Use of video camera expedites tank inspection procedure

Floating roofs should not be landed with this much water on them. To prevent roof collapse, the water should be drained before the roof is landed.

Shell stains are signs of leaks and corrosion. Stains such as these usually indicate internal shell corrosion.

An expedited method of performing these inspections on in-service tanks reduces the potential for accidents while meeting API 653 requirements.

In the expedited method, the inspector documents the procedure by using a video camera to tape the inspection process. The method is applicable to several industries, including petroleum, petrochemicals, chemicals, and pulp and paper.

The use of video greatly reduces the paperwork involved in the inspection process. In addition, the technique can reduce by an order of magnitude the cost and time associated with performing the inspections.

Because API 653 is still voluntary in most states, a large number of facilities either do not perform external inspections or defer them beyond the appropriate intervals. The availability of the Expedited External Inspection (EEI) technique will encourage more facilities to inspect tanks properly, in accordance with API 653.

A large percentage of aboveground storage tanks are owned and operated by the petroleum industry. The goal of API's Strategies for Today's Environmental Partnership (STEP) program is to "operate our plants and facilities...in a manner that protects the environment, and the safety and health of our employees and the public."²

The EEI procedure can help accomplish this goal.

The standard

The implementation of API Standard 653 is not as difficult or costly as it may first appear. Through the use of a new procedure, smaller facilities and tank operators can embrace the principles of API 653 without excessive concern for financial impact. Larger companies can employ these methods to reduce the cost and increase the effectiveness of their existing tank programs by judicious and selective use of the principles outlined here.

The development of API Standard 653 can be traced to a catastrophic tank failure known as the Ashland Oil incident. This incident was caused by a brittle fracture of a reconstructed tank. The fracture suddenly and without warning split the tank shell vertically, from top to bottom, resulting in an oil spill of more than 1 million gal into a major Pennsylvania river in January of 1988.

The response was predictable and immediate. Legislators and others called for sweeping new regulations on both a state and local level to prevent these kinds of events.

This event was the wake-up call that initiated development of a standard to prevent the recurrence of these incidents. API vigorously embarked on a fast-track program which ultimately ended in publication API 653 in 1992.³

Historically, API 653 was the first standard aimed at ensuring the integrity of existing tanks through assessment and inspection. API 653 has improved the reliability of aboveground storage tanks significantly and, as a result, protected the environment, as it will continue to do so.

To accomplish these goals, API uses a systematic approach involving assessment, inspection, and documentation. Historical information, including construction drawings, inspections, and repairs, also is used.

The standard has gained widespread acceptance and is required by legislation in a few states. These include Alaska, New Jersey, Pennsylvania, New York, and Florida.

Tanks generally are reliable and do not often cause plant operating problems. For this reason, before API 653 was issued, tanks often were ignored with respect to implementation of serious tank-integrity programs.

Industry acceptance of API Standard 653 has varied. Some facilities have no formal tank-integrity program, while other facilities make every effort to comply.

Because financial times are tough, programs such as API 653 may be sacrificed to some degree for short-term financial objectives. And, because tanks tend to be reliable and forgiving to many deterioration processes, this sacrifice sometimes can continue for many years with no adverse effects.

It must be remembered, however, that, given enough time, serious incidents will occur and most likely will overwhelmingly outweigh any savings resulting from a shortcut, short-term approach.

The issue of most interest in this arena today is how to gain the most value from inspections. To make this determination, one must understand that the inspections required by API 653 are only a subset of a large group of elements. Together these components make up an inspection program, the function of which is to prevent unscheduled shutdowns, incidents, environmental problems, or business interruptions.

Although there are many potential areas for reducing costs in a tank-inspection program, procedures in which substantial savings can be achieved are the informal monthly and formal visual inspections.

Effective resource use

API 653 does not prescribe exactly how to perform each aspect of the inspection process. In fact, it does not provide even minimal guidance on how to inspect and check things.

API 653 is a performance-based specification and must cover myriad site-specific conditions. This means that the standard has requirements that must be fulfilled, but it does not necessarily state how to fulfill those requirements.

For example, 653 does not require that ultrasonic thickness (UT) readings be taken during the formal external inspection. Rather, it leaves the challenge of developing the details of the inspection process to the tank owner or operator.

