Chapter 7

PRESSURE SAFETY AND CRYOGENICS

Contents

Approved by Joe Dionne
Revised 09/12

7.1 Policy
7.2 Scope and Applicability
7.3 Exceptions
7.4 Roles and Responsibilities
7.5 Definitions
7.6 Work Processes

Work Process A. General Requirements
Work Process B. Low-Pressure Gas Systems
Work Process C. Low-Hazard Pressure Systems
Work Process D. High-Hazard Pressure Systems
Work Process E. Vacuum Systems
Work Process F. Cryogenic Systems
Work Process G. Training Requirements

7.7 Source Requirements
7.8 Reference Documents
7.9 Appendices

Appendix A. Design Criteria for Responsible Designers
Appendix B. Facility Pressure Systems
Appendix C. Safety Note
Appendix D. Pressure Testing and Inspection
Appendix E. Stored Energy of a Pressurized Gas Vessel

NOTE:

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7.1 Policy

The Pressure and Cryogenic Plan at Lawrence Berkeley National Laboratory (Berkeley Lab) manages gases and cryogenic liquids used at the Laboratory site by:

Berkeley Lab makes every effort to ensure that no injury or property loss will occur from pressure system failures or collapse of systems under vacuum. Whenever possible, Berkeley Lab designs, builds, tests, maintains, and operates pressure vessels and systems in accordance with applicable codes and standards, including the State of California Unfired Pressure Vessel Safety Orders.
For research pressure vessels and systems, Berkeley Lab follows and/or advances the best current industry practice for ensuring personnel safety and protection against environmental releases.

7.2 Scope and Applicability

These safety requirements apply to all work at Berkeley Lab involving air, liquids, or gases at, above, or below atmospheric pressure. They also apply to any use of cryogenic liquids, since these liquids pose serious potential for over pressurization in the case of inadvertent confinement.

7.3 Exceptions

None

7.4 Roles and Responsibilities

Role

Responsibility

Division Directors

Responsible for ensuring that all pressure systems are designed, assembled, and operated in accordance with the requirements of this chapter

Environment, Health, Safety, and Security (EHSS) Division Integrated Health and Safety Group

  • Administers and maintains the Laboratory Pressure Safety Program
  • Arranges the Laboratory Pressure Safety Training Courses
  • Maintains copies of all Activity Hazard Documents (AHDs) and Safety Notes

Engineering Division

  • Reviews and approves the design, fabrication, installation, and testing of research pressure systems, including vacuum systems, as required by this chapter
  • Reviews and approves pressure system AHDs, which are written to ensure that pressure operations are within the design limitations of such systems. This is in addition to the normal review process for AHDs, and it does not cover AHDs required for other reasons.

Engineering Division Director

  • Designates qualified engineers as Designated Pressure Engineers to provide guidance on pressure vessel and pressure system design and to review such designs prepared by vendors and by Laboratory personnel
  • Approves any Safety Notes for pressure systems

Facilities Division

  • Design, fabrication, installation, and testing of all Plant-Facility pressure equipment, as well as the requisite AHDs
  • Maintains a sufficient staff of qualified and certified pressure installers, who are available to all groups at Berkeley Lab

Designated Pressure Engineer

Designated Pressure Engineers are experienced mechanical design engineers who have specific knowledge pertaining to pressure safety and have been designated as Designated Pressure Engineers by the Engineering Division Director. Designated Pressure Engineers are responsible for:

  • Completing required training
  • Providing advice and guidance to Berkeley Lab staff in matters pertaining to pressure safety
  • Reviewing and approving pressure-related Safety Notes and AHDs on behalf of the Engineering Division Director

Responsible Designer

Responsible Designers are competent mechanical designers and usually members of the Engineering Division responsible for:

  • Completing required training
  • Developing or selecting a safe design in accordance with all applicable codes and standards:
    • Specifying procurement, fabrication, installation, maintenance, testing, retesting, and labeling requirements
    • Preparing all required Safety Notes

Responsible User

  • Safe use and maintenance of the equipment, including retesting of pressure systems in accordance with the requirements of the Safety Note or AHD
  • Ensuring that all training requirements have been met. Typically, this individual is the principal investigator or researcher who is responsible for the overall work.

Employees

  • Completing the Berkeley Lab course Pressure Safety (EHS 0171).
  • Employees who work with pressure systems over 1 MPa (150 psig) or with pressure vessel systems at any pressure must review training requirements with the EHSS Division Pressure Safety Representative.

7.5 Definitions

Term

Definition

MAWP

Maximum Allowable Working Pressure: The pressure at which the design of pressure systems is based

MOP

Maximum Operating Pressure: The highest pressure at which a system will operate

Pressure Installer

Pressure Installers are usually technicians or mechanics in the Facilities Division who have completed specialized training and who have been designated and certified as such by their department head.

Pressure Regulator

A valve or device designed to cut off flow at a set pressure

Pressure Relief Devices

Pressure relief devices are valves or rupture disks designed to vent pressure above a set point. Their purpose is to ensure the pressure within the vessel does not exceed MAWP.

Test Pressure

 

The pressure at which a vessel is tested to validate it can withstand the MOP. Test pressures vary from 125% to 200% of the MAWP.

