Terry G. Clevenger
Director of Marketing for Industrial NDT Company, Inc.
Level II inspector in the major nondestructive testing disciplines
Summary: The following article is a part of the
National Board Technical Series. This article was originally published in the
July 1991 National Board BULLETIN. (6 printed
To say that pressure vessels and piping systems have received an extraordinary
amount of attention in recent years is a gross understatement. Even storage
tanks at atmospheric pressure have been more heavily scrutinized by the
Occupational Safety and Health Administration (OSHA), the Environmental
Protection Association (EPA), and industry in general.
The planning or process engineer is faced with a multitude of adverbs when
considering the best approach to a vessel, piping, or system inspection
program; why inspect, where to inspect on which vessels, how to inspect and
This paper attempts to organize the planning process for an inspection program
into four (4) basic phases, and discusses each phase at length. Topics include
categorizing or prioritizing vessels, assigning inspection techniques and
scopes to various categories, implementing inspections, documentation formats,
engineering evaluation, and applications of the program to future purchases of
Let us first establish some common denominators for planning and implementing a
vessel, tankage and piping inspection program. The objective of the program can
be to establish a QA/QC (Quality Assurance/Quality Control) system which
ensures that all pressure vessels, tanks, and piping systems are scrutinized on
a regular, timely and cost-efficient basis. This objective will clearly enhance
the concept of a mill life extension effort. The purpose of such a program is
to reduce the risks of personnel injuries, property or production losses, or
environmental damage which could result from an unexpected catastrophic failure
of a system. The benefits, aside from reducing the risk factor, are enhanced
predictability in maintenance, repair and replacement functions as well as
assurance that QA/QC standards are applied toward new systems. Again, these
benefits are aimed at enhancing mill life extension decisions.
With these common goals in mind, all vessels, tankage, and piping systems will
generically be referred to as "systems." Planning or organizing the thought
process of a systems inspection program (SIP) can then proceed as follows:
- Feasibility study to determine the appropriate course of action
- Implementation of the systems inspection program (SIP)
- Engineering evaluation of data gathered during implementation
Phase IV - Application of SIP to future purchases
Phase I - Feasibility Study
The obvious purpose of the feasibility study is to determine the appropriate
course of action for the SIP.
Our first step is to perform a comprehensive inventory of the targeted systems.
As an example, each pressure vessel and storage tank within the facility will
be physically located and inventoried by name, location and responsible
During the inventory process, the technician will perform a limited visual
survey of each system. Results of the survey can be recorded in the form of a
field drawing. When possible, the field drawing will include information such
as size, coating material, accessibility, location of weld seams, location of
openings or penetrations, alterations, surface conditions, and other pertinent
The comprehensive inventory is essential in subsequent planning of inspection
time frames, costs, support activities, etc. The final product of the inventory
process should be individual field drawings accompanied by data unique to each
system and a plan view of how the systems can be "grouped" for inspection.
Classifying or categorizing each system is the next step. Input from facility
management is beneficial to ensure that systems are evaluated objectively and
in accordance with company goals of production, safety, and environmental
impact. Obviously, a pressure vessel situated outside a plant cafeteria will be
classified and inspected differently than a warm water storage tank in the
middle of a field!
While classification guidelines will vary, some of the considerations in
determining classification standards are:
Systems affecting personnel safety
Systems regulated by federal, state, or local agencies, the insurer, or by
Systems critical to production or those affecting plant reliability or
Staying with our example of pressure vessels and storage tanks, the following
classification categories could be applied:
- ASME code unfired pressure vessels which meet any of the following criteria:
Failure poses safety risk to personnel
Failure jeopardizes other critical components
Vessel contains hazardous or toxic contents
- All pressure vessels serving as heat exchangers or ASME code stamped National
Board registered vessels which do not meet the risk criteria of P-1 vessels.
Additionally, any vessels whose operating and service conditions are different
from their original design and construction.
- All remaining pressure vessels not classified as P-1 or P-2 systems.
- All vented storage or process tanks whose rupture or leakage could pose
significant risk of injury to personnel, environmental pollution, or loss of
- All remaining vented storage tanks whose rupture poses little or no risk to
personnel or continued operation because of remote or protected location, low
temperature, or mild contents.
Determining a Course of Action
With the inventory and classification system completed, the owner's
representatives will need to make two decisions: first, determine the
inspection scope of work desired for each category of system; and secondly,
determine the timetable or milestone schedule to complete the inspections.
It is helpful to consider a scope of work matrix to consistently organize the
inspection format for similar types of systems. The matrix can offer varying
degrees of inspection thoroughness depending on the owner's need.
