Appendix_DD_-_Thule_M-Plant_Site_Visit_Summary_Notes_(2016-08-08)_.pdf

Memorandum

1100 North Glebe Road, Suite 500 Arlington, Virginia 22201 United States T +1.571.218.1000 F +1.571.218.1600 www.jacobs.com

Date August 8, 2016

To Rafal Turek, PE - USACE Project Manager

From Anhtan Le, AIA, LEED AP – Jacobs Project Manager

Subject Thule M-Plant D/B RFP Site Visit Summary Notes

Copies to Edward Clautice, PE – Jacobs Mechanical Engineer

Heating sources

Conversion of Boilers B3, B4, and B5 is the first priority of the project. Work done on the boiler must be done by workers qualified and approved by Danstoker, the boiler manufacturer. This entity will be referred to here as the boiler subcontractor. The performance of this will require close coordination between the contractor and M-plant operation. B1 and B2 conversion will follow.

The boiler subcontractor is responsible to block off the tubes within the boiler and maintain/provide a warranty of performance and longevity. Blocking of tubes is required to maintain the flue gas at a sufficiently high temperature. As tubes are blocked there is an increase in backpressure on the engine generators. This places a limitation on the number of tubes which can be blocked without causing the engine to stall.

The successful bidder is responsible for all piping from the boilers to the distributions system and for the demolition and capping of steam and feed-water systems when the final boiler is converted.

The end result shall be a non-condensing boiler with the same flue gas control dampers are now in place. An important part of this requirement is the maintenance of the water temperature entering the boiler at a temperature no lowers than 60C. If the water entering the boiler falls below 60C a shunt pump recirculates supply water back into the return until the return water is greater than 60C. Current base standard calls for design of systems with heating water temperatures of 80/40. Using those temperatures 50% of the water out of the boiler would be recirculated to the return. We propose designing the system with a temperature of 85C out of the boiler. Assuming a return of 45C, 38% of the supply water would be recirculated.

Actual performance across the base generally results in a return water temperature drop of less than the design 40 degrees. The shunt pump would be controlled based on actual return water temperature and not a theoretical return temperature. Design engineers should still be instructed to design to an

August 8, 2016 assumption of an 80/40 system. Systems receiving 85C will perform better than design as compared to an entering temperature of 80C.

M-Plant boiler conversions will be controlled by a modified Weithaupt control system that has been prepared on its manufacture for this conversion. This should be tied into the overall M-Plant control system. The successful bidder, with work done on the Danstoker boiler done by a qualified subcontractor that shall be approved by Danstoker, is responsible to commission the conversions and demonstrate proper operation.

When all boilers are converted to heating water, and buildings have been converted, it will be necessary to provide some form of backup heating source. A steam to water heat exchanger will be required. This will be specified to tap from steam mains in the vicinity of M-Plant. The contractor may provide a new steam to water heat exchanger or may salvage unit(s) from converted buildings, if the heat exchangers are from newer buildings.

The backup heat exchanger location may be an outdoor containerized solution or it may be located indoors. Potential outdoor containerized locations include the east side of the building, the west side of the building and at the bottom of the slope down at Crescent Road.

Distribution

Distribution to the base will be variable primary based on pumps located in the M-Plant. One redundant pump will be provided. Our recommended configuration is to have 3 pumps sized at 50%. This limits the size of each pump, provides better turn down, and limits the size of motors required. Space for these pumps exists in the mezzanine level of M-Plant. The pumps will be controlled to a differential pressure in the system. The layout of the distribution will likely require two or three differential pressure sensors. The pumps will ramp to meet the most demanding sensor.

Exterior pipe distribution will be divided into two types; “backbone” piping, and “branch” piping.

Backbone piping will be sized to accommodate the eventual installation of a district heating loop in the center portion of the base and described on plans. There will be a specified minimum size for backbone piping. It will be 6 inches from the M-Plant and 8 inches in the center area pipe loop. Branch piping shall be sized by the contractor with a minimum size of 2 inches. Drain valves will be provided at all low