7.6 Work Processes

Work Process A. General Requirements

Work Process B. Low-Pressure Gas Systems

Work Process C. Low-Hazard Pressure Systems

Work Process D. High-Hazard Pressure Systems

Work Process E. Vacuum Systems

Work Process F. Cryogenic Systems

Work Process G. Training Requirements

 

Work Process A. General Requirements

P&C Flowchart.png

  1. Pressure Safety Principles and Requirements for All Systems. Pressure system safety is achieved by careful engineering, hazard controls, ensuring structural integrity of components, regulation of pressures and flow, and provision for pressure relief. In some form, these principles must be addressed in every pressure system. Therefore, the following concepts and terminology are basic to any discussion of pressure safety. Note that this information is not intended to provide sufficient guidance to design pressure systems, but only to facilitate implementation of Laboratory policies. General guidance is provided in Appendix A, Design Criteria for Responsible Designers, and specific design guidance can be obtained through the Engineering Division.
  2. Maximum Allowable Working Pressure (MAWP) and Maximum Operating Pressure (MOP)

    a.     Pressure system design is based on the Maximum Allowable Working Pressure (MAWP). At MAWP, the lowest rated component in a manned, ductile system typically has a design safety factor of at least 4.0 guarding against ultimate failure. To ensure that the MAWP is not exceeded, pressure relief devices must be provided. Pressure relief devices must not be set higher than the MAWP for the system. It is important to note, however, that pressure systems actually cannot be operated at the MAWP because the relief devices open at that pressure.

    b.     The highest pressure at which any pressure system may be operated is the Maximum Operating Pressure (MOP). The MOP should be 10 to 20% below the MAWP to minimize borderline actuation of pressure relief devices. Pressure system design begins with establishing the desired MOP, since all else follows from this.

    c.      Standard components often support an MAWP that is substantially greater than the MOP for any given system. In such cases, the pressure relief device still should be set at 15 to 20% above the desired MOP. This is recommended because operations with unforeseen pressure excursions in excess of 15 or 20% may be out of control.

    3.     Test Pressure. All pressure vessel systems must be tested to ensure their integrity. Low-pressure piping or tubing without vessels may be leak-checked only. Commercial systems that have been tested by the vendor need not be retested. Depending on the contents and system configuration, the Responsible Designer will specify hydrostatic or pneumatic testing. Test pressures vary from 125% to 200% of the MAWP (see Appendix D). Pressure relationships are illustrated in Table 1.

    Table 1. Relationships of Defined Pressure Terms

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  3. Pressure Relief Devices
  4. a.     Pressure relief devices are required for all systems unless the supply pressure is inherently limited to less than the MAWP of the lowest-rated component. Pressure relief valves and rupture disks must be set at no more than the MAWP. The capacity of the pressure relief device must be calculated for systems containing pressure vessels and systems with potentially reactive contents. For pressure vessels, relief capacity must be sufficient to vent the contents of the vessel without exceeding the MAWP by more than 10% under all conditions. For systems with potentially reactive contents, the pressure relief device must be capable of venting the contents of the vessel without exceeding the MAWP by more than 10% when the contents undergo an exothermic reaction at the fastest possible rate.

    b.     Adjustable pressure relief valves must only be set by authorized personnel in the Berkeley Lab Facilities Division Regulator Shop, ext. 7669. Rupture-disk assemblies must be certified by the manufacturer or pressure tested by rupturing three disks selected at random that have been made from the same sheet. Permanent test records must be kept.

    c.      Relief devices used with hazardous (flammable, toxic, oxygen depletion, etc.) gases must be vented to a location that will be safe in the event of a large release of gas. Flammable gases must be vented to prevent accumulation of ignitable gas/air mixtures. Health hazard gases (as defined in Chapter 13, Gases) must be vented to a location that will not cause inhalation of an unsafe concentration of gas. Venting to a suitable exhaust system is typically required. Contact Employee Health & Safety (EH&S) Field Support for specific guidance. Venting to a building’s exterior may be acceptable for flammable gases. Exceptions for small quantities or concentrations of gas may be approved by EH&S.

    d.     In use, the activation of a safety relief device is a danger signal, like the blowing of a fuse. The system should not be put back into operation until the cause of the over pressurization has been determined and corrected.

  5. Component Requirements
  6. a.     Pressure systems must be constructed of components rated for the intended service. Typically, this means ductile metal tubing and rated pressure fittings that are compatible with the contents of the system. Hoses and flexible tubing may be used, but additional protective measures may be required. See also Chapter 13, Gases.

    b.     Nonrated components, such as tygon tubing, surgical rubber tubing, hose barbs, RL fittings, etc., are unreliable for pressure use and must not be used where failure could create a hazard. However, such components may be used with low-pressure inert gases, or in fume hoods that could safely vent any leaks or ruptures.

  7. Brittle Components. Pressure systems (including vacuum systems) with brittle components generally will be operated behind a barrier that can contain shrapnel from failed components. This includes systems with glass and quartz components. The use of safety glasses with side shields is usually adequate for work around view ports and glass feed-throughs on vacuum systems. Pressure systems with brittle components that must be operated without a barrier must have a safety factor of at least 8 guarding against ultimate failure and must be specifically designated for such operation in the Safety Note. The Safety Note is the Engineering Division mechanism for ensuring safe design of pressure systems.

  8. Pressure Regulation. Pressure systems must have a reliable means of pressure regulation. All systems supplied by compressed gas cylinders must be equipped with industry standard regulators. It is recommended that regulators be inspected and that regulator relief devices be set by the Facilities Division Regulator Shop. Specifically, the use of needle valves and other manual flow controllers without pressure regulators is prohibited on gas cylinder systems unless components are rated for full cylinder pressure.

  9. Pressure System Design
  10. a.     Pressure vessels and systems are to be designed, tested, and installed in accordance with applicable codes.

    b.     Research pressure vessels and systems often pose challenges that require a deviation from standard designs (e.g., target vessels with thin film windows that do not provide a safety factor of 4). In such cases, the design must provide equivalent personnel safety through alternate means, and these alternate means must be analyzed and documented in the Safety Note. General guidance for pressure system design is contained in Appendix A, Design Criteria for Responsible Designers, and additional guidance for utility systems and other facility pressure systems is contained in Appendix B, Facility Pressure Systems.

    c.      Safety Note requirements are illustrated in the flow chart shown in Table 2. A template for Safety Notes is provided in Appendix C.

    d.      Excellent technical guidance for pressure system design is found in the DOE Draft Pressure Safety Manual. Contact the Facilities Division for questions about conventional plant systems and the Engineering Division for questions about research pressure vessels or systems.

