TL;DR

Tray weeping happens when vapor flow is too low to prevent liquid from draining through the tray. Increase vapor load or inspect for damaged valve caps at the next shutdown.

What you might see

overhead product purity low at moderate feed rate
low vapor-to-liquid ratio on operating map
column differential pressure below normal
bottoms contaminated with overhead component

Likely causes

Tap to mark as ruled out

Vapor rate below the minimum stable operation point for the tray design
Valve caps damaged or stuck open reducing vapor seal
Feed rate reduced beyond the design turndown ratio
Valve cap corrosion from aggressive process chemistry

Required tools

Process heat duty balance calculation
Tray design specification document
Valve cap replacement set (matching Provalve type)
Level instrument for tray levelness check

Safety first

Column access through manways requires a confined space permit, atmospheric gas testing, and isolation of all inlet and outlet streams.
Hot tray surfaces and residual process liquid are present during a hot shutdown inspection. Wear thermal and chemical PPE.
Do not enter any section of the column until a positive atmospheric test (O2, combustibles, H2S as applicable) has been completed.

Procedure

7 steps · ~30 min

1
Confirm the current vapor rate by checking the reboiler heat duty and the overhead condenser duty balance.[1]
2
Compare the current operating point to the tray design turndown ratio. Weeping typically begins at 40 to 60 percent of design vapor rate.[1]
3
Review any recent feed rate reductions or reboiler setpoint changes that could have reduced vapor load.
4
If vapor rate is adequate but weeping symptoms persist, suspect mechanical valve cap damage or fouling.
5
Plan a tray inspection at the next available shutdown. Access the affected tray section through the column manway.
6
During inspection, check valve cap actuation, look for corroded or deformed caps, and verify tray levelness.
7
Replace damaged valve caps in kind. Do not substitute a different valve type without engineering review.

Sources

Koch-Glitsch (internals) Koch-Glitsch FLEXIPAC / IMTP / Provalve Distillation Column general technical documentation, Koch-Glitsch (internals)
Koch-Glitsch FLEXIPAC / IMTP / Provalve distillation column general tray inspection and weeping procedures (general)

More guides for Koch-Glitsch (internals) Koch-Glitsch FLEXIPAC / IMTP / Provalve

How to diagnose column flooding on a Koch-Glitsch FLEXIPAC / IMTP distillation column

Column flooding causes purity loss and pressure drop spike. Reduce vapor or liquid rate to below the flood point, then diagnose the root cause.

~30 min7 steps

How to diagnose packing fouling on a Koch-Glitsch FLEXIPAC / IMTP distillation column

A slow rise in differential pressure over months indicates packing fouling. Track the trend, plan an inspection at the next turnaround, and consider a column wash before opening.