There are, in fact, many different ways of meeting the requirements of API 653, as most users are to some degree aware. It is on this basis that the level of effort and expense associated with tank inspections can be matched to acceptable risks.

Tank inspections

To understand how to reduce inspection efforts and boost effectiveness, it is important to understand the overall inspection requirements of API 653 (Table 1 [28500 bytes]).

API 653 requires that all tank owners use three types of inspections, implemented periodically, to monitor the integrity of aboveground storage tanks. These procedures are intended to prevent all possible modes of failure over the life of the storage tank.

The three inspection types are:

• The informal monthly inspection (IMI)

• The formal external inspection (FEI)

• The formal internal inspection (FII).

All three inspections are vital to tank integrity, but the IMI and FEI are the most useful for increasing value while reducing costs. To see how this is possible, the purpose of API 653 must be examined.

One of API 653's performance-based criteria requires that the operator conduct an evaluation to determine a tank's suitability for continued service. Although the standard does not clearly state the purpose of this requirement, one can infer that it is to prevent leaks, spills, fires, explosions, or other catastrophic events.

The IMI often is handled by personnel who have had no training. These workers sometimes are unable to identify potentially serious problems. It is possible to increase their awareness enough to make the IMI a very effective tool for incident prevention.

For example, some facilities regularly land the roofs of floating-roof tanks that have significant amounts of water or product on their decks. These owners do this either because they are not aware of the potential of collapsing the roof and damaging it, or because they do not know that water or product is on the roof.

Performing a simple visual examination of the roof prior to landing it, and incorporating this examination into an operating procedure, would prevent these incidents. Yet, they happen all the time. They often cost hundreds of thousands of dollars to remedy, and performing the repairs increases safety hazards.

Another example of a high-value inspection is making sure that lightning shunts on floating-roof tanks are in place, properly mounted to the tank walls, and touching the walls.

Experience shows that operable roof shunts prevent rim-seal fires initiated by lightning, yet as many as half of the existing floating-roof tanks have damaged or noncontacting shunts.

Table 2 [.pdf file] shows an example of a checklist designed to be used by operations personnel during the IMI. This approach focuses on high-value inspections that should be performed to prevent incidents.

It should be noted that almost all of the inspection items in Table 2 require little time or effort.

Even though a high-value IMI or FEI may be conducted without access to the top of floating-roof tanks, it is preferable for the inspector to walk the roof. When this is not possible, however, a visual inspection conducted with binoculars from the tank rim still is highly valuable.

In many instances, the space can be downgraded from a permit-required enclosed space to a non-permit-required enclosed space so that operators can readily access the roof when it is within 5 ft of the top of the tank.

Since API 653 places no restrictions on who performs the IMI, the logical personnel to do it are in operations. They know when the roof will be at a high level and can make the inspection if they are taught to understand and identify the hazards associated with tanks (Table 2).

It also should be noted that there are not a great number of items to view during the IMI. Altogether, the inspection effort has little or no impact on costs, if conducted by operations, and will prevent most major types of incidents from occurring.

The FEI

Because the formal external inspection is conducted while the tank is in service, there is no way to examine the condition of the bottom of the tank directly during this procedure. Therefore, the focus of the FEI is to verify the integrity of everything possible without shutting down the tank and entering it. For this reason, the FEI often is called an "in service" inspection.

The primary function of the inspection is limited to evaluation of the integrity of the shell and roof components. Another purpose of the FEI (or its substitute, the EEI) is to document that an inspection was conducted, what was inspected, and to establish a documented baseline of conditions at the time the inspection occurred.

This documentation not only satisfies regulatory requirements (if applicable) but also is good practice.

In many instances, tank facilities comply with API 653 requirements for an FEI by contracting inspection companies to perform this work. While this can be costly and time consuming, it stems from a perceived, rigorous adherence to API 653.

At the other end of the spectrum, some facilities implement FEIs by an informal approach that uses a brief walk-around with minor note-taking. In many cases, the FEIs simply are not done because there is no state regulation requiring them, and there is pressure to cut costs.

Condensing and abbreviating certain aspects of a typical FEI and using special tools creates an expedited form of external inspection that can reduce by an order of magnitude the costs, efforts, and time associated with inspection. This program has been developed and pilot tested at two major tank facilities. The results are compared in Table 3 [71636 bytes].