  11. Pressure System Installation
  12. a.      Pressure systems must only be installed by competent personnel. For personnel who routinely install pressure systems, completion of the Lawrence Livermore National Laboratory (LLNL) course Intermediate Pressure Safety (HS-5040) is recommended. Technicians from the Engineering Division and from the Maintenance and Operations section of the Facilities Division are available to assist with installation of pressure systems.

    b.      Pressure systems operating at pressures greater than 20 Mpa (3,000 psig) gas or 35 Mpa (5,000 psig) liquid may only be installed by certified Pressure Installers. Contact the Facilities Division Regulator Shop for assistance.

  13. Pressure Testing and Inspection. All pressure systems that include pressure vessels require testing, retesting, and inspection in accordance with the requirements of the Safety Note. (Exception: utility systems tested and inspected in accordance with State of California Boiler and Pressure Vessel Safety Orders.) Detailed procedures for pressure testing and inspection are given in Appendix D.

  14. Pressure System Use. A Responsible User must be identified for each pressure system. This Responsible User is accountable for the safe use and maintenance of the equipment and for ensuring that all training requirements have been met. Typically, this individual is the principal investigator or researcher who is responsible for the overall effort.

 

Work Process B. Low-Pressure Gas Systems

  1. Description. Low-pressure gas systems are pressure systems operating below 1 MPa gauge (150 psig) and consisting only of regulator, tubing, gauges, valves, and fittings. Low-pressure gas systems represent the lowest hazard category of pressure systems at Berkeley Lab.

  2. Low-Pressure Gas System Inspections. Prior to initial operation, all low-pressure gas systems must be inspected by the user. The purpose of this inspection is to verify the suitability of the components, the quality of the installation, and the absence of vessels or components that pose a serious hazard.

  3. Low-Pressure Gas System Documentation. Low-pressure gas systems may be covered by a Safety Note or an Activity Hazard Document (AHD), but such documentation is not required unless mandated by the hazards of the contents. See the description of documentation below.

  4. Training Requirements for Low-Pressure Gas Systems. See Work Process G, Training Requirements.

 

Work Process C. Low-Hazard Pressure Systems

Low-hazard pressure systems consist of equipment with a low-hazard level, involving routine risks that are accepted as such by the general public.

  1. Low-Hazard Pressure Systems. Low-hazard pressure systems include:
    1. Low-pressure gas systems
    2. Air and inert gas systems to 1 MPa gauge (150 psig) and inert liquid systems to 10 MPa gauge (1,500 psig) with a total stored energy of not more than 100 kJ (75,000 ft-lb). To determine stored energy, see Appendix E.
    3. Utility systems to 2 MPa gauge (300 psig), including water, compressed gas, natural gas, butane, propane, and steam systems in compliance with Facilities Division standards. These systems are inspected and maintained by the Facilities Division.
    4. Compressed gas cylinder manifolds assembled by the Facilities Division Regulator Shop.
    5. Unmodified, commercially manufactured hydraulic systems to 35 MPa gauge (5,000 psig), such as hydraulic presses, machine tools, and motorized vehicles, provided routine inspection and maintenance are done.
    6. Department of Transportation (DOT) shipping containers supplied by regular commercial suppliers.
    7. Air-pressure tanks, boilers, and certain other vessels inspected periodically in accordance with the Unfired Pressure Vessel Safety Orders or the Boiler and Fired Pressure Vessel Safety Orders of the State of California.
  2. Training Requirements for Low-Hazard Pressure Systems. See Work Process G, Training Requirements.

 

Work Process D. High-Hazard Pressure Systems

  1. High-Hazard Pressure Systems. Pressure systems that do not fall into the low-hazard category are high-hazard pressure systems. Specifically, high-hazard pressure systems include:
    1. All pressure vessel systems that contain irritant, toxic, infectious, and/or radioactive fluids at any pressure
    2. All pressure vessel systems with oxygen or flammable contents
    3. All pressurized equipment (including ASME-coded vessels that have been structurally modified) that operates at gas pressures over 1 MPa gauge (150 psig) or at liquid pressures over 10 MPa gauge (1,500 psig) or that contains over 100 kJ (75,000 ft-lb) of stored energy
  2. Documentation Requirements for High-Hazard Pressure Systems
    1. All high-hazard pressure systems must be covered by an approved Safety Note or by manufacturer’s documentation or certification that represents an equivalent degree of safety. In borderline cases, an engineer must review the manufacturer’s specification and verify that appropriate safety factors are present.
    2. A Safety Note documents the system’s engineering design and defines its operating parameters as well as pressure test procedures to ensure the safety of the system. For commercial systems, the vendor’s documentation may be substituted for a Safety Note. Safety Notes or the equivalent vendor’s documentation must be approved by the Engineering Division Director or the Director’s Designated Pressure Engineer. A template Safety Note is provided in Appendix C.
    3. An AHD is required for high-hazard pressure systems when:
      1. The material contained in the pressure system is hazardous and requires an AHD (see also Chapter 13, Gases, and the Chemical Hygiene and Safety Plan).
      2. The Responsible Designer has determined that the system poses pressure or process hazards that demand an AHD.
      3. AHDs for pressure systems require approval by the Engineering Division Director or the Director’s designee.
  3. Other Requirements. Requirements for pressure testing, retesting, periodic maintenance of pressure systems, barricades, use limitations, and special procedures may be contained in the Safety Note or AHD for any given system.

