Dwyer NSS - Manual

The Series NSS are self-contained rotation monitoring systems that are
ideal for detecting the unwanted slowdown of process equipment. These
systems bring efficiency and safety to your operations by preventing
machine damage, product waste and costly downtime. The non-contact
speed switch is commonly used to monitor drive trains, power-driven
components, crushers, exhaust fans, screw conveyors, or tail pulleys on
belt conveyors and elevators. The standard system includes either an
NSSM-series or an NSSP-series switch and a pulsar DISC.
Miniature speed switches contain a sensor and switching electronics in
either a heavy duty, explosion-proof cast aluminum housing (NSSM
series) or a chemical/corrosion resistant PVC housing (NSSP series).
Each switch is used with a shaft-end mounted pulsar DISC (or optional
split collar pulsar wrap) which generates an alternating magnetic field
that is picked up by the speed switch. The switch decodes this frequency
signal to determine shaft speed and compares this to the pre-adjusted
set point, easily calibrated via a single-turn potentiometer. In the event of
rotational failure, such as a broken drive, belt slippage, product overloads
or clogs, the relay can be used to provide an alarm or equipment
shutdown, assuring machine protection and process integrity. The
miniature speed switch series is fail-safe; any malfunction during
operation will de-energize the control circuit.
The primary difference between the NSSM/P and NSSM/P is the set
point range. The actual operating speed of the monitored shaft is not the
critical factor when selecting which model use, it is the desired set point
speed at which the relay is to energize and de-energize. The NSSM-A
and NSSP-A can be adjusted to trip from 10 to 100 rpm. The NSSM-B
and NSSP-B can be adjusted to trip from 100 to 5,000 rpm.
Principle of Operation:
The NSS-Series Switches contain a sensor and switching electronics
within the same housing. A pulsar disc, or an optional pulsar wrap,
rotating in front of the sensing surface produces a control signal which
increases with advancing shaft speed. When the control signal is above
the set point setting, the control relay is energized. When the control
signal drops blow the set point setting, the relay de-energizes. The relay
has Form C Dry contacts rated at 5 amps 115 Vac resistive, so the
NSSM may be used for switching motors and/or alarms.
Pulsar Disc:
The end of the shaft to be monitored must be center drilled to a depth of
1⁄2 inch with a No. 21 drill and tapped for 10-32 UNF. After applying
Loctite® or a similar adhesive on the threads to keep the pulsar disc
tight, the pulsar disc should be attached, decal side out, with the
supplied 10-32 UNF machine screw and lock washer.
Series NSS Non-Contact Speed Switch
Specifications - Installation and Operating Instructions
Bulletin L-32
SPECIFICATIONS
Temperature Limits: Operating -40 to 140ºF (-40 to 60ºC).
Enclosure: Cast aluminum. (NSSM); Polyvinylchloride (PVC) (NSSP).
Enclosure Rating: NSSM: Class I, Group D; Class II, Groups E, F, G;
Class III. NSSP: NEMA 4X.
Switch Type: SPDT.
Electrical Rating: 5A @ 115 VAC.
Electrical Connections: Terminal block.
Conduit Connections: 1˝ female NPT.
Power Requirements: 115 VAC, 60 Hz standard.
Input Signal Type: NPN Open Collector.
Set Point Adjustment: Single turn (270°) Potentiometer.
Gap Distance: 3/8˝ ± 1/8˝.
Pulsar Wrap (optional)
Pulsar Wraps are custom manufactured to fit the shaft they will be
mounted on. When the wrap is shipped, four allen-head cap screws hold
the two halves of the wrap together. These screws must be removed so
that the wrap is in two halves. Place the halves around the shaft, reinsert
the screws and torque them to 8 foot pounds.
Switch Selection Guide:
Refer to the Switch Selection Table, to determine which model is
appropriate for your application. The primary difference between the
NSSM/P and the NSSM/P is the set point range. The actual operating
speed of the monitored shaft can range from 10 to 5000 rpm with either
switch. The main criteria for selecting a speed switch is the speed at
which the relay energizes and de-energizes.
The NSSM/P can be adjusted to trip from 10 rpm to 100 rpm. The
NSSM/P can be adjusted to trip from 100 rpm to 5000 rpm.
Switch Selection Table:
PROXIMITY CONTROLS
Phone: 219/879-8000 www.dwyer-inst.com
A DIVISION OF DWYER INSTRUMENTS, INC. Fax: 219/872-9057 e-mail: [email protected]
P.O. BOX 373 • MICHIGAN CITY, INDIANA 46360, U.S.A.
NSS-A Shaft Speed Range
NSS-B Shaft Speed Range
NSS-A Adjustable Set Point Range 10-100 RPM
NSS-B Adjustable Set Point Range 100-5,000 RPM
3-1/8
(79.38)
2-1/8
(53.98)
1-25/32
(45.24)
6-1/4
(158.75)
Ш1-17/32
(Ш38.89)
4-9/32
(108.74)
2-3/8
(60.33)
3-3/8
(85.73)
5-17/32
(140.49)
1˝ NPT
M
NSSP NSSM
NSSP NSSM