EEI's basic elements

To understand the EEI, it is necessary to know how typical FEIs are conducted. Although API 653 does not specify how to do an FEI, it does state when it shall be done.

A review of a cross section of inspection reports produced for the petroleum industry by inspection companies shows a wide variation in inspection procedures. This is expected because of the flexible nature of API 653.

Certain elements, however, are common among inspection procedures. These typically include:

• The checklist provided in Appendix C of API 653 (sometimes with minor modifications)

• Complete shell and roof-plate layout drawing made with CAD software

• Extensive UT testing data for metal thickness determination

• Settlement survey data

• Photographs.

The photographs should document the condition of the roof or roof components by showing items that do not comply with 653.

Photos should show components such as: weld seams; shell-to-bottom projection plate (chime); roof seal and components; venting devices; past tank repairs; foundation, general grade, and drainage; attached piping and valves; sumps; mixers; spiral stairway condition; stitch-welded attachment corrosion; roof pontoon manways; rolling-roof ladder components and pivot points; lightning shunts; and leak evidence on shell or roof.

The final inspection report for an FEI usually includes:

• Historical inspection data, construction records, and descriptions of work performed on the tank previously

• Historical discussion of items such as service history, construction date and standard used, and any repairs, alterations, or relocations that have been performed

• A completed inspection checklist identical or similar to those presented in API 6531

• Calculations specified by API 653, including maximum safe oil height, minimum wall thickness, time period between the current inspection and the next FEI, and settlement computations

• A list of items not in compliance with the specifications outlined in API 653

• A list of recommendations

• CAD drawings, including shell-plate layout, appurtenances, and locations of inspected items

• Discussion of tank condition

• Color photography

• Raw data from UT measurements.

The EEI abbreviates the time-consuming elements of the inspection and captures many of the checklist items in ways described below, or postpones them until the FII.

Some elements of the EEI that distinguish it from the typical FEI are:

• Elimination of the photography and CAD drawings by videotaping the tank during a walk around the base and up the ladder to the roof.

• This is the single biggest time and cost saver in the EEI process.

• Elimination of much of the written report by documenting the inspection on videotape.

• There is no requirement that the inspection report be written, only that it be "documented."

• Limitation of entry to the top rim of the tank and elimination of entry onto the floating roof.

• Elimination of much of the inspection work that typically results in the inspector judging the risk of problems to be minimal.

• For example, a simple check using a level may be used to screen the need for settlement readings and associated computations and plots. If a quick check indicates that the settlement around the perimeter is within acceptable tolerances, it is not necessary to record multiple readings, plot the data, feed them into a computer program, and compute the best fitting plane.

• Deferral of many items on the standard checklist until the FII, provided this does not degrade the reliability of the external inspection.

• When the settlement conditions for an entire tank site have been shown to be acceptable, for example, the owner may opt to eliminate settlement readings and computations.

• Reduction of the amount of ultrasonic testing based on knowledge of the service.

• An inspection agency performing an FEI will take 1-3 days/tank to perform the work, depending on the scope of work, the number of tanks being inspected, and the site-specific conditions.

Related issues

There are some fundamental questions associated with expediting the procedure for external tank inspection. While the scope of this article does not permit listing them all, the most obvious ones are:

• Does the EEI meet the intent and requirements of API 653?

  A performance-based standard such as API 653 does not specify the "how-to" aspects of inspections; rather, it focuses on the essential requirements. That is why inspection reports from tank-inspection companies differ slightly. For example, API 653 does not mandate the use of UT for external inspections. If it is used, however, specific requirements apply.

  Chevron believes that EEI meets the intent of the standard and has used EEI to comply with regulations in some states.

• Does EEI meet the documentation requirements?

  Most people would agree that video/audio recording is a far better tool than still photography. The most important benefit of using video documentation is that it eliminates the need for much of the drawing work that typically is done to locate fittings or describe problems.

  This reduction is responsible for the greatest time savings associated with EEI. It also eliminates the need for written documentation because the inspector uses the video camera to create both a visual and auditory record of the items of interest that come up during the tank walk-around.

  The disadvantage of this procedure is that, typically, there will be only one or two copies of the video recording available, and these "documents" cannot be transmitted by fax or electronically.

• Is the elimination of settlement readings and computations justified?