 

Work Process E. Vacuum Systems

Vacuum systems that are back-filled from a pressurized supply must be equipped with a pressure-relief valve to ensure that the system will not be subjected to pressures in excess of the MAWP. The MAWP of vacuum systems containing commercial glass view ports is limited to 3 psig, unless a higher MAWP has been determined and documented by the Responsible Designer in a Safety Note. Pressure testing of new vacuum systems is not generally required.

 

Work Process F. Cryogenic Systems

The most severe hazard of cryogenic systems is the possible confinement of even small amounts of cryogenic liquid. Closed cryogenic systems will quickly become pressure systems when trapped cryogenic fluids warm up and cause pressure build-up. Any system that contains values or fittings designed to ensure cryogenic fluid does not make direct contact with the atmosphere is a closed system.

  1. Requirements for Closed Cryogenic Systems. In addition to the requirements applying to all pressure Safety Notes, cryogenic systems must have:
    1. Independent pressure relief devices for each component or segment of tubing that can be isolated by valves
    2. Independent pressure relief for each closed space that is in contact with cryogenic temperatures (e.g., vacuum insulation spaces) because air may leak in, liquify, and accumulate in these spaces
    3. Low temperature rating of relief valves or thermal isolation for relief valves to prevent ice formation, which will disable the relief valve
    4. Exclusion of air features for flammable cryogens and for cryogens capable of solidifying air
    5. No pressurized components subject to low temperature embrittlement
    6. Compatible shrink rates of materials
    7. Adequate ventilation provisions in case of large-scale spills or continuous venting. See Chapter 13, Gases, for detailed requirements pertaining to oxygen-deficiency alarms.
  2. General Requirements for Liquid Nitrogen Handling. Small-scale use of inert cryogenics that are not confined (e.g., the filling of cold traps with liquid nitrogen) poses few hazards and does not require safety documentation. The following rules apply to such use:
    1. Wear eye protection appropriate to the hazard. When pouring liquid nitrogen from a Dewar, use safety glasses with side shields. However, when transferring liquid nitrogen from a pressurized Dewar, use face shields.
    2. Wear loose-fitting gloves (e.g., welding gloves) when working on systems with exposed components at cryogenic temperatures to ensure that skin will not freeze to cold pipes or metal parts. Gloves need to be loose fitting so they can be thrown off readily if cryogen is spilled into them. This ensures that the cryogen will not be trapped against the skin. Small spills of liquid nitrogen on the skin will evaporate without damage unless the liquid is trapped against the skin.
    3. Do not use cryogens in unventilated spaces, such as closets or experimental caves, without exhaust ventilation.
    4. When transferring cryogen from pressurized Dewars with hoses or tubing, be sure to verify that there are pressure relief devices between all valves because cryogen is easily trapped in the transfer hose or in the tube between two valves. In such a case, the hose will rupture and whip around out of control.

 

Work Process G. Training Requirements

Class

Required

Cryogen Safety EHS0170

  • For all employees using Cryogen systems
  • Designated Pressure Engineer
  • Responsible Users
  • Responsible Designer
  • Pressure Installers

Pressure Safety EHS0171

  • For all employees using pressurized systems
  • Designated Pressure Engineer
  • Pressure Installers
  • Responsible Designer
  1. Additional Training Requirements for High-Pressure Systems. Employees who work with pressure systems over 1 MPa (150 psig) or with pressure vessel systems at any pressure must review training requirements with the Environment, Health, Safety, and Security (EHSS) Division Pressure Safety Representative.
  2. Additional Training Requirements for High-Hazard Pressure Systems. Personnel training requirements for high-hazard pressure systems must be reviewed and agreed on by the user in conjunction with the EHSS Division Pressure Safety Representative. Prior to use of any high-hazard pressure system, each user also must be trained in the requirements contained in the AHD for the given system and in the operating requirements contained in the Safety Note. Additional training requirements may be specified in the Safety Note.

 

7.7 Source Requirements

 

7.8 Reference Documents

 

7.9 Appendices

Appendix A. Design Criteria for Responsible Designers

Appendix B. Facility Pressure Systems

Appendix C. Safety Note

Appendix D. Pressure Testing and Inspection

Appendix E. Stored Energy of a Pressurized Gas Vessel

 

Appendix A. Design Criteria for Responsible Designers

The following criteria apply to all pressure systems designed at Berkeley Lab. These criteria are intended to supplement required codes and standards and do not provide exemptions from more stringent code requirements.

  1. General. The maximum allowable working pressure (MAWP) must be stated on all pressure-system (and pressure-vessel) assembly drawings.
  2. Relief Devices. The following requirements apply:
  3. Pipe and Tubing
  4. Pressure System Inspection. The Responsible Designer must review newly completed pressure vessels and systems to ensure that they are free from manufacturing defects and/or shipping damage.
  5. Safety Markings and Signs. Experimental pressurized gas equipment operating at pressures greater than 3-1/3 MPa (500 psig) must be painted yellow, must have the operating pressure clearly marked thereon, and must bear the sign: DANGER, HIGH-PRESSURE EQUIPMENT.
  6.  

Table A-1. Pressure Vessels in Pressure Range of 1/10 to 34 MPa (15 to 5,075 psig)

Title

Design Notes

Safety Note Required

HAZARD CATEGORIES FOR PRESSURE EQUIPMENT

 

 

Low-Hazard Pressure Equipment

 

 

Air and inert gas systems

Maximum Allowable Working Pressure (MAWP) up to 1 MPa (150 psig).

No

Inert liquid systems

MAWP up to 10 MPa (1,500 psig) and energy <100 kJ.

No

Utility systems: water, gas, butane, propane, and steam are to be designed to Plant Engineering Department standards.

MAWP up to 2 MPa (300 psig).

Refer design to the Facilities Division.

Compressed-gas cylinder manifolds assembled by the Regulator Shop

Comply with Chapter 13, Gases.

