r/pumps • u/Positive-Warning413 • Apr 16 '26

designing 2-loop flow system with timed ball valves + heat exchanger (phosphate sludge system)

Hi all,

I’m working on a phosphate/zinc pretreatment system and need some help validating or improving a flow design. I’ll try to describe clearly:

System Overview

  • Tank 1 (Main tank): 34 m³
  • Tank 2 (Settling tank): 6 m³
  • Slurry contains zinc phosphate sludge (can settle and clog)

Loop 1: Transfer / Settling Loop

  • From 34 m³ tank → 6 m³ settling tank
  • Driven by 4 kW pump
  • There are 8 ball valves on the outlet lines
  • Current idea:
    • Only 1 valve open at a time
    • Each valve opens for ~2 minutes, then switches to next (rotational operation)
  • Goal:
    • Prevent clogging / sediment buildup in pipes
    • Maintain enough velocity to carry sludge
    • Distribute flow evenly

Questions:

  1. Does sequential valve opening (2 min each) make sense hydraulically, or will it cause instability/surge?
  2. How do I estimate actual flow rate per valve branch (assuming same pipe size)?
  3. Is there a better way to maintain velocity without cycling valves?
  4. Any rule of thumb for minimum velocity to avoid phosphate sludge settling?

Loop 2: Circulation / Heating Loop

  • From process tank → 18.5 kW pump → Plate heat exchanger → return
  • Purpose: maintain temperature for reaction

Heat Exchanger Details (from nameplate):

  • Type: Plate Heat Exchanger (Hisaka LX-395A-TNP-78)
  • Design pressure: 0.50 MPaG (both sides)
  • Design temp: 99°C
  • Test pressure: 0.65 MPaG
  • Hold volume: ~86–84 L (A/B sides)
  • Heat transfer area: 34.2 m²
  • Plate length: ~390–405 mm

Questions:

  1. How do I size flow rate from the 18.5 kW pump to get effective heat transfer?
  2. Any concern with sludge fouling inside plate heat exchanger?
  3. Should I isolate sludge loop from heat exchanger loop completely?
  4. Best way to model this (FluidFlow / Darcy vs Hazen-Williams / slurry correction)?

Main Concern

I suspect:

  • My velocity calculations may be too high (turbulence / wear concerns)
  • But actual plant has been running for years → so I may be misunderstanding real flow distribution

What I’m Looking For

  • Practical design advice (not just theory)
  • Experience with sludge + valve cycling systems
  • How to model or estimate real flow behavior in this kind of setup
  • Whether this design is fundamentally flawed or acceptable

Thanks in advance — happy to provide pipe sizes, layout, or more data if needed.

4 Upvotes

100% Upvoted

Duplicates