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Facilities Sand Management: Particulate Solids Transport – Piping Design (B-FSM026)

Concentrated sand slurry introduced upward into horizontal gas-liquid flow stream

The next series of four articles will cover the topic of sand and slurry transport; the first three articles will look at piping design, and the fourth will cover transport in gravity separators. The particular focus is hydraulic transport of solids – not multiphase or pneumatic.

These articles will be focused on piping design specific to Facilities Sand Management (FSM) systems in the oil & gas industry. They are adopted from slurry transport principles in the mining industry modified with lessons-learned in design and operation of FSM systems offshore.

The three topics in piping design are;

General Design Principles

  • ASME B31.11 for piping design
  • Lessons-learned principles

Erosive Limit – Upper Transport Boundary

  • Maximum velocity for tolerable erosion
  • API RP 14E – too conservative
  • McLaury & Shirazi – better approach but limited availability

Saltation Limit – Lower Transport Boundary

  • Minimum velocity to carry particles in a liquid
  • Horizontal transport – Durand, Turian, Wilson, etc.
  • Vertical transport – Stokes Settling Limit
  • Multiphase flow is too complicated for this discussion – consult flow assurance modeling specialist

Mechanical Design:

  • ASME B31.11 provides piping mechanical (not process) design codes
  • Horizontal runs sloped downward (1:100)
  • Elbows as long radius minimum, with 5R/10R preferred
  • Elbows placed no closer than 10D
  • Use eccentric reducers
  • Does not provide process design (flow rate or velocity)

Process Design:

  • Valve type should be full port gate or rotating disc
  • Sample ports placed on vertical runs (upward flow) only
  • All piping and process equipment should be pre-filled with liquid
  • Never introduce concentrated slurry into empty piping or process equipment

The last statement is underlined, as that should be the basic, core, imperative design principle when dealing with sand slurry. Never put sand slurry into empty piping or tanks. That will guarantee plugging. Always introduce the slurry into piping with moving water.

The next article will provide an introduction to the topic of erosive limit.

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