Riken Keiki SD-1, compact fixed gas detector
Sottotitolo
Divisions: Fire and Gas
Product Description
The SD-1 series detects combustible gases, hydrogen sulphide, carbon monoxide and oxygen in hazardous areas. It weighs about 2 kilograms and takes up 148 × 167 mm on the wall.
It is the choice for standard installations, where weight and footprint matter and the gas is among those covered by the six available models. For harsher environments or gases outside the list, the answer is the SD-3 series.
At a glance
| Detected gases | Combustible, hydrogen sulphide, carbon monoxide, oxygen |
| Measuring principles | Catalytic combustion, new ceramic, non-dispersive infrared, semiconductor, electrochemical, galvanic cell |
| Weight and size | From 2.0 to 2.5 kg, 148 mm wide |
| Protection | IP65 equivalent, flameproof enclosure |
| Output | 3-wire 4-20 mA, power and signal on the same cable; HART 7 on specific versions |
| Certifications | ATEX, IECEx, Japan Ex, MED on specific models, CE marking, SIL2 according to IEC 61508 on SD-1RI, SD-1EC and SD-1OX |
| Hydrogen and acetylene | Suitable for atmospheres containing hydrogen and acetylene thanks to the explosion-proof enclosure |
Key features
Three wires instead of four
Transmission is 4-20 mA analogue over three conductors, with power and signal sharing the same cable.
On a plant with many detection points this means less cable laid and fewer terminals to wire, for the same function.
Compact, yet flameproof
The enclosure is explosion-proof, with IP65 equivalent protection and a weight of about 2 kilograms.
Riken Keiki declares it suitable for atmospheres containing hydrogen and acetylene, the most critical gases for the integrity of a flameproof enclosure.
Self-diagnostics with error code
When there are no faults, the display shows the concentration. In case of a fault it shows an error code identifying the probable cause. The fault LED is yellow, the gas alarm LED is red.
The technician who goes to check knows what to look for before opening the instrument.
Aspiration detection too
By fitting the aspiration cap to the sensor, the instrument can work by aspiration instead of diffusion. A separate pump and aspirator are required, in addition to the power supply.
HART over the analogue line
On the enabled versions, the instrument transmits digital data over the same 4-20 mA line. The HART option must be specified when ordering.
Typical applications
- Basic refineries and petrochemical plants
- Technical and service tunnels
- Construction sites and temporary installations
- Ships and offshore installations, for MED-certified models
- Plant rooms and confined spaces, for oxygen monitoring
Available models
| Model | Measuring principle | Detected gas |
|---|---|---|
| SD-1 TYPE GP | Catalytic combustion | Combustible gases |
| SD-1 TYPE NC | New ceramic | Combustible gases |
| SD-1RI | Non-dispersive infrared | Combustible gases |
| SD-1GH | Semiconductor | Combustible and toxic |
| SD-1EC | Electrochemical | Hydrogen sulphide and carbon monoxide |
| SD-1OX | Galvanic cell | Oxygen |
How to choose
- Combustible gas in a normal atmosphere: SD-1 TYPE GP, catalytic, the standard solution
- Combustible gas without oxygen or with risk of sensor poisoning: SD-1RI, infrared, which needs no oxygen to measure
- Combustible and toxic gases at the same point: SD-1GH
- Hydrogen sulphide or carbon monoxide: SD-1EC
- Oxygen deficiency: SD-1OX
Available accessories
| Accessory | Function |
|---|---|
| Sun shield for wall or pole | Reduces body heating from solar radiation |
| Protective cover | Protects the instrument body |
| Display cover | Sun shield for the display area |
| Solvent-resistant cover | Protects the display from solvents |
| Calibration adapter | Allows field calibration |
| U-bolt kit | Mounting on 2B pole |
| Round splash guard | Protects the sensor; available on SD-1, SD-1RI and SD-1GH |
| Aspiration cap | Enables aspiration detection; requires pump and aspirator |
Specifications by model
| Model | Range | Setpoint | Temperature (ATEX/IECEx) | Consumption | Dimensions W × H × D | Weight |
|---|---|---|---|---|---|---|
| SD-1 TYPE GP | 0-100 %LEL | 25 %LEL standard | -20 / +60 °C | 3 W | 148 × 167 × 88 mm | 2.0 kg |
| SD-1 TYPE NC | Depends on gas | Depends on gas | -20 / +60 °C | 3 W | 148 × 167 × 88 mm | 2.0 kg |
| SD-1RI | 0-100 %LEL | 25 %LEL standard | -20 / +60 °C | 2 W | 148 × 167 × 88 mm | 2.0 kg |
| SD-1GH | Depends on gas | Depends on gas | -20 / +60 °C | 3.1 W | 148 × 167 × 88 mm | 2.0 kg |
| SD-1EC | H2S 0-30 ppm; CO 0-75 ppm | Depends on gas | -10 / +40 °C | 1.1 W | 148 × 203 × 88 mm | 2.2 kg |
| SD-1OX | 0-25.0 vol% | 18.0 vol% | -10 / +40 °C | 1.1 W | 148 × 208 × 88 mm | 2.5 kg |
Humidity up to 95% RH non-condensing; from 30 to 80% RH on the SD-1EC. Under Japan Ex certification the maximum temperature drops to +53 °C. Dimensions exclude protrusions.
