Valve Maintenance - Packing Gland Adjustment

[tschmidt2]

What is the proper procedure for adjusting the packing gland in a valve leaking through the stem? Does the valve (any type) need to be in a certain position or relieved of any line pressure?

I know most maintenance guys will crank on the packing bolts until there is no more leak but this has developed problems of crushing valve packing deep within the body.

 

[Danlap]

First: You need to obtain all Gland bolts torque data from related OIM book.
If not available, generate your own calculation based on seating stress packing used e.g. Graphite ring, etc. Minimum torque value would be minimum seating stress. And maximum torque value is maximum seating stress.
Note: when operator applying torque above "maximum" and still not tight or even tight. Then Operator should replace it in the next window.

Second:
During "live" situation, its better to do it in Close position. This is due to safety reason, once the packing loose its sealing capability, there is a good chance that it will burst without notice towards maintenance face who is doing the tightening.
But valve in close position? How do ones knows that it is still leaking (assuming the Globe/gate is tight)?
After re-tightening (first with minimum torque value applied on your spanner), do 3 times stroke fully close to fully open vice versa.
If still leaking, increase the torque 3-5 Nm more (or calculated increment).

PS: After tightening, if the leaking grown bigger than before. STOP, put the valve back on fully close again, replace the packing as a whole or at least the top 3 packing ring.
Be cautious, leaking is not necessarily only due to packing. Spindle condition and other factor do matters


Regards,
MR

All valves will last for years, except the ones that were poorly manufactured; are still wrongly operated and or were wrongly selected

 

[gerhardl]

Hello tscmidt2,

This is what 'the best in the class' do : Any company, quality certified, must have a procedure for this. Any quality certified valve producer will have a procedure and maintenance instruction for this.

In all cases the instructions would require revision valve(s) (for and possibly after the leaking valve) to be closed and the pipeline depressurised and at normal temperature before any maintenance.

... but yes, it is quite common to lightly tighten the gland sealing under conditions as well described by Danlaps comment, all on the responsible engineers risk!

Anyway, having this leakage problem and question, my guess is that the best way to improve is to get a (better) regular inspection and maintenance cyclic routine for the whole plant.

Good luck!