The measurement specification for the range of MERLIN monitors was drawn up with input from pipeline operating companies and independent CP consultants. It includes all the measurements conventionally taken at rectifiers, solar stations, test stations, cp posts, riser posts and pipeline sleeves.
MERLIN rectifier (including solar station) monitors have been designed to carry out the functional checks of rectifier output (voltage and current) required in order to comply with regulatory guidelines. They will quickly repay their capital cost when compared to manual monthly checks.
MERLIN rectifier monitors offer additional CP measurements (ON and OFF potentials) as well as the facility to synchronize remotely with other rectifiers on a pipeline for Close Interval or DCVG (Direct Current Voltage Gradient) survey measurements in the field. Pipe-to-soil potential measurements at the rectifier require a reference cell and relay.
MERLIN CP monitors channels are fully independent. A MERLIN CP Monitor can be configured to monitor either two pipe-to-soil inputs (the second input could be a sleeve or foreign pipe) or, if a coupon is fitted, one pipe-to-soil input and an instant OFF input. The MERLIN unit incorporates an internal relay, which is opened just before channel 2 is read.
All MERLIN CP monitors measure DC and AC voltages on each channel simultaneously. This has become extremely important as operators now recognise that induced AC on pipelines can have detrimental effects. If a coupon is fitted at the test post, channel 3 can be used to calculate the DC and AC current by measuring the voltage across a shunt of known value (Abriox can supply suitable shunts and cable assemblies). Once the shunt value and coupon surface area have been entered in the CPSM software, the data can be displayed either as the current in mA or as the current density in A/m².
Another configuration enables the DC potential of an unprotected (“native”) coupon to be monitored. By comparing this to a protected coupon (one that is electrically connected to the pipeline and therefore receives cathodic protection) the effectiveless of the CP system can be verified.
High and low alarms can be set for each measurement channel (for DC and AC values). A MERLIN unit will alarm as soon as a measurement is detected outside the acceptable “window” set by the user.
MERLIN Nitrogen Sleeve monitors allow the pipeline operator to check that the sleeve is maintaining the required pressure without undertaking a site visit. They are typically installed in remote areas inside GRP Cabinets, M28 Posts and at Sleeve Fill Points. Remotely monitoring these key points eliminates routine site visits and labour can be freed for data interpretation and follow up.
Now the pipeline operator can check that the sleeve is maintaining the required pressure without undertaking a site visit. Even if the gas is leaking, the operator can monitor the pressure drop and schedule maintenance accordingly. In this way unnecessary site visits can be avoided. The MERLIN measures the sleeve pressure automatically, checks that it is within specification and reports immediately if an alarm threshold is exceeded.
In addition to monitoring the gas pressure in the sleeve, the voltage of the batteries powering the sensor is also monitored and data is seamlessly sent in a management report to the system HQ where it is displayed and archived in Abriox’s MERLIN CPSM software or online via iCPSM.