It is a loose interpretation that you have to define or tune by yourself. Below is my experiences.
My sites has more than 1 million valve with various ages (1 week to 40 years old), various brand (some already obsolete), 60% of those valves are with graphite (maybe some still asbestos) gland and with various condition (good/new, fair, bad condition). I think we had around 80-100 record-able, more than 1 ppm (gas) or 1 kg but less than 10 kg (liquid) leakage per yaer.
What I proposed is to do quarter turn tightening on gland every 4 years. And for valves above 300 degC to do extra quarter turn tightening after cold situation (newly installed, after shut down)
PREVENTIVE ACTION
I did some campaign to several stake holders and multi discipline with following summary:
a.Tighten able valve is only Gate and Globe. NOT TO TOUCH Ball and Plug valve simply because they use PTFE packing, and it might be ‘crushed’ due to over-tightening
b.Segregate field team into three: common operator (they operate valves every day), maintenance team (have better understanding of gland and torque) and fire fighter team along with valve specialists.
c.Segregate valve condition into three: Good, fair, bad.
Good: acceptable rust condition, thread still ok, sufficient remaining gland bolts length for tightening, no leak
Fair: minimum to no leak, if there is a leak it should be non-very toxic medium, thread and gland flange are fair (might be slightly tilted is ok), minimum but there is still bolts length
Bad: minimum to big active leak, no thread remaining, gland flange not align, thread worn out, etc.
Note: I prepared pocket size quick reference guide with pictures for each condition.
d.Prepare general training for operator for them to identify types of manual valves (Globe, gate), and valve condition.
Note: not to touch control valve as gland torque indeed manufacturer specific.
e.Color coding with tie-wrap per year, according to maritime standard color, so it will not be re-tightened again until the next years.
f.Convince stake holders that:
-It is safe.
-Torque value might not be applicable. As this practice might be limited due to the fact that bolts are rusty, already reach bottom of thread, torque wrench is a luxury item for some production unit.
-Operator to tackle good and fair condition valve every 4 years
-Maintenance to tackle fair and bad condition valve every 4 years
-Fire fighter to tackle live leaking condition.
Wont provide details, but reason for:
300 degC --> all graphite packing consist of residue which bonds graphite together. This residue are mainly Zinc and PTFE which are malleable after 250oC (conservative number)
4 years --> friction (opening/closing) valve will deteriorate gland stress. Let say 400 cycles is the statistical number before leaks begin to penetrate bottom first gland (out of 5 rings). And valve operated 100x per year.
Quarter turn (in Dutch: kwartslaag) --> so we know that gland flange is moving down. Justification for example we may apply 25 Nm for corroded gland bolts 1”-150# gate valve. torque spanner might ‘click’ but most likely it will not even rotate due to corrosion. Plus quarter turn is ALARP in harming valve.
Outcome after 2 year implementation:
-A lot of questions and challenge to me
-Sense of ownership by operator
-Recordable gland leakage is reduced to 30-50 reports per year.
OEM SPECIFIC TORQUE
Just simply apply specific torque periodically as per OEM
Excessive leakage due to blow out, etc.
Fire fighter or maintenance tighten gland up to a point where leak stops. if not possible than isolate the line.
Regards,
MR
All valves will last for years, except the ones that were poorly manufactured; are still wrongly operated and or were wrongly selected