Gems Sensors & Controls 144600 Instruction Bulletin
3.
Installation of Sensor Switch and Running of Field Wiring: (Cont)
Reference: Item D, previous page:
SAFE-PAK Model 144600
PIN 144600
GROUP CAPACITANCE INDUCTANCE
A & B 0.6 uf 1.3 mh
C, E 1.9 uf 5.4 mh
D,F,G 1.9 uf 10 mh
Example: Typical values of capacitance for a twisted pair of copper wires
is between 20 and 60 pf per foot. Using a maximum value of 60 pf/Ft,
groups A & B could have a run of 1500+ feet with safety. Inductance of a
typical twisted pair is between 0.10 and 0.20 uh/Ft, thus making a cable
run in this example essentially determined by the capacitance.
Important Points!
Product must be maintained and installed in strict accordance with the National Electrical Code and GEMS technical brochure and instruction bulletin. Failure to observe this warning could result in serious injuries or damages.
An appropriate explosion-proof enclosure or intrinsically safe interface device
must be used for hazardous area applications involving such things as (but not
limited to) ignitable mixtures, combustible dust and flammable materials.
Pressure and temperature limitations shown on individual catalog pages and
drawings for the specified GEMS products must not be exceeded. These pressures and temperatures take into consideration possible system surge pressures/temperatures and their frequencies.
Selection of materials for compatibility with the media is critical to the life and
operation of GEMS products. Take care in the proper selection of materials of
construction; particularly wetted materials.
Life expectancy of switch contacts varies with applications. Contact GEMS if
life cycle testing is required.
Ambient temperature changes do affect switch set points, since the specific
gravity of a liquid can vary with temperature.
GEMS products have been designed to resist shock and vibration; however,
shock and vibration should be minimized.
Liquid media containing particulate and/or debris should be filtered to ensure
proper operation of GEMS products.
Electrical entries and mounting points may require liquid/vapor sealing if located in an enclosed tank.
GEMS products must not be field repaired. Physical damaged sustained by
the product may render it unserviceable.
Instruction Bulletin
No. 121440
For use as “intrinsically safe switch connections” to non-voltage producing
sensors in the hazardous location. When the SAFE-PAK installation is in
accordance with this guide, these switch terminals are suitable for connection to Class I; Division 1,2; Groups A, B, C & D and Class II; Division 1, 2;
Groups E, F, G and Class III, as defined by Article 500 of the National Electric
Code.
IMPORTANT!
Read the following carefully and completely
before installing or connecting SAFE-PAK units:
*** Warning: To prevent ignition of flammable or combustible atmospheress,
disconnect power before servicing.
1. Associated Equipment - Caution: The SAFE-PAK must be mounted outside the
hazardous area. Only the switch or sensor terminals provide an intrinsically safe
switch circuit (see Fig. 1.) [Exia] means associated equipment: “Appareillage
connexe”; located in safe area.
Connection Diagram: Gems SAFE-PAK Models
Neutral
VAC
Hot
FUSE F1
Apparatus
Fig. 1.
LOAD
**
[Exia]
SAFE-PAK
Non-Hazardous
Location
Hazardous
Location
Simple
P/N 121440
Rev. J
Note: For 120V application, only one fuse is required in the ungrounded
circuit of the input line.
** Required torque on these terminals not to exceed 10 IN-LB on
stranded wire; 8 IN-LB on solid wire.
2. Mounting and Enclosure Considerations:
Field wiring of intrinsically safe circuits is to be segregated from non-
A.
intrinsically safe wiring by use of suitable barriers, separate wireways or
trays (See Fig. 2). Wire insulation to be .010", minimum.
Fig. 2.
Multiple Pak units Grouped on
Common Earth-Grounded Mounting Plate
Located in Non-Hazardous Area
Earth Ground
(2 Places)
Common
Earth Ground
Mounting Plate
Resistance to Gnd.
must be less than 1
ohm from mounting
screw or bracket to
earthing member to
insure integrity.
Non-Intrinsically
Safe Wiring
Fig. 3. Unit Mounting Detail
SAFE-PAK
* Note:
Lockwashers to be internal
or external tooth-type.
Mounting Plate
Mounting Plate Grounding Detail
Fig. 4.
Mounting Plate
* Lockwasher
Nut
* Lockwasher
Notes:
Installation of Sensor Switch and Running of Field Wiring:
3.
1. Grounding Hardware to be #8 or larger and Stainless Steel.
2. * Lockwashers to be internal or external tooth-type.
Screw
* Lockwasher
Nut
#10 Screw
* #10 Lockwasher
* #10 Lockwasher
#10 Nut
Terminal Lug
Intrinsically Safe
Wiring to Sensors
Located in Hazardous
Area
Note:
All intrinsically safe wiring must be segregated from non-intrinsically
safe wiring and shall have a minimum insulation thickness of .010”.
Intrinsically safe and non-intrinsically safe connection points should be
B.
located sufficiently apart to prevent any possibility of bypassing or miswiring
during installation or servicing of equipment.
The enclosure shall contain a cautionary statement as follows: “CAUTION:
C.
ANY SUBSTITUTION OF COMPONENTS MAY IMPAIR INTRINSIC
SAFETY”.
The PAK mounting bracket must be grounded to insure intrinsic safety.
D.
Resistance between bracket and ground electrode should be below one
ohm. (See Fig. 3 and Fig. 4 for recommended selection of grounding
hardware and refer to Article 250 of the National Electrical Code for methods
and practices.)
A. It is expected that the installation will be in accordance with Article 504 of the N.E.C.,
ANSI/NFPA 70 and/or C.E.C. Part 1*.
*Note: This is a CSA requirement. C.E.C. = Canadian Electrical Code.
B. The nature of the sensor switch must be that it is a non-voltage-producing, essentially
resitive device, containing no energy-storing components. (Simple Apparatus -flow
switches, level switches, pressure switches.)
C. The conductors of the intrinsically safe circuit should be sealed in a rigid metal conduit
at the point where the wiring enters the hazardous area. The wiring and contacting
device should be such that conductive dusts in the area will not close the circuit in
place of the contacts.
D. Hazardous area field wiring will store energy due to distributed capacitance and
inductance in proportion to its length. It is therefore recommended that the characteristics (available from the manufacturer) of the cable be known and judged against the
length of run and atmosphere of exposure. The conservative chart on the next page is
presented as a requirement in determining the limits of reactance for signal loops in
the hazardous area wiring for the SAFE-PAK series.
E. Whenever possible, the actual measured parameters should be used in making the
determination of allowable length.
F. Shielded cable is not required; but if used in the application, the shield must be returned
to ground - the same as the PAK mounting bracket.
G. Non-intrinsically safe wiring cannot be run in conduit or open raceways together with
intrinsically safe wiring.
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