ES&H Manual



6151 Appendix T5

Requirements for Vacuum Design



This document is currently under review.  All requirements outlined within this document apply to current laboratory operations until new content is approved, released, and published.


1.0            Purpose


This appendix provides requirements and Jefferson Lab experience for the design and testing of vacuum systems that pose some personnel and/or economic risk but are not covered by the requirements for Pressure Systems as provided in ES&H Manual Chapter 6151 Pressure Systems.  Vacuum systems pose a potential hazard to equipment and personnel from rupture due to back-fill pressurization or implosion due to failure.


2.0            Scope


The requirements of this appendix apply to all vacuum systems with the following exception.  A system under vacuum may be excluded from these requirements if all of the following hold:



Requirements for vacuum systems are determined by the following categories:


Category I – Vacuum systems in which the differential operating pressure can never exceed 15 psi.  Examples of Category I vacuum systems include HMS and HRS vacuum systems, injector chambers and dog-leg chambers.

Category II – Vacuum systems which can be protected from pressurization exceeding 15 psig through engineering controls (e.g. pressure relief devices).  Examples of Category II vacuum systems include cryostats, cryogenic transfer lines, cold boxes, and target vessels.

Category III – Vacuum systems which are not or cannot be protected against pressurization exceeding 15 psig.


3.0            Responsibilities


3.1              Responsible Engineer shall ensure that the vacuum system design, fabrication and testing of Category I and II vacuum systems meets the requirements of this technical appendix.


3.2              Design Authority shall ensure that the vacuum system design, fabrication and testing of Category III vacuum systems meets the requirements of ES&H Manual Chapter 6151 Pressure Systems.


4.0            Process Steps or Expectations


4.1              A competent technical individual shall determine whether a proposed vacuum system design is subject to the requirements of this technical appendix and shall categorize the vacuum system according to those described in 2.0 Scope.

4.2              Category III vacuum systems are designated as pressure systems as defined in ES&H Manual Chapter 6151 Pressure Systems and, as such, must follow the requirements listed in  Chapter 6151 and its technical appendices.  A Design Authority is required for Category III vacuum systems and that Design Authority shall follow all project and documentation requirements provided in ES&H Manual Chapter 6151 Appendix T1 Pressure System Project Implementation and Documentation Requirements.

4.3              Category I and II vacuum systems do not fall within the criteria identified in the definition of a pressure system and as such are not subject to the rigor of design, fabrication, testing, and documentation provided in ES&H Manual Chapter 6151 and its technical appendices.  A responsible engineer shall use sound engineering practices throughout the design, fabrication, and testing of Category I and II vacuum systems.  These practices shall include:

4.3.1        Design: Vacuum systems in Category I and II are not required to be “U” stamped.  These systems shall be designed to ensure that the system maintains its elastic stability (precludes buckling).  This can be verified using applicable paragraphs from ASME Section VIII, Div 1, Div 2, or ASME Pressure Vessel Code Case 2286, July 17, 1998.[1]  Alternatively, vacuum system design may be verified using other peer approved methods that have equivalent, or greater, factors of safety to those used by the ASME codes (e.g, the factor of safety for Div 1 is 3.5).

4.3.2        Welding: All welds on Category I and II vacuum systems shall be designed, performed and inspected in accordance with ES&H Manual Welding and Brazing Program Supplement.

4.3.3        Pressure Relief: Pressure relief of Category I systems need not be considered.  For Category II systems, the responsible engineer shall ensure, using sound engineering practices, that there is adequate pressure relief for the entire system and that the maximum system pressure does not exceed 15 psid.  Coded relief devices are not required.  Non-coded relief devices shall be qualified through operability tests demonstrating function and flow capacity or calculations showing adequate flow capacity.  A properly designed and relieved purge system may be used provided a current SOP/TSOP/OSP describes proper use.  A responsible engineer shall assure that the purge system is designed properly using sound engineering practices.


4.3.4        Testing: In addition to any leak testing to demonstrate performance, Category I and II vacuum systems with an internal measurement above 6 inches and with a volume greater than 35 cubic feet shall require a pressure test documented by an SOP or TSOP with a responsible engineer witnessing the test.


For ordinary vacuum systems the test pressure shall be full atmospheric pressure differential.  For vacuum systems not intended to be pumped out to the full atmospheric pressure differential, the test pressure shall be 110% of the maximum allowable external differential pressure, but not more than full atmospheric pressure.


For a vacuum system within a pressure vessel, the test differential pressure shall be 110% of the maximum allowed working pressure differential.  Thin windows and other delicate equipment may be removed while testing the vacuum system.


4.3.5        Records: Documentation for Category I and II systems (design calculations, material certifications, relief device calibration data, etc.) shall be maintained by the responsible engineer.  A Category I and II Vacuum System folder within the Pressure Systems Directory in DocuShare is available for documentation storage.


5.0            References



·         ES&H Manual Chapter 6122 – Hot Work (i.e. Welding, Brazing, Cutting and Grinding) Safety Program

·         American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel (BPV) Code, Section VIII: Rules for Construction of Pressure Vessels, Divisions I & II

·         ASME Pressure Vessel Code Case 2286, July 17, 1998

·         Vacuum Systems Consensus Standard for Department of Energy Accelerator Laboratories, July 20, 2008 Draft


6.0            Revision Summary


Revision 0.1 – 05/17/13 – Added notice to reflect current lab operations.









ESH&Q Division

Kelly Dixon




This document is controlled as an on line file.  It may be printed but the print copy is not a controlled document.  It is the user’s responsibility to ensure that the document is the same revision as the current on line file.  This copy was printed on 5/17/2013.





[1] Code Case 2286 is fully incorporated into the 2007 ASME Code Section VIII, Division 2.   Code Case 2286 still exists as a Code Case, but it will disappear in about 1 year since it is now the Code itself.