by By Jeff Bernthisel & Rob Garlock, FSA Member
January 20, 2016
Image 1. Tamping toolImage 1. Tamping tool
Figure 3. Cutting with packing cutter toolFigure 3. Cutting with packing cutter tool

Lubrication should not be used on the seal unless otherwise specified. Load the ring to the required packing stress according to the manufacturer's specifications.

Repeat this procedure for all remaining rings. Be certain that the skive-cut for each ring is positioned 90 to 180 degrees from the previous ring for all braided sets, and for those with two end rings. These steps are not always necessary, but they will allow the packing to increase its life expectancy and in the end will save time and money.

It is imperative to cycle the stem a minimum of three and a maximum of five times. A rising stem should be elevated, and a rotating stem should be turned. Each increase or decrease in elevation represents one cycle. Each completion of a quarter-turn (back and forth) represents a cycle. Re-torque again to the manufacturer's recommended value after the valve has been cycled. After the valve has been in service for three days under normal operating conditions, the packing should be re-torqued one final time.

In the 1970s, it was acceptable for packing to lose a few drops a minute in each valve. But today there are specific laws mandated by the U.S. Environmental Protection Agency and guidelines set up by Leak Detection and Repair programs that establish strict limits for leaks of any kind to prevent contaminating plants and the environment. One plant, for instance, did 700,000 inspections last year alone. Each valve is inspected, tagged if it leaks, scheduled for repair and then inspected again.

A key motivator is to avoid consent decrees. The amount of fines can run from hundreds of thousands to millions of dollars. This never-ending cycle improves plant efficiency, reliability and safety.

Next Month:
What are the considerations to upgrade or change pre-specified gaskets?

See other Sealing Sense articles here.

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