PIPING ENGINEERING NOTE - REV.6 (Download PDF)

 

Table of Contents :-

• Introduction
• Design code and evaluation criteria
• Materials
• GAr line from heat exchanger to condenser
• Condenser
• Detector
• GAr line from detector to condenser
• GAr line from detector to heat exchanger
• Weld documentation
• Pressure relief system
• Pressure test
• Summary

Introduction

The SCENE detector, has been designed and installed at the Fermilab building PAB in 2012. It has run successfully with liquid argon since then.In 2014, for Rev 3, this document was updated to run it with liquid xenon. The design pressure remains the same, but the temperature is now 170K. No changes in the design are needed. At this time, Appendix E was added to verify that the Pressure Relieving Device is suitable for these conditions as well. A note was added to Section 11.0 to that effect.

The P&ID shown in Appendix A was changed, but the changes were in warm piping. A pressure vessel has also been added: PPD-10120. It is U-stamped and it already has the PPD sticker.All the rest remained the same.In December of 2016, for Rev 4 of this document, the inner vessel was changed. The4” diameter vessel that was used for the original design was replaced by a 6" diameter vessel.In addition, a differential pressure transducer was inserted between the inner vessel and the condenser. These changes are detailed in new Sections 7.2, 7.3, 8.2 and 8.3, including a new P&ID relevant just for those sections. A paragraph was also added to Section 11.0 confirming that the original pressure relief is still correctly sized for the new inner vessel. The two vessels are meant to be interchangeable. In the course of preparing Rev. 4, it was noticed that many of the previous calculations used 15 psig for the working pressure. While this is true relative to atmosphere, the detector itself and much of the piping operates in an insulating vacuum, and so the differential pressure is 30 psid. The previous calculations were not updated, but all new calculations use 30 psid. All other details, including the pressure relief devices, are unchanged.

In August of 2017, for Rev 5 of this document, the pressure relief valve was replaced by a slightly larger pressure relief valve with a relieving pressure of 20 psig. As a result, the MAWP of the system was changed to 20 psig, and all calculations were updated, including Appendix D containing the PRV sizing calculations.Revision 6 was created for this document on January 31, 2018. The current SCENE cryostat has one primary relief valve. This valve (PSV-01) has already been approved and meets the flow capacity requirements for both argon and xenon cases. A small leak, suspected to stem from this relief valve, is affecting the purity when the experiment is operating under normal conditions. For this revision, a burst disc was added between the relief valve and the vessel to prevent the leaking relief valve from contaminating the xenon or argon inside.

Additionally, a check valve was added to prevent the relief valve from going off during the filling process. The check valve leads to a large 440L dewar (PPD-10120) with a MAWP of 200 psi. The check valve is manufactured by Swagelok and has part number SS-8CPA2-3. It has a cracking pressure of 30 psi.

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