Pipeline blockage

A critical parameter in Equation (4.13) is pi. This is on the bottom of the equation and so any increase in its value will cause a corresponding lowering of Ci. A pipeline is quite likely to block, therefore, if the compressor is operated above its pressure rating, even for a short period of time. It must be stressed that absolute values of pressure must be used throughout in these equations. If p is taken as a gauge pressure, or the pressure at the end of the conveying line, the design is likely to be seriously in error. 

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Unfortunately, many new and old systems have not been designed properly and are being operated inefficiently. Some of the major consequences include high energy consumption, excessive system erosion, inadequate conveying capacity, unexpected pipeline blockages, excessive product damage and hence, poor quality control and/or increased maintenance. These problems have resulted mainly from... 

Flow instabilities or even pipeline blockage during start-up procedures due to surge effects caused by the initial high pressure drop across the blow tank (and hence high instantaneous flow rate of material),... 

Pipeline blockage during shutdown procedures due to surge effects caused by the sudden venting of high pressure air down the pipeline (and hence, acceleration of product towards the end of the pipeline). 

Hydrate formed in pipelines has been identified as a problem by the gas and oil industry since the 1930 s, there being both hazards and economic factors in actual pipeline blockage, and the prevention and control of hydrate formation in pipelines is of major importance. Although emphasis has been placed on finding practical solutions in this area by inhibiting hydrate formation with various additives it is clear that modem practice requires better alternatives to those in common use today that are safe and environmentally benign even for the ever more... 

In 1934, Hammerschmidt showed that gas hydrates are implicated in a natural gas pipeline blockage and since then hydrate control has been a major activity in the gas and oil industry with a substantial associated cost factor. The recent (2010) Deep Star Horizon oil well problems in the Gulf of Mexico again brought to the fore that gas hydrates often show up where they are not wanted. Gas hydrate control comes under the discipline of flow assurance in petroleum and chemical engineering. A comprehensive text in this area is the book by Sloan and Koh. ... 

Non-return valves Non-return valves need to be considered in terms of system protection, particularly in the event of a pipeline blockage, for blowers and compressors with positive pressure conveying systems. Should a pipeline block there is always a risk of particulate material flowing back along the pipeline when the compressor is switched off. 

If the leakage air does interfere with the material feed it could result in a significant reduction in the bulk density of the material, and hence affect the material fiow rate. It is important, therefore, to ensure that the vent is correctly designed and maintained. On start-up, after a shut down, the bulk density of the material in the hopper could increase considerably and this could result in pipeline blockage at this time due to over feeding. If this is a possibility the material in the supply hopper should be aerated prior to start-up. 

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