|Content Type||Conference Paper|
|Title||Inspection of Rubber Lined Equipment|
|Authors||Allen D. Book, Monsanto Company|
|Source||CORROSION 98, March 22 - 27, 1998 , San Diego Ca|
|Copyright||1998. NACE International|
|Keywords||Rubber lining, inspection, spark testing, hardness testing, thickness testing, rubber lining failure mechanisms,|
This paper describes the criteria and methods to be used for inspecting and assessing the condition of new and used rubber lined carbon steel process equipment. It provides methodology for evaluating and determining appropriate repairs to rubber lined vessels. It does not address safety requirements such as confined space entry, airborne exposure, or fire protection.
A good inspection plan will provide the inspector with necessary guidance for evaluation of the lining. It should define the minimum quality expected to provide acceptable service until the next planned inspection. The plan should also define acceptance limits and direction for correction of deficiencies.
The plan should focus on the most effective tool for inspection, the eye. Plans should direct the visual inspection process and provide definition of when, where and how to focus testing methods. The inspection should directed to address service requirements such as exposure to vacuum and or aggressive chemicals and temperatures and the expected interval of operation between future inspection and maintenance activities. Inspection history, conditions observed in equipment in similar service, the age of the lining and expected MC should be used to determine these requirements.
A general knowledge of the performance characteristics and failure mechanisms of the various compounds provides the final necessary ingredient for sound inspection planning. At elevated temperatures and in vacuum service blistering can be a serious defect which may normally be repaired when relatively small in size and distribution. In mild temperature or pressure environments blisters of considerable size may give satisfactory performance without additional repair.
Similarly, surface layer deterioration and peeling may be of little importance in a commodity chemical but may be of serious consequence in a process stream requiring high purity. Loss of the top layer of a three ply soft, hard, soft stock may have many years of remaining life in an aggressive chemical exposure but may be near the end of its useful life in an abrasive environment,
INSPECTION OF NEW LININGS
The first step in obtaining a quality elastomeric lining is to clearly define and communicate the expected minimum quality level. A prejob review should be conducted with the applicator, the specifier and the inspector. ah parties to participate in and reach agreement on: It is important for
Responsibilities of ah parties
Weld and edge contour
Method of metal work repair
Number of patches before and after cure
Lining repair materials
Location of seams and orientation
Method of curing
Acceptable size, number and density of blisters.
Tests before and during application
Final inspection requirements
Customer hold points and advance notification
Unusual or project specific requirements
During application, the inspector should remain focused on insuring that the equipment is being built to specifications. The inspector is also responsible for noting deficiencies that were overlooked in design and specification. Although such conditions are not rejectable, they should be reviewed with the purchaser or responsible engineer.
All equipment metalwork, nondestructive testing and repairs should be complete and approved.
|File Size||382 KB||6|