Boiler and Pressure Vessels

General Requirements

Certificate of Insurance

Certificates of Inspection are received from the State Inspector by Risk Management and are then forwarded to the designated service and maintenance department for posting, such as Mechanical Services, Electrical Services, or Student Programs Maintenance. You may request a pressure vessel inspection or Certificate of Insurance by submitting the required information to Risk Management. Certificates of Inspection should be posted at the equipment it applies to - preferably in a protective cover or sleeve on the wall next to the equipment.

1. All boiler and pressure vessels (not exempt by the code) must have a Certificate of Inspection posted at/on the equipment.
2. Proper access must be provided to the equipment location for the inspector at all times. Notification to departments for annual or biannual inspections is not provided. Where proper access is not provided, the inspector will notify Risk Management at 231-7439 to coordinate efforts and schedule the follow-up visit. If access is not provided to the equipment within a reasonable time, the Certificate of Inspection will be denied and the equipment must be rendered inoperable (i.e. disconnected from all power sources and not used).
3. Proper access must also be provided around the equipment including a minimum of two feet on all sides, which must be accessed for servicing or maintenance.

New Installation Inspections

Once the installation of boiler and pressure vessels (not exempt by the code) are near completion, the project manager should contact Risk Management at 540-231-7439 to coordinate a preliminary review and walk-through of related facilities with the State Inspector. This walk-through should be with a knowledgeable person who can answer technical questions regarding the purpose and operation of the vessels. Once the preliminary review has been completed, the project manager and State Inspector will schedule follow-up visits and certifications directly with each other.

All boilers that are required by the Virginia Code to have a Certificate of Inspection before operation must be constructed and installed in accordance with the American Society of Mechanical Engineers (ASME) Code and, except for cast iron boilers, be registered with the National Board of Boiler and Pressure Vessel Inspectors.

Existing Installations

Boiler and pressure vessels that have already had an initial inspection and have been issued a VA12345 number, will automatically be reinspected by the third party inspection company on a one or two year basis. The Certificate of Inspection will be forwarded to Virginia Tech's Office of Risk Management and then to the responsible party for coordination of distribution and posting at the equipment site. If you have existing equipment that you believe should have a Certificate of Inspection that does not, you may contact Risk Management at 540-231-7439 for more information and/or coordination of inspection.

Research Vessels

Contact Environmental Health & Safety at 540-231-2341 to coordinate research vessel inspection by the contracted third party inspector if it's not permanently installed on campus (and already a part of this inspection process). Associated costs, typically $20 per vessel, shall be the responsibility of the department. If third party inspection does not result in a Certificate of Insurance (COI) being issued, a variance must be obtained from the Virginia Department of Labor and Industry for non-exempt vessels. This process must prove equivalency to ASME standards and can take several months. The variance process will be coordinated by Environmental Health & Safety, and the sponsoring department shall be responsible for gathering all required information. If at the end of the variance process, a COI is denied, the department should contact Risk Management for guidance. Basic requirements for pressure vessels include:

• Vessels must be ASME stamped.
• Maximum Allowable Working Pressure (MAWP) shall be indicated on the vessel.
• Burst disc cannot exceed the MAWP and shall be ASME stamped.
• Pressure Relief Devices cannot exceed the MAWP, shall not be adjustable, and shall be ASME stamped.

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Pressurized Vessel Safety Guide

Pressurized systems at Virginia Tech include everything from small, unheated, low-pressure laboratory setups to large, extremely high-pressure heated metal vessels weighing several tons. The stored energy associated with these systems has the potential to cause injuries ranging from eye injuries to multiple fatalities. A pressure vessel as small as a few liters volume at 200 psi contains enough stored energy to cause fatal injuries as a result of a catastrophic failure.

Pressurized metal vessels and components can fail as a result of fatigue cracking due to cyclic loading, overheating, and stress-enhanced corrosion cracking. Pressurized glass components can fail as a result of corrosion, manufacturing and assembly stresses, and scratches on the glass surface due to improper handling. In both types of materials, failure can occur after a period of use at the originally designed pressure and temperature and without warning.

Failure can also occur due to overpressurization due to direct pressurization or through chemical reactions that liberate heat or volumes of gas or both. In some cases chemical reactions can result in such a sudden increase in volume that the pressure cannot be relieved, resulting in an explosion or even a detonation. 

It is absolutely critical, therefore, that pressurized systems be designed by a person knowledgeable in the properties of materials under room and elevated temperature, stress, and fatigue conditions, and who is experienced in pressurized system design. Except for small low pressure laboratory setups and compressed gas distribution systems, this means it is best to purchase the system rather than design it in-house. In all cases, it is best to work closely with the manufacturer of the components and materials to ensure that they are suited to the intended conditions of use.

If you are constructing a pressure vessel that is subject to the Virginia Boiler and Pressure Vessel regulations, it must be designed by a qualified, licensed professional in accordance with the American Society of Mechanical Engineers (ASME) "Design Standards for Pressure Vessels."

The following guidelines must be followed in the design, construction, and use of pressurized systems.

Small-Scale Laboratory Setups

• Retain all manufacturer's documentation related to the environmental, temperature, and pressure ratings of each component in the system and retain it with other written design specifications for future reference.
• Limit the maximum allowable working pressure, MAWP, and temperature to that of the lowest-rated component in the system.
• Use the minimum size system possible to minimize the amount of stored energy.
• Make sure all components, including soldered or brazed joints, in the system, are rated for the chemical environment(s) to which they will be exposed.
• Use pressure relief devices set at or below the MAWP of the system unless it is impossible to be over-pressurized. A gas regulator is not a pressure relief device.
• Isolate hazardous substances, components, and operations through the use of barricades, shielding, gas cabinets, or remote operation if the consequences of component failure or a process gas leak are unacceptable.
• Do not subject glass equipment to pressure above atmospheric, except specially constructed glassware that is rated for pressure use and that is thoroughly shielded or barricaded on all sides.

