ZT-610 Interface Detector
Capacitance-based oil-water interface and transition sensing
Detect Oil-Water Transitions in Real Time
The ZT-610 Interface Detector is a capacitance-based probe designed to sense the transition between oil and water phases inside tanks, vessels, and drain lines. It measures the dielectric properties of the fluid in contact with its sensing element and outputs a continuous signal proportional to the water content at the measurement point.
Where a conventional level switch gives a simple on/off signal, the ZT-610 provides a graduated reading across the full oil-water transition zone. This allows control systems to distinguish between dry oil, wet oil, emulsion layers, and free water with a single instrument.
The ZT-610 is the core sensing component of the ZT-620 Tank Dewatering System, which pairs two ZT-610 probes with task-specific control software to automate the entire dewatering cycle.
Measurement Principle
Capacitance Sensing
The probe measures the dielectric constant of the fluid between its electrodes. Oil and water have very different dielectric values (oil ~2, water ~80), producing a large and reliable signal change at the interface.
Continuous Output
Unlike a float switch or guided wave radar, the ZT-610 outputs a continuous 4-20mA signal proportional to water content at the sensing point, giving visibility into the transition zone.
Fast Response
Sub-second response time allows the ZT-610 to track rapid phase changes during drain operations, separator upsets, or slug flow events.
Set Point Control
Configurable high and low water cut thresholds drive relay outputs or valve commands. Set points are adjustable to match the specific process requirements.
Key Features
Graduated Interface Reading
Continuous 4-20mA output across the oil-water transition, not just an on/off contact closure. Provides visibility into emulsion layers and rag bands.
Compact Probe Design
Threaded or flanged process connections from 1" to 4". The probe body is short enough for side-entry tank nozzles and drain line tees.
Hazardous Area Certified
ATEX and IECEx certified for Zone 1 and Zone 2. Intrinsically safe or flameproof housing options.
No Moving Parts
Solid-state capacitance sensing with no floats, displacers, or mechanical linkages. Nothing to stick, corrode, or foul.
Temperature Compensated
Built-in temperature measurement compensates for dielectric changes caused by process temperature variations.
Simple Integration
4-20mA output with HART or Modbus RTU. Two configurable relay outputs for high/low set point control.
Specifications
| Measurement Principle | Capacitance-based dielectric measurement |
| Measurement Range | 0 – 100% water cut |
| Accuracy | ±1% of reading (interface detection mode) |
| Response Time | <1 second |
| Output | 4-20mA + HART / Modbus RTU (RS-485) |
| Relay Outputs | 2x configurable (SPDT), rated 5A @ 250VAC |
| Process Connection | 1" to 4" NPT/BSP threaded or flanged |
| Pressure Rating | Up to ANSI 600# (100 barg) |
| Wetted Materials | 316L stainless steel, Hastelloy C-276 optional |
| Power Supply | 24V DC (loop powered or 4-wire) |
| Hazardous Area | ATEX / IECEx Zone 1 & 2 (Ex d IIB T4 or Ex ia IIC T4) |
| Operating Temperature | -40°C to +120°C |
| Ingress Protection | IP66 / IP67 |
Part of the ZT-620 System
The ZT-620 Tank Dewatering System uses two ZT-610 Interface Detectors working together with task-specific software to fully automate the dewatering cycle:
- Probe 1 (drain outlet): Monitors the fluid at the tank drain nozzle. When water is detected, the system opens the drain valve.
- Probe 2 (drain line): Monitors the fluid downstream of the drain valve. When oil appears, the system closes the valve to prevent carry-over.
Each ZT-610 can also be used independently for interface detection in separators, wash tanks, desalters, and other vessels where knowing the oil-water boundary position matters.
Applications
Tank Dewatering
Core sensor for ZT-620 automatic dewatering systems. Detects the oil-water interface at tank drain nozzles to control motorised drain valves.
Separator Interface
Monitor oil-water interface level inside gravity separators, heater treaters, and free water knockouts to control water dump valves.
Desalter Monitoring
Track the interface in electrostatic desalters to optimise wash water injection and maintain separation efficiency.
Slop Oil Processing
Detect oil-water transitions during slop oil treatment to separate recovered oil from waste water streams.
Need Interface Detection?
Whether you need a standalone interface detector or a complete automated dewatering system, we can configure a solution for your application.
