PDIC TAPPING POINTS FROM PDCV IN PROCESS CONNECTED PIPING

[Nelly2818]

Hello, I've been trying to resolve this issue and would appreciate if anyone can share some ideas on the above subject. We are trying to install two PDIC's (Fisher Model 4194H) upstream and downstream of a PDCV (Fisher Model 657). A note on the PID states that "minimum distance from PDCV: 20ft". As seen on the attached PID, I'm really confused as to this requirement of a 20ft installation distance. My company specs puts upstream and downstream tapping points for instruments at 3ft and current installation of the downstream PDIC stands at 12ft measured along the centre line of pipe fittings and valves(see attached offshore photo shots). So here lies the confusion. I really don’t think it matters where the PDIC is located as long as it can receive steady and accurate readings upstream and downstream of the pressure inputs and hence maintain the correct DP. I'm very confident that at the present location of the downstream tapping point for the PDIC, 12ft from the PDCV, it should be able to get steady readings (also note that this point is > 5D from the last bend (turbulent point) 35" from the last bend i.e. considering that the upstream valve is full bore type. Presently I dont have any industry spec or vendor installation guide that cites a maximum or minimum distance for the PDIC installation with respect to the PDCV. Therefore, my major question is can we be sure if the upstream and downstream pressure inputs will be accurate and steady with the tapping points (especially downstream) as they are presently located? Any clarification and advice on this subject will be most appreciated.
Nelly 2818