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OHC-800 Ultra fast responding Fuel Gas Calorimeter

Opt-Sonic Gas Calorimeter

The Riken Keiki OHC-800 is a fixed gas Calorimeter in a flame and explosive proof enclosure.

Calorific Value:

Calorific Value is the amount of energy generated by perfect combustion of fuels. In the current Energy Saving environment it is important to make progress in improving energy efficiency at all levels . Using a Calorimeter at the Electricity Generation plants and Gas energy distribution stations can help enormously to increase efficiency as well as reducing environmental impacts.

For Example Variations in the Calorific value of LNG gas used on Power stations caused by an increased diversification of sources means it is important to measure and adjust the air / fuel ratio burnt in the turbines. This is becoming even more important with the increasing adoption of Shale and Bio Gas.

OHC-800 LNG Application

Product Features

Explosion Proof Calorimeter:

The Riken Keiki OHC-800 is a fixed gas Calorimeter in a flame-proof enclosure (explosion-proof class: Ex dⅡB+H2 T4). It is designed for continuous,  measurement of the “Calorific value,” “Density,” and “WOBBE index” of various fuel gases. Examples of these include  natural gas, coke oven gas, blast furnace gas, converter gas as well as biomass gas, and biogas.

OPT-SONIC Technology : Low Interference High Accuracy:

The OHC -800 is based on Riken’s Patented  “OPT-SONIC” Calculation technology. This technology uses and Optical as well as a Sonic sensor and combines the two measurements. This minimizes interference from other gases as well as enabling high accuracy and reliable measurements.

Easy to use:

The OHC-800 can change display between “Calorific Value ” , “Density ” and “WOBBE” index with a simple press of a button. Laborious calculations are not required.  Self Diagnosis function is included. This includes a fault diagnostic that prevents the Calorimeter being unable to measure gas.

Low Running Costs:

The OHC-800 is extremely reliable as well as having  low maintenance requirements. It requires Zero calibration.  There are also very few consumables. The unit is comprised of only 4 replaceable parts meaning cost of ownership is kept low.

Fast Response and High Repeatability:

The Calorimeter has an fast T90 response time of only 5 seconds and a repeatability of +/- 0.02MJ/m3 in addition to  a very wide opertating temperature range of -20 to +60 Degrees Centigrade . In addition the OHC-800 demonstrates remarkable temperature characteristics of below 0.10MJ/m3 fluctuation for the temperature change in a day ( <20 degrees C )

Very Rugged and Robust Explosion Proof Construction:

The Robust structure and explosion proof construction, even for Hydrogen ( ATEX in addition to IECex compliant ), means it can be installed in many different locations . It has a high ingress rating level of IP-66/67 .

The types of fuel gases that can be measured depend on the specifications. For information on the types of gases that can be measured please contact Weatherall

See Artcle Method for Calculating Calorific Value of Hydrogen-Blended Natural Gas using Speed of Sound and Light

Calorimeter Applications Include:

Gas as well as Biomass Power Plants.

Gas Energy (LNG Terminals etc).

Biogas to Grid.

Oil Refineries as well as Petrochemical Plants.

Iron and Steel works (Coke ovens etc).

LNG Gas Engines for Ships.


Model OHC-800
Measuring Principal OPT-SONIC Calculation through the measurements of refractive index and sound speed
Measuring Gas CH4 basis Paraffinic Hydrocarbon Gases as represented by Natural Gas *1
Measuring Targets Calorific Value ( Density / WOBBE index selectable
Measuring Range *2 Calorific Value : 25 – 50 MJ/M3 (Gross, 0 Degree C 101.325kPa Converted .

Density : 0.5 -1.5 MJ/m3 (Specific gravity converted )

Measuring Method Constant –Flow-Rate gas introduction using external sampling devices
Display Full-dot LCD ( with backlight ) 3 colour LED Lamp
External Output 4-20mA DC ( Isolated source current type ) Maximum load current resistance of 300 ohms / RS485 communication
FAILURE alarm Low flow , Sensor abnormality , low light
FAILURE alarm display Lamp (Red) / Content indication on LCD
FAILURE alarm contact *3 No-Voltage contact 1a or 1b De-Energise ( Energise when alarming ) or Energise ( De-energize when alarming ) Contact Capacity of 2A , 30VDC ( resistance load )
Self-diagnostic function FUNCTION CHECK ( Warm up or Maintenance mode , MAINTENANCE REQUIRED , OUT OF SPECIFICATION
Self-diagnostic display FUNCTION CHECK , OUT OF SPECIFCATION : Lamp (Orange ) / Content indication on LCD

MAINTENANCE REQUIRED : Lamp ( Green ) / Content indication on LCD

Self-diagnostic contact FUNCTION CHECK OUT OF SPECIFCATION No-Voltage contact 1a or 1b De-Energise ( Energise when alarming ) or Energise ( De-energize when alarming ) Contact Capacity of 2A , 30VDC ( resistance load ) : SSR contact , contact capacity of 20W , 240VAC ( resistive load )
Power supply 100-240VAC +/-10% , 50/60 Hz, Max 18VA or 24VDC +/-10% max

5W ( the setting can be changed to either AC or DC )

Ingress Protection Level IP66/ 67
Operating temperature -20 to +60 Deg C ( ATEX / IECEx)
Operating Humidity 95% RH or less ( Non condensing )
Outer Dimensions / Weight Approx 286(W) x 453 (H) x 150 ( D) mm / Approx 23Kg
Explosion Proof Structure Flame-proof enclosures ( Explosion-proof Class ATEX / IECEx)

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