System Separator

My friend, in this posting, I will share my experience in checking the typical separator system or pressure vessel system. This check list is only general rule or general engineering practice. as we know, each project has a specific requirements, so this guideline should be modified as per specific requirement.

My friend, we can use the following table as a guidance when we check P&ID . Hopefully, it is useful .

Number	Check Point Description for Separator System	Remark
1	Proper symbol of vessel shall be used and shall consistent with the legend sheet of particular project. ( The symbol may be different between one project and another project)
2	The Equipment Tag Number shall be indicated and shall consistent with the PFD document.
3	The vessel data shall be provided at top/bottom side P&ID and shall consistent with the datasheet document.
4	Separator vessel internal shall be indicated if it is applied. The Internals can be :
	# Inlet type : vane, half pipe, etc
	# Vortex breaker on the outlet line
	# Demister pads on gas outlet
	# weir plate separate the oil and water
	# dip pipe
	# ……. Other ?
5	Check line pipe FROM and To vessel
	# line number shall be correctly assigned
	# material class to be specified
	# the pipe size shall be clearly specified
	# …..etc
6	All nozzles shall be presented with size and flanges. The number of nozzle and size shall be consistent with the datasheet.
7	Isolation valves, or spectacle blind, or spacer for maintenance purpose shall be provided.	Note 1
8	Pressure indicator to be provided on pressure vessel, if possible the indicator should be readable by operator
9	Temperature indicator to be provided on pressure vessel which the temperature more than ambient condition is possible, the indicator should be readable by operator
10	A valve vent with a blind flange end shall be provided for venting requirement.
11	1 inch vent size can be applied only for vessel which has inside diameter less than 1.5 meter, otherwise 2 inch should be used
12	A valve with a blind flange end for utility connection shall be provided for vessel handling toxic or flammable fluid.
13	2 inch size utility connection generally applied. The minimum size is 1 inch.
14	Process drain connection (with manual valve with blind flange end) shall be provided. The drain line can be taken directly from vessel or from low point of the bottom line of the vessel upstream of the first block valve.
15	1 inch drain size can be applied only for vessel which has inside diameter less than 1.5 meter, otherwise 2 inch should be used.
16	Where drain fluid is discharged to an oily water sewer system during operation, the permanent pipe connection shall be provided
17	If the drain fluid will only be drained during shutdown period, it is shall have a valve with a blind flange end without permanent pipe connection o sewer system.
18	Minimum one man way (Man Hole) shall be provided. Except for small vessel, a hand hole is adequate
19	Generally hand hole is applied for vessel with inside diameter less than 1.0 meter ( depend on the particular project specification)	Note 2
20	The size of both man hole and hand hole shall be clearly defined in the drawing. Commonly, the manhole size is either 20 or 24 inch.
21	The level instrumentation is clearly defined and consistent with the legend sheet.
22	When two or more level instrumentation including level gauge is required, a stand pipe shall be provided on a vessel for installing level gauges and level detector.
23	Isolation valves shall be provided between the stand pipe and each instrument for maintenance.
24	Generally 2 inch stand pipe is used
25	A level detector initiating a shutdown sequence shall be directly mounted on a vessel ( shall not mounted on a stand pipe)
26	Nozzle equipment for stand pipe and external level instrument shall be horizontal, connecting pipe shall be NO POCKET
27	Nozzle on equipment for stand pipe and external level instruments shall be directly connected to vessel and shall not be connected to process line or nozzle. ( unless a fluid velocity in the line is less than 0.6 m/s)	Note 3
28	Various control valves to be provided wherever applicable, such as; level control valve and pressure control valve.
29	Proper valve symbol should be used and consistent with the legend sheet. Generally, globe valve type is used for control valve.
30	Generally, Control valve is smaller than the corresponding line size but not less than 0.5 of pipe diameter. The reducer and expander size shall be clearly indicated
31	For shutdown and maintenance purpose, block valve shall be provided both at upstream and downstream of the control valve. The block valve can be either ball valve or gate valve type depends on the particular project specification.
32	Generally glove valve type is used as the pass control valve up to 6 inch (this type give better control with opening). The gate valve type can be used for above 8 inch.	Note 4
33	Normally, a handwheel is required for large size control valve or for control valve without by pass ( the requirement is depend on project specification)
34	By pass is not required if any other system can be used as by pass. For instance; if two or more control valves are installed in parallel.
35	Failure position of the control valve shall be indicated, either Fail Closed (ATO) or Fail Open (ATC)
36	For Fail Open; one(1) drain valve is sufficient, can be located both at downstream or upstream control valve. ( between isolation block valve and control valve)
37	For Fail Closed ; two(2) drain valve shall be provided both at downstream and upstream control valve ( between isolation block valve and control valve)
38	For control valve is equipped with handwheel ; one(1) drain valve is sufficient.
39	Signal symbol (pneumatic, electric or data link etc) shall be correctly used. Ex: electric signal symbol to be used for LIC to control valve and data link symbol to be used for LIC to LI at DCS.
40	Setting point of initiating alarm and shutdown shall be clearly presented
41	Indication for normally close valve (NC), normally open valve (NO), Tight Shut Off (TSO), Lock Open (LO), Car Seal Open (CSO), Lock Closed (LC) and Car Seal Closed (CSC) etc shall be clearly defined
42	Overpressure protection (PSV) shall be provided for pressure vessel which has design pressure above 15 psig.
43	Information such as; set pressure, case, size of orifice, and PSV’s nozzle size shall be stated.
44	Set pressure of PSV shall not exceed the vessel’s MAWP. If the MAWP data is not available, the PSV’s set pressure shall equal or less than design pressure of the vessel.
45	If required, the spec break between inlet system (vessel system) and outlet PSV system (flare network system) is commonly located at the PSV’s outlet nozzle.
46	Isolation valves/ block valve at line inlet PSV shall be LO or CSO
47	Isolation valves/ block valve at line outlet PSV shall be LO or CSO
48	Line inlet PSV shall be FREE DRAINING. The indication of this requirement shall be indicated.
49	Provide ¾ inch bleed valve between inlet block valve and PSV.
50	By pass line of PSV shall provide block valve with LC or CSC, a globe valve type to be provided at downstream block valve. If required, the spec break material is located at downstream end of the glove valve.
51	Spare PSV (Not Operating) shall be isolated with block valve at inlet line and LC or CSC.
52	The isolation valve for outlet line of spare PSV (Not Operating) shall be LO or CSO.
53	A purge line with a gate valve by passing PSV should be provided for depressurizing a process system to a flare system, unless there is a process line used for this purpose. The purge line size shall be the same as the vessel vent valve size.
54	For vessel which the minimum elevation is critical (e.g. for pump performance), the elevation of the vessel from ground level shall be stated. (e.g. Deaerator, Flare KO Drum etc)
55	Shutdown valve shall not have a bypass and handweel.
56	The shutdown valve shall be TSO

Note 1 : Please let me know, if you know the standard, from what size we can applied those isolation type?.
Note 4 : It is only engineering general practice, The owner specification should be followed.
Note 1 , 2 ,3, 4 : please share in comment section below, and let me know if you have another reference.

That's all I can share this time,
Thanks