Refer Attachment for the Process flow scheme of the LPG storage and export system.
LPG produced from Gas Processing trains is stored in the horizontal mounded LPG bullet. Operating conditions of the LPG at the bullet is 14.3 barg @ 65 degC. These conditions are very close to its bubble point of the LPG. Inlet flow rate to the bullet depends on the number of train/s in operation since LPG produced from each train is 4 m3/h (600 bpd) which is 50% of the rated capacity of the pump (i.e. 8 m3/h). Dimensions of the bullet are 4.6 m ID X 26 m L and it is sized to store 2 days of LPG production from both trains (i.e. 1200 bpd).
On-off valve is provided in the pump suction line to enable batch operation during single train operation. Pump start is manual (either local or remote) and permitted once on-off valve open position is ensured.
In order to satisfy NPSHR of 2.5 m as specified by pump supplier in the performance curve, trim cooler has been provided in the pump suction. This option was found to be cost effective instead of the instead of elevating the LPG bullet to meet NPSH requirements. Cooling medium for the trim cooler is cooling water with inlet temperature of 35 degC. The trim cooler is designed with sufficient margin on surface area to ensure that LPG is remains completely sub-cooled in the pump suction piping. Cooling water inlet flow is controlled based on LPG temperature in the pump suction. LPG operating conditions at the pump suction are considered as 14.06 bag @ 55 degC (max temp). Two pumps are provided (1 operating + 1 stand by) each having rated capacity of the 8 m3/h.
During pump flow is maintain using discharge flow control valve (set at 8 m3/h). Protection of the pump assured by following:
• Low low pressure trip at the pump suction (set @ 13.5 barg)
• Low low liquid level trip in the LPG bullet
• High high temperature at the pump suction (set @ 60 degC)
• Automatic Recirculation Valve (ARV) is provided by pump supplier which is set @ 5.5 m3/h
• Pump discharge pressure over-ride (over flow) @ 58 barg is provided avoid pump running at the end of curve operation. However this over-ride can be deleted if pump motor has been sized for the end of curve operation. Please suggest.
LPG pressure at the battery limit of the CPF (Central Processing Facility) is taken as 70 barg and LPG is exported to the metering station via 45 km, 4” underground pipeline. Pressure control is provided downstream of the custody metering skids to maintain tie-in pressure of 60 barg at the transfer point.
Attached Files
Edited by shekhar dhuri, 13 December 2014 - 11:23 PM.