Campbell Scientific PVS4100/4120/4150 Portable Automatic Samplers - Manual (Page 24)

Section 1. Product Overview
1-16
TABLE 1-12. Horizontal Velocity
25’ 50’ 75’ 100’ 175’ 200’ 250’ Distance
3/8” ID Large pump
(BVS 4300, CVS 4200, PVS4100)
7.1 6.2 5.6 5.0 4.0 3.7 2.6 Ft/sec
3/8" ID Small pump
(PVS4120, PVS4150)
5.1 4.7 4.2 4.1 3.4 3.1 2.3
5/8" ID Large pump 5.0 4.7 4.3 4.2 3.7 3.3 2.4
1.3.8.1 Using Velocity to Calculate Purge Time
Purge time of the sampler needs to be programmed based on the length of hose
and the velocity at which the liquid will travel through the hose. The formula is
l / v = p (length / velocity = min. purge time). Adding a few second to the
purge time is recommended to ensure the line is fully cleared of any
obstructions.
Example: 100 ft of hose, at 5 ft/sec, requires a minimum 20 second purge time.
100 / 5 = 20 seconds. The number input for purge time should be a minimum
of 20, but preferably 24.
Standard purge time for 25 ft of intake tube is 10 seconds. Although a standard
25 ft hose will sample in less than 4 seconds, 10 seconds is the minimum
recommended for proper clearing of the line.
1.3.8.2 Horizontal/Vertical Combinations
The velocity charts above measure only horizontal or only vertical. Most
applications will have combinations of both. With 200 feet of intake tubing,
PVS Samplers are capable of drawing a sample above 2 ft/sec at 20 feet of
vertical. At 23 feet of vertical with 200 feet of intake tubing, sampling may or
may not be successful, depending on altitude and other factors. For more