What is Plan 11 ?
Seal flush from pump discharge through orifice.
What’s function of Plan 11 ?
1,Seal chamber heat removal.
Heat casued during running of mechanical seal, if heat over appropriate value of this medium, that will make films between stationary seal and rotary seal in a bad condition. Finally, that will cause failure or leakage.
2, Seal chamber venting on horizontal pumps.
As we know, wet seal always need to operate in a good fluid condition. But sometimes, bubble or gas will be involved and flow with process fluid. If some bubble contact with seal face, that will make seal face operate in a gas condition, it’s not good for sustainable running.
3, Increase seal chamber pressure and fluid vapor margin.
Especially for light hydrocarbon C1~C4, those medium are always been gas state in room temperaturer or pressure. So we need Plan 11 so as to maintain pressure of medium of seal chamber higher than minimum vapor Pressure.
How can we do preventative Maintenance for Plan 11 ?
1, Use an orifice with a minimum 3 mm (1/8 inch) diameter.
2, Calculate flow rates to size orifice for adequate seal chamber flow.
3, Increase boiling point margin with proper orifice and throat bushing sizing.
By adjusting flow rate of orifice, it can properly increase boiling point margin. To make seal face alwasy work under fluid conditon instead of gas condition.
4, Flush should be directed over seal faces with piping at 12 O’clock position.
This angle will make sure Plan 11 make its function maximum worthy.
5, Typical failure mode is a clogged orifice
In order to monitor orifice is working well or been clogged, we can check temperature at pipe ends. In this case, we won’t use Plan 11 if medium is freezing or polymerizing.
