DTI guidance notes for Petroleum Measurement Issue 7.0.

An integrated cargo transfer metering system designed to provide fully verified flow data and fluid property information when moving bulk quantities of hydrocarbons during the oil production and offloading process. Notable for its low weight and small footprint, unrestricted flow throughput and negligible maintenance requirement, the system is ideally suited to the Floating Production, Storage and Offload (FPSO) unit, as well as the FSU, Semi-Sub or Fixed production platform. The flexibility of the system configuration is a key feature in being able to meet legislative requirements for a particular installation and at the same time being able to cost effectively integrate all other related operator requirements.

Flow metering stations for export and allocation metering purposes have conventionally used turbine style devices, often with prover loop systems for in-situ calibration verification. Increasing pressure to drive down capital and operational costs has been the motivation for users to seek out an alternative metering philosophy. The clamp on ultrasonic flow meter has found wide application in the offshore and oil processing industries. A high precision derivative, using unique ultrasound beam technology provides the performance which has allowed it to become the heart of a new regime for cargo transfer metering. CTMsystem™ provides a complete cargo metering system. Fully compensated flow throughput measurements are cross verified with slave metering units and cargo tank level measurements for absolute integrity. 

In addition, the system can integrate as many or few customer specified media measurements as required - density, viscosity, pressure, temperature or other ancillary inputs. Samplers, BS&W units and even cargo load calculators can be included in a fully specified CTMsystem™.

The mode of operation of CTMsystem™ particularly in regard to the flow stations, offers considerable benefit to the operator.

• Maintenance Free - 
  CTMflowstation™ components are totally non invasive and have no moving parts. It requires no routine maintenance and is not liable to damage by entrained solids, high flows or aeration. The overall life cost of the system, taking into account installation, maintenance, calibration and availability, is substantially lower than invasive measurement devices such as turbine, positive displacement or Coriolis flow meters.

• Unrestricted Flow Throughput - 
  The flow throughput of the cargo transfer line is not inhibited by the flow meter. This can result in significantly increased volume transfer rates over conventional metering systems. The knock-on effects in terms of reduced transport costs and lowered risk of hindrance to production has been calculated on live installations to give a system payback period of less than 6 months.
• Significantly Reduced Capital and Engineering Costs -
  A CTMflowstation™ has negligible weight and footprint when compared to a conventional metering skid and prover loop. The simplified pipe work and valve requirements also ensure that engineering requirements are kept to a minimum. These features alone represent significant cost savings, put as high as £2m by some operators. Inherent determination of viscosity and density parameters by the flow station can further reduce the need for ancillary equipment, and the use of a radar level system for tertiary verification also makes use of equipment which is typically fitted as standard to cargo handling vessels.
• Increased Safety - 
  Through a combination of faster offload rates, reduced tanker on-station periods, and fewer potential product leak paths the environment and operational safety of the export metering procedure may be enhance

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