Riken Keiki DC-3A Slop Indicator

RIKEN KEIKI SLOPE / SLOP INDICATOR DC-3A

The Riken Keiki DC-3A Slop Indicator (Part/Model Identifier: M-73) is a Marine Grade Water Level Surface Detector used to monitor the oil water interface and verify Slop Tank levels on commercial ocean going vessels, chemical tankers and offshore installations. The DC-3A is used to accurately track liquid boundary levels in the engine room automation and cargo monitoring systems during de-slugging, tank wash operations and discharge processes in accordance with MARPOL Annex I rules.

The equipment is constructed with rugged Japanese industrial parts and features an electrode white-tape sensing assembly that offers high-precision conductivity or surface detection signals to marine warning panels. With a durable casing and IP-rated design, it’s resistant to harsh sea-spray situations, corrosive petroleum fumes and constant hull vibration.

Model Details

• Primary Model: DC-3A
• Manufacturer Part Number (MPN): M-73
• OEM Brand Partner: Sato Parts / Riken Keiki Co., Ltd.
• Type Approval / Test Number: ClassNK Type Test No. 8IT639
• Internal Reference ID: 79786

Key Features

1. Nippon Kaiji Kyokai (ClassNK) Certified: Full compliance with international maritime safety protocols and classification society standards.
2. High-Precision Surface Detection: White tape electrode assembly provides accurate boundary detection between oil layers and decanted slop water.
3. Heavy-Duty Galvanic Isolation: Eliminates nuisance tripping caused by static charges or wandering earth faults in tank piping.
4. Corrosion-Resistant Japanese Engineering: Built with high-grade marine alloys and specialized synthetic polymers to survive petroleum hydrocarbon vapors.
5. Plug-and-Play Marine Retrofit: Standard terminal spacing allows seamless integration into existing Riken Keiki ODME and slope monitoring cabinets.

System Applications

• Oil Discharge Monitoring Equipment (ODME): Works as a dedicated sensor or interface check unit within MARPOL discharge lines.
• Slop & Decanting Tank Monitoring: Prevents accidental overboard oil discharge during slop decanting on crude oil carriers (VLCC/ULCC) and product tankers.
• Bilge Water Separator Alarm Loops: Secondary check unit for oil-water separators (OWS) prior to bilge overboard discharge.
• Offshore FPSO Cargo Tanks: Liquid interface detection in offshore oil production and storage units.

Marine Equipment Compatibility

The Riken Keiki DC-3A / M-73 is compatible with the following systems and shipboard infrastructure:

• Riken Keiki ODME Series: Direct replacement unit for older and current generation Riken Keiki oil discharge monitoring panels.
• Sato Parts Terminal Interfaces: Standardized pinouts for Sato Parts marine terminal rails.
• Standard Marine Alarm Monitoring Systems (AMS): Reads seamlessly into 24V DC discrete digital input channels across KONGSBERG, Wärtsilä, Yokogawa, and SAM Electronics monitoring suites.

Pro Tips from a Marine Automation Engineer

1) Insulation Resistance (Megger Test) Warning:

Prior to landing field cables on the DC-3A terminal strip, disconnect the DC-3A completely before running a 500V/1000V megger test on the field wiring. High-voltage megger testing directly across the unit’s internal detection circuits will destroy the solid-state components.

2) White Tape & Electrode Care:

Slop oil residue can build up an insulating film over the white tape sensor surface, causing false “no-water” or erroneous level alarms. During routine dry-dock or pre-discharge checks, wipe down the sensing head using a non-aggressive solvent (like isopropyl alcohol or approved electrical contact cleaner). Avoid abrasive wire brushes that scratch the sensing surface.

3) Shield Grounding Protocols:

To prevent electromagnetic interference (EMI) from shipboard variable frequency drives (VFDs) and high-power cargo pumps, ensure the cable shield is grounded at the control panel end only. Floating or double-grounded shields introduce ground loops that affect signal accuracy.

Frequently Asked Questions

What is the primary function of the Riken Keiki DC-3A in a marine cargo system?

The DC-3A acts as a slop tank water-level and oil-water interface indicator. It detects the precise boundary layer between water and oil during decanting operations to ensure compliance with international maritime environmental laws (MARPOL).

Is the Riken Keiki DC-3A interchangeable with the M-73 part number?

Yes. The model number is DC-3A, and its official manufacturer/part identifier is M-73. They refer to the exact same physical component manufactured by Riken Keiki / Sato Parts.

Which marine class society approves the DC-3A Slop Indicator?

The DC-3A holds ClassNK (Nippon Kaiji Kyokai) approval under Type Test Certificate Number 8IT639.

Can this unit be used in hazardous gas areas aboard chemical or oil tankers?

Yes, provided it is installed in conjunction with the appropriate intrinsically safe (IS) zener barrier or galvanically isolated amplifier as specified in the original Riken Keiki system manual.

What are the primary signs of a failing DC-3A indicator unit?

Common indicators include erratic level alarms on the ODME main panel, continuous open-circuit fault indication, or failure of the internal conductivity loop to respond when submerged in seawater during routine maintenance testing.