No

Manifolds on tube banks and tube trailers

Periodic retest required if rated at 20 MPa (3,000 psig).

Yes if >20 MPa (3,000 psig).

Unmodified ASME pressure vessels that are ASME code stamped and operate with inert fluid

Low hazard when operating with less than 1 MPa (150 psig) gas pressure, less than 10 MPa (1,500 psig) liquid pressure, or less than 100 kJ stored energy.

Yes if > 1 MPa (150 psig) gas, >10 MPa (1,500 psig) liquid, or if >100 kJ.

Refrigeration systems that comply with ASME and Air Conditioning and Refrigeration Institute (ARI) codes

 

No

Pressure vessels DOT stamped used to supply and transport fluids

Retest per Federal Regulation, CFR-49, Transportation, parts 100-199.

No

Air pressure tanks, LPG tanks, anhydrous-ammonia tanks, and fired steam boilers. (M&O inspects LBNL air pressure tanks and boilers. Materiel Management, Industrial Gas Section, ensures that vendor-owned LPG and anhydrous-ammonia tanks are inspected.)

Inspect periodically in accordance with Unfired Pressure Vessel Safety Orders or Boiler and Fired Pressure Vessel Safety Orders of State of California.

Responsible user must notify M&O before installing.

Unmodified commercially manufactured hydraulic systems (used on hydraulic presses, motorized vehicles, machine tools, and the like).

MAWP up to 34 MPa (5,075 psig). Periodically inspected and maintained by user.

No

High-Hazard Pressure Equipment

 

 

Containing hazardous materials or pressures.

Must be reviewed by the Engineering Division Director or his or her designee.

 

Vessels and systems containing irritant, toxic, infectious, and/or radioactive fluids.

EH&S approval required.

Yes, except where LBNL Gas System Inspection Certificate is allowed

Vessels and systems containing oxygen or flammable fluids.

 

Yes, except where LBNL Gas System Inspection Certificate is allowed

Vessels and systems operated at gas pressures over 1 MPa or liquid pressures over 10 MPa or for systems that contain more than 100 kJ isentropic energy, including structurally modified ASME-coded vessels

 

Yes

PRESSURE VESSEL DESIGN

Pressure vessels within the scope of ASME codes must comply with the code except for Research Pressure Vessels approved by the Engineering Division Director or his or her designee.

Yes

CONTAINMENTS FOR PRESSURE VESSELS

 

 

Outer protective vessel enclosing gas pressurized vessels containing hazardous fluids.

 

 

Designing Safety Factors

 

 

Containment vessel for a contained pressure vessel made of ductile material.

Design for a safety factor of 4 to ultimate stress.

Yes

Containment vessel for a contained pressure vessel made of brittle material.

Design for a safety factor of 8 to ultimate stress.

Yes

Testing and Labeling

Pressure test to 1.5 times the maximum permissible equilibrium pressure. No leak > 1.0 E-08 atm cc/sec permitted.

Fix label showing working pressure and operating temperature range.

PRESSURE SYSTEM REQUIREMENTS

Show MAWP on all assembly drawings.

Yes

Relief Devices

Requirements of Chapter 7 apply.

 

Pipe and Tubing

Requirements of Chapters 7 and 13 apply.

 

Piping for nonflammable fluid

Pressure Test to 1.5 times MAWP or 1 MPa (150 psig), whichever is greater.

 

Piping for nonflammable cryogenic fluid surrounded by a vacuum jacket

Test to 1.5 times maximum allowable differential working pressure.

 

Flexible Nonmetallic Hose

Not recommended, must be approved by a Designated Pressure Engineer.

 

Pressure Gauges

Calibrate gauges to at least 1.2 times MAWP.

 

Gauges for gas systems

Use gauges graduated to about 2 times MAWP.

 

Gauges for liquid systems

Use gauges graduated to at least the test pressure.

 

Safety-type gauges for gas systems

Use safety-type gauges when gauge is over 100 mm in diameter and graduated to over 1.33 MPa (200 psig).

 

Safety-type gauges for liquid systems

Use safety-type gauges when gauge is over 100 mm in diameter and graduated to over 133 MPa (20,000 psig).

 

 

Appendix B. Facility Pressure Systems

The following information applies to utility systems and other facility pressure vessels and systems.

  1. General. The safety requirements for Plant-Facility utility unfired or fired pressure vessels and boilers have been defined earlier in this chapter and by the State of California Administrative Codes, as described below.
  2. Unfired Pressure Vessels
    1. Requirements for unfired pressure vessels are contained in:
    2. State of California Administrative Code; Title 8: Department of Industrial Relations; Part 1: Department of Industrial Regulations; Chapter 4: Division of Industrial Safety; Subchapter 1: Unfired Pressure Vessel Safety Orders

