Planning A Successful UT Investigation

Where To Begin A Piping Investigation

The decision to conduct an ultrasonic investigation (UT) has many different origins. In the overwhelming number of cases, the interest to establish the condition of any piping system only begins after a failure occurs, and generally – a significant failure. Where major damage and losses have occurred to property or services, documenting the condition and weaknesses of the pipe may be part of a legal action requiring the most thorough and meticulous effort.

Testing may also be pursued in preparation of building renovations where the condition of the existing pipe has been raised. Age is another major factor, with most of America’s high rise building properties now characterized as being in their “senior years” at over 60 years old. Although advanced pipe failure problems at newer buildings have excluded age as a prerequisite, any piping system in service for 75 years or more should always be of concern.

Building acquisitions raise another interest to uncover any piping related vulnerabilities prior to purchase. Since most due diligence engineering surveys are textbook related, and are based upon no information whatsoever regarding corrosion activity and the condition of the pipe itself, providing hard wall thickness data often changes a building assessment dramatically. Building service records may date back 10 years or during the period of the most recent owner, but will never cover the entire operating and maintenance history of every piping system. Corrosion coupon reports are so in error as to be essentially worthless as an evaluation tool.

In addition, not all exchanges of property ownership will divulge the catastrophic flood that drained the condenser water system into the lobby, the last 7 years of pipe repairs, nor a pipe leak catch basin constructed above ceiling tiles leading to a bathroom drain – all of which we have documented.

Establishing a baseline of pipe conditions at a new property is another yet less common initiator of an ultrasonic investigation showing planning and foresight. Given that most pipe is today manufactured undersized, it also adds to the accuracy of any future ultrasonic investigation by ensuring that low wall thickness values are not misinterpreted as due to high corrosion conditions when, in fact, the pipe was supplied and installed in that condition.

For fire protection systems, regulations require an internal visual examination every 5 years, with ultrasonic investigation an accepted alternative. Unlike investigations at virtually all other piping systems having the primary concerns relating to leaks and resulting water damage, far greater threat to human life exists for fire protection systems given the potential for internal rust deposits to actually stop all water flow through the fire sprinkler heads – as our own experiments have documented.

Ultrasonic investigation offers the best evaluation method for all such questions given that it provides a cumulative assessment of the piping system throughout its entire history, not just the past 1, 5, or 10 years. Properly performed, such an investigation can define whether that old wrought iron condenser water pipe from 1941 has zero or an additional 10, 25, or 50 years of service life, or whether the new condenser water pipe installed with a chiller upgrade offers only 8 more years of reliability. Is the pipe failure just the beginning of a much greater system wide problem, a limited problem related to threaded pipe only, or an isolated issue not likely to occur again?

Is UT Applicable?

Ultrasound provides a highly accurate measurement of wall thickness, but may not be suited for nor provide the answers sought under all conditions. Although probably 90% of all failed pipe is tossed in the garbage or sold for scrap, the quickest and most direct answer to most piping failures can be found at the failed pipe section itself. Saving all failed or leaking pipe is therefore always recommended. For copper pipe, which is subject to many different forms of failure, ultrasound may not provide the answers sought, with metallurgical analysis the better direction to pursue.

A general rule is that where the failure is specific, such as at a weld or ERW weld seam, or impacting only one area of the system, such as the threaded connection between galvanized steel pipe and brass isolation valve, a more focused ultrasonic investigation or metallurgical examination of failed sections is appropriate. Where large volumes of rust product have reduced heat transfer and interfered with operations, the problem is likely systemwide requiring a more thorough ultrasonic investigation.

Below is a useful checklist of questions to consider in planning any piping investigation:

Where To Start

The beginning to any ultrasonic piping investigation relates to its purpose.

- - Is testing in response to a piping failure, building acquisition, or general assessment?
  - Is there a potential legal issue involved?
  - What piping systems are of interest?
  - What are their size, pipe diameter, length, extent throughout the building
  - Are there life safety issues with fire protection systems?
  - What is the size of the property in sq. ft., cooling tonnage?
  - How accessible is the pipe? Behind walls and ceilings?
  - Will an engineering firm be involved?
  - Have test locations already been specified?

