ST-35C - Technical Manual
General
Page 6.
1.1.5 Indicator Light on Control Module
An internal red LED light is provided on the control module for convenience in checking the output
status when the cover is open. The light is ON when power is applied and dry and functional
sensors are connected to the unit. Thus, the internal light is ON when external green light is ON.
1.2 Technical Specications
Degree of protection of enclosure IP65. The rating of the enclosure is negated if the holes in the
enclosure are unplugged/unscrewed or any holes are drilled into the enclosure.
The ST-35C control unit has been designed to be impact-resistant. Do not subject to excessive
mechanical or thermal stresses. Do not allow the unit to come in contact with aggressive
substances that may degrade the integrity of the enclosure.
The ST-35C may only be repaired by replacing the internal control module. The internal control
module is non-repairable.
Do not open when an explosive gas atmosphere is present.
Temperature Range -20°C to +60°C
Power Requirements 120VAC Models: 100 – 130 VAC, 50/60 Hz, 20VA Max.*
240VAC Models: 200 – 250 VAC, 50/60 Hz, 20VA Max.*
*20VA does not include circuits controlled by the output relay contact
Sensors: Up to 12 of Scully’s 5-wire optic sensors, Model SP-FU series.
Output Relay: One normally open volt-free contact rated 250VAC, 5A resistive max.
The output contact closes when all sensors are dry and functional.
Response Time: 0.5 second maximum
Indicator Lights: Output status indicator lights:
Red: Non-permissive
Green: Permissive
Output Control Fuse: Internal 5 Ampere
Connections: Provided by internal terminal strips.
Enclosure: Explosion-proof, weatherproof IP65.
Dimensions: See Appendix 4.1 for outline drawing.
Weight: 12.7 Kg (28 Lbs.)
Approvals: Baseefa02ATEX0047 Ex db [iaGa] mb IIB T5 Gb Ta=-40°c to +60°c
or Ex db mb [ia Ga] IIB T6 Gb
The enclosure contains associated electrical apparatus to
Baseefa02ATEX0148U [Ex ia] IIB (Tamb-40°C to +70°C) Gb
The ST-35C Control Unit is used for overll prevention at loading terminals. In most tank truck
loading applications, volume to be loaded into each compartment is pre-set via a pre-set meter.
Under normal conditions the pre-set meter shuts down the loading after the pre-set volume is
loaded. The liquid does not reach the overll sensor as it is set at a level higher than the rated
capacity of each compartment. However, if the liquid level goes above the rated capacity of a
compartment, Scully’s ST-35C Overll Prevention system detects this overll condition and shuts
down the loading. Thus, it acts as a secondary (emergency) shutdown system, primary shutdown
control being provided by the pre-set meter.
The ST-35C Overll prevention Control Unit interfaces with 5-wire optic sensors. It is typically used
for overll prevention on bottom loading or top loading vehicles. It can monitor multiple sensors
(i.e. multi-compartment vehicles). It is mounted at the loading rack/gantry and connects to the
vehicle via a Scully plug and cable assembly.
The system incorporates Scully’s unique and exclusive Dynacheck® concept. To ensure that it will
always detect an overll condition, the controller uses pulsed signals which continuously check the
entire system operation including the controller, wiring connections and sensors. If a sensor comes
in contact with liquid, or in the unlikely event of a system fault, the pulsed signals cease, and the
controller automatically signals for immediate shutdown of the loading operation.
The ST-35C uses intrinsically safe voltage and current to connect to Scully liquid level sensors and
provides control for external electrical devices by opening and closing relay contacts.
Scully loading rack overll protection monitors have been carefully engineered to provide reliable
and safe performance when installed in conjunction with related Scully equipment according to the
instructions in this manual. Adaptations of, and additions to this equipment such as the use of
multiple cables and plugs, loading arm position indicating switches, enclosure heaters and similar
peripheral devices may void warranties unless authorized in writing by Scully Signal Company.
Please contact Scully prior to performing any installation or maintenance not specically described
in this manual.
1.1 Description
The ST-35C is for use with Scully 5-Wire Optic Sensors, Model SP-FU series. It can monitor up to
twelve (12) of these sensors in a “series” signal path. If any one of the connected sensors senses
liquid, the ST-35C will respond to this “wet” condition; output relay contact opens, and red light
turns on. Although its typical application is monitoring of sensors mounted on multi-compartment
vehicles, it is also used for high level detection in storage tanks (tank farms). One relay output
contact is provided, which opens if any sensor detects liquid.
ST-35C is also used with vehicles equipped with Scully’s IntelliCheck® series or ONBOARD Overll
Prevention Monitors. It interfaces with 5-wire optic socket on these vehicles. The ST-35C Control
Unit has an explosion proof enclosure for mounting in locations that are classied as hazardous.
