Thumb rules to prepare Equipment Layout

Dear all,
What are the most basic things to keep in mind while preparing Equipment Layout for Gas Pipeline Stations.

Equipment list-
Pig Launcher/Receiver, Intake Valve station, Knock-Out Drum (KOD), Filter Separators Skid, Water Bath Heater, Pressure Regulating Skid, Metering Skid & Condensate Tank.

Pipeline Size- 30", Natural Gas Transmission Pipeline.

I like to add one more category to JOP’s list and that is COST! Having equipment that is piped up with exotic alloys and having them place at opposite ends of the facility, when it would be acceptable to place them side by side, is a better way to go!
You have the major requirements for doing an equipment layout, BUT the real trick is that some requirements have a higher priority over others, and it changes from project to project! A designer’s job is to know those priorities and be able to “juggle” them around appropriately. Not an easy task on some projects!!!

Another important thing ......the sequence of these important thought are just put in perfectly.
The thought process should start with SAFETY first...& so on..

Thanks to both of you!!

Okay let's update the list as we have it so far.
The basic things to keep in mind while preparing Equipment Layout for any project:
- Safety
- Constructability
- Operations
- Maintenance
- Code Compliance
- Cost

Thanks to all of you, now I understood priority sequence...