Specifications and Ordering Information
Part Number 141500-01
Rev. J (06/07)
Page 1 of 6
3300/20 Dual Thrust Position Monitor
BUFFER ED TR ANSD UCER S
DANG ER
A
GA P
ALERT
B
BYPASS
ALERT
DANG ER
A
B
OK
3300/20
DUAL THRUST
D
D
12
4
R
N
T
0
25
20
S
P
A
C
E
M
E
L
15
10
U
N
T
E
C
O
8
5
I
0
R
N
25
20
T
A
10
15
U
E
N
T
O
C
M
E
E
C
0
5
S
L
P
I
MONITOR
vdc
16
N
20
M
S
L
I
/
5
10
15
M
O
R
20
25
24
20
N
10
5
L
/
S
I
M
15
M
R
O
25
Description
The 3300/20 Dual Thrust Position Monitor provides early warning of thrust
bearing failure. It continuously measures and monitors two independent
channels of shaft axial position relative to the axial clearances within the
machine. Ideally, the axial probes are installed to observe the thrust collar
directly, so the measurement represents the position of the collar relative to the
thrust bearing clearance.
Caution
Because thrust measurements are made by observing the gap voltage of the
proximity probe used as an input, a transducer failure (gap out of range) can be
interpreted by the monitor as thrust position movement and result in a false
thrust alarm. For this reason, Bently Nevada LLC. does not recommend the use
of a single probe for thrust position applications. Instead, these applications
should use two proximity probes observing the same collar or shaft and
configure the monitor as AND voting whereby both transducers must
simultaneously reach or exceed their alarm setpoints for the monitor’s alarm
relays to actuate. This 2-out-of-2 voting scheme (also known as AND voting)
provides optimum protection against both false trips and missed trips. While the
3300/20 monitor can be programmed for either single voting (OR) or dual voting
(AND), dual voting is strongly recommended for all thrust position applications.
Caution
Probe adjustment and range is critical in this monitor for machinery protection.
Improper adjustment of the transducer may prevent the monitor from alarming
(no machinery protection). For proper adjustment, follow instructions in the
manual.
