HomeControl Valve Sizing Services
Burns Bridge has encountered two types of valve sizing problems as follows:
- Valve is too small; the process is not capable of achieving the desired outcome.
- Valve or controlling action is too large; the process will hunt and has the potential to become unstable.
While Burns Bridge has presided over the resizing of dozens of control valves in combustion, compressed air, hydraulics and motion control applications. The following two examples are provided to illustrate the problems that each condition can cause.
- Three crucible furnaces with modern energy saving recuperators had long melting times of over 12 hours to melt 1000 lbs of aluminum. An inspection of the combustion piping found that 2 inch diameter combustion air piping had been used to pipe the furnaces, whereas the combustion air inlet ports were 4" NPT. Ceteris paribus a 4" pipe will have 4 times the capacity of a 2" pipe. The 2" piping and associated control valves and combustion fan were all scrapped. A larger capacity combustion fan was procured and 4" piping with larger variable port control valves were installed. Melt preparation times decreased to less than 3 hours, approximately quadrupling melting and holding capacity.
- On a piston casting deck in an automated OEM casting cell, the three axis liquid aluminum pouring ladles controlled by three proportional Parker hydraulic valves suffered many motion faults causing down time and cold moulds (casting scrap). After analysis, the proportional valves were found to be too large. The valves were replaced by smaller units with the result that after re-tuning, the motion faults were eliminated. With the ladles now able to operate at a 20 per cent faster speed, throughput more than doubled from 6000 to 14500 pistons per day due to 1. reductions in downtime, 2. reductions in cold mould related scrap due to frequent starts, 3. a twenty percent faster cycle time, and 4. elimination of a solidification porosity problem due the moulds running too cold, and 4. A complete elimination of shrinkage solidification defects in the ring lands. The employees were happy because there was much less work needed to maintain the process.
Burns Bridge has experience with dozens of other valve sizing issues. As a matter of course Burns Bridge believes that the probability of selecting the correct size valve during the process design phase is low and that it should not be considered unusual to have issues with valve sizing.