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Large-Scale Laboratory Setups

In addition to the guidelines for small-scale laboratory setups, follow these requirements for larger-scale vessels:

• All pressure vessels and piping must be constructed, repaired, altered, and tested according to the ASME Boiler and Pressure Vessel Code.
• Protect all pressure equipment by installing pressure-relieving devices that vent to a safe location.
• Set safety or relief valves to activate at a pressure not to exceed the MAWP set for the intended operating temperature. Be sure that all components of the system are rated at or above the MAWP.
• Be sure the capacity of the pressure-relieving device is sufficient to carry off the maximum quantity of liquid or gas that can be generated in or supplied to the attached equipment without permitting a rise in pressure in the vessel to more than 10 percent above the maximum allowable working pressure.
• Take the nature of the vessel's contents into account in the design of pressure-relieving devices.
• Do not install a valve between a safety valve or similar device and the vessel being protected by it.
• Test safety valves at frequent intervals.
• Locate apparatus to be used under pressure only in areas specifically designed for that purpose.
• Do not subject pressure equipment to any pressure exceeding the maximum allowable working pressure as determined by the ASME Boiler and Pressure Vessel Code or as recommended by the manufacturer.
• If pressure equipment is to be used above 650 degrees Fahrenheit, display the maximum allowable working pressure on the apparatus.
• Follow the manufacturer's recommended maintenance and inspection procedure.

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Special Handling Procedures

Perform high-pressure operations only in special chambers equipped for this purpose. Commercially available high-pressure reactor vessels are designed and manufactured to ensure safe operation when used within the temperature and pressure limits for which they are rated. Any documentation and manuals that pertain to the reactor vessel in use must be thoroughly read, understood, and consulted regularly. However, in the end, it is the user’s responsibility to make sure that the selected vessel is compatible with the reagents and conditions to which it will be exposed during the experiment.

To this end, the user must:  

• Select a vessel that has the capacity, pressure rating, corrosion resistance, and design features that are suitable for its intended use.
• Operate the vessel within a suitable barricade/shield, if required.
• Establish training procedures to ensure that any person handling the equipment knows how to use it properly.
• Maintain the equipment in good condition, and test periodically per the vendor’s instructions to ensure that the vessel remains structurally sound.
• Complete a hazard assessment before initiating the experiment, including:
  • Assessment of any intermediates, side-products, and products that may form and their behavior within the vessel, including their corrosive nature and their tendency to violently decompose at elevated temperature and pressure.
  • Determination of maximum temperature and pressure limits expected, taking into account the energetics of the reaction being conducted and any pathways that might cause the reaction to run out of control.

• Maintain adequate ventilation. This can be achieved by installing the reactor within a fume hood, attaching tubing to the rupture disk that extends to an appropriate exhaust such as the interior of a fume hood, or by ensuring that the lab area as a whole has adequate ventilation and that the reactor is installed near an exhaust fan (in the case of larger reactors).
• Run preliminary experiments using small quantities of reactants when starting work with new or unfamiliar materials.
• Use appropriate PPE, including safety glasses, chemical resistant gloves, a lab coat, and also a face shield for operations that present particular hazards.
• Keep a log of usage for each vessel. Information on the log should include temperature, pressure, reagents/solvents used, and any inspections and tests it has undergone.

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Potentially-Explosive Material Safety

There are a number of functional group categories whose presence within a structure is a common indication of explosive potential. Use of reagents containing these functional groups in a high-pressure reactor is contraindicated. Some of these groups are:

• Metal acetylide
• Amine oxide
• Azide
• Chlorate
• Diazo and diazonium
• Fulminate
• N-haloamine
• Hydroperoxide
• Hypohalite
• Nitrate, nitrite, nitro and nitroso
• Ozonide
• Peracid
• Perchlorate
• Peroxide

For an excellent reference on chemical safety related to the use of pressure vessels, see Safety in the Operation of Laboratory Reactors and Pressure Vessels.

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Loading Limits

Overloading of a pressure vessel is a significant hazard. Dangerous pressures can develop suddenly and unexpectedly when a liquid is heated in a closed vessel if adequate head-space is not available to accommodate the expansion of the liquid. This is particularly true of water and aqueous solutions, whose volume may increase up to a factor of three when heated to 374oC. A vessel must never be filled to more than three-fourths of its available free space. Frequently, the maximum fill level must be reduced even more to ensure safe operation. If a table of volume multipliers is available for the solvent in use, use this data to calculate to maximum allowable loading using the formula:

Max. Loading Volume = (0.9)(Vessel Volume)/Volume Multiplier at Max. Temp.

Volume multiplier tables for water can be found in “Steam Tables: Thermodynamic Properties of Water Including Vapor, Liquid, and Solid Phases/With Charts” Joseph H. Keenan, Frederick G. Keyes, Philip G. Hill, Joan G. Moore, Krieger Pub Co, 1992, as well as in the Parr Instrument Company document No. 230M: “Safety in the Operation of Laboratory Reactors and Pressure Vessels” – see above.

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Limitations of the Material of Construction

Pressure vessels of identical design but of different materials of construction will have vastly different pressure and temperature limits, as well as differing corrosion resistance towards solvents and reagents (acids and bases in particular). The material of construction of the vessel must be known and its limitations understood before initiating an experiment. For commercial reactor vessels, the user’s manual and other documentation is an excellent resource for this information.

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