From huge storage tanks, crude oil and its purified form pass through thick pipelines in refineries and depots. Beverages such as milk, juices, beer and high grade medicines run through sterilized stages in large vats before they enter a network of pipelines first before they reach the consumers in the supermarkets.
One can imagine the dire consequences if the lethal rust or lead which came as a result of substandard materials used in manufacturing these pipes were unknowingly bought by the specifiers or designers. It cannot be overstated then that the right kind of stainless steel pipes, whether welded or seamless, is a must in the selection process. There is a high price to pay if the wrong choice is made. For once they are installed, there is no turning back.
It is highly recommended that before any installation is made, a major commitment of time, study and a great deal of attention and consultation is done. Public safety after all lies at the core of all these investments.
Piping is often used to describe the high-performance (high-pressure, high-flow, high-temperature or hazardous-material) conveyance of fluids in specialized applications.
Sanyo Seiki complies with the Philippine National Standard for seamless, welded and heavily cold worked austenitic stainless steel pipes which is the standard issued under the fixed designation ASTM A312/A312M: 2016 (recorded on the first quarter of 2016 of BPS) has indications which Sanyo Seiko complies with strictly.
The material furnished under this specification shall conform to the applicable requirements of the current edition of ASTM A999/A999M and the manufacture of these is governed by the following processes:
- Seamless (SML) pipe shall be made by a process that does not involve welding at any stage of production;
- Welded (WLD) pipe shall be made using an automatic welding process with no addition of filler metal during the welding process;
- Heavily cold-worked (HCW) pipe shall be made y applying cold working of not less than 35% reduction in thickness of both wall and weld to a welded pipe prior to the final anneal. No filler shall be used in making the weld. Prior to cold working, the weld shall be 100% radiographically inspected in accordance with the requirements of ASME Boiler and Pressure Vessel Code, Section VIII, Division 1 (latest revision, paragraph UW-51).
- Welded pipe and HCW pipe of NPS 14 and smaller shall have a single longitudinal weld. Welded pipe and HCW pipe of a size larger than NPS 14 shall have a single longitudinal weld or shall be produced by forming and welding two longitudinal sections of flat stock when approved by the purchaser.
- All weld tests, examinations, inspections, or treatments shall be performed on each weld seam.
- At the option of the manufacturer, pipe shall be either hot finished or cold finished.
- The pipe shall be free of scale and contaminating exogenous iron particles. Pickling, blasting, or surface finishing is not mandatory when pipe is bright annealed. The purchaser is permitted to require that a passivating treatment be applied to the finished pipe.
- Pipe and tube shall be one of the following grades as specified below:
The H grade versions of familiar grades like 304, 316 and 321 have a minimum carbon content to produce increased high temperature strength, particularly creep strength or a measure of a part’s ability to withstand prolonged stress or load without significant continuous deformation.
Compared to 304, 316 and 321 these H grades combine the following characteristics:
- Similar general corrosion resistance
- Reduced intergranular corrosion resistance
- Improved high temperature 0.2% proof strength
Carbon is an important element in stainless steels. It is usually kept low in order to aid weldability, especially in the avoidance of chromium carbide, which gives rise to intergranular corrosion. However, carbon is an important strengthening element. In certain cases, notably at high temperature, strength may take precedence over the risk of intergranular corrosion. The minimum carbon level of 0.04% in the H grades provides this extra strength. Creep strength is enhanced with a large grain size. Therefore, it is usual for standards to specify an ASTM grain size of 7 or coarser for the H grades.
The largest tonnages of welded process pipes are found primarily in chemical, petrochemical, energy, pulp & paper, water treatment and desalination industries which could involve acidic or caustic environments, high pressure, abrasive conditions and both high and low temperature.
The need for stainless pipes increases in more corrosive, low maintenance and high risk (failure) applications. Welding is also done on exhaust systems, process plants, seals and expansion joints. Within offshore, welded pipes are used below the sea level in flowlines, umbilicals and riser pipes.
Label on each product should be clear and complete.
eg. ASTM A312/A312MPipe. 304 NPS 12 SCH 40S SMLS
There are tables with specific chemical composition, annealing requirements that pertain for various grades specially when applying heat treatment on pipes. Likewise, lists of standardized dimensions of welded, seamless stainless steel pipe (ref. ANSI B36.19) and heavily cold worked pipe are made readily available by Sanyo Seiki to any company that orders any of its pipes.
In addition to the information required by Specification A999/A999M, the certification shall state whether or not the material was hydrostatically tested. If the material was nondestructively tested, the certification shall so state and shall state which standard practice was followed and what reference discontinuities were used.
The details of the following PNS are described in a document which can be obtained and discussed more lengthily with a Sanyo Seiki Quality Assurance personnel:
- Product analysis
- Permissible variations in wall thickness
- Permissible variations in length
- Dimensions of welded and seamless stainless steel pipe
- Conduct of mechanical tests, grain size determinations, weld decay test required
- Hydrostatic or nondestructive electric test
- Workmanship, finish, and appearance
- Repair by welding (weld repairs shall be made only with gas tungsten-arc welding process)
- Pipe and filler metal specification
- Other supplementary requirements which shall apply when specified in the purchase order. The purchaser may specify a different frequency o test or analysis than is provided in the supplementary requirement. Subject to agreement between the purchaser and the manufacturer, retest and retreatment provisions of these supplementary requirements may also be modified: transverse tension tests, flattening test, etching tests, radiographic examination, stabilizing heat treatment, inter granular corrosion test, minimum wall pipe, use of hydrochloric acid, and other methods relevant in the proper care and handling of the pipes.