  There is really no difference between the FEI and the EEI here. The EEI simply uses a "Yes/No" criterion to establish whether settlement readings and calculations are necessary.

  If settlement is within acceptable tolerances, all of the related documentation is eliminated. Some inspection reports contain thousands of readings and computations that show that the tank is well within acceptable settlement tolerances. The EEI does not require documentation of this when the tank is within acceptable tolerances.

  When the tank is not within tolerances, all of the readings should be collected and the computations performed, just as in the FEI.

• Should the owner or an inspection company perform the EEI?

  Either the tank owner or an inspection company can perform this work. To date, very few inspection companies are practicing any form of the EEI because tank owners have not attempted to formalize this methodology.

  A few tank-inspection companies provide reduced-cost FEIs by eliminating many of the typical burdens such as making complete layout drawings. It is up to the tank-facility owner to demand lower-cost FEIs; supply will then meet demand, either through the owner's API-certified inspectors or through inspection companies.

• What other way does EEI optimize resources expended on tank inspections?

  Because API 653 requires both internal and external inspections, the duplication of work can be eliminated. Duplicated work often results when owners hire different inspection companies to perform the FEI and FII at different times.

  For the FEI, the inspection company prepares complete layout and appurtenance drawings. When the FII is conducted, the second inspection company makes a complete set of drawings from scratch, often using different software. The EEI supports the deferral of the drawings until the time the FII is conducted. At that time a complete set of drawings, including the bottom plate layout, can be made and kept on hand.

Another important difference between the FEI and the EEI is that the EEI does not require entry onto floating roofs. Confined-space entry rules and company policies are making it increasingly difficult to gain access to floating roofs.

The basic principle of the EEI is that it is sufficient to perform a visual examination from the roof of the tank using aids such as binoculars to assess the overall condition of the roof. Binoculars are effective for inspecting small components like shunts and roof-leg pins.

If, during inspection, the inspector sees pools of liquid on the roof, lightning shunts that are not in contact with the shell, or other serious conditions, he or she notes that the tank roof should be entered and inspected when it is near the top of the tank and accessible.

This risk-based approach will reduce the number of roofs that must be entered. The call is made by the inspector based on a visual examination.

Conclusions

There are never enough resources to do all of the things that would be ideal in the arena of equipment reliability and integrity. It is up to the petroleum and tank-inspection industries to work together to optimize resources.

The concepts presented here have been field-tested and have shown that, by eliminating unnecessary steps, EEI can cut costs while protecting the environment and increasing safety.

While this program may appear to be easy, it is not. The understanding and cooperation of operating personnel must first be obtained so that they can shoulder the major portion of both the IMI and FEI.

The certified API inspector must know what to look for. It is important that he or she eliminate unnecessary tasks and be able to identify potential hazards. The facility must determine, for example, the "Yes/No" conditions for settlement in advance of the inspection.

The underlying basis for the EEI is that it meets the intent of API 653, which is to make a "best effort" to ensure the reliability and integrity of storage tanks. Tank owners and operators need to examine every aspect of the inspection process and determine the best method of doing this, considering site-specific and internal company needs.

This videotaping technique can be used to perform much of the job, but not all of it-some written documentation is required. It also is important to note that the EEI is only one approach in the evolutionary improvement of the tank inspection process.

References

1. API Standard 653, "Tank Inspection, Repair, Alternation, and Reconstruction," American Petroleum Institute, 2nd ed., December 1995 (addendum, August 1996).

2. "STEP: To change how our industry it perceived, we must demonstrate we are serious about protecting the environment," American Petroleum Institute, December 1992.

3. API Standard 653, "Tank Inspection, Repair, Alteration, and Reconstruction," American Petroleum Institute, January 1991.

The Author

Philip E. Myers is a senior engineer at Chevron Research & Technology Co. in Richmond, Calif. He has performed process and project engineering and has served as project manager for a number of major projects. He has an extensive background in tanks and pressure vessel technology.
Myers has a chemical engineering degree from the University of California. He is vice-chairman of the API subcommittee for tanks and pressure vessels and vice-chairman of the American Society of Mechanical Engineers B96.1 committee for aluminum tanks. Myers is a registered professional engineer in California.

Copyright 1996 Oil & Gas Journal. All Rights Reserved.