Testing Refractory Lined Vessels Using the NDT Technique P-Response ®
P-Response is an NDT method for fast external screening of damaged refractory concrete linings, non-destructively, as opposed to visual inspection or core drilling. The P-Response technique has been adapted to test anchored refractory concrete in process vessels and is used in the cement, minerals, alumina industries to determine refractory lining stability from the outside of the vessel.
Assessing refractory lined vessels in cement plants, eg cyclone roofs, is a serious issue for maintenance managers. Assessing the condition of vessel linings has generally been carried out visually. Visual inspection obviously cannot detect if a refractory lining has failed at the interface allowing a section to fall while personnel are working in the vessel. Palmer Technologies has recently carried out an assessment of refractory lined vessels using the P-response® techniques.
The P-Response® system is a fast screening method for identifying suspect areas of civil and refractory concrete, non- destructively, as opposed to visual inspection or core drilling.
The advantage of the P-response® test is that it is a fast test method and can be performed on relatively rough surfaces. It can be used for vessel linings or concrete slabs, using an impact from the modal hammer to induce a vibration (flex) over a small area which is directly related to the lining stiffness and thickness.
The basic principal is flexibility of the plate is measured by a transducer (geophone) and the frequency response is normalized by the impact force. The mobility from one location to another is compared as part of the assessment.
The assessment of the refractory lining condition before entry is a significant safety issue as unstable slabs of dense refractory can cause severe injury to personnel entering the vessel.