PUB-3000 Chapter 7 | PRESSURE SAFETY AND CRYOGENICS

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:

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. Primary relief devices (relief valves or rupture disks) must be set at no more than the MAWP. Secondary or backup relief devices are encouraged. They may be set at up to 120% of 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.

When the pressure of an evacuated vacuum vessel is raised to the level of atmospheric pressure with a pressurized-gas source, a relief device must be installed between the gas source and vacuum vessel.

Berkeley Lab personnel are not permitted to set, seal, or stamp relief devices on utility water boilers, steam boilers, and compressed-air receivers that are under the jurisdiction of the State of California.

Only authorized Facilities Maintenance technicians and other specifically authorized persons are permitted to set and seal adjustable relief devices on noncoded pressure vessels and systems.

3. Pipe and Tubing

The following requirements apply. See also Chapter 13, Gases.

Use flexible nonmetallic hose only when it is impractical to use rigid metal pipe or tubing.

Keep hose lengths as short as possible, protect them from mechanical damage, and anchor the ends to prevent whipping in case of hose or hose-fitting failure.

Avoid sharp hose bends, and do not bend hoses more sharply than recommended by the manufacturer.

Replace or repair any hose showing leaks, burns, wear, or other defects.

Do not use nonmetallic hose on flammable, toxic, and/or radioactive gas systems. (Gases tend to permeate nonmetallic hose.)

On liquified-gas systems, ensure that all terminal-block (liquid-withdrawal) valves are rated above the vapor pressure of the liquid gas at 38°C (100°F) or that a properly set relief valve is permanently installed on the outlet side of each terminal-block valve.

All work on pressure equipment requiring a Safety Note must be performed by trained personnel under the direction of a responsible designer or responsible user.

All systems must be securely fastened to resist seismic forces.

For gas systems, use gauges graduated to about twice the MAWP of the system; for liquid systems, use gauges graduated to at least the test pressure.

Calibrate pressure gauges, switches, and other devices through 120% of their maximum operating points. These devices must be capable of withstanding the operational and emergency, temperatures of the system, and their material must be compatible with the system fluid.

When large pressure gauges (over 100 mm in face diameter) are used on gas systems with MAWPs over 1.4 MPa (200 psig) or on liquid systems over 140 MPa (20,000 psig), they must be of a special safety-type design. Such gauges have shatterproof faces, solid fronts, and blowout or generously vented cases. If such a gauge is not installed, operators must be protected by a Lexan safety shield securely mounted over the existing gauge face.

Protect a gauge subject to pressure surges or cyclic pulses by installing a needle valve or orifice for damping.

Ensure that there is no oil in gauges used on gas systems. This is important on oxygen systems because hydrocarbons and oxygen can combine explosively. Clean all gauges to be used on high-purity gas systems.

Equip every flammable-gas drop or regulator-hose connection with a flash arrester or a check valve, a pressure gauge, and a shutoff valve. If the flammable gas is to be (or could be) cross connected with oxygen or compressed air, a flash arrester must be installed in the flammable-gas line and a check valve in the oxygen or compressed-air line.

Equip all oxygen drops with a check valve. This applies to all single- and multiple-station installations and portable equipment.

4. Pressure-System Inspection

The responsible designer must review newly completed pressure vessels and systems to ensure that they are free from manufacturing defects.

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.

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 Facilities Department.
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).

_____________________