What is “CODE” (in pressure related equipment and systems)
The word “code” [in construction] is used frequently and generally means:
A set of rules and standards covering the design, manufacture, and testing of construction or existing subjects.
For us, in the industrial sector, it more commonly applies to fabrication, installation and repair of pressure vessels, boilers and piping.
Prior to the establishment of the Uniform Boiler and Pressure Vessel Laws Society in 1915, some 50,000 Americans died or were injured each year from boiler accidents. The Society was formed to inform and guide the jurisdictions toward acceptance of what has now evolved into the ASME Code.
Often, it is difficult for the owner to determine if a repair is governed by “code”. The more taxing questions relate to boilers, heat exchangers and other pressure vessels. First, it is imperative to know the boundaries that define a code repair or alteration. Second, the extent of repairs dictate the involvement of a third party, commissioned inspector.
The most important questions a client should ask when evaluating their pressure related equipment:
• What are my legal responsibilities?
• What are my insurance requirements?
• What is the firm’s social responsibility (safety)?
Power or HP Boilers are governed by ASME Section I. This group of equipment is defined as any fired, electric, or waste heat boiler designed to generate steam or vapor at a pressure more than 15 psig.
Pressure Vessels are governed by ASME Section VIII. This group of equipment is defined as any containment of solid, liquid, or gaseous material under internal or external pressure, capable of withstanding the pressure of the contained materials and various other loadings.
Steam Heating and Hot Water Boilers are governed by ASME Section IV. This group of equipment is defined as a boiler in which steam is generated at a pressure not exceeding 15 psig. The hot water pressure shall not exceed 160 psig and the temperature must not exceed 250F at or near the boiler outlet.
Power Piping is governed by ASME Section I. These systems are Boiler Proper (BP) and Boiler External Piping (BEP). Superheaters, Economizers, and other pressure parts connected directly to the boiler without intervening valves are considered parts of the BP. BEP is considered as that piping which begins where the boiler proper or a separately fired superheater terminates. Note that BEP falls out of the boundaries of Boiler Proper and is covered by ASME B31.1 Code.
The boundaries for the boiler and pressure vessel are quite simple. However, the Code boundaries for the piping systems connecting boilers to Main Steam, Feed Water, Blow Down, and Control Piping can be confusing. The difficulty or confusion often results from the erection, installation, modifications and or additions after initial install/construction.
Typically, the original manufacturer’s data sheet defines the boundaries in accordance with Section VIII; however, where external piping is connected to the vessel, the boundary is defined as:
• the welding end connection [for the first circumferential joint for welded connections]
• the first threaded joint [for screwed connections]
• the face of the first flange [for bolted flanged connections]
• the first sealing surface [for proprietary connections or fittings]
• where non pressure parts are welded directly to the internal or external pressure retaining surface of a pressure vessel
• the pressure retaining covers for vessel openings (i.e. manhole or hand-hole covers)
• the first sealing surface for proprietary fittings or components for which rules are not provided by this division, such as gages, instruments, and non-metallic components
Types of Repair
There are three distinctions of repair covered by the National Boiler Inspection Code (NBIC):
• Routine Repair
All repairs must be inspected by a third party inspector, who has the authority to set any hold or inspection point necessary to ensure the work is acceptable to the specific code.
A common misconception surrounds the “inspection” involved in Code repairs. An Authorized Inspector (AI) is an independent subcontractor commissioned by the NBBI. He or she does not perform nondestructive testing or other standard practice quality assurance. These functions fall on the owner or contractor. Zuuk Inspection, a division of Zuuk International, provides MT, PT, UT, VT and other services to determine the integrity of the repairs; however Hartford Steam Boiler is Zuuk’s governing AI and is required to review the work package and in certain cases, witness the repair.
A repair is defined as:
“The work necessary to restore a component or system to a safe and satisfactory operating condition, such that existing design requirement are met.”
The primary difference between a Repair and a Routine Repair is the involvement of the AI. Under the Routine Repair, the AI need not look at the work. He/she will only review the completed work package and sign the R-1 form (Report of Repair form). There are four definitions of routine repairs:
• Welded repairs of replacement of valves, fittings, tubes, or pipes (NPS 5 (DN 125) in diameter and smaller, or sections thereof, where neither postweld heat treatment nor NDE other than the visual is required by the original code of construction. This includes their attachments such as clips, lugs, skirts, etc., but does not include nozzles or pressure retaining items.
• The addition or repair of any non-load bearing attachment to a pressure boundary where postweld heat treatment is not required.
• The weld buildup of wasted areas of shells, heads, tubes, pipe when the total area of buildup does not exceed 100 sq. inches or the thickness does not exceed 25% of the wall thickness at the point of repair of ½” whichever is less.
• Repair of the corrosion overlay not exceeding a total of 100 sq. inches.
A (“full-blown”) repair requires the AI to be present and witness the repair and a repair name plate is physically attached to the equipment.
• ASME are the construction codes covering original fabrication of pressure related equipment.
• NBIC is the code used for repairing the constructed equipment with respect to the ASME standards.
• The AI is a subcontractor and required by the NBIC.
• The AI does not do NDT.
• All participating welders have to be qualified to proven welding procedures owned by the Certificate Holder (contractor).
• A Contractor’s Quality Program mandates that welding