    3. The Safety Orders of this subchapter of Title 8 establish minimum standards for the following:
    4. The Safety Orders of subchapter 1 of Title 8 are not applicable to the following:
    5. The following vessels must be constructed, inspected, and stamped in accordance with the appropriate American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code section:
    6. LNG tanks for low-temperature storage at 1/10 MPa (15 psig) or less must be designed, constructed, inspected, and certified in accordance with American Petroleum Institute (API) Standard 620.
    7. LPG vaporizers with a volume greater than one U.S. gallon must be constructed in accordance with the State of California Boiler and Fired Pressure Vessel Safety Orders, Title 8, Subchapter 2.
    8. State of California Permits to Operate are required for LPG tanks and for air tanks larger than 0.04 m3 (1.5 ft3) within relief valves set to open above 1 MPa (150 psig).
  3. Boilers and Fired Pressure Vessels
    1. Requirements for boilers and fired pressure vessels are contained in the State of California Administrative Code; Title 8. Industrial Relations; Part 1. Department of Industrial Relations; Chapter 4. Division of Industrial Safety; Subchapter 2. Boiler and Fired Pressure Vessel Safety Orders.
    2. The Safety Orders of this subchapter of Title 8 establish minimum standards for the design, construction, installation, inspection, operation, and repair of:
      1. All power boilers, including nuclear power boilers,
      2. All low-pressure boilers and high-temperature water boilers, and
      3. Any other fired pressure vessels in California not specifically exempted from these Orders.
    3. These Safety Orders are not applicable to:
      1. Boilers and fired pressure vessels under the jurisdiction of and inspected by the United States Government,
      2. Boilers and fired pressure vessels used in household service, and
      3. Boilers used exclusively to operate highway vehicles, including automobiles.
  4. Design and Construction
    1. All new power boilers, high-temperature water boilers, and low-pressure boilers must be constructed, inspected, and stamped in full compliance with the ASME Boiler and Pressure Vessel Code.
    2. Pressure vessels not included in the scope of the ASME Boiler and Pressure Vessel Code must be designed and constructed according to good engineering practices with a safety factor of at least 4 to accommodate required pressures and temperatures. “Good engineering practices,” as defined in this chapter, encompass details of design and construction that are at least as safe as those required by the rules in the ASME Boiler and Pressure Vessel Code, including those rules covering shop inspection.
    3. State of California Permits to Operate are required on all boilers and fired pressure vessels except for:

Appendix C. Safety Note

A Berkeley Lab Safety Note is generally used to document engineering calculations or tests of specific equipment or activities where there is a safety. The following guidelines have been prepared to assist in writing Safety Notes for pressure vessels and pressure systems.
In preparing a Safety Note, consider the following:

Safety Notes are to be filed in the Berkeley Lab Document Control Center (dcc.lbl.gov).

 

 

Figure C-1. Safety Note Template title page format

 

1. Description

2. Hazards

3. Calculations

4. Pressure Testing
All pressure testing requires a procedure. Use this section to write the test procedure. Specify: barricade requirements, test sequence, test pressure, test fluid, test temperature, hold time, and acceptance leak rate. Record actual test procedure and results.
Is a retest procedure required? Is it different from the original procedure? Should the frequency of inspection or retest be specified?

5. Labeling

PressureTestedLabel.png

Figure C-2. LBNL Pressure Tested Label

 

6. Associated Procedures

List all procedures to be read and understood by all personnel operating the equipment.

7. References

List the references you have cited in your Safety Note.

8. Signature Authority and Distribution

The signature authority and standard distribution are shown on the sample title page. Distribute the Safety Note to others having safety responsibility for this equipment, such as Building Managers, Division Safety Coordinators, and Area Operations Management.


Appendix D. Pressure Testing and Inspection

    1.     General. Whenever practical, pressure vessels and systems should be sent to the Facilities Maintenance Technician Shops (Building 76, ext. 7669) for pressure testing. When this is not practical, the vessel or system must be tested in accordance with the in-place pressure testing procedures described below. Pressure tests performed at Berkeley Lab must be conducted by a certified Pressure Installer, and must be observed (or conducted) and certified by the Engineering Division Director or the Director’s designee.

    2.     Pressure-Vessel and Pressure-System Testing Summary

    a.     A summary of pressure-vessel and pressure-system testing is given in Table D-1.

    b.     The person who certifies the test must complete the Pressure Test Record form (Figure D-1) and then attach an “LBNL Pressure Tested” label (Figure D-2) to the vessel or system if it has passed the test. When pressure vessels or systems are fabricated for Berkeley Lab by outside vendors, pressure testing may be performed by the vendor, but must be witnessed and documented by a Berkeley Lab Responsible Designer.

    c.      Pressure-test and pressure-inspection records must be maintained for the life of the vessel by the Facilities Maintenance Technician Shop, ext. 7669.

     

    Table D-1. Summary of Pressure-Vessel and Pressure-System Testing

    Testing for pressure vessels and systems in the pressure range of 0 to 20 MPa (0 to 3000 psig). Set pressure-relief device no higher than the Maximum Allowable Working Pressure (MAWP). Pressure Test Record and LBNL Pressure Tested Label are required.

    Title

    Pressure Test

    Pressure Vessels (Testing)

    Pressure vessels for low-hazard systems. See Table A-1 for definition.

    Hydrostatic test to 1.5 times MAWP or pneumatic test to 1.25 times MAWP. Pneumatic test only if electrical or research requirements prohibit hydrostatic test. Use an inert liquid.

    Pressure vessels for high-hazard systems. See Table A-1 for definition.

    Test to 1.5 times MAWP with inert liquid (preferred) or gas. Reinspect and retest at MAWP as specified in Safety Note or AHD. Reproduce special temperature conditions or cycles as closely as possible.

    Pressure Systems (Testing)

    Pressure systems (containing low-hazard substances) that will operate with nonhazardous liquids, inert gases, or compressed air

    Hydrostatic test to 1.5 times MAWP (preferred) or pneumatic test to 1.25 times MAWP. Pneumatic in-place testing is limited to 20 MPa (3,000 psig) maximum. Use an inert liquid.

    Pressure systems (containing high-hazard substances) that will operate with oxygen or with flammable, toxic, and/or radioactive fluids

    Test to 2 times MAWP using an inert liquid (preferred) or gas. Pneumatic in-place testing is limited to 20 MPa (300 psig) maximum. Reinspect at least every 3 years. Retest at MAWP at least every 6 years unless otherwise specified in Safety Note or AHD.

