There are three basic types of pipeline systems:
- Direct system
- Ring main system
- Free flow system.
Direct line system
- Quick loading & discharging.
- Short pipe line.
- Less bend.
- Less loss of pressure due to pipe line friction.
- Direct line to provide better suction.
- Time of washing the line is short.
- System is cheaper than the other system.
- Leak is minimized.
- Easy to operate so less training is required.
- It is easy to separate each cargo.
- In case of leaking the control of leakage is difficult.
- This system is very inflexible.
Fig : Direct line system
Ring main system
- In this system any tank can be discharged by any pump. Thus different grade of the cargo can be loaded.
- It is expensive to build due to the extra length of the piping required.
- Extra bend is required. Thus decreasing in rate.
- Risk of leakage from radius of bend exists.
Fig : Ring main system
Free flow system
- Main pipe line is not used for discharge.
- Less pipe line.
- Less bend.
- Less friction & more pressure cause very high discharge.
- Is not flexible.
- One grade is dischargeable if more risk of contamination exists.
- Risk of overflow exists if level of all tank doses not carefully monitoring.
Fig: Free flow system
Points to Pounder for all types of Pipe lines
THE FREE FLOW SYSTEM
THE DIRECT LINE SYSTEM
THE RING MAIN SYSTEM
|Used on large crude||Used on VLCC||Used on Product|
|Carry only one garde||Carry two or three grade||Carry several|
|Of cargo||Of cargo||Different products|
|Large gate valve built in||Simple lines leading in the|
|Stern trim cause the oil||Due to straight length of||Due to the number of|
|To flow to the||Pipeline, there is better||Bends, joints and valve|
|Aftermost tank||Suction & less loss of||It take longer time|
|Suction main cargo pump||Fewer valve & bends||Due to the number of|
|Situated in aft||Means less erosion & leak||Bends, joints and valve|
|Means more erosion &|
|Less maintenance||More maintenance|
|Thorough washing of line is||Thorough washing of|
|Not possible unless the||Line is possible without|
|Washing are flushed into||Flushing into the tank|
|The tank & discharged|
|Due to fewer valves leaks|
|Are difficult to control|
|Valve segregation not||Required two valve|
|The initial cost of fitting||The initial cost of|
|Is less than ring main||Fitting is higher|