Biodiesel custody transfer line

Background

Client request referred to a state-of-the-art biodiesel jetty loading metering system.

Measurement requirements

The request was to design metering systems with class 0,3 for biodiesel river barge loading.

Custom-made solution

Measuring line represents complete skid, with mounted equipment, wired and calibrated, and supplied with appropriate certificates for each skid’s items (PED, ATEX, EMC, PTB…) and metrological certificate for the flow meter.

The proposed measuring installation and equipment are designed to obtain required measuring accuracy and comply with the obligatory standards and regulations (domestic standards, OIML R 117 recommendation, ATEX 94/94/EC standard for equipment in potentially explosive atmospheres, IEEE 802.3, EIA RS-485 and, EIA RS-232C standards for communication and control network, API-11.1 - temperature correction factor, API-11.2.1., API-11.2.1.M, API-11.2.2., API-11.2.2.M - compressibility factor...).

Measuring skid for automatic custody transfer is equipped with degassing vessel, strainer with differential pressure transmitter, density measuring skid with KROHNE OPTIMASS 6400 densitometer, control valve, ISOIL LBM1000 flow-meter (PD meter), temperature transmitter, pressure transmitter, prover connections, and connection boxes for Foundation Fieldbus, pulse, digital signals, 4-20 mA signals and power supply. Flow computer (SMAR HFC302), HSE controller (SMAR DF63), safety barriers, ethernet switch, touch screen display for local supervision and control with auxiliary electrical elements are placed in electrical cabinet.

The flow computer is designed to attend International Standards focusing custody transfer in oil and gas measurements. Applied flow computer is also capable to perform process control functions, but for the predicted extensive points for measuring and regulation, it was necessary to include, beside flow computer, a local controller to execute required control task. The both flow computer and controller are connected with the central loading point by integrated system for monitoring and regulation.

Physical layer of this system is the high speed Ethernet network. By this way, the control and communication network are under the same protocol TCP/IP. This fact enables considerable capability of applied system – easy and low cost redundancy, simple vertical integration of loading control system (LCS) with appropriate corporation levels (commercial, marketing, executing) and modular extensions of existing installation for custody transfer or addition of new loading units. Accordingly, the control function is distributed in the field. That enables modular, easy extended, reliable, fault-tolerant and low-maintenance cost system, which is integrated through fast, open and common accepted protocol – TCP/IP.

Applied software for supervisory control and data acquisition enables monitoring and control of loading/unloading process, alarm management, asset management and trend tracking. There is a single loop integrity feature of the LTS system. Besides that, by Ethernet network and appropriate SCADA system, every transfer of fluids on the measuring locations is normally under the LCS supervision. These solutions granted that audit flow is always realized. The LCS system is the mandatory, but in the case of failure of the communication/control network between the LTS and LCS systems it is possible continue with regular custody transfer application by the LTS. Appropriate data about this transaction FC302 stores in its memory, and later after HSE network re-establishing, it is possible to upload these data.