Recently, a group of parts involving air filter heads and bowls were developed for high pressure pneumatic applications. The stringent specifications include design pressure exceeding 20 bar, leak testing pressure exceed­ing 30 bar, burst test pressure up to 150 bar and S1 porosity levels (as per ASTM E505), in addition to other requirements.

This case study is an example of an approach towards the application of flow and solidification simulations to cor­relate the location and inevitability of shrinkage porosity.

Analysis of Results

Flow analysis followed by solidification simulations were conducted for each and every part of the whole group.

The results are correlated with areas of thick wall sec­ tions, solidification results, radiography and cut-sections, as shown in Figure 3 and 4.

The correlation between the location and inevitability of the shrinkage porosity was well-established and shared with the customer. The new acceptance levels were established based on the simulation results and the trials.

Figure 4 - a) & b) Section views of a bowl model showing significant wall thickness variations; c) & d) cut- sections of a bowl indicating shrinkage porosity.

ASTM E505 porosity level of  acceptance relaxed to S3 without compromising any other requirements, including the test pressures.

Key Benefits

• Practical establishment of porosity levels
• Resolving tbe gap between the specification and actual
• Establishment of cut-section and radiography standards
• Enhancement of feasibility
• Shortened time to mass production
• Low rejections due to new standards
• No leaking parts, no burst test failure in mass production
• No customer complaints in supplies