4 replies to this topic

[AFFAN]

we are in Engineering phase of Gas processing plant, with Potential production of LPG & Condensate as well.

Initial plan is transport both these products throug approx 80 km pipe line to highway terminal. Transfer will be done in batches. Apart from capacity constraints, can same line be used for both these products.

Or please suggest me pecuilar design measures specific with LPG pipeline, LPG composition is approx 45 % butane & 55 % propane, so to keep it in liquified form do we need some special measures, of mantaining some pressure or temperature both for pipeline and storage purposes.

[ankur2061]

To answer the first part of your question, yes batching of different products trough the same pipeline is possible and is routinely done by many operators. This is specifically true for white oil products such as gasoline, gasoil, naphtha. Switching products may involve pigging of the pipeline to remove the previous product and / or flushing a specific quantity as off-grade product which would be recycled subsequently. The quantity to be flushed before it is established that the product has been completely substituted with the new product is obtained through operating procedures and experience.

To answer the 2nd part of your question the pumping pressure of the LPG should be above the vapor pressure at the pipeline maximum operating temperature to maintain it in liquid state. Since there will be frictional losses in the pipe you should be looking to maintain a pressure of 30 to 50 psi above the vapor pressure at the terminal end of the pipeline which means that the pressure will be even higher at the start of the pipeline. As a calcualted value the pressure at the start of the pipeline will be the terminal end pressure plus the pipeline frictional loss.

Hope this helps.

Regards,
Ankur

[AFFAN]

To answer the first part of your question, yes batching of different products trough the same pipeline is possible and is routinely done by many operators. This is specifically true for white oil products such as gasoline, gasoil, naphtha. Switching products may involve pigging of the pipeline to remove the previous product and / or flushing a specific quantity as off-grade product which would be recycled subsequently. The quantity to be flushed before it is established that the product has been completely substituted with the new product is obtained through operating procedures and experience.

To answer the 2nd part of your question the pumping pressure of the LPG should be above the vapor pressure at the pipeline maximum operating temperature to maintain it in liquid state. Since there will be frictional losses in the pipe you should be looking to maintain a pressure of 30 to 50 psi above the vapor pressure at the terminal end of the pipeline which means that the pressure will be even higher at the start of the pipeline. As a calcualted value the pressure at the start of the pipeline will be the terminal end pressure plus the pipeline frictional loss.

Hope this helps.

Regards,
Ankur

[AFFAN]

Hi Ankur

Thanks for the post it will be really helpful.

However I am very interested in knowing about the nature of pig to be run in that sort of pipeline. should it be a simple mechanical/ disc type pig, with out any inhibition used in gas flowlines for dewatering and cleaning purposes, or there should be some chemical inhibition package to be swept across the line with the help of pig?

I assume even if some mixing occurs b/w the two products, there will not be any harmful reaction except for initially some impurities in the product.

[ankur2061]

Affan,

Refer the attachment. It talks about a "Batching Pig" which allows segregation of dissimilar fluids. Very nice article on pigging.

Regards,
Ankur.

Attached Files

•  An_Inro_to_Pipeline_Pigging.pdf   393.08KB   37 downloads