Rosemount Incus Ultrasonic Gas Leak Detector, Emerson GDU-Incus Acoustic Gas Leak Detector

What is the Rosemount Incus ultrasonic gas leak detector?

The Rosemount Incus (GDU-Incus in Emerson’s data sheet) is an ultrasonic gas leak detector: instead of measuring gas concentration, it listens for the ultrasound that pressurized gas makes as it escapes. Four acoustic sensing heads monitor a wide area for sound between 25 kHz and 100 kHz, which Emerson says only a highly pressurized gas release produces, and the detector alarms when it hears it. Because it reacts to the leak itself, it responds the same way to toxic, combustible or inert gas.

The heads are piezoceramic with no moving parts, sealed against moisture, corrosive atmosphere and industrial contaminants, and work independently: the output follows whichever head measures the most ultrasound, and coverage is not completely lost if one or more heads fail. Emerson lists the Incus as active, with a warranty of 36 months after shipment.

Selection note: Ultrasonic detection does not need the gas to reach the detector: Emerson’s data sheet says it does not wait for a hazardous concentration to build or for the cloud to touch a sensor. Its analog output scales to sound level (4-20 mA = 40-120 dB as standard), not gas concentration, so Emerson pairs it with point gas and optical flame detectors in one safety system rather than using it alone.

What are the Rosemount Incus specifications?

Detection technology	Ultrasonic (acoustic), four piezoceramic sensor heads
Detection frequency range	25 kHz to 100 kHz
Detection coverage	40 m coverage in low noise applications (~54 dB); 20 m coverage in high noise applications (~74 dB)
Detection range	2 to 40 meters (7 to 130 feet)
Response time	Instantaneous (less than 1 second with HART outputs); alarm delay in 1 second variable increments, customer programmable
Operation modes	Stepped analog (4 mA = no alarm, 12 mA = alarm); 4-20 mA = 40-200 dB; 4-20 mA = 40-120 dB (standard)
Analog output	4-20 mA normal operation range; 0-2 mA fault outputs
Relays	Two form C contacts: configurable fault relay, configurable alarm relay
HART protocol	Supplied as standard
Self-test	Continuous electronic check of sensor integrity, every 320 ms
Operating range voltage	15 to 30 Vdc
Power consumption	Standard unit: 6 W in normal operation; heated unit: 1.5 A at maximum display brightness with heaters at maximum current (at 131 °F (55 °C))
Cable entry	Signal entry 1 in (25 mm) x 0.75 in (19 mm) NPT; double entry 2 x M20 (not available for FM certified units)
Operating temperature	Standard unit: -40 °F (-40 °C) to 185 °F (85 °C); heated unit: -67 °F (-55 °C) to 185 °F (85 °C)
Storage temperature	-40 °F (-40 °C) to 185 °F (85 °C)
Relative humidity	0 to 95% RH non-condensing
Enclosure and bracket	AISI 316 stainless steel; mounting bracket included
Ingress protection	IP66/IP67 and Type 4X
Weight (with bracket)	Approximately 40 lb (18 kg)
Warranty	36 months after shipment

Selection note: Background noise sets the coverage radius. Emerson rates the Incus at 40 m where ultrasonic background is low (about 54 dB) and at 20 m where it is high (about 74 dB), so a noisy area needs detectors spaced for the 20 m figure. Programmable alarm delays, set in 1 second steps, screen out intermittent background ultrasound.

Where is the Rosemount Incus used, and when is another Emerson model the better fit?

Emerson calls the Incus ideally suited to ventilated outdoor applications and built it for extreme conditions. It states that inclement weather, wind, leak direction and gas dilution or stratification do not affect the response. The data sheet’s own illustration places it beside a point detector and an open path beam, with wind direction marked.

Choose another Emerson detector when the question is different:

• How much gas is at a point: the Rosemount 625IR (methane or propane, 0-100% LEL) or the Rosemount 925FGD.
• How much gas is along a line: the Rosemount 935 for combustible gas or the Rosemount 936 for H2S or ammonia.
• Remote spots without cable: the Rosemount 928 wireless gas monitor.
• Fire, not gas: the Rosemount 975 flame detector.

Maintenance note: The calibration burden differs sharply across Emerson’s detectors. Incus: Emerson says the sensors are immune to poisoning and never require field calibration. 625IR: factory calibrated and cannot be calibrated in the field, with a 5-year proof test interval. 628 sensors in a 928: calibration at least every 180 days for H2S and every 90 days for CO and O2, per the 628 Quick Start Guide.

Which approvals, outputs and documents apply to the Rosemount Incus?

Emerson does not print the certification markings in the GDU-Incus data sheet; it refers to the GDU-Incus Quick Start Guide for them, and the product page describes the detector as certified worldwide for hazardous locations. The data sheet does show which certification options exist, because some features depend on them:

• Double cable entry (2 x M20) is not available for FM certified units.
• The heated unit, rated down to -67 °F (-55 °C), is available for ATEX low temperature and EAC certification options only.
• A customer cable entry for dual entry or relay output is offered on ATEX/IECEx units only.
• A “DNV” certified bracket is available.

Name the approval your site needs with the quote. Outputs: 4-20 mA analog or stepped, two configurable form C relays (fault and alarm), and HART as standard.

Documents: GDU-Incus data sheet, April 2024, 00813-0100-3003 Rev AB and the Rosemount Incus page on Emerson.com. Background: PE Energy gas detection systems guide.

Maintenance note: The Incus checks itself every 320 ms by sending an amplitude signal through the sensing circuitry, and Emerson states detection is not lost during the test, in contrast to detectors based on diaphragm microphones. Under normal operating conditions the sensors do not age, drift or need replacing. For a functional test, Emerson’s GDU-01-TT battery test transmitter carries a warning that it needs a hot work permit.

How do I request a quote for the Rosemount Incus?

The data sheet has no coded ordering table, so describe the configuration you need. Send PE Energy:

• Standard or heated unit (heated for -67 °F (-55 °C) service)
• Certification required (for example ATEX/IECEx, FM, ATEX low temperature or EAC)
• Cable entry: M20 is standard; the listed alternatives are M25, 0.5 in (13 mm) NPT and 0.75 in (19.0 mm) NPT, plus double M20 entry on non-FM units
• Output mode: stepped, 4-20 mA = 40-120 dB (standard) or 4-20 mA = 40-200 dB
• Accessories and quantity

GDU-01-TT	GDU test transmitter, battery-operated, and charger (needs a hot work permit)
GDU-01-TT-CHARGER	18 V 0.83 A standard charger for the GDU test transmitter
GDU-02-360-KIT	2 in (51 mm) pipe U-bolt kit
GDU-02-370-KIT	4 in (102 mm) pipe mount bracket kit, stainless steel
GDU-INCUS-MTBR-S	Wrap-around mounting bracket, 316 stainless steel
GDU-02-TCFK	Terminal fastener kit
GDU-02-TCL / GDU-02-TCU	Terminal cover O-ring, lower / upper

PE Energy confirms price, availability and lead time with the quote. Request a Rosemount Incus quote from PE Energy.

Installation note: Plan the mount for the load: the Incus weighs approximately 40 lb (18 kg) with its bracket. The standard AISI 316 bracket is included, U-bolt kits handle pole mounting, and the identification tag is sold separately and can be fitted on either side of the bracket.