Rosemount Level Switch 2120

Detailed Product Description

Easy terminal access, polarity insensitive and
short circuit protection
No moving parts or crevices means virtually
no maintenance
Electronic, self-checking and condition
monitoring - Heartbeat LED gives status and
health information
Adjustable Switching Delay for
turbulent/splashing applications
Magnetic test point makes functional test easy
Small in size and weight
Fast Drip Fork Design gives quicker
response time especially with viscous liquids
Explosion/Flameproof and Intrinsically
Safe options
SIL 2 of IEC 61508
DIBt/WHG overfill protection
MEASUREMENT PRINCIPLE
The Rosemount 2120 is a liquid point level switch
designed using the principle of a tuning fork. A
piezo-electric crystal is used to oscillate the forks at
their natural frequency. Changes to this frequency
are continuously monitored. When the 2120 is used
as a low alarm, the liquid in the vessel drains down
past the fork, resulting in a change of natural
frequency; this is detected by the electronics which
switch the output state. When used as a high alarm,
the liquid rises in the vessel, makes contact with the
fork and again the output switches.
Short Fork Technology
The natural frequency (~1300Hz) of the fork has
been chosen to avoid interference from plant
vibration which may cause false switching. This
allows for minimum intrusion into the vessel or pipe
through the use of a short fork. Using Short Fork
Technology, the Rosemount 2120 is designed for use
in virtually all liquid applications. Extensive research
has maximized the operational effectiveness of the
fork design making it suitable for almost all liquids,
including coating liquids (avoid bridging of forks),
aerated liquids, and slurries.
SPECIAL FEATURES
Mode Switch/Adjustable Time Delay
A mode switch allows the 2120 to be set to switch
from wet to dry (typically low alarm) or from dry to
wet (typically high alarm). There is also a user
selectable time delay from 0.3, 1, 3, 10, or 30
seconds. Increasing the time delay in turbulent or
splashing applications virtually eliminates the risk of
false switching.
Heartbeat LED
The Rosemount 2120 has a status indicating
heartbeat LED which can be seen at all times and
from all angles through a lens in the cover (no lens in
metal housings). The LED will flash when the 2120 is
off and will be constantly lit when it is on. The LED
gives constant indication that the 2120 is functioning
correctly (different flash rates are used to indicate
product malfunction) and gives local indication of the
process state.
Magnetic Test Point
A magnetic test point is located on the side of the
housing, allowing the user to perform a functional
test of the 2120 and the system connected to it. By
holding a magnet to the target, the 2120 output will
change state for as long as the magnet is held.
Electrical Hookup
The terminal blocks extend above the housing and
give easy terminal access. The polarity insensitivity
and short circuit protection make electrical hook-up
safe and easy.
Fork Design
The fast drip fork design (liquid is drawn away from
the fork tips) together with a short switching delay
allow the 2120 to react more quickly and have
greater sensitivity to density variations.
Overfill Protection
Spillage caused by overfilling can be hazardous to people and the environment,
resulting in lost product and potentially high clean up costs. The 2120 is a limit
level switch used to signal overfill at any time. The 2120 is available with
DIBt/WHG overfill protection approval.
Limit Detection
Batch processing tanks often contain stirrers/agitators to ensure mixing and
product fluidity. The standard user selectable time delay ranging from 0.3 to 30
seconds virtually eliminates the risk of false switching due to splashing caused
by stirrers/agitators.
Pipe Installation (Pump Protection)
Short forks mean minimum intrusion wetside and allow simple low cost
installation at any angle into your pipes or vessels. With the fork projecting only
2-in. (50 mm) (dependant on connection type), the 2120 can be installed in
even small diameter pipes. By selecting the option of direct load switching
electronics, the 2120 is ideal for reliable pump control and can be used to
protect against pumps running dry.
High and Low Level Alarm
Maximum and minimum level detection in tanks containing many different types
of liquids are ideal applications for the 2120. The robust 2120 operates
continuously at temperatures up to 302°F (150°C) and operating pressures up
to 1450 psig (100 barg) making it perfect for use as a high or low level alarm. It
is common practice to fit an independent high level alarm switch as a backup
device to any other level device installed in case of primary device failure.
Hygienic Applications
With the option of highly polished forks providing a surface finish (Ra) better
than 0.8μm, the 2120 meets the principle design criteria of the most stringent
hygienic requirements used in food and beverage, and pharmaceutical
applications. Manufactured in stainless steel the 2120 is robust enough to
easily withstand steam cleaning (CIP) routines at temperatures up to 302°F
(150°C).
Tank Connection and Fork
Fork Length
Short fork for minimum intrusion installation
(minimum 2-in. [50 mm]) or fork extensions up to
118-in. (3m) are available. See Dimensional
Drawings on page 10.
Threaded Connection
Threads: R 3/4-in. and 1-in. (BSPT); G 3/4-in. and
1-in. (BSPP); 3/4-in. and 1-in. NPT
Material: 316L SST, Hastelloy C
Accessories: A stainless steel adjustable clamp
gland is available for use with extended length
2120 (1-in. models only). This is threaded 11/2-in.
BSPP for connection to the vessel, and allows the
1-in. extended length 2120 to be raised or
lowered as desired then clamped in position. See
Spare Parts and Accessories on page 16.
Flanged Connections
Flange: ANSI B16.5 (1.5-in. or larger), BS4504
(DN40 or larger)
Material: 316L SST, Halar/PFA coated,
other on request
Hygienic Connections
Fittings: 1.5-in. (38 mm) or 2-in. (51 mm)
Tri-Clamp, 1-in. BSPP (G) O-ring seal, or other on
request
Material: 316L SST
Options: Hand polished wetside to a finish better
than 0.8μm meets the principle design criteria of
the most stringent hygienic requirements.
Accessories: A mounting kit comprising vessel
fitting, Nitrile seal and clamp ring is available for
use with 2-in. (51 mm) Tri-Clamp 2120. A fitting
boss with Fluorocarbon (FPM/FKM) O-ring is
available for use with O-ring seal 2120.