I have doubts: for a ball valve or butterfly is a good practice lubricate the stem for example with antiseize before install the packing rings (packing rings materials: molded graphite, composite graphite)?
Process condition : air @ 400 °C and 50 Kg/cm2.
Is necessary lubricate the stem and/or packing rings before install?
Is also possible install packing ring directly without lubricate?
which case is necessary lubricate and which case no need?
please answer my 4 questions