Rack Phase Differential Monitoring (RPD)
The retrofit advanced M1000 RPD monitoring system provides an extremely fit for purpose, automated, real time management tool for safely and speedily lowering and positioning the legs of jack-up rigs in all types of seabed terrain. M1000 RPD also provides the operator with the corrective action to be taken to solve problems identified by the system and includes a fail-safe monitor that automatically shuts down the jack-up process if the operator does not respond fast enough to a warning signal.
Monitoring of rack phase difference during jacking operations can give an early indication of possible leg over-stresses. Taking continual manual rack phase measurements during jacking operations is both difficult and labour intensive. The Monitor Systems Engineering rack phase differential monitoring system provides an accurate electronic / mechanical system for measuring and recording the rack phase difference of each leg.
The rack pitch differential monitoring system is based around the Siemens S7-300 PLC. The S7-300 Series PLC provides high level control functions, programme structuring, networking and software integration.
The main user interface is via a 15” Industrial Panel PC running Windows XP Professional and WinCC Flexible Runtime Scada package. This interface will display all RPD information graphically and numerically as well as displaying all alarm information, historical trending data and maintenance procedures. Three 8” remote mobile hand held HMI’s are also provided. The mobile HMI’s can be connected to Connection Points at each leg chord to display RPD information to the operator whilst operating the legs from the Remote Jacking Control Stations.
As well as RPD information the RPD Monitoring System also tracks the position of each leg and in doing so can perform calculations to monitor such variables as Leg Penetration, Distance to Tag Bottom and Total Draft. These additional calculations will be based upon manually entered data such as Air Gap and Tidal Water Depth.
All RPD alarms are fully configurable and the alarm levels can be set by the operator. If any alarms are generated an internal buzzer / beacon located on the PLC Station will be triggered.
- reliable, error free, real time data feedback
- faster leg deployment with less down time
- central control console, local chord and hand held mobile monitors
- 0.3mm resolution derived from 32bit absolute encoders
- unaffected by lateral leg movement to plus or minus 100mm
- unaffected by vibration and shock
- eliminates high risk of serious damage and safety implications to legs, jack-house equipment, rack chords and surrounding braces and girder-work
- extreme weather coated robust steel frame
- bearing and encoder housing in 316L grade stainless steel
- shaft pins 17/4ph stainless steel
- all shafts “O” ring sealed to provide long-life reliability
- minimal obstruction to walkways
- highly reliable Profibus DP network
- alternative radio telemetry network with SIL2 approval reducing cabling installation costs
Reporting Critical Data
- leg length
- RPD error indication and alarm at 75mm
- chord problem correction instructions
- trending and historical logging with provision for comments and notations
- self checking
- optional local chord HMI’s for chord correction
- built in error and redundancy measurement ensuring no leg damage ensues
- provides operator corrective action instructions with auto-shutdown if ignored