Pump Circuits

Chapter from the Piping Design Guide.

PUMP CIRCUIT HYDRAULIC DESIGN

Suction Circuit Design

Design Principles for Pump Suction Piping:
1. Minimize friction losses — keep suction piping as short and straight as possible
2. Avoid high points — potential vapor pocket formation
3. Eccentric reducer at pump: flat-on-top for horizontal suction from above
4. Concentric reducer OK if suction from below (vertical upflow)
5. Minimum 5 pipe diameters of straight pipe before pump suction flange
6. Suction strainer: temporary (startup) or permanent (dirty service)
• Startup strainer: conical, sized for 2× pipe area
• Permanent strainer: T-type or basket, ΔP at 50% plugged in NPSH calc
7. No butterfly valves in pump suction (creates non-uniform flow)
8. Gate valve for isolation — full bore, full open
9. Consider suction piping warm-up for hot services (deadleg prevention)

Discharge Circuit Design

Design Principles for Pump Discharge Piping:
1. Check valve immediately after pump (prevent reverse flow on trip)
2. Isolation valve downstream of check valve
3. Pressure gauge between pump and check valve (for shutoff head check)
4. Minimum flow takeoff between pump and check valve
5. Size for economic velocity (7-10 ft/s liquid, typical)
6. Include PSV if pump shutoff head can exceed downstream MAWP
7. Control valve sizing: allocate 30-50% of total system ΔP to CV at design flow
• This ensures adequate rangeability and control authority
• Remaining ΔP: piping friction + static head + equipment ΔP
8. Warm-up line: for hot service, provide small bypass around check valve for warmup

Source: Piping_Design_Guide_v1.xlsx · sheet “Pump Circuits”

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