T20 & T21
Top mounting
Liquid level switches
®
INSTRUCTION MANUAL AND REPLACEMENT PARTS
AGENCY APPROVALS
DESCRIPTION
T20 and T21 units are simple, reliable fl
oat switches
designed for top mounting to tanks or vessels. T20 units
utilize a single switch mechanism and float. T21 tandem
units utilize two switch mechanisms and two separate
floats when widely spaced actuating levels are required.
T20 and T21 tandem models are available for any type of
open or closed vessel with either threaded or flanged type
mounting and actuating depths up to 1219 mm (48 inches)
OPERA
TING PRINCIPLE
A permanent magnet
①
is attached to a pivoted switch
actuator
②
. As the fl
oat/ displacer
③
rises following the liq
-
uid level, it raises the attraction sleeve
④
into the fi
eld of
the magnet, which then snaps against the non-magnetic
enclosing tube
⑤
, actuating the switch. The enclosing tube
provides a static pressure boundary between the switch
mechanism and the process. On a falling level, an inconel
spring retracts the magnet, deactivating the switch.
②
⑤
④
③
①
pivot
return spring
rising level
falling level
UNP
ACKING
Unpack the instrument carefully
. Inspect all units for dam-
age. Report any concealed damage to carrier within 24
hours. Check the contents of the packing slip and purchase
order. Check and record the serial number for future refer-
ence when ordering parts.
Agency
Approval
ATEX
II
2G EEx d
II
C T6, explosion proof
II
1G EEx ia
II
C T6, intrinsically safe
CENELEC
EEx d
II
C T6, explosion proof
CCE
➀
R1 (1) 136/MI/433, explosion proof
FM
Class
I
, Div. 1,
Groups C & D
Class
II
, Div. 1,
Groups E, F & G, Type NEMA 7/9
FM/CSA
➁
Non-Hazardous area
Explosion proof area –
Groups B, C, D, E, F & G Type NEMA 4X/7/9
SAA
➁
Explosion proof area
LRS
Lloyds Register of Shipment (marine applications)
GOST/
Russian Authorisation Standards
GOSGORTECHNADZOR
➁
Other approvals are available, consult factory for more details
➀
For CCE approved units, use the A
TEX explosion proof model
numbers.
➁
Consult factory for proper model numbers.
