The ASTM A691 91 Pipe specification covers electric-fusion-welded alloy steel and carbon steel pipes produced with the addition of filler metal. These pipes are manufactured from pressure-vessel quality plates and are designed for applications requiring high strength and reliability in high-pressure and high-temperature service conditions. Heat treatment may be applied to achieve the required mechanical properties and to comply with applicable codes and standards. Supplementary requirements may also be specified when additional inspection or testing is required.

Typically, these pipes are produced with an outer diameter starting from 16 inches (400 mm) and wall thickness up to approximately 3 inches (75 mm). However, other dimensions can be supplied according to specific project requirements. Pipes are classified based on steel grades and class designations depending on the heat treatment applied during manufacturing. Surface finishes may include bare, galvanized, black painted, anti-corrosion coated, or varnished. The pipe ends can be supplied in various forms such as plain end, beveled end, threaded, grooved, coupling, or cut square. Length options usually include single random, double random, or customized cut lengths as requested by the client.

To ensure quality and reliability, the pipes are subjected to various inspection and testing procedures including eddy current testing, ultrasonic examination, hydrostatic testing, and verification of chemical and mechanical properties. For safe transportation, ASTM A691 91 Pipe products are typically packed in bundles secured with strong steel strips, while larger pieces may be supplied loose and wrapped with protective plastic coverings suitable for handling and lifting operations. The pipes are generally shipped in 20-foot or 40-foot containers or as bulk cargo depending on shipment requirements.