     


    LAWRENCE BERKELEY NATIONAL LABORATORY

    PRESSURE TEST RECORD

    Date: _______________

    Location of vessel (or system): Build. _____ Rm. ______

    Description: ___________________________________

    _____________________________________________

    _____________________________________________

    Pressure Vessel  Pressure System  (check box)

    Pressure Tested Label attached 

    TEST INFORMATION

    http://www.lbl.gov/ehs/pub3000/Image81.gif1. Test pressure ____________________ Pa (____________ kpsi)

    2. Testing Fluid (oil, He, etc.) __________________________________________________

    3. Test Temperature _________________­­­­_°C (______________°F)

    4. Design Temperature ________________°C (______________°F)

    5. Safety Note Number _______________________________________________________

    6. Responsible Designer Name: ________________________________________________

    7. Responsible User Name: ___________________________________________________

    Dept. _______________________________ Divn. _______________________________

    8. Diameter measurements (for pressure-vessel tests only) ___________________________

    Location (marked) before testing __________After testing difference (+ or –)___________

    Remarks: __________________________________________________________________

    Test by: ___________________________________________________________________

    M&O, Mech. Shop

    CERTIFICATION

    The vessel identified above has been pressure tested and is approved for operation within these test conditions.

    Certified by: Signature: _____________________________Date: _____________________

            Print name: ______________________________________________________

    Figure D-1. Pressure Test Record

     

    http://www.lbl.gov/ehs/pub3000/Image81.gif

    Figure D-2. LBNL Pressure Tested Label

     

    3.     Testing Pressure Vessels. Pressure vessels must be tested using an inert fluid in accordance with the rules in this section.

    a.     Pressure vessels for low-hazard inert systems for operation with nonflammable, nontoxic, and nonradioactive fluids. These vessels must be hydrostatically tested to at least 1.5 times the MAWP or pneumatically tested to at least 1.25 times the MAWP when safety considerations or research requirements do not permit a hydrostatic test. Any special temperature conditions or temperature cycles to which these vessels will be subjected in use must be reproduced as closely as possible during testing. ASME pressure-test procedures are in ASME Boiler and Pressure Vessel Code, Division 1, UG-99, 100.

    b.     Pressure vessels for high-hazard reactive systems for operation with oxygen or flammable, toxic, and/or radioactive fluids.

                                                        i.     These vessels must be hydrostatically tested to at least 1.5 times the MAWP or pneumatically tested to at least 1.25 times the MAWP when safety considerations or research requirements do not permit a hydrostatic test. Any special temperature conditions or temperature cycles to which a vessel will be subjected while in use must be reproduced as closely as possible during testing. In addition, vessels may need to be inspected ultrasonically, or with a magnetic-particle test for surface cracks, or with a fluorescent-dye penetrant test.

                                                       ii.     During tests of pressure vessels in which the yield strengths of their construction materials are approached, strain-gauge measurements must be made at high-stress locations. Diameter measurements accurate to within ±0.025 mm (±0.001 inch) must also be taken both before and after testing to determine whether detectable plastic yielding has occurred during pressurization.

                                                      iii.     When the strength of the vessel is questionable (old or unknown design), strain-gauge measurements must be made during testing, and diameter measurements must be taken before and after testing. In this case, the MAWP for ASME-coded pressure vessels made of the acceptable ductile materials listed in the code must not exceed 0.4 times the test pressure and must comply with ASME Boiler and Pressure Vessel Code, Division 1, UG-101, Proof Test to Establish MAWP.

    4.     Testing Pressure Systems

    a.     Inert-substance (low-hazard) pressure systems that will operate with nonhazardous liquids, inert gases, or compressed air. These pressure systems must be tested hydrostatically (preferred), using an inert fluid, to at least 1.5 times the MAWP or pneumatically to at least 1.25 times the MAWP.

    b.     Reactive-substance (high-hazard) pressure systems that will operate with oxygen or with flammable, toxic, and/or radioactive fluids. These pressure systems may be tested using an inert liquid (preferred) or gas to at least 2.0 times the MAWP.

    5.     Leak Testing. Pressure vessels and systems may be leak tested at their MAWP level after successful pressure testing. Preliminary leak testing of nonpressure-tested or nondocumented pressure vessels or systems must be limited to a maximum of 20% of the test pressure (or proposed test pressure).

    6.     Repairs

    a.     If a leak is detected during pressure tests of a vessel or system and it is decided to locate the leak before completing the test, the pressure must be reduced to by at least one-half or more of the immediately preceding test pressure while the leak is being located.

    b.     A system or vessel must not be repaired while it is pressurized unless specifically authorized by the Responsible Designer.

    7.     Modifications

    a.     Any modification to a pressure vessel or system, other than repair or replacement with an exact duplicate of existing components, must be approved by the Responsible Designer and recorded in a revision to the applicable engineering drawing, to the Safety Note, and to the AHD (if applicable). The initial pressure test must be repeated before any further use of the modified vessel or system.

    b.     If an ASME-coded vessel is modified, the code stamping must be obliterated, and the Engineering Division Director must be notified.

    c.      When pressure equipment has been modified for use at a pressure below the original design pressure, all modifications (e.g., use of fewer bolts in flanged joints) must be approved by the Responsible Designer. All safety requirements for the lower pressure must be met, and the reduced working pressure and the number of bolts or other supports required must be clearly marked on the equipment. If high-strength bolts or other special bolts are required, this must also be clearly marked on the equipment near the bolt holes.

    d.     Instructions on precautions for operation of the modified equipment must be sent to all concerned personnel, and one copy must be filed in the Safety Note file of the Engineering Division.

    8.     Reinspection and Retesting

    a.     All high-hazard equipment that is neither a part of Facilities nor under the jurisdiction of the State of California must be as specified in the Safety Note or AHD.

    b.     Pressure reinspection is performed by a Pressure Inspector or by a Responsible Designer and is recorded on a Pressure Inspection Record form (Figure D-3). The completed form must be signed by the Responsible User and sent to the Facilities Maintenance Technician Shop, where it is kept for the life of the vessel.

    c.      The results of the retest must be certified on a Pressure Test Record Form (Figure D-1) to be filed with the initial Pressure Test Record by the testing organization, and an LBNL Pressure Tested label (Figure D-2) must be affixed on the vessel or system.

