Process control
In the process of pressure vessel manufacturing, the first thing to do is to prepare a complete set of process documentation and inspection plan for each pressure vessel, these documents, with the role of guiding production, quality assurance, efficiency. Of course, the preparation of these documents is often not enough, the key is in the construction process, to the strict implementation of these documents, so that in the manufacturing process of the product, the upper process does not check nxot confirm not sign, the product or parts shall not enter the next process. This involves the key points that need to be controlled in the process of pressure vessel manufacturing.
Downcutting and Nesting Diagrams
The cutting and layout drawings are a key point to be controlled. The head and barrel material, the barrel grouping and even the hole opening of the line are all based on the cutting and layout drawings. Before the head and the cylinder are undercut, the technicians make the undercutting drawing according to the provided plate size and the design drawing, and draw the layout drawing according to the undercutting drawing and the design drawing for the hole opening orientation and size. Because the workshop opening orientation and opening diameter are based on the layout drawing made by the technician for line opening, so in this process, the technician should carefully and meticulously verify the drawn layout drawing, especially review the layout drawing for the opening orientation and size to avoid irreparable loss due to the wrong size and orientation of the receiver opening.
Welding work instructions
Pressure vessel manufacturing quality is directly related to its safety, reliability and service life in operation. The welding quality control in the manufacturing process is the key to ensure its quality. How to ensure the quality of welding and better control of welding quality, which requires the welding process assessment and combined with the actual manufacturing plant to develop a reasonable welding work instructions, in the development of work instructions, welding technicians in the development of work instructions can not be divorced from the actual, in this process, to be combined with the welding operator, what kind of welding, open what kind of bevel form. What kind of welding method is used, what kind of bevel angle is opened, how much blunt edge is left, all these need to be cooperated by welding technicians and welding operators, and work out the operation instruction which is in line with the process evaluation, can guarantee the quality and easy to operate by welders.
Technical handover
How to better transform the design of the drawings into the entity, less detours, to avoid errors in the manufacturing process, resulting in waste, which requires technical personnel according to the manufacturing difficulties found in the process of drawing review, technical requirements and manufacturing process requires special attention to the technical briefing. The construction drawings and the requirements of the standards and norms are transmitted to the operators in a timely, accurate and clear manner so that they can carry out the construction in accordance with the drawings, standards and norms and thus produce products that meet the requirements and satisfy the quality.
Stop inspection point
For pressure vessel manufacturing, what are our stopping points and how can we better control them? Among them are the head and the simplified material, release line, plate welding, welding seam inspection, cylinder section rounding, cylinder grouping, cylinder opening, receiver grouping welding, etc. To make pressure vessel manufacturing without mistakes, we have to strictly control these stop inspection points in the manufacturing process, so that the stop inspection points are not checked, not confirmed, not signed, and the products or parts are not allowed to enter the next process. For example, a link in the process is: take over, manhole cylinder section, forging and flange grouping prefabricated welding, in this process requires stop inspection check, to achieve strict construction according to the drawings, according to the drawings focus on monitoring, verification of flange form and specifications, sealing surface form, pressure level, forging level and flange standard number is consistent with the drawings, in order to ensure that the case is correct before grouping and welding, to avoid rework caused by not construction according to the drawings and cause rework. At the same time in this link should also focus on the supervision and control of the use of welding materials, to avoid the use of the wrong welding materials due to differences in materials.
Connection of the tube and the shell
The connection between the receiver and the shell is a difficult point in welding, mainly due to the diversity of the form of connection between the receiver and the shell, the complexity of the force, bevel processing and assembly quality is not easy to operate. The connection between the receiver and the shell is divided into flush type, internal extension type and placement type. The construction drawings have requirements for the connection form of the receiver and shell, and there is more than one form on a vessel, how can we ensure that the connection form of the receiver does not make mistakes, which requires the pressure vessel manufacturing process first based on the requirements of the construction drawings on the connection form of the receiver to produce welding instructions, and technical instructions to the pipefitters and welders, pipefitters in the receiver for the grouping based on the connection form of the drawings to produce Beveling and grouping, welders strictly in accordance with the type of welding required by the drawings for welding operations. The connection between the receiver and the shell is relatively complex, in the receiver and the container shell intersection of the corner area structure is not continuous, easy to cause a high degree of stress concentration, coupled with the possible existence of residual stress, resulting in high stress levels in this area, often become the most serious concentration of stress in the entire container parts, coupled with the plasticity of the weld metal is usually lower than the parent material, the root of the weld and heat-affected zone under fatigue load is easy to become cracked origin. So in this process to strictly control, do not allow strong group, weld to achieve a smooth transition, to avoid defects such as not fused not welded through and biting edge. Bevel processing and assembly quality is difficult to operate and control, in terms of welders construction operation, this type of weld is the most difficult to control the manufacturing process of all welds on the vessel, but also the most likely to produce problems. This is because the shell on the saddle-shaped hole is still a large number of gas cutting, gas planing and other manual opening methods, it is not easy to ensure the bevel angle and blunt edge size; bevel surface oxidation is difficult to remove, the operating position of the welded pipe and often unfavorable welders control molding, etc., so it is easy to produce cracks, not welded through, not fused, slag and other defects. At the same time, due to the specificity of the structure, RT, UT detection is difficult to operate and the drawings on the receiver and container connection is not clearly defined, which reduces the responsibility of the welder resulting in the quality of the weld is not easily guaranteed. So in this process the operator should increase the bevel processing and assembly quality control, improve the accuracy of the bevel size, bevel cleanliness. At the same time in the receiver grouping in strict accordance with the requirements of the drawings to control the receiver height and flange surface inclination, to ensure that these parameters in the standard requirements of the range, after the grouping to be confirmed by the technical quality inspection personnel before welding operations, so as to effectively avoid errors, causing unnecessary rework and waste.