ST-35 Overfill Prevention Control Unit

Multiple-Point, Optic-Sensing Overfill Prevention Control Unit

  • Interfaces with five-wire optic sensors
  • Used, typically for bottom and top-loading of tank vehicles
  • Mounted at the loading rack/gantry and connects to the vehicle via the Scully plug and cable assembly (sold separately).
  • Features Dynacheck® circuitry for automatic and continuous self-checking of all system components
  • For vehicle ground/earth verification options, consult Scully for information on the Groundhog Self-Proving Grounding System.

  • ST-35 models monitor 1 to 8 compartment vehicles. ST-35C models monitor 1- to 12-compartment vehicles.
  • Signals for automatic shut off of product flow within a half-second of detecting a potential overfill condition.
  • Complete compatibility with Scully five-wire optic sensors, IntelliCheck® and Load Anywhere® onboard tank vehicle mounted overfill prevention systems.
  • Will not permit loading under any fault or wet sensor condition.

The ordering information below is for FM and FMC approved units. For International ATEX and SIL approved models see:



Part NumberModel NumberDescription
07901ST-35-115-ELMulti-Point Optic Overfill Prevention Control, explosion-proof housing w/ lamps
07903ST-35-115-ELKMulti-Point Optic Overfill Control, indicator lamps and bypass control (115 VAC)
07931ST-35-240-ELKMulti-Point Optic Overfill Control, indicator lamps an bypass control (240 VAC)


Part NumberModel NumberDescription
08161SC-6AOSculcon® Junction Box Kit, Blue Plug, Blue Coil Cable, 30′
08160SC-6AOSculcon Junction Box Kit, Blue Plug, Blue Straight Cable, 20′
08159SC-6WSculcon Junction Box Kit, Blue Plug, Blue Coil Cable, 30′
08139SC-6WSculcon Junction Box Kit, Blue Plug, Blue Straight Cable, 20′


Part NumberDescription
08808Module Assembly- ST-35-115 Multi-Point Optic Controller
07923Module Assembly- ST-35-240 Multi-Point Optic Controller

Temperature Range:-40° to +140° F (-40° to +60° C)
Weight:28 lbs. (12.7 kgs.)
Response Time:0.5 seconds maximum
Approvals:ST-35: FM for use in Class 1, Division 1, Group D hazardous locations
Power Requirements:100–130 VAC, 50/60 Hz, 20 W max, 200–250 VAC, 50/60 Hz, 20 W max
Connections:Provided by internal terminal strips
Output Relay:One normally open volt-free contact, rated 250 VAC 5A Resistive; energized when the sensors are dry
Output Control Fuse:Internal 5 Ampere
Housing Options:Consult Scully for optional epoxy painted housings for corrosive atmospheres

NOTE: For maximum safety, use only in conjunction with sensors manufactured by Scully to not jeopardize the conditions of these approvals.

Scully Signal