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Ratio Control

ZZ_1317032757_Image1.tifRatio control in-line blending is the technique of blending two or more products together by volume or mass. Ratio control is the preferred method of in-line blending when the quality parameters (i.e. density, viscosity, sulphur etc.) of the components being blended are consistent and unlikely to vary. If these are known then a high quality final product can be produced by accurately blending the components together to the correct ratio, assuming the blend ‘recipe' is accurate. However, when the quality of the feedstock varies or there is uncertainty in the blend recipe, as is often the case in bunker fuels, quality trim in-line blending should be considered as it may deliver incremental savings over ratio control. Ratio control in-line blending produces a blended product to an extremely accurate component ratio on the assumption that the sample and analysis of the fuel is accurate, the recipe (i.e. blend ratio) is correct and that there is no layering of the feedstock in the tank(s) being blended. Ratio control in-line blenders operate on either a volumetric or mass ratio. This ratio is maintained during blending by closed-loop control between the flow meters fitted to every stream, the blender control system and the control valves or pump control used to adjust the ratio of each stream.

High blend ratio accuracy – The flow measurement and/or control of all streams within JISKOOT™ ratio control in-line blenders enables them to deliver a blend accuracy of better than 0.5%.
Integrated flow meters and closed loop control – JISKOOT™ blenders are designed to ensure that at all times the blend remains on specification, even in the event of feedstock starvation and the 3-term PID control ensures that fast blend response time with no stored errors, unlike traditional ratio in-line blenders.
Simple user interface with ‘recipe' storage – JISKOOT™ blender control systems are simple to use with multi-level security and store multiple recipes for ease of operation.
Mass or volume flow meters – JISKOOT™ in-line blenders can be built with mass or volume flow meters to meet client demands.
Automated blend documentation – JISKOOT™ in-line blending systems can automatically produce blend delivery documents including calculated quality parameters (such as sulphur etc) based on the high accuracy blend ratio.
Guaranteed custom design – JISKOOT™ blenders are supplied with a performance guarantee and are custom designed to meet your application giving you the highest flexibility, compatibility with your facility and return on investment.
 IP/API temperature compensation – JISKOOT™ in-line blenders all include the facility for the streams being blended and the final product can be compensated for temperature/volume ensuring high accuracy blend ratio minimising ‘give-away'.
 Distributed Control System (DCS), Oil Movement and Storage System (OMSS) integration and emergency/safety facilities – JISKOOT™ in-line blenders can be fully integrated with new or existing DCS or OMSS systems and feature built-in blending monitoring and alarms in the rare event of component failure.
The principle of operation for a JISKOOT™ ratio control in-line blender is that the flow of each component (e.g. Heavy Fuel Oil and Cutter) is measured by a flow meter and controlled using a control valve or a positive displacement pump. Flow meters can be positive displacement, ultrasonic, turbine or mass to suit the application. In operation the JISKOOT™ blender control system generates a demand flow rate (called a set-point) for each component, which is compared to the measured flow. Any deviation between the set point and the measured flow is stored in the blender controller memory and an appropriate adjustment is made automatically to the control valve/pump to increase or decrease the respective component flow to the required flow rate. If there is starvation of flow in a stream, the control valve will open to compensate. However, if it reaches a point at which it can no longer blend, the system will reduce the total blend rate to the maximum flow rate at which the lagging component can maintain correct ratio and accuracy to keep the blend on specification.

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