Malvern Instruments Spraytec, User Manual

Page: 68 / 221

Particle size range
Check that the lens used is suitable for the particle size range. The lens ranges are:
.
300 mm lens: 0.1 - 900
m
m. Dv(50): 0.5 - 600
m
m.
.
750 mm lens: 2 - 2000
m
m. Dv(50): 5 - 1600
m
m.
If the Dv(50) is close to the limits given above, the measurement resolution may
be affected.
Extraction
Extraction is used to draw the spray through the measurement zone. The reasons
for using this, in order of importance, are:
.
To protect the user from sprays.
#
Warning!
.
To ensure that the spray passes through the measurement zone at a con-
stant velocity.
.
To prevent rain-down . This occurs when a spray is sprayed vertically up-
wards; the coarser particles may fall back down through the measurement
zone, introducing bias to the results. This affects nasal sprays especially and
may cause
vignetting ; Chapter 6 has details.
Follow these guidelines:
.
Always extract the spray in the direction the spray is moving in, not at an
angle to the spray direction.
.
Do not use extraction in such a way that it changes the plume geometry in a
way that changes the particle size distribution.
Setting up an actuator
The Spraytec Accessories manual gives full details of the Spraytec NSS. The
actuator manufacturer’s documentation describes the setup of the actuator itself.
C H A P T E R 5
S p r a y t e c
P a g e 5 . 4
M A N 0 3 6 8
Extraction must be used with any material which may harm the
test personnel
.