PD Pump Problems in Fertigation – Part 3: Compatibility, Pulsation & Startup Control (Copy)
In this third installment of our 4-part series, we look beyond the pump itself and focus on system-level design flaws that cause internal wear, pipe failures, and unreliable startup behavior.
From chemical attacks on seals to hammering pipes and controller mismatches—these are preventable with the right technical oversight.
Issue 7: Material Compatibility Failures
Symptoms:
Cracked or softened pump head or tubing
Discoloured or swollen seals
Corrosive smell or internal pitting
Leaks after a few weeks/months in use
Why It Happens:
Using PVC or standard EPDM with strong acids, chlorides, or oxidizers
Peristaltic tubing incompatible with organics or micros
Non-rated seals exposed to pH extremes or solvent-based fertigation products
Solutions:
✅ Always match chemical material safety data (MSDS) with pump component spec sheets
✅ Upgrade to PVDF, Viton, PTFE or SS316 for harsh fluids
✅ Replace peristaltic tubing every 3–6 months based on use
✅ Use dual-seal systems for aggressive acids like nitric or sulfuric
✅ Confirm compatibility not just for the pump head, but for all fittings and valves
🔹 Issue 8: Pulsation Damage in Dosing Lines
Symptoms:
Hammering noises or vibrations
Cracks at elbows, joints, or sensor housings
Inconsistent readings from inline sensors
Leaks at plastic fittings or threaded connectors
Why It Happens:
PD pumps create pulsed flow unless dampened
Rigid lines transmit vibration instead of absorbing it
No pulsation dampener or flexible coupling installed
Solutions:
✅ Install a pulsation dampener near the pump outlet
✅ Use short flexible tubing to absorb shocks before rigid lines
✅ Secure pipework with vibration isolation clamps
✅ For long dosing lines, include a pressure snubber or back-pressure valve
✅ Monitor vibration with sensors if dosing near delicate inline instruments
🔹 Issue 9: Startup Sequence & Controller Timing Failures
Symptoms:
Pump runs with outlet valve closed (backpressure spike)
Fertilizer injected into dry lines
Dosing continues after irrigation shuts off
Alarms triggered on flow meters or EC sensors
Why It Happens:
Solenoids and pumps not properly synchronized
Manual override of one component (e.g., valve left closed)
Controller logic doesn’t manage interlocks or delays
Solutions:
✅ Use irrigation controllers that sync valves and dosing pumps
✅ Add flow sensors or valve position feedback to trigger pump enable/disable
✅ Program start delays to allow lines to pressurize before injection
✅ Set interlocks to shut down the pump if mainline flow is lost
✅ Never run dosing pumps in isolation—always verify system state
📆 Coming in 2 Weeks – Final Part (4 of 4):
🔟 Dosing under variable flow pressure
🔟 Filter fouling due to micro-precipitates
🔟 Poor maintenance routines & missed diagnostics
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