Chatter pilot

When the pilot exhausts to the atmosphere, a pilot-operated PR valve is fully balanced. Like the balanced bellows valve, therefore, its opening pressure is unaffected by back pressure, and high built-up back pressure does not result in chattering. 

Chattering caused by undersized inlet piping may sometimes be eliminated on pilot operated PR valves if the pilot valve pressure tapping is taken directly from the vessel being protected. However, it is recommended that the above inlet pressure drop limitations still be applied, to avoid the capacity reduction that would result from excessive inlet losses and to ensure freedom from chatter. 

One can also consider replacing the chattering valve with a pilot-operated safety valve with modulating action. This option would require a new capac-... 

Oversizing of the valve (as a rule of thumb chatter is starting at 25% above necessary/calculated capacity) 1. Use smaller size valves. 2. Reduce the lift of the valve (only possible with pilot-operated safety relief valve, POSRV). 

Typical solutions to meet the 10% rule include installation of a bellows kit or a pilot-operated safety relief valve. Alternatively, piping modifications can be considered, or a more rigorous analysis can be performed to further define the risk of chattering. 

Any misalignment between workpiece and reamer will cause chatter, oversize holes and bell-mouthing of hole entrance. Piloted reamers ensure alignment of the workpiece and reamer. 

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