Pigging or Flushing a 15 km Non-Uniform pipeline

[Finchh]

Hello all,

I’m looking for some guidance on cleaning a 15 km non-uniform pipeline that alternates between 4" and 6" Schedule 80 sections, with reducers, bends, and a non-barred tee section (P&ID attached for reference). We’ve calculated a total pressure loss of approximately 30 bar at a flow velocity of 1 m/s, accounting for friction, bends, and head loss. There are no vent points available, so air displacement is a concern for both flushing and pigging operations.

Pipeline Details:​

• Length: 15 km
• Diameters: Alternating 4" and 6" Schedule 80 sections
• Pressure Loss: Around 30 bar at 1 m/s flow velocity
• Tee Section: Non-barred tee included in the line
• Vent Points: None available

Given the diameter transitions and the non-barred tee section, I’m evaluating both pigging and flushing options. If anyone has insights on handling non-uniform lines with tees in terms of pig selection (such as dual-diameter or adaptable pigs) or advice on flushing setups to manage air displacement without vent points, I’d appreciate it. Additionally, any suggestions on pump requirements to consistently achieve the 30 bar head for this configuration would be extremely helpful.

Thanks in advance for your input!

 

[LittleInch]

That P&ID tells us very little I'm afraid.

You need a profile and also a better description of what fluids you're talking about and how you've got to 2bar per km for 1m/sec flow velocity??

Multi diameter pigs are difficult at that size but exist, but is the pipeline piggable?

You can get "gel" pigs or fluids which act as the same.

Flushing sounds like liquid displacing liquid?

Pumps shouldn't be an issue - why do you think it is?

But describe a bit better what you want to do and what your constraints are.

 

[Finchh]

The P&ID snippet was just to show the reducers and non-barred tee. This is a 15 km flow line with a 40m elevation change, where reduced flow suggests possible debris buildup.

The pressure requirement is estimated at 30 bar (23 bar calculated for elevation, friction, and bends, with a safety margin). Considering using a gel pig given the 4" and 6" diameter changes, though I have limited experience with this approach.

Is this method suitable, or is there an alternative to effectively remove the buildup?

Thanks !