stem key engagement with actuator

[7016]

Details::
Stem of a gate valve has a bigger length by 24 mm.
Only 45 mm is engaging with the drive sleeve (bush) of electrical actuator. Remaining 24 mm extra length is hanging above the drive sleeve of the actuator without any engagement/support.

In other words, only 40mm key length is in engaging with keyway of drive sleeve and remaining 20mm key length is not engaged/supported. Which means, only 66% of key is engaged.

Valve Operating torque is 110 NM.
Actuator maximum output torque is 150 NM.

Please refer the attachment for better understanding.

My Limitations:
I don’t have option to change the drive sleeve. Because the actuator doesn’t support.
I must go with the existing actuator. No chance of changing the actuator.


My doubt::
Is it Okay to go ahead with 66% key engaged or does there will be any fatigue in the key in long run of usage, as it is only partially engaged? Please suggest with your experiences.

 

[hydtools]

If the engaged portion of the key is sufficient to bear the load, there should not be a problem. Another way to look at it is that the sleeve keyway is fully engaged.

Ted

 

[Nick_Gray_88]

I’d imagine you have a MAST figure for the gate valve if yourselves designed it or it was supplied from a reputable manufacturer?

By the looks of your figures you MAST will be high enough to handle the load. If in doubt you can calculate the shear stress in the stem which is engaged when the full actuator torque is going through it.

 

[gerhardl]

See the two previous posts. If the valve itself and the actuator are supported adequatley by the total assembly and solid enough and within constructional allowance: no problem.