Spillback Measurement

Chapter from the Instrumentation & Control Design Guide.

PUMP SPILLBACK FLOW MEASUREMENT

Flow Measurement for Automatic Spillback Control

For automatic spillback systems (flow-controlled recirculation), accurate flow measurement is essential.

Common Flow Meter Types for Spillback Service:

1. Orifice Plate (most common):
• Install in pump discharge, upstream of control valve
• Standard concentric orifice per ISO 5167
• Minimum 10D upstream, 5D downstream straight pipe
• Accuracy: ±1-2% with proper installation
• Low cost, no moving parts

2. Vortex Meter:
• Good for clean fluids, moderate turndown (10:1)
• Minimum velocity: ~1 ft/s for liquids
• No pressure taps, no impulse lines
• Accuracy: ±0.75-1%

3. Coriolis Meter:
• Direct mass flow measurement
• Highest accuracy (±0.1-0.5%)
• No straight pipe requirements
• Expensive, but worth it for critical pumps
• Excellent for two-phase or varying density fluids

4. Magnetic Flow Meter:
• For conductive liquids only
• No pressure drop, good turndown
• Accuracy: ±0.5%
• Not suitable for hydrocarbons (non-conductive)

Source: Instrumentation_Control_Design_Guide_v1.xlsx · sheet “Spillback Measurement”

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