FIFTH CANADIAN CONFERENCE ON NONDESTRUCTIVE ... - IAEA

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1. Pipe stops at inspection station.
2. Radiation source is positioned at the weld location.
3. Film is wrapped around the joint.
4. Film exposure is made.
5. Film is transported to the dark room.
6. Film is developed.
7. Film is dried.
8. Film is interpreted.
The minimum cycle time for conventional radiography on pipeline operations is
four minutes to read film wet and four and one-half minutes to read film dry.
These numbers represent the physical minimum times using hot chemicals and
high speed dryers while not sacrificing image quality.
7. COSTS OF CONVENTIONAL RADIOGRAPHY
The obvious cost items for provision of offshore film radiographie inspection
services are labor, materials, and transportation. Based on estimates
obtained from proposals submitted to Brown & Root during the past year, an
average cost breakdown was developed for an example job. The chart is based
on a single joint 30" 0 pipeline contract where 180 joints are radiographed
on the firing line every twelve hour shift. This assumes a four minute cycle
time. Total cost of the job, neglecting mobilization and demobilization, is
figured at $53,800 when a 10 day duration of work is assumed. One major cost
item in the job is the cost per joint which is 50% of the total cost of the
work. This single item accounts for the expendable items involved in the
work, film and processing chemicals. These figures were derived from formal
telexed quotes for work from inspection companies for jobs in 1983. As pipe
becomes smaller in size, the expendable costs become a smaller fraction of
total operation costs. For any diameter pipe, the total day rate for labor
and equipment remains constant.
Some costs of film radiography are not so obvious but are substantial. In
bidding work, the difference in cost between the requirement of reading wet
film and reading dry film might be disparate. In bidding, the difference has
translated to time and money lost. Another subtle cost factor is attributed
to barge downtime caused by the inspection station. The time and cost of
this factor have not yet been quantified. Also, radiographers do not know
until at least four minutes after an exposure is made whether or not the
radiograph is qualifiable. The costs of reshoots and crawler breakdowns
comprise other unseen costs of film radiography.
8. OPERATING RELIABILITY
Mechanical and human operations are the main parameters which govern the
operating reliability of conventional radiographie systems. Operating
personnel control such functions as exposure time, chemical temperatures,
placement of film in cassettes, lead shielding, record keeping, and
interpretation. Exposure time is currently regulated manually and controlled
with a timer. Film development has become almost fully automated and less