    9.    In-Place Pressure Testing

    a.     If it is impractical to pressure test a vessel or system at the Mechanical Shop, M&O Shop, or some other approved location, pressure test it in place, in accordance with the provisions of this section.

    b.     The Responsible User of the pressure equipment must ensure that In-place retesting of pressure equipment is performed. Although other individuals may be designated to observe and direct testing or retesting, responsibility for safely conducting the test and for the safe functioning of tested pressure equipment cannot be delegated.

    c.     The Responsible Designer of the pressure equipment must prepare the required test procedure, direct the test personnel, and witness in-place pressure testing of vessels and systems.

    10.  Test Procedures

    a.     A written test procedure must be prepared for every high-hazard pressure test conducted in the field. When in-place pressure testing occurs, the test procedure must be included in, or appended to, the Safety Note.

    b.     Procedures for in-place testing of high-hazard vessels and systems must be approved by the Engineering Division Director or the Director’s designee.

    c.      When pressure tests are planned in a facility, the Building Manager or Area Supervisor must be advised, and EH&S must be notified if toxic and/or radioactive material is involved.

    d.     All pressure tests must be conducted by either the Responsible Designer or a person designated by the Responsible Designer, or by a Facilities Maintenance Technician, Facilities Mechanic, or Machinist in the Assembly Shop. Pressure tests must be observed and certified by the Responsible Designer or a Pressure Inspector.

    11.  Precautions

    a.     For in-place testing with liquids, all air must be carefully removed from both the testing system and the equipment to be tested. This is because compressed air will expand violently in case of vessel failure. Spongy action of pumping equipment usually indicates the presence of trapped air.

    b.     Pressure testing with a gas is far more dangerous than testing with a liquid. Therefore, tests must be conducted with liquids, whenever practical.

    c.      Before testing, barricade the equipment being tested, shield the controls and operators, and evacuate all unauthorized personnel from the test area. Signs reading “Danger — High-Pressure Test in Progress — Keep Out” must be posted at all approaches to the test area.

 

 

LAWRENCE BERKELEY NATIONAL LABORATORY

PRESSURE INSPECTION RECORD

 

Date: ____________________

Location of vessel (or system):  Build. _____ Rm. ______

Is vessel or system still in use?  Yes _____  No _______

Pressure Vessel  Pressure System  (check box)

INSPECTION INFORMATION

Inspect the following and check (4) appropriate column, explaining under Remarks as required. (Enter N/A under Remarks if item is not applicable.)

 

Satisfactory

Unsatisfactory

Remarks

1. General appearance of system (or vessel)

 

 

 

2. Relief devices:

 

 

 

a. Properly set (have been checked; reset as required)

 

 

 

b. Properly sealed

 

 

 

c. Pointed in safe direction or safely vented

 

 

 

3. All fittings are tight.

 

 

 

4. Replaced or added fittings, gauges, valves (and piping) are properly rated.*

 

 

 

5. All system components are adequately secured.

 

 

 

6. Valve packing nuts are tight and locked (if of the locking type).

 

 

 

7. Oil is not apparent on or in gas (especially oxygen) systems.*

 

 

 

8. The outside surface of the vessel shows no evidence of strain, damage, or corrosion.

 

 

 

9. The inside surface of the vessel shows no evidence of strain, damage, or corrosion.

 

 

 

10. Lined-vessel vent path is unobstructed. Check with helium.

 

 

 

11. Vessel or system seals are leaktight. Have replaced as required.

 

 

 

12. The vessel or system is safe for continuing operation.

 

 

 

 

Inspected by: __________________________________________________________

Pressure Inspector

                       __________________________________________________________

Responsible User

Send this completed form to the Facilities Maintenance Technician Shop.

*Assurance by the responsible user is considered satisfactory verification.

 

Figure D-3. LBNL Pressure Inspection Record

 

 

Appendix E. Stored Energy of a Pressured Gas Vessel

Although the pressure section of this publication is not intended to be a primer on pressure calculation, the following formula is used sufficiently frequently, but is obscure enough, that it has been included.

When a gas is compressed, it stores energy. If the energy is released in an uncontrolled way, it will cause damage. Stored energies in excess of 100 kJ are considered high hazard. Sometimes it is helpful to think of stored energy in terms of grams of TNT. One gram of TNT contains 4.62 kJ of energy.

Vh = The volume of the vessel.

Ph = The absolute pressure of the vessel.

Pl = The absolute pressure to which the vessel would drop if it burst. Generally this would be one atmosphere (14.696 psi or 101,300 pascals). A pascal is one newton per square meter.

g = The adiabatic exponent or ratio of specific heats, Cp/Cv. The value is 1.666 for monatomic gases such as argon and helium; 1.4 for diatomic gases such as nitrogen, oxygen, hydrogen, and air; and variable for polyatomic gases such as methane, water, and carbon dioxide, but generally very nearly 1.3.

http://www.lbl.gov/ehs/pub3000/Image82.gif

Note that the bracketed value is dimensionless but that Ph Vh is not. Therefore, the length units used in Ph and Vh must match.

Example:

The gas is air (g = 1.4)

Vh = 1.0 stere (1.0 cubic meter) or 35.3 cubic feet

Ph = 10 atmospheres (150 psi) gage or 11 atm absolute or 1.1 MPa

Pl = 1 atmosphere or 100 kPa or 14.7 psi

http://www.lbl.gov/ehs/pub3000/Image83.gif

A N-m is a joule, so the stored energy is 1.4 MJ, which is equivalent to somewhat more than half a pound of TNT.

 

 

_____________________

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