THE latest Servomex process oxygen analyser, the 2200, enables companies in the petroleum and gas industries to analyse the oxygen content of gas close to the burners of flare stacks, while installing the actual gas analyser in a remote control room. They 2200 analyser is distributed by Pryde Measurement .
Monitoring the oxygen at the burner prevents a potentially explosive mixture of flammable gas and oxygen building up, eliminating the risk of it igniting and causing a flash-back of burning gases into the plant.
The recommended method of determining the oxygen level in a flare stack is to use an analyser fitted with a magneto-dynamic cell, which measures the paramagnetic properties of the gas. Oxygen is paramagnetic where other gases are not, making the Servomex paramagnetic cell in the analyser one of the safest and most reliable means of monitoring the presence of oxygen in hazardous situations. Typically, in a flare stack application, alarms are generated by the analysis equipment when the oxygen level exceeds about 1%.
The Servomex 2200 analyser consists of a paramagnetic oxygen measurement transmitter and a separate microprocessor-based control unit capable of accepting inputs from up to six transmitters. It is therefore possible to mount one or more paramagnetic transmitters close to the sample points of flare stacks and to monitor remotely the oxygen content of the gas at the burners. The 2200 provides digital data communications to mainframe production control computers and offers all the key features needed by current and projected process plant technology.
Flare gas monitoring systems usually operate with flare stack pressures of ±250mm wg. In some circumstances the flare stack pressure can be higher than this and additional equipment will be necessary to regulate the pressure of the process gas. If required, a catch pot can be inserted at the lowest point in the sample line, before the pump, to collect any condensing vapour. A flame trap is usually installed close to the sample discharge point.
Servomex can supply a complete analytical system to ensure that all analysers, sample conditioning equipment and other items such as cubicles and recorders are fully compatible with the site requirements.
Since the paramagnetic transducer of the 2200 analyser provides a physical measurement, there are no chemicals or electrolyte to replace and the maintenance requirement is very low. The 2200 transmitter is certified for use in ATEX category 2 areas and the 2200 control units can be used in ATEX category 2 or 3 areas without the need for purging.
The 2200 provides digital data communications to mainframe production control computers and offers all the key features needed by process monitoring systems. The 2200 hazardous area transmitters are locally powered to ensure continued operation and are linked using single twisted pair cables to one or more remote control units. The control units have digital communications, full auto-calibration and validation facilities and a user-friendly multilanguage user interface. The transmitters have a single 4-2OmA intrinsically safe output, two 4-2OmA inputs for cross-interference and external pressure compensation, three status relay contacts and two flow sensor inputs.