1. PURPOSE
1.1 This engineering specification defines the general requirements for inspecting profile wire distributor screens by the equipment specifier or Air Products representative.
2. Scope
2.1 This specification, along with the equipment specification and design drawings, applies to the workmanship and cleanliness of profile wire distributor screens, which are installed in pressure vessels.
2.2 This specification applies to inspections at both the distributor screen supplier’s and vessel fabricator’s facilities.
3. Related documents
3.1 Air Products Engineering Documents
4WEQ-1040 Profile Wire Screens – Cylindrical
4WPI-SW70002 Process Clean (Class B) Inspection and Acceptance Requirements
4WPI-SW70003 Oxygen Clean (Class AA) Inspection and Acceptance Requirements
PES Project Equipment Specification
Form Release Notification
- PHILOSOPHY
4.1 Because of a history of problems with these items and because of the high cost associated with failure after being put in service, all profile wire screen assemblies which retain sieve material (that is, lower baskets and side mounted scallops) must be inspected for compliance with specification and satisfactory workmanship.
4.1.1 Inspection of profile wire screen assemblies which do not retain sieve material (that is, upper baskets) shall be at the specifier’s discretion, based on past experience with the supplier.
4.2 Inspections may be made either at the screen supplier’s shop or at the vessel fabricator’s shop. The specifier shall make this decision based on the screen supplier’s past performance and on the logistics of performing the inspections.
4.3 In all cases, the screen supplier shall provide self-inspection in the form of an “As-Built” drawing as called for in 4WEQ-1040. This inspection shall include a check of slot size, overall dimensions, weld type and size, and cleaning.
5. Inspection requirements
5.1 Screen Supplier Facility
5.1.1 Review the supplier’s quality assurance test results (‘Peel tests’) of the strength of the weldment that attaches the profile wire, known as wedge wire or V-wire, to the support rod. If the profile wire snapped at the support rod and the weldment was left intact, the screen is acceptable. However, if the weldment broke away from the support rod and the profile wire remained intact, the screen is unacceptable.
5.1.2 For “High reliability” screens review the supplier’s quality assurance test results (‘Push-Off tests’) of the strength of the weldment that attaches the profile wire to the support rod. The individual values obtained from these tests shall not be less than 5000 N (1124 lb).
5.2 Vessel Fabricator Facility
5.2.1 The inspection should take place after the screen has been welded into the vessel head but before the head is welded to the vessel.
5.2.2 Inquire about the condition of the screen crating when it arrived at the vessel fabricator’s receiving department. The condition of the shipping crate might determine the level of inspection required.
5.3 Either Facility
5.3.1 Check the screen for damage.
5.3.2 Check the slot size of the screen with a feeler gauge as compared to the design drawing. Unless noted otherwise in the screen specification, the general tolerance on the slot size is ±0.13 mm (0.005 in).
5.3.2.1 Check for areas where the slot might have opened up locally adjacent to welded areas. These might present leak paths for the sieve material. Localized opening of the screen is acceptable if it does not exceed the dimensions specified below and the affected area is a small portion of the entire screen area (<5%). If the maximum slot size is exceeded, then the affected slots shall be welded shut with an approved procedure. If the affected area is greater than 5% of the entire screen, then the screen shall be rejected.
| Sieve Material Minimum Bead Size “b” from the process specification |
< 1.5 mm (0.06 in) |
1.5 – 2 mm (0.06 – 0.08 in) |
> 2 mm (0.08 in) |
|
|
Maximum Slot Size |
2/3 x b |
1 mm (0.040) |
1/2 x b
|
5.3.2.2 Localized closing of the slot is acceptable if the affected area is a small portion of the entire screen area (<5%). If the affected area is greater than 5% of the entire screen, then the screen shall be rejected.
5.3.3 Check the screen dimensions to ensure that they are in accordance with the profile wire drawing.
5.3.4 Check the weld size and type against the weld details of the profile wire drawing. Weld quality (weld penetration, weld uniformity, undercut, and burn through) shall be checked.
5.3.5 Inspect screens for cleanliness using Class B (as defined by 4WPI-SW70002) or Class AA (as defined by 4WPI-SW70003) acceptance criteria. Refer to the equipment specification or specification transmittal for the required cleaning specification.
5.3.6 Check the squareness and condition of any flange facings.
5.3.7 The Screen Inspection Checklist shown in Appendix A shall be completed.
- DOCUMENTATION
6.1 A copy of the Screen Inspection Checklist form shall be sent to the specifier upon completion of inspection. In addition, a copy shall be given to the screen supplier/vessel fabricator to be attached to the Release Notification form that accompanies the screen/vessel.
Appendix A
Screen Inspection Checklist
Project Number: Item Number:
Inspector:
| At Screen Supplier Facility Only | Acceptable | Not Acceptable |
| Review weldment strength test results (that is, Peel tests) | ||
| (Profile wire snapped/Weldment remained – Acceptable
Profile wire remained/Weldment broke away – Unacceptable) |
||
| For “high reliability” screens, review weldment strength test results (that is, Push-Off tests) | ||
| (The individual values obtained from these tests shall not be less than 5000 N (1124 lb). | ||
| Condition of crate and marking for shipping | ||
| At Vessel Fabricator Facility Only | ||
| Condition of crate at arrival | ||
| At Screen Supplier or Vessel Fabricator Facility | ||
| Condition of screen (that is, Damage) | ||
| Check screen slot size (in accordance with paragraph 5.3.2) | ||
| Check screen dimensions (in accordance with the profile wire drawing) | ||
| Check weld size and type (in accordance with weld details on profile wire drawing) | ||
| Check cleanliness (in accordance with equipment specification or its transmittal form) | ||
| Check squareness and condition of any flange facings | ||
| Corrective Actions: |
______________________________
Signature/Date
Note: Inspection at vessel fabricator facility should be done after the screen has been welded into the vessel head but before the head is welded to the vessel.