Hello Guys,
This is first time, I am going to post a topic for your value able comment. Actually I am working on as Process Engineer on Green Field Project, which have both oil & gas production wells and then onward oil & gas processing facility. Basically this is a sour oil & gas treatment facility.
In said project I am working on Gas Wellhead, Onplot Manifold, then further gas processing including separators, Compression, TEG Dehydration. Here I have a challange in Design Review regarding GRE Flowline protection with Wellhead HIPPS. Below are the complete details for the system and I have also attached a sketch for better understanding.
Multiphase fluid is produced from Gas wellhead at about 250 bar FTHP and 40~60 C FTHT depending on the production flowrate. The pressure is reduced to <110 bar at the wellhead through an automated choke. The gas well fluid stream flows to Gas Inlet Separator operating at 100~103 bar.
If the choke valve fails in open condition or Gas Inlet Separator inlet valve closes on ESD activation, then 900# flowlines and piping downstream of the choke valve will be exposed to high pressure well fluid. For each well head, over pressure protection system is provided to safeguard the underrated GRE flowline from overpressurisation. According to initial proposed design, four gas wells connected through GRE flowline from wellheads to On Plot Manifold at station. The gas well flow lines have GRE segments of approx 5 kilometers length with design pressure of 120 barg. As per Shell Guideline on SIL Assessment & Implementation , Partial relief Valve with HIPPS is provided on production header to protect flowlines for over pressurization from wellhead side for ‘blocked in’ condition. HIPPS failure for one well (for 5 number of wells) is considered for the sizing of this relief valve as per EP Guideline on Process Safeguarding. During project Design Review workshop, there was an action requesting to confirm that GRE flowline would not be over pressurized (from wellhead side) with relief valve provided on common production header set at 113 barg. I worked out on TGNET that RV on common manifold will overpressurize the GRE line when it will reach its releving condition 124 barg. So Now I am trying to close this action with the following basis." As the HIPPS System is SIL 3 rated as per PFD calculations, so this HIPPS only is adequate to protect the GRE flowline from overpressurization from wellhead. Partial relief valve is only provided to protect the On Plot Manifold incase of failure of one well HIPPS out of 4 wells." Any one can advise me either this is correct approcah to close this action or I need to make some other changes.