Kongsberg SENTRY GB-300 WIRELESS TEMPERATURE MONITORING

The KONGSBERG SENTRY GB-300 is a unique product developed for

temperature monitoring of crank pin/crosshead bearings in diesel

engines and other rotating machinery.

Features

•  Fast and reliable temperature response.

•  By providing an early warning the consequence of o bearing

seizure is reduced to a minimum.

•  The sensor is passive, has no battery and does not need an external

power source.

•  Flexible mounting, compact and simple installation.

•  Approved by classification societies as an alternative to traditional oil

mist detectors.

•  Approved for hazardous area.

Functional description

Figure 1 shows the arrangement of the SENTRY Wireless

Temperature Monitoring System installed on a 4-stroke diesel

engine.

• A wireless sensor is fitted to the moving part (e.g. the

connecting rod of an engine)

• A Stationary Antenna is fitted to a bracket inside each cylinder

compartment in a position so that the sensor will pass nearby as

the engine runs.

• Coaxial cables connect the stationary antennas with the

Signal Processing Unit fitted outside. The bulkhead penetration

is made by use of a special, high IP-grade cable gland in which

the coaxial cable shield is terminated to ground.

• The Signal Processing Unit calculates the temperature and

transmits the result to the engine control system.

The SENTRY GB-300 system is based on Surface Accustic

Wave (SAW) -and radar technology. The sensors are passive,

have no battery and are in no need of an external power source.

Technical description

4 - 20 mA

CAN/RS-485 Modbus

Power 24 VD

Low energy, high frequency radar pulses are generated by

the Signal Processing Unit (SPU) and transmitted via coaxial

cables to the Stationary Antennas installed inside each cylin

der compartment.

The antenna transmits the signal further into the open space

of the crankcase. When the sensor passes the antenna,

the radar pulse is picked up. The SAW element at the tip of

the sensor then reflects the signal which is picked up by the

stationary antenna and sent back to the processing unit for

interrogation.

The shape and characteristics of the reflected pulse deter

mine the temperature of the sensor, i.e. the bearing temper

ature. The processing unit software calculates the tempera

ture and transmits this to the engine control and monitoring

system.

The SPU uses a multiplexer to monitor up to 16 channels in

sequence. Calculation time for each channel is appr. 25 ms.

Installed on a 10 cylinder engine running at 600 rpm all 10

channels are up-dated in less than one second.

The multiplexing and low signal strength reduces noise and re

moves any danger of overhearing from one cylinder to another.

All sensors and antennas can therefore be similar. This reduces

number of variants and represents a huge benefit in terms of

keeping spares.

Mechanical design and installation