First CTA Crystalliser vent separator B265GR1/A516GR70

B265 Gr1/A516 Gr70 first CTA Crystalliser Vent Separator 

This separator is the key equipment in the 450,000 tons/year PTA plant of a chemical fiber company. It is a vertical container. The diameter of the equipment is DN1600, its length is 3640mm, and there are ASTM B265GR1 partitions inside.

Design parameters：

Design press:1.71Mpa

Design temperature:133℃

Medium: Acetic +water+bromide

Hydrolic press: 2.17Mpa

Class: Ⅱlevel

Main material:

Oval head: B265 GR1/A516GR70

Cylinder:B265 GR1/A516GR70

reinforcing nozzle forgings: 16MnⅡ

Flange forgings:16MnⅡ

1.0  Its structure is shown in Figure 1:

2.0 Head forming

Before forming the head, 100% ultrasonic flaw detection shall be carried out to ensure that the bonding rate of the base and cladding materials meets the requirements. Secondly, clean the B265Gr1 surface and the stamping die surface and keep them clean. Polish the stamping die smooth. Apply high temperature resistant protective layer on the surface of head B265Gr1 to prevent the titanium layer surface from being oxidized and polluted during stamping. The head is integrally hot pressed, and its heating temperature is controlled within the range of 550~650 ℃. The minimum thickness of the formed head is 15.7mm. Through 100% ultrasonic testing, the bonding rate meets the requirements of the material.

3.0 Cylinder forming

The blanking dimension of the cylinder circumference is determined according to the developed length of the outer circle of the formed head and the measured value of the wall thickness of the straight edge, so as to ensure that the butt joint misalignment of the head and cylinder welded joints meets the process requirements. The length of the cylinder is set at 2340mm. In order to pre bend smoothly, reduce the number of circumferential welds, improve work efficiency and reduce processing cost, an arc striking plate (used as pre bending heading) is welded at the end of the cylinder. Because the arc striking plate needs to be cut off and the cylinder end face needs to be polished after the cylinder is rolled. In order to make the positioning of the cylinder end face accurate during grinding, two lines are drawn on the side and inner surface of the cylinder respectively. The first line is for viewing, and the second line is the long net dimension line of the cylinder, When the cylinder is unfolded and unloaded, add 15mm to the medium diameter unfolded length to pre bend the cylinder and the arc striking plate assembly. The pressing dimension is shown in Figure 2.

Check the end radian with a 60 ° plane arc template to ensure that the gap between the template and the inner surface of the workpiece does not exceed 1mm, and strictly control the pressing amount to ensure that the base course and multiple layers will not peel off due to excessive pressing force during cylinder rounding. For the protection of the composite board, kraft paper is used and fine hemp rope is wrapped around the roller. After pre bending, the clad surface is effectively cleaned and protected. After the pre bending is qualified, the run on plate shall be cut off by gas, and the groove shall be reground until it meets the requirements specified in the drawing. 100% Pt inspection shall be carried out on the groove surface, and there shall be no cracks. After the cylinder is rounded, welded and calibrated, 100%RT inspection shall be conducted for the circumferential weld. According to the technical requirements for titanium material manufacturing and the technical requirements for titanium material procurement, 100% ultrasonic testing was carried out on the material, and the results showed that the material could still meet the specified requirements after forming.

4.0 processing of main weld groove

According to the characteristics of vertical vessels and the thickness of base metal, the cylinder and head welds (all pressure bearing welds) are of full penetration structure, and their grooves are machined by planer. See Figure 5 for the specific groove form：

5.0 WELDING

Welding process:

1. clean carefully before welding.

2. shave off the multiple layers according to the drawing requirements and clean them.

3. control the heat input of base metal welding to avoid the formation of brittle Intermetallics at the steel and titanium interface.

Table 1

Table 2

6.0  Initial hydrostatic test

In order to ensure that the pressure bearing weld is free of defects, after the base course is welded, the equipment is subjected to a hydrostatic test at 2.17mpa according to the requirements of the construction drawing. After passing the inspection, blow the interior with high-pressure air until it is completely dry. In order to ensure that there is no peeling of the composite layer, 100% coloring inspection is carried out in the edge area of the composite layer, and no peeling is found.

7.0 heat treatment of the final welding 

In order to eliminate the welding stress, improve the structure of the heat affected zone of the weld and improve the toughness of the welded joint, after passing the preliminary hydrostatic test, we conducted the final post weld heat treatment on the equipment. See Fig. 5 for the heat treatment curve. In order to ensure that the flange sealing surface is not deformed after heat treatment, all sealing surfaces are connected by flanges. An appropriate number of thermocouples shall be set on the inner and outer surfaces of the vessel for physical temperature measurement. The furnace shall be heated by electric furnace, and the furnace shall be in a micro oxidation environment. After the final heat treatment, all inspections are qualified at one time.