9.4        HVAC Pipe Flushing

All newly installed HVAC piping systems shall be cleaned and flushed prior to placing the pipe into operation. These HVAC piping systems include chilled water piping, condenser water piping, high temperature hot water (HTHW) piping, and primary / secondary heating water piping. This design standard is intended to cover HVAC piping installed at BWI Marshall and Martin State Airports as part of the Maryland Aviation Administration capital projects, as well as tenant improvements, and other equipment procurements.

9.4.1            HVAC Pipe Flushing Background

Due to the increase in occurrences of contaminated HVAC piping systems during construction at the Airport, the following standard has been created. It is the intention of this standard to provide contractors with methods to clean and flush all new HVAC piping prior to placing the piping into operation. This will reduce the chance of damage to the chilled water, HTHW, and heating water systems within the Main Terminal and Central Utility Plant.

9.4.2            HVAC Pipe Flushing Design Specification Requirements

Add the following in PART 3 of applicable hydronic piping specification sections.

“3.XX             CLEANING AND FLUSHING OF PIPING SYSTEMS

A.     The following applies to all temporary and permanent HVAC piping installations, both aboveground and underground. All of the following items must be completed prior to placing new connected HVAC pipes into operation with existing and/or new piping systems. The following items apply to condenser water piping, chilled water piping, high temperature hot water (HTHW) piping, and heating water piping systems.

1.      Use clean potable water source. If not available from the Airport’s water supply, then the Contractor must provide his own source of clean potable water. If high volumes of water are to be drawn from the Airport’s water supply system, then the Contractor will provide a strainer to remove sand and grit which may be drawn from this water supply system.

2.      The Contractor shall provide temporary pumps and strainers with fine mesh screens to obtain minimum eight (8) feet per second flushing velocity within the HVAC piping systems.

3.      (This should be deleted if not desired for a particular project. This option may be considered if pre-approved by MDOT MAA Maintenance and Engineering, and if the logistics and costs for temporary pumps cannot be easily provided by the Contractor.) It may be possible to use existing pumps in the HVAC system, or pumps which are new as part of this project to obtain the minimum eight feet per second flushing velocity. If the Contractor wishes to utilize any new pumps or existing pumps within the HVAC piping system to obtain the minimum flushing velocity, this must be approved by the Engineer and MDOT MAA Maintenance. In addition, the Contractor shall provide additional strainers with fine mesh screens to insert into the existing strainers during flushing operations. Once the flushing is complete, the temporary strainers will be replaced with new strainer inserts matching existing and/or new pumps as utilized. In addition, if the new or existing pumps are used, the Contractor shall replace all pump seals after flushing operations, and then provide an additional set of pumps seals for Maintenance’s use.

4.      During the flushing operation, the Contractor shall add chemicals (cleaning agent) as necessary to clean all piping process oils and dirt/debris from within the piping systems. These chemicals shall not harm the new piping systems and any connected piping systems, including all valves, pumps, equipment, seals, gaskets, and other items associated with the piping systems. All cleaning agents subject to approval by the Engineer and MDOT MAA Maintenance.

5.      The cleaning operation for each section of piping installed shall be for a minimum of three (3) hours, or as necessary to completely clean all pipes. This water shall then be drained. Once drained, the piping shall be flushed with clean potable water.

6.      (Delete this item if #3 is selected, or if not necessary due to the size of the piping additions.) After the cleaning and flushing operations are completed, the Contractor shall provide an additional set of pump seals and strainer inserts for each existing pump in each respective HVAC piping system which has been affected by this project. The pump seals and strainer inserts shall match existing.

7.      (Consider the following for applicable projects with underground piping installations.) For underground pipes installed, prior to flushing the piping systems as described above, the Contractor shall provide television inspection of the entire pipe installation. This can be accomplished as the pipes are installed in several hundred foot sections (or the limit of the camera equipment used by the Contractor). The Contractor shall provide DVDs of the pipe interiors to show that no (or very minimal) excavation and backfill dirt has entered the piping systems. Two copies of these pipe inspections shall be provided to the Engineer. The DVDs should clearly indicate the date, time, and section of piping being videoed. If these DVDs indicate that there are large amounts of debris within the piping system, the Engineer may either direct the Contractor to open the pipes in the areas of question and clean them out, or have the Contractor re-record the pipe sections after the pipes are flushed. This will be at no additional cost to the MDOT MAA.

B.     The above noted items are minimum requirements for the Contractor to complete to clean and flush the HVAC piping systems. The Contractor is fully responsible for a satisfactory flushing operation. Any damage to existing pumps, boilers, chillers, cooling towers, control valves, and other associated items within the piping systems due to poor flushing and cleaning of the piping systems will be the responsibility of the Contractor. The Contractor shall make all necessary repairs at no additional cost to the Owner.

After flushing and refilling each HVAC piping system, provide chemicals (match existing chemicals used by MDOT MAA Maintenance) to bring new piping additions and existing piping system which are affected back to existing Central Plant or Terminal Piping system chemical level conditions. Coordinate introduction and verification of chemical concentrations with MDOT MAA Maintenance through the Engineer.”