Even with all the advances in technology today, the wholly welded piping system has for decades remained the best choice for use in high pressure and high temperature application.
Many piping jobs in schools, industrial plants, refineries and factories have benefited from the inherent advantages of a completely welded system. It becomes a closed container joining pipes, вентили, ФИТИНГИ, and flanges. A welded joint actually becomes part of the pipe, minimizing leak potential. This provides greater margins of safety, especially under conditions of high internal pressures. Освен това, welding fittings form a continuous metal structure with the pipe, adding forged-in strength to any piping system. Furthermore, smooth forged fittings simplify insulation and take up less space.
АСТМ А 234
This standard covers wrought carbon steel fittings of seamless and welded construction which are manufactured to the dimensional specifications of ИАНМСП B16.9 and B16.28. These fittings are primarily for use in pressure piping and in pressure vessel fabrication for service at moderate and elevated temperatures.
The starting material for fittings shall consist of killed steel, изковки, решетки, плаки, seamless or fusion-welded tubular products with filler metal added and shall conform to the the chemical requirements of ASTM A 234. Unless otherwise specified, carbon steel plates may be either coarse grain or fine grain practice.
Forging or shaping operations are performed by hammering, pressing, пронизителен, екструдиране, Връщам, карам, търкаляне, огъване, machining, or by a combination of two or more of these operations. The forming process shall be applied so that it will not produce injurious imperfections in the fittings.
Hot-formed WPB fittings, upon which the final forming operation is completed at a temperature above 1150°F and below 1800°F, need not be heat treated. Cold-Formed WPB fittings, upon which the final forming operation is completed at a temperature below 1150°F, shall be normalized, or shall be stress relieved at 1100°F to 1275°F.
Химически Изисквания (в %):
Carbon Manganese Phosphorus (Макс) съдържание на сяра (Макс)
.30 Макс .29-1.06 .050
Silicon Chromium Molybdenum Nickel
.10 мин .40 Макс .15 Макс .40 Макс
.08 Макс .02 Макс
Якост на опън 60,000-85,000 PSI
Граница на провлачане (мин) 35,000 PSI
Удължение – Longitudinal:
Butt-welding fittings and butt-welding short radius elbows and returns purchased in accordance with this specification shall conform to the dimensions and tolerances given in the latest revision of ANSI B16.9 and B16.28, съответно.
When requested by the purchaser, the manufacturer shall provide a certificate of compliance to this specification. If requested to provide test reports, the manufacturer shall also provide the following where applicable:
* Chemical analysis results. When the amount of an element is less than .02%, the analysis for that element is reported as “<0.02%."
* Tensile property results, report the yield strength and ultimate strength in ksi [or MPa] and elongation in percent,
* Hardness acceptable in accordance with Section 10 of ASTM A-234,
* Seamless or Welded,
* Type of Heat Treatment, if any,
* Starting material, specifically pipe, plate, и т.н.,
* Statement regarding radiographic or ultrasonic examination.
* Any supplemental testing required by the purchase order.
All fittings shall have the prescribed information stamped or otherwise suitable marked on each fitting in accordance with ASTM A 234/MSS SP-25. A Weldbend fitting is marked as follows:
Weldbend’s Name, Номинален тръба размер, Pipe Wall Thickness Designation, Материалът Е Клас (WPB/WPC) and Heat Identification Number.
Забележка: All information contained in this document, and for a complete description of all requirements, refer to ASTM A 105. Sheets are subject to change without notice.