Control System Issue

Whenwe are setting up our vacuum tank the vacuum set point on the controls is -98 KPa. However our actual never reaches this ( the actual only goes to -97) also whe nset at 65- 70 Kpa the actual reading is usually ~5Kpa away from this.
So in effect our set point has no reflectino on our actual results.

Can anyone suggest what needs to be done in such an instance as this impacts on the process validation. I realise that there is the issue of ‘lack of control’


try to set it manually, if it reaches your required setting start by setting your P at between 25 and 35% PB wait for cycling then close your PB to some agreeable setting and wait for a few seconds then set your reset and derivative settings. Use safety and caution when going manual!!! Also, make sure the pump is capable of reaching the vacuum you need.