The maximum scope of work would be utilized when the test component is
suspected of having varied potential defects, is an extremely critical
component, and has no prior history of inspection. The average scope would be
applied to components which have targeted areas of concern and are of a less
criticality. The minimum inspection scope is utilized on components of less
criticality which have been inspected previously and/or only require
spot-checking of certain areas.
The desired time frame for completion of the program will dictate manpower
loading, degree of support costs, and other factors. Obviously, the size of the
facility and the number of systems to be examined weigh heavily in this
decision. Time frames can be as little as six weeks to as much as several years
depending on the factors we have discussed.
With inventory, classification, scope of work and time frame established, the
feasibility study is completed. Costs of the program can now be calculated and
implementation can begin.
Phase II - Implementation of the SIP
The tasks in this phase are to establish a documentation/report format, gather
the baseline inspection information, and compile a QA/QC package for each
The agreed-upon documentation format should suit the needs of the owner and can
be in hard copy form or maintained on a computerized database. As a minimum,
the documentation format should contain the following elements:
Baseline Data - includes all pertinent system data such as location, size,
temperature, pressure, manufacturer, design criteria, material specification,
Maintenance Records - all information regarding repairs, modifications, or
special requirements of the system
Nondestructive Testing - all technical reports documenting NDT results should
be compiled and displayed, when possible, on system drawings.
Electronic files (computerized documentation) is ideal for the SIP as it allows
for features such as easy access and supplementation to reports, establishment
of a "tickler file" to remind the engineer of upcoming actions, and storage of
large amounts of information in a relatively small area.
The documentation system should automatically incorporate the system
classification criteria already established, as well as the inspection
procedures and methods chosen for that particular system. This allows for easy
recall when planning future inspections and assures consistency in the QC
Gathering Inspection Information
Once the documentation format has been established, the process of gathering
baseline information on each system begins. The methods and sources for
obtaining this information are
System General Information - including engineering or maintenance files,
drawing files, original equipment manufacturer's (OEM) records, contractor
System Condition - determining the current condition of the system through
nondestructive test methods including visual, magnetic particle, dye penetrant,
ultrasonic, radiographic, and other appropriate disciplines. Each system is
inspected per the guidelines established in the scope of work matrix with any
additions or deletions to the scope clearly documented.
Compiling a QA/QC Package
The Phase II activities are concluded with the assembly of a QA/QC package on
each targeted system. To recap what constitutes this package, the engineer will
have at his/her disposal an organized documentation format consisting of:
A classified listing of all systems
Historical information on each system
Targeted inspection procedures/methods
Inspection results from all examinations
Once a comprehensive package is available, we are ready to make use of the
information as a routine planning tool for preventive/predictive maintenance,
repair or replacement activities.
Phase III-Engineering Evaluation
To this point we have organized and compiled a tremendous amount of valuable
information and documented it into a useable format for review. The information
is practically worthless, however, without a concerted effort to evaluate each
system as to its current performance/condition and take corrective actions
Competent engineering personnel should be utilized for this effort from
in-house staff, insurer authorized inspectors, or outside engineering
consulting firms. At least three areas of evaluation should be considered by
Systems which require immediate remedial measures to comply with the mandated
level of compliance
Systems which will require future maintenance or less critical action
Determining reinspection guidelines including frequency and extent based on
initial baseline findings. These reinspection guidelines would typically be
inserted back into the QA/QC package for each system and result in the "tickler
file" previously mentioned.
Phase IV - QA/QC for Future Systems
To effectively close the loop on the SIP, we should consider applying the same
scrutiny to future systems. Indeed, during the examination (Phase II),
situations will probably be found where "design thickness was not suitable" or
"workmanship on the welding was poor." These situations lead us to consider how
we can assure that future purchases meet the desired quality levels. Topics for
this consideration can be, but are not limited to:
Weld and Welder Qualification
By implementing and documenting a SIP, it becomes increasingly clear which
areas of a future system purchase need to be better controlled. Naturally, all
information gathered during a new installation is documented in the same manner
as "on line" systems, and becomes an automatic member of the program.
An attempt has been made to organize the thought process of planning and
implementing an inspection program for pressure vessels, tanks, and piping
systems. Programs will vary from one facility to another, but the basic
ingredients are still similar.
Because it can be a monumental task, the engineer should consider performing
the program in phases and even concentrating the effort on individual sections
of larger facilities to keep the program manageable. When thought out and
implemented, however, the program allows for regular, timely and cost-efficient
monitoring of critical systems.
Editor's note: Some ASME Boiler and Pressure Vessel Code requirements may have changed because of advances in material technology and/or actual experience. The reader is cautioned to refer to the latest edition and addenda of the ASME Boiler and Pressure Vessel Code for current requirements.