It is always best to provide some clear focus to the investigation. In general, a full day of investigation should be applied to any single piping system in order to gain sufficient data upon which to produce an accurate and reliable fitness for service evaluation. Any broad based investigation to all existing piping systems within a typical high rise building property may in fact need to address 12 or more piping systems during 2 weeks of field testing. A common alternative to reduce cost, however, is to apply less testing focus at each piping system – thereby reducing both the level of information provided as well as its degree of certainty.

Background Knowledge

Taking an accurate wall thickness measurement is often the easiest aspect of an entire piping evaluation. Translating that raw thickness data into a useful and informative report typically requires 4-5 times more effort, and requires further information often only available from representatives of the building property itself. In order to estimate corrosion rates we need to know when the pipe was installed. Was it installed during building construction or at a later date? When was the system upgrade performed? What pipe was replaced and when?

Pipe schedule is often quite obvious, but for much older buildings where significant loss may have occurred, questions may remain as to whether standard or extra heavy pipe was installed. In that respect, investigating newer properties where building design documents are still available will answer most questions. Nevertheless, having answers to certain questions is always beneficial in that it enables us to produce the most accurate building piping evaluation. A 10 year mistake in citing when the building and its piping systems were constructed will narrow the window during which corrosion took place resulting in a higher corrosion rate estimate and lower service life prediction.

- - What month and year was the pipe installed?
  - Have there been renovations, and when?
  - Have pipe failures occurred, and where?
  - Are original piping plans and specifications available?

Physical Access

While the physical act of ultrasonically testing the pipe remains the same, each piping system presents certain challenges in actually reaching the pipe. Limited access, or no access at all, as commonly exists for domestic water, sanitary waste, and dual temperature systems, can require months of advance planning and preparation. For residential properties, the need to access the pipe behind an apartment owner’s finished walls will always be met with resistance. Most condenser water risers are in a shaft requiring access and safety preparations in order to fully assess its condition.

While the condenser water pipe within a chiller plant can be easily reached by ladder, the fire sprinkler lines at a 500,000 sq. ft. warehouse will be mounted at the roof 50 ft. or more above the floor requiring a lift. Condenser water pipe within a chiller plant may be un-insulated, but then have insulation as well as a heavy metal jacketing as it moves outside to the cooling tower. For such reasons, a major consideration of all piping investigations is to the need to make the pipe of interest physically available for inspection. In order to be ultrasonically tested, we must be able to touch the pipe. Being able to see the pipe 6 ft. away on the opposite wall of an open 20 floor shaftway does not count.

CorrView cannot provide any services to access pipe behind walls, above ceilings, below ground, encased in concrete, or within shaftways. While we can remove isolated examples of fiberglass or foam insulation in order to not delay our progress, a separate insulation contractor or individual dedicated to that responsibility is required not only to ensure that the insulation will be returned to its original condition, but that we can focus all of our attention to gaining as much wall thickness data as possible. Some obvious questions are:

- - Is the pipe located behind walls or otherwise inaccessible?
  - Is the pipe buried underground or encased in concrete or other pipe?
  - Is the pipe insulated?
  - Is there asbestos present?
  - Will an insulator be available?
  - Is there an outer vinyl or metal insulation jacket?
  - Are ladders and lifts required, and are they available for our use?
  - What other potential obstacles may slow our progress?

What To Test And Where

Excluding critical services such as aviation, nuclear, and petrochemical, it is unnecessary to ultrasonically scan and inspect every linear foot of pipe nor even every pipe length in order to answer the corrosion related questions common to most building properties. All building piping system have well known and documented corrosion related issues at specific areas. Dry fire sprinkler pipe will have the highest level of corrosion exiting the main valve at its horizontal lines, whereas a wet fire system will experience highest corrosion loss at is feed line from the city water supply.

A simple condenser water system serving two chillers will contain far fewer areas for rust deposits to produce high secondary corrosion loss in comparison to a major data center having built into it multiple by-pass and crossover lines now serving as rust settling chambers. In general, we recommend that all ultrasonic investigations begin at the source of the water – whether that is within the chiller of boiler plants, or in the fire pump room. From there, the investigation can branch out to different areas of the property.

