Application Example: Low Temperature and High Pressure
We received an inquiry from a petrochemical customer in Norway about a high-pressure sight glass for low temperatures, which had to be seawater resistant. The exact requirements were:
- Medium: CO2, oil, methane gas, and seawater
- Temperature range (TSmin/max): -60°C / +150°C
- Class / PN (PSmax): Class 900 / 150 bar (125 bar)
- Connection nominal size: 3“ (DN80)
Our customer was particularly concerned with seawater protection and low temperature at -60 °C. For this, we could rely on our ACI Type 520A, high-pressure flow sight glass with ANSI flanges.
As the material for the housing of the Type 520A high-pressure flow sight glass, we used stainless steel 1.4462. This material is particularly resistant to seawater and also very resistant to CO2, oil, and methane gas. The connection flanges according to ASME 16.5 B RF in 3" Class 900 were also made from this material. For this material, we required a 3.2 certificate with suitability evidence. Furthermore, we classified the sight glass according to AD2000 leaflet W10 (Materials for low temperature) from stress group I to stress group II. This step allowed the chosen material (1.4462) to achieve the required -60 °C instead of the approved -40 °C. The welding process of the main housing required a 100% X-ray inspection of both weld seams due to this reclassification. The glass was specially manufactured borosilicate glass similar to DIN 7080. This is standardly resistant to the aforementioned media and is also suitable for seawater. As the sealing material, we used the novaphit® MST graphite gasket, as it is perfectly suited for high-pressure applications in the low temperature range due to its special structural design.
We successfully conducted a pressure test with water at room temperature for 60 seconds at PN 150 bar x 1.5 (225 bar) on our own pressure testing device.
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