Chesterton Knowledge Hub: Valve Packing: Know your Valve Gland Torque

All valve stuffing boxes should be tightened with a calculated, known gland torque. It seems obvious that higher gland stress results in lower leakage and it seems just as obvious that higher gland stress results in higher (unwanted) stem friction.

Therefore the challenge is to find the packing stress that gives the right balance between acceptable leakage and acceptable stem friction. Since both parameters are of high importance to the performance of the valve it is crucial that the right gland stress is calculated. Packing stress is directly linked to the torque value. For this reason we need to know how the correct gland stress and gland torque can be calculated.

In particular for low emission valves this becomes an issue because the forces that need to be applied to the packing set in low emission valves are considerably higher than in comparison with, for example, a steam valve. This is because leakage (read fugitive emissions) from volatile organic compounds such as methane is a lot more problematic than low level leakage from steam, which is plain water. We are talking here about diffusion through the packing material that can only be stopped by increasing the density of the packing material.

So in order to keep stem friction and leakage to an acceptable level we need to calculate the gland torque.

Chesterton tools to calculate gland torque:

The Valve Management Tool on the Sales Toolkit