Nordson 25B - Pump Fails to Siphon Coating Material; Pump Continues to Operate Even after Drain and Circulation Valves

© 2024 Nordson Corporation
1044131-06
5-5
Troubleshooting
Problem Possible Cause Corrective
5. Pump fails to siphon
coating material
Blocked siphon strainer screen, rod, or hose
Check and clean the hose,
rod, and strainer.
Air leak in siphon system
Check the siphon hose
for leaks. Break apart all
connections in the siphon
system. Remove old sealant

wrap them with PTFE tape
before reconnecting them.
Coating material too viscous
Check the material viscosity.
Add solvent to the material to
lower the viscosity.
Siphon hose too long, hose ID too small, or strainer screen

Use a correctly sized siphon
hose. Check the strainer
screen. If the strainer screen
is clogged with pigment, use
a coarser mesh screen or a
strainer without a screen.
Contact your Nordson
representative for advice.
6. Pump continues to
operate even after
drain and circulation
valves are closed
and spray devices
󰀨
Coating material supply low, pump siphoning air Fill the supply container.
Leaking drain valve
Rebuild or replace the drain
valve.
Leaking circulation valve
Check for a damaged or
worn circulation valve as
follows:
1. 󰀨
supply.
2. Open the drain valve
to relieve the hydraulic
pressure.
3. Close the drain valve.
4. Immerse the siphon rod in
coating material.
5. Disconnect the return
hose from the circulation
valve.
6. Connect an air hose to
the circulation valve in
place of the return hose.
7. Apply compressed air
to the circulation valve.
If air bubbles from the
siphon rod, replace the
circulation valve needle
and seat.
Leaking ball check valve
Rebuild the ball check
valves.
Continued...