Specifications

Guide to Selecting and Using Dymax UV Light-Curing Systems
Page 17
U
U
V
V
L
L
I
I
G
G
H
H
T
T
-
-
C
C
U
U
R
R
I
I
N
N
G
G
S
S
A
A
F
F
E
E
T
T
Y
Y
Dymax ultraviolet light-curing technology has been used
successfully for over 30 years. The fast cure, one-component
nature of our UV light-curing technology has made it the process of
choice for many manufacturers requiring a “Cure on Demand”
assembly process. There are three common questions/concerns
related to UV light-curing systems: UV exposure, ozone, and bright
visible light.
UV EXPOSURE
Standard Dymax UV light-curing systems and bulbs have been
designed to primarily emit UVA light
1
. UVA light is generally
considered the safest of the three UV ranges: UVA, UVB, and UVC.
Although OSHA does not currently regulate ultraviolet light exposure
in the workplace, the American Conference of Governmental
Industrial Hygienists (ACGIH) does recommend Threshold Limit
Values (TLVs) for ultraviolet light. The strictest interpretation of the
TLV (over the UVA range) for workers’ eyes and skin is 1 mW/cm
2
(intensity), continuous exposure. Unless workers are placing bare
hands into the curing area, it is unusual to exceed these limits. To
put 1 mW/cm
2
limit into perspective, cloudless summer days in
Connecticut regularly exceed 3 mW/cm
2
of UVA light and also
include the more dangerous UVB light (primarily responsible for sun
burns) as well.
The human eye can not detect “pure” UV light, only visible light. A
radiometer should be used to measure stray UV light to confirm the
safety of a UV light-curing process. A workstation that exposes an
operator to more than 1 mW/cm
2
of UVA continuously should be
redesigned. UV adhesive light curing can be a regulatory-compliant,
“worker-friendly” manufacturing process when the proper safety
equipment and operator training is utilized. There are two ways to
protect operators from UV exposure: Shield the operator and/or
shield the source.
SHIELDING THE OPERATOR
■ UV-Blocking Eye Protection – UV-blocking eye protection
is recommended when operating UV light-curing systems.
Both clear and tinted UV-blocking eye protection is available
from Dymax.
■ UV-Blocking Skin Protection – Where the potential exists
for UV exposure upon skin, opaque, UV-blocking clothing,
gloves, and full face shields are recommended.
SHIELDING THE SOURCE OF UV
Any substrate that blocks UV light can be used as a shield to
protect workers from stray UV light. The following materials can
be used to create simple shielding structures or blind corners:
■ Sheet Metal – Aluminum, steel, stainless steel, etc. Sheet
metal should be coated black or black anodized to minimize
reflection of UV and visible light.
■ Rigid Plastic Film – Transparent, UV-blocking plastics
(typically polycarbonate or acrylic) are commonly used to
create shielding where transparency is also desired. These
rigid plastic films are available either water-clear or tinted, (to
reduce visible light glare).
■ Flexible Film – UV-blocking, flexible urethane films can be
used to quickly create workstation shielding. This UV-blocking,
flexible urethane film is available from Dymax.
OZONE
Standard Dymax bulbs (UVA type) generate an insignificant amount
of UVC and therefore essentially no ozone
1
. Some UV light-curing
systems, like those used to cure UV inks, emit primarily “shortwave”
(UVB and UVC) energy. Upon exposure to UVC light (specifically
<240 nm), oxygen molecules (O
2
) split into oxygen atoms (O) and
recombine with O
2
to create Ozone (O
3
). The current, long-term
ozone concentration limit recommended by ACGIH, NIOSH, and
OSHA is 0.1 ppm (0.2mg/m
3
).
BRIGHT, VISIBLE LIGHT
The bright, visible light emitted by some UV light-curing systems may
be objectionable to some workers and may cause eyestrain. Tinted
eye protection and/or opaque/tinted shielding can be utilized to
address this concern.
SUMMARY
UV light sources can be more “worker friendly” than many commonly
accepted industrial processes, provided the potential concerns are
addressed. Contact your Dymax representative for information
regarding the proper use of Dymax UV light-curing systems.
1
Dymax also provides special order “shortwave” bulbs that emit primarily UVB
and UVC light. Contact Dymax directly for information regarding the use of
“shortwave” bulbs.
Tinted “Over the Eyeglasses” Eye
Protection 99.9% UV Blocking
PN 35285
Clear “Over the Eyeglasses” Eye
Protection 99.9% UV Blocking
PN 35284