Questions_and_Answers_0003.docx

INDE: Chilled Water Pipe Inspection 140P4225Q0038 Contractor Questions

1. Water System Composition:

Can you please confirm whether the chilled water system contains any corrosion inhibitors, glycol, or other chemical additives, or if it is strictly filled with water?

Chilled Water Piping is strictly filled with water. We do not use corrosion inhibitors, glycol, or other additives in the piping loop to be inspected.

2. UT Inspection Methodology:

The PWS specifies a UT thickness survey using ultrasonic testing equipment. Would Remote Field Testing (RFT), an electromagnetic inspection technique that locates and sizes both internal and external corrosion, be an acceptable alternative for this portion of the work?

RFT is potentially viable. I am not familiar enough with the technology to understand it's limitations. I would note that the piping is insulated and buried at varying depths which may present issues with this methodology. Some technical details would be needed to evaluate this technology.

3. Video Probe Inspection Limitations:

There may be challenges associated with the use of video probe inspection for this scope. Video probes are generally effective for short piping runs and only in dry conditions. For extended piping runs, a remote-control probe vehicle would likely need to be rented. Even with such equipment, there have been instances where the vehicle becomes immobilized due to pipe seams or obstructions. Additionally, if water—especially murky or moving—is present in the piping, visibility is significantly compromised, often rendering the video inspection ineffective.

Video survey is to be conducted within the parameters listed. Piping must remain filled, although flow can be stopped for up to 8 hours at a time during the season listed in the PWS (November-April). Thus a video probe is NOT a viable solution where probe can only survey short runs and in dry conditions. Only one entry point per pipe (i.e, one suppy line and one return line entry point are available).

4. UT Thickness Testing Methodology:

Ultrasonic Thickness (UT) testing is typically the preferred method to assess pipe condition. Multiple UT readings are taken, which are then reviewed by a certified API 570 inspector. The inspector would interpret the data and provide recommendations along with an estimated remaining service life.

Piping is buried and insulated. Conventional UT measurement techniques are not an option for the follow-on survey. Alternate methodology will be needed. This solicitation does not require thickness measurements be taken. Only that a proposal, with explanation of proposed methodology be provided with final report.

5. Data Point Frequency:

Clarification is needed regarding the desired frequency and locations for UT measurements. For example, readings can be taken at 0°, 90°, 180°, and 270° around the pipe circumference at regular intervals (e.g., every 2 feet, 8 feet, 20 feet, 100 feet, etc.). Please advise on the preferred measurement spacing.

The 0o, 90o, 180o, and 270o readings are preferred. Spacing should be 2’ or less. Some technologies exist for continuous measurement and are preferred, but not required. Proposal should make clear equipment, spacing and whether 0, 90, 180, 270 readings will be provided.

6. Access to Bare Pipe Surface:

It is noted that the piping is PVC-clad and insulated. For accurate UT readings, the transducer must be in direct contact with the metal surface of the pipe. Therefore, cladding and insulation will need to be removed at all designated test locations.

This is buried piping and therefore no access to bare piping is available. UT readings to be taken via inserted equipment or other valid technical means which should be described in proposal.

7. Material Composition Confirmation:

Please confirm whether the piping is made from a cast material, as this affects both inspection technique and interpretation of results.

Piping is assumed to be ASTM A53 Seamless steel piping. Contractor will be able to examine above ground portion of piping while conducting the Video survey to inform their proposal for follow-on UT thickness survey to inform survey proposal.

8. Access Requirements:

Any scaffolding, lifts, or other means necessary to safely access the piping for inspection must be provided by the client.

Access to piping for inspection is via pipe tee connection roughly 3’ above Finished floor of chiller plant. Therefore no scaffolding, lifts or other means to access piping is needed. In general, contractor to assume responsibility for providing and tools, equipment, or labor required to perform this survey. Any exceptions taken by contractor should be clearly noted in their proposal for evaluation.