Design Tips

FEED/ Simulation

• Feed Verification: Take it seriously. Check thoroughly to take 100% ownership without pointing fingers later on at others when things go wrong. Cost of verification is minor c.f. later changes

• Simulation: Capture outputs for various cases in separate worksheets. Summarize min and max values for each parameter in a Summary sheet with Hlookup functions. Good for equipment sizing, control valve range etc. See ‘Simulation Summary’ in Sizing

• Instead of separate files for each and every Line/PSV/Pump sizing, have a single calculation sheet. Transfer outputs to a table, e.g., Line List to minimize pages and ease of review. See ‘Line Size Robo’ in Sizing. Note: Sizes 100 lines in less than a minute

P&IDs

• Notes: Minimize. Insert short notes inside P&ID. Common repeated notes in Legend Sheets

• Add caution box e.g. “Do NOT drain under pressure”. “Purge the firebox before lighting a burner”. Glossy operating manuals stay locked in glass cabinets. P&ID Caution Boxes help in daily operation

• Don’t run flare/drain/utility headers across P&IDs. Piping connections are NOT as in P&IDs but are based on physical location. 1 cm in a P&ID may be a 1 km away in a plant. Route the connections to a box marked HP/ LP Flare; Open /Closed Drain; CM/HM Supply/ Return etc

Wellheads & Flowlines

• Riser SDV: Avoid 2” pressurization across SDV to avoid small bore pipe rupture due to dropped objects. Pressurize the downstream cavity with diesel via a portable pump. Or go for a 4” line

• Choke: High upstream pressure during start-up may result in low temperature in downstream piping, brittle failure, hydrate / icing blockage. Add a P&D Caution Box: “Throttle choke and pressurize slowly watching for low temperature/ icing downstream”. Best: Pressurize with diesel. Use suitable metallurgy

• Waxy Oil: High pour point oils cool, congeal and plug. Plugged lines impose high backpressure on pumps/wells and make restart difficult. Heat trace/ insulate/ flush the lines with hot water (produced or seawater) as soon production is stopped

• HIPPS: It takes time to sense and close HIPPS valves. Perform transient analysis and check Process Safety Time (PST) w.r.t downstream obstruction/ hydrate blockage. Provide minimum length of HP piping (fortified section) downstream of HIPPS valve to allow pressure build up during PST. Locate HP/LP break accordingly. Add a PSV in LP section sized for 2*HIPPS valve leak rates, per API 14C and 14H. No PSV for export pipeline as it’s large volume can handle pressure spikes

• Lower Rated Inlet Headers: Fully rate to headers. If the header is lower rated, go for PSV sized for 2 out of 5 wells, an old rule of thumb. Do SIL study with probability of individual well to decide ESDVs failure to close on demand to size PSV

• Production Header / Flowlines: Mark in P&ID: “Slug prone lines. Support properly”. New hire pipers miss

• Water Injection line: P&ID Caution Box: “Oil, Gas and H2S may backflow. Caution while breaking flanges”

• No small-bore fittings or instruments take-off outside of well SDV envelopes. See Safety Alert

Pipelines

• Offshore SSIV Location: Dropped objects or boat hit damage riser or pipeline. SSIVs minimize inboard (platform side) inventory and release. Assist if Riser SDV fails to close or passes during a topsides fire. (1) Min distance: Dropped object = Crane Boom + Water depth. DNV 107 5.3.3. Assumes 45° deflection when dropped object hits sea surface. If water depth is 100 m, drop point is 100 m away from surface hit. (2) Max distance: Safety Zone or no-go area for vessels. ≈ 500m. SSIVs not required for oil lines; only for gas lines in shallow waters. Not for deep waters: large inboard inventory renders SSIV use questionable. In <100m waters, locate risers inside jacket as boat hits are common than dropped objects

Pig Launchers/ Receivers

• Occasional ID mismatch with pipeline creates operational problems. P&ID Note: “IDs of minor barrel, outlet valve bore and main line should match”. (DGK Murti, ex-KOC)

• Design Pressure: Usually same as upstream. Upstream PSV sized for all demands except fire. Usually  thermal PSV. Launchers/ Receivers are kept isolated at atmospheric pressure - filled with N2 or HC gas. Practice varies + H2S level. PSV required if designed to ASME. No PSV to pipeline code. Agree early

• Pressure Balance: Add 2” line with a Normally Open valve, from inlet piping to door end to equalize pressure across a pig stuck in neck. Allows simultaneous venting from either end of a pig before opening door. Unrelieved pressure upstream of pig will shoot it out causing injury. See Safety Alert. Balance line helps to keep lower dP across a pig preventing sudden pig movement that can damage it and valves while launching or receiving

• Drain: Close to the door in Receiver. Close to outlet in Launcher. Mark slope towards drain

• Nozzles: Minimize holes. All tappings for vent, UC, PSV and PI from 2” balance line

• Door: P&ID note: “Door to face seaside or fence.” (Precaution against pigs that may fly off!)

• Drip Tray: Below door with a drain line (no valve) terminating at the nearest Open Drain funnel

• Dead leg: Potential dead leg in the cavity between DBB valves. High corrosion