Pipeline System Operation
How Centrifugal Pumps Work Working Principals of Centrifugal Pumps How to select a Pump and Motor Pump Cavitation
Pipeline Operations: Business Physical Physical: covers the product movements and pipe cleaning or pigging and integrity management Products are gathered in central points and then dispatched to various destinations. --> this is done through scheduling which involves product pumping schedule that is based on: pipeline capacity shippers requirements Controlling of pipeline pressure is important it sets certain operating limits: MAOP Maximum discharge pressure to protect piping & equipment Minimum suction pressure to avoid cavitation Max/Min pressure at a control point Max/Min delivery pressure for contractual obligations Min/Max flows through pumps for efficient pump operation Maximum power of pumps Minimum discharge temperature for pipelines in permafrost Booster Pumps are installed between the tanks and the pump station because tanks don't provide sufficient suction head Tight Line Operations --> when there are multiple intermediate pump stations and open station pumps directly into the suction side of the pumps at the next station.the advantages over the previous operation: tanks are not necessary at the mainline stations extra operation of pumping into and out of tankage is not required interfacial mixing is minimized for batch operation Pressure monitoring and controlling points: suction set point: suction pressure limits, a lower limit under which the pump will not operate and shut down. An Upper limit needs to be reduced to avoid over pressuring the discharge pressure at the upstream station. discharge set point: this pressure is to be maintained as a maximum pressure. if pressure is equal to or higher than the discharge set point the pressure regulator is activated to reduce the actual pressure level. tight line operation--> liquid density and viscosity changes can occur in batching or blending operation if stations have centrifugal pumps are operating at maximum pressure the flow will decrease and the density and viscosity increase Sphere:form of pig that is put in place to separate the two adjacent products. it can be inserted at the injection point or the running pump stations and received at the delivery point or at running pump stations further along the pipeline without the pig, interfacial mixing or transmit takes placethis depends on the pipe length and reynolds number There are rules that outline the handling of transmix: interface mixture maybe cut into one or the other product, or divided between two adjacent products Slop--> when the transmix doesn't meet the shippers specifications if the size of transmix is larger than the specified amount and cannot be blended into other products the company must pay Batching trackingmonitors the volume of each batch, its origin and its destination, current location and ETA its tracking begins when the batch is launched and tracked using difference in density or value status or on batch schedulevolumes are updated based on injection and delivery volumes obtained at metering locations Batch interfaces can be detected by a densitometer or by dye detector.
Pipeline System Design Pipeline system design is concerned with--> line sizing, route selection, equipment sizing and facility locationsystem operation is concerned with--> steady-state operations at different flow rates, pipeline system/facility start up and shut down. product receipt & delivery flow rate change Transient state--> flows in transit from one steady state to the other. transient solutions provide hydraulically realistic results. it occurs when the flow is disturbed or changed in the pipeline system large transients can occur suddenly and in a short time when fluid flow is interrupted Pressure Surge change in pressure of the pipeline that occurs abruptly during a change from normal steady state or another transient state flow in the pipesurges travel at acoustic speed if pressure is higher than normal operating pressure upsurge if pressure is lower than normal operation pressure downsurge Behaviors of surge Wave if a vale is suddenly closed a sequence of changes in pressure takes place in the pipeline: Valve: velocity stops instantaneously and the pressure or head the value increases by the amount of the surge this results in a slightly enlarged pipe and a density increase in the fluid. the pressure increase causes a sharp fronted pressure wave to propagate upstream at acoustic speed.At time L/a seconds: the wave front reaches the end of the pipe. the velocity becomes zero throughout the pipe, the pressure is the same and the pipe is enlarged and the fluid is compressedAt time 2l/a seconds: the pressure throughout the pipe has returned to its original value. the critical period occurs when: the velocity experiences a reversal in direction mirroring the reflection of the pressure wave.this causes the pressure to decrease from the initial conditions of steady state flow. causing the pipe to shrink and the liquid to expand At time 3l/a seconds: the negative wave reaches the reservoir, velocity is zero At time 4l/a seconds: the wave returns to the valve and original conditions are restored.
Transients are two types: Pressure transient : when change in energy occurs flow transients: change in flow rate caused by change in energy The main causes of Transient flow: change in valve settings including opening or closing status change starting and stopping of pumps changes in pump speed or head pipeline rupture or leak collapse of column separation or trapped air arrival of batch at interface of pump Line Packing and Line unpacking the fluid volume increases or decreases dependent on the line pressure. packing = high volume unpacking = low volume EQUATION of potential surge ( magnitude of surge wave) LECTURE 4A, SLIDE 12The magnitude of the pressure increases when the pressure surge is traveling upstream, this is due to the fact that the pressure increase at the stoppage point is the sum of the potential surge pressure and the pressure rise due to line packing. To avoid pipe failure due to transient flow one should take into account changes to pump operations power failures valve operation