent claims

A sampling assembly for the time integrated passive collection of a gas or ambient air comprising a sample vessel having a negative atmosphere, said vessel having a gas inlet and being operatively connected to a sampling flow controller comprising an elongated capillary tube having an inlet port and an outlet port with a gas flow passage therebetween, said outlet port communicating with the vessel, said capillary tube having a length and an internal diameter in accordance with the relationship ##EQU23## wherein L is the length of the capillary in meters,

R is the internal radius of the capillary in meters,
V.sub.f is the final sampled volume in cubic meters,
t is the time in seconds, and
K.sub.5 and K.sub.6 are constants for the system in which ##EQU24## wherein P.sub.atm is atmospheric pressure (Pa)
V is the molar volume (m.sup.3 /mole)
is the gas constant (N.m/mol.k)
T is the temperature (.degree. K.), and
V.sub.s is the volume of the vessel in cubic meters
so as to provide flow control of gas or ambient air at said gas inlet of the vessel.

6 more elements

A sampling flow controller for time integrated flow of gas or ambient air during collection comprising, in combination:

an elongated capillary tube having an inlet port and an outlet port with a gas flow passage therebetween,
means for communicating said outlet port with a sample vessel adapted to be held under a negative pressure, and
a filter operatively connected to said inlet port for prevention of entry of particulate matter into said flow passage,
said capillary tube having a length and an internal diameter in accordance with the relationship ##EQU27## wherein L is the length of the capillary in meters,
R is the internal radius of the capillary in meters,
V.sub.f is the final sampled volume in cubic meters,
t is the time in seconds, and
K.sub.5 and K.sub.6 are constants for the system in which ##EQU28## wherein P.sub.atm is atmospheric pressure (Pa)
V is the molar volume (m.sup.3 /mole)
is the gas constant (N.m/mol.k)
T is the temperature (.degree. K.), and
V.sub.s is the volume of the vessel (m.sup.3),
so as to provide flow control of gas or ambient air at said outlet port.

10 more elements

Dependencies are inferred from the claim text.

Capillary sampling flow controller

Life of this patent

Capillary sampling flow controller

Life of this patent

Abstract

Claims17