Common specifications
| Detection method | Diffusion; aspiration with accessory |
| Transmission | 3-wire analogue, 4-20 mA DC, shared cable for power and signal |
| Communication | HART 7 on specific versions, to be specified when ordering |
| Display | 4-digit 7-segment LED |
| Gas alarm | Red ALM LED |
| Fault alarm | Yellow FAULT LED with error code |
| Alarm accuracy | Within ±25% of setpoint for combustibles, ±30% for toxics |
| Alarm delay | Within 30 seconds of reaching 1.6 times the setpoint |
| Enclosure | Explosion-proof, flameproof |
| Protection | IP65 equivalent |
| Power supply | 24 V DC ±10% |
| Self-diagnostics | At power-on, with error code on display |
Explosion protection classes
| Model | ATEX | IECEx |
|---|---|---|
| SD-1 TYPE GP and TYPE NC | II 2G Ex db IIC T5 Gb | Ex db IIC T5 Gb |
| SD-1 TYPE GP H and TYPE NC H | II 2G Ex db IIC T6 Gb | Ex db IIC T6 Gb |
| SD-1RI | II 2G Ex db IIC T5 Gb (T6 on H version) | Ex db IIC T5 Gb (T6 on H version) |
| SD-1GH | II 2G Ex db IIC T5 Gb | Ex db IIC T5 Gb |
| SD-1EC | II 2G Ex db IIC T6 Gb | Ex db IIC T6 Gb |
| SD-1OX | II 2G Ex db IIC T6 Gb | Ex db IIC T6 Gb |
Certifications
| Scope | Reference |
|---|---|
| Explosion protection | ATEX, IECEx, Japan Ex |
| Marking | CE |
| Marine | MED, available on SD-1 and, in a dedicated 4-20 mA version without contacts, on SD-1OX. Availability depends on the gas |
Functional safety
Certificate exida RK 1310015 C001, revision 4.4 of 13 August 2025, with surveillance audit due by 31 August 2027. Assessment according to IEC 61508:2010, parts 1 to 3.
| Models covered | SD-1RI, SD-1EC, SD-1OX |
| Systematic capability | SC 3, therefore suitable up to SIL 3 |
| Random capability | Type B element |
| Achievable level | SIL 2 with HFT = 0; SIL 3 with HFT = 1, route 1H |
| Safe failure fraction (SFF) | SD-1RI 95.6%, SD-1EC 96.4%, SD-1OX 94.3% |
The SIL level of an entire safety instrumented function must be verified case by case, calculating PFH and PFDavg on the actual architecture, proof test interval and repair times. The certificate does not replace that calculation. The instrument must also be integrated according to the safety manual of the chosen model.
Frequently asked questions
How much does a Riken Keiki SD-1 detector weigh?
Models for combustible gases weigh about 2.0 kg, the SD-1EC model for hydrogen sulphide and carbon monoxide about 2.2 kg, the SD-1OX model for oxygen about 2.5 kg. All models are 148 mm wide.
Can the SD-1 be used where hydrogen or acetylene is present?
Yes. Riken Keiki declares the SD-1 series suitable for atmospheres containing hydrogen and acetylene, thanks to the explosion-proof enclosure. Hydrogen and acetylene are the most critical gases for the integrity of a flameproof enclosure, because they ignite with very low energy. The exact protection class varies by model, from T5 to T6.
SD-1 or SD-3 series: which is better?
The SD-1 weighs 2 kg, has IP65 protection and operates between -20 and +60 °C. The SD-3 weighs from 6 to 7.6 kg, has a stainless steel IP66/67 housing, operates between -40 and +70 °C and offers digital outputs in addition to 4-20 mA. The SD-1 covers standard installations, the SD-3 harsh environments and gases outside the list.
Does Socrate supply spare parts for the SD-1?
Yes. Socrate handles spare parts for the SD-1 series, sensors included, also on Riken Keiki instruments purchased from other suppliers. Service, functional testing, scheduled maintenance and calibration are carried out on instruments supplied directly by Socrate. A spare part request requires the code of the installed model.
See also
Documentation
- PDFSD-1 series datasheet in English (PC2E-0341, April 2025)
- PDFSD-1 series datasheet in Italian (PC2E-0341, August 2026)
- PDFFunctional safety certificate exida RK 1310015 C001 rev. 4.4
Datasheets are available in English and Italian; certificates are in their original language.
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