3 replies to this topic

[Tom Berenger]

I'm updating my first isometric drawing. How do I include instrumentation and electrical (tubings) on the drawings? I have a sketch of what I want to incorporate into the iso drawings, but don't have any dimensions. So, do I need dimensions to incorporate I&E into the iso? Does the I&E have to be drawn to scale?

Thanks for your anticipated assistance.

[Fr3dd]

Hi Dayo,

If you're a process engineer, it's kind of strange that you're asked to update isometrics. Usually, isometrics are made by Piping (nowadays with dedicated software which generates a really accurate 3D model) and the input for this model is given by process on the P&ID's. As a process engineer, you will see isometrics when you need to perform hydraulic calculations (i.e. if an existing pump is relocated, or in systems which are really sensitive to static head changes.

In principle, if any modification is required, you should put it on P&ID's and piping should arrange it in the model, or generate the new isometrics. If you're reviewing isometrics and you see something wrong, you can put comments in it (but just in the case that the isometrics are different of what's in the P&ID's).

And yes, all the elements need to be drawn in scale. But placing them is, in most of the cases, the role of the piping team.

Regards,

[Art Montemayor]

Dayo:

If you are doing project engineering work at an engineering contractor or at an operating plant, I can relate to what you are doing. I’ve done countless exercises like yours in the past.

When updating any produced drawing to submit your comments, revisions, corrections, or comments you usually use a local standard color for your notes – such as the following:

• Green = material is to be removed, eliminated;
  
• Red = material is to be included, added in the revised version;
  
• Blue = written comments to complement changes shown.

I have always remembered the above as: Green = Out; Red = In.

Isometric drawings are used as 3-D visual depictions of piping and equipment to show relative locations and positions within a process. They are dimensioned drawings, but I have never seen or used one that was (or claimed to be) scaled to size. I have never seen any need for scaling such drawings; as long as they are dimensioned properly, there should be no requirement for scaling. This is a tool for showing the relative positions of piping and equipment.

You may need dimensions to show I&E equipment as it is installed – such as solenoid valves, control valves, transmitters, etc., etc. But you are not required to show the I&E equipment to scale nor its dimensions – unless they affect the installation or the allowed space or volume that they occupy. Again, this is a tool to bring close to reality the actual installation of the subject items or equipment. Therefore, it is your responsibility that you show and ensure that the isometric can be built, installed and comply with what is needed without suffering any negative results such as constructability, maintenance space, operability, access, etc., etc.

[ankur2061]

Dayo,

Installation of instruments on piping is dictated by instrument hook-up drawings for a given type of instrument. Piping isometrics can cross-reference the standard instrument hook-up drawings for instrument installation of a given type in the notes or remarks section instead of showing the instrument hook-up on the piping isometric itself. This is a widely adopted practice in the enginnering consulting industry.

Regards,
Ankur