PROBLEM
The current method of determining wall thickness is radiography and ultrasound. Both methods require lengthly time to acquire data, which all needs to be recorded manually with respect to pipe location for future analysis.
PROFILE DENISITY
Profile density measurement has been developed by Lixi, Inc. as a very fast method to determine total wall thickness of a pipe that has process fluid inside and insulation outside. This method will also work with non-insulated pipes. All X-Ray absorption is non-linear. This new technique converts the absorption to a linear response after calibration of a pipe. It could be insulated and have process fluid inside of it. The current system can measure the difference with 75 mCi of Gadolinium-153 (100Kev energy) between 2" of lead and 0.85" of lead.
A 75mCi Gd-153 source with the current scintillator can measure the the difference in thickness of lead that is from 0.85" to 2.00". This amount can change with a different scintillator if needed.
| Weight (detector) | 8.9 pounds | ||||||||||||||||||||||
| Opening | 13"
| Optional openings | 13"/segment
| Added weight | 13 pounds/segment
| Calibration points | 10
| Range | 0 - 8,000,000 count/sec
| Weight computer | 3 pounds
| Battery life | 3 hours
| Battery belt | 8 hours
| Type | 486 75 MHz
| Memory (disc) | 260MB
| Software | Windows 3.11
| Length is 13"/segment on an extendable arm system.
Windows 3.11 on the portable computer and Windows 95 on the notebook
| | |
SPECIFICATIONS
Refineries, chemical plants and electrical power plants have MANY thousands of miles of pipe that are insulated to prevent heat loss or heat absorption. This insulation is often made up of several materials, with calcium based material being the most dense. The insulating material is usually wrapped with an aluminum or stainless steel outer wrap. Verification of wall thickness of these pipes can be accomplished by removing the insulation and doing an ultrasound inspection or by taking X-Rays at a tangent to the edge of the pipe through the insulation. Both of these processes are slow and expensive. The time required to obtain data is measured in hours per meter. The ultrasound method requires that the insulation be plugged after the inspection. The surface needs to be cleaned or the resulting data will not be accurate. The tangent X-Ray only shows two thicknesses and requires that the area be roped off because of radiation safety.Calcium silicate is the most dense insulation material I have seen. There may be others of which I am not aware. Lixi has developed a unique portable instrument based on the GAD Scope now being sold by Sentinel, who is a division of Amersham. Instead of obtaining visual information, the output of the same Gd-153 isotope goes to a special scintillator that is coupled to a photomultiplier tube, whose electronics are matched to the output of the scintillator. The resulting output is coupled to a 486 palm computer that has the software calibrated for the materials being inspected and linearized so that the photon counts can determine the thickness of material absent or present. Note that all X-Ray/Gamma absorption is non-linear (1/2 layer).
The system has a clocked time that can be set to match the output of the isotope and the time to scan an area. The results are that large lengths of pipe can be inspected and an overview can be obtained. This data can be transferred to another computer so that it can be compared in the future. The data is an electronic strip chart recorder. It can be monitored at any time, even while new data is being obtained. Global positioning could be added to confirm the location of the instrument. Also, bar codes can be created and placed at strategic locations as markers for concerned readings. The bar codes label would be carried by the operator and then scanned into the computer with the data. The bar code would be placed at the TML (thickness measuring location).
For further information, please contact:
Lixi, Inc.
1438 Brook Dr.
Downers Grove, IL 60515
TEL: 630 620 4646
FAX: 630 620 7776
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