3.5” Thick Plate Tap Utilizing Specialty Tank Cutter

CLIENT CHALLENGE

When a 16” #150 gate valve failed in the open position, the plant requested a re-stop of the pipeline through a 20+ year old linestop fitting from a defunct competitor.
Internal corrosion of the completion plug was locked in place, making it impossible to remove.
Fitting installation required drilling an 11.875” hole through the completion plug. This plug was 3.25” thick and made of a106 Carbon Steel.
It was imperative that both the cut coupon and the majority of the metal chips were recovered, in order to avoid clogging intake strainers downstream.

COLT SOLUTION

COLT technicians and management determined that a specialty tank cutter would be required to complete the plate tap for several reasons:

The cutter allows cut material to clear once the cut depth is beyond 1” due to its extra Gullet depth.
The tank cutter was designed to cut flat surfaces and requires less torque from the drive unit.
This cutter allowed COLT to use a small machine that was portable to the confined position.
The design of the tank cutter produces ribbons of steel and evacuates them back into the cutter sub-adapter as it cuts. The large volume of this material would require a sub-adapter for the collection of this material so that it wouldn’t interfere with the function of the tapping valve once the plate tap was complete.

The plate tap was a success. COLT produced the plate tap required for our technicians to perform a linestop in the 90° fitting. The coupon was caught and only a tiny fraction of the “shavings” actually entered the pipeline, having no effect on downstream strainers. The entire project allowed the customer to regain control of the mill water system and replace a faulty valve without any effect on operations.

CLICK TO DOWNLOAD

Resources