Fundamentally, we treat all pipe testing projects as an investigation rather than as a procedure. The important difference being that instead of following a procedure to ultrasonically test pipe at equal 10 or 20 ft. intervals, for example, we focus on the most common problem areas, and then continue in the same direction or re-focus testing as suggested by our prior results. All investigations should:

- - Address all sizes of pipe from largest to smallest
  - Different construction methods – welded, threaded, clamped, soldered
  - Pipe of different ages and installation dates
  - Different pipe schedules
  - Insulated and non-insulated pipe
  - Pipe under significantly higher pressures
  - Indoor and outdoor pipe
  - Pipe at upper and lower floors
  - Pipe at different risers or wet stacks

System Age

The long standing expectation that corrosion problems should only be expected for older buildings is quickly vanishing as newer building properties start experiencing pipe failures within 5 years or less. Deteriorating quality and a higher susceptibility to all forms of corrosion have reduced service life expectations of some of today’s pipe products five times and more. Add to that change the move toward thinner piping schedules and thinner wall thickness.

Green demands in the form of variable speed pumps further increase pipe corrosion, as does the reclamation of rainwater. LEED credits for purchasing lower cost thinner foreign pipe may satisfy political correctness, but is guaranteed to greatly limit the service life of any piping system into which it is installed. Then add in the fact that almost all pipe today, foreign or domestic, is manufactured to near its maximum allowable limit below its stated ASTM wall thickness.

As a result, newly installed pipe to any older system is likely to fail before the original pipe which had been installed decades prior. For any newer piping system, specific areas of interest exist:

- - Any new steel pipe added into an existing system will experience far greater corrosion loss
  - Almost all new pipe is manufactured below its ASTM thickness specification
  - Any hot or chill water system operating at extreme temperatures likely has an internal corrosion issue
  - Cast iron hubless pipe is showing far advanced failures
  - Galvanized steel pipe offers limited reliable service in virtually all applications
  - The lack of galvanic insulators for newer systems adds a point of focus to any UT investigation

Cooperation

In recent years, probably the greatest impediment to a thorough investigation has been a lack of cooperation and assistance during our field surveys. At as many as 50% of our investigations, we have gained far less wall thickness data than expected simply due to a lack of planning on the part of the client, and in many cases no preparation or cooperation whatsoever. Having been informed that all defined domestic water test locations have had their walls opened and are ready for inspection, then learning that no such work has been performed once arriving on-site, slashes the benefit of such investigation dramatically. Being informed that all asbestos has been abated after weeks of work but finding it still in place stops our piping investigation in its tracks.

With security a concern almost everywhere, we must rely upon building personnel to escort us to the many areas the pipe exists; unlocking doors, key cards to restricted areas, etc. Spending 10 minutes in one area to inspect 2 examples of pipe and then waiting a full hour because the escort disappeared greatly impacts the amount of data we can gather. Wasting a half hour while a helper wanders around hoping to find the next mechanical area in a building in which they have no familiarity raises equal frustration when the sole focus of our investigation is to gain as much wall thickness data as possible.

- - What is the level of security?
  - Is the pipe located in one specific area, or throughout the entire building?
  - Will we require access through all doors, mechanical rooms, and other areas?
  - Will we be provided access badges, keys?
  - Will we require a full time escort?
  - Will the escort be dedicated to assisting our progress or be on call for other responsibilities?
  - Will property owners and tenants question our presence without an escort?

Often overlooked, every ultrasonic inspection requires some level of cooperation from the client. For an inspection of condenser water pipe specifically located within the chiller plant, we can often work independently and without assistance. For more complex investigations involving all building systems, critical data centers, secure government facilities, of where physical access is required through every door, the client’s assistance in not only the preparation but also the execution of the investigation can make the difference between a full or partially successful result.

Progress Delays

For most ultrasonic piping inspections, our field work is defined or limited by the client to just one or a few days. During that time, our intent is to capture as much useful wall thickness data as we possibly can in order to produce the most informative and useful report. Anything slowing our progress, whether it be incomplete advance preparations or the lack of cooperation by building staff can dramatically reduce the benefit of any report.

Where safety seminars, exams, and such are a prerequisite to beginning the work day, we strongly recommend scheduling that time as an addition to the inspection in order to not reduce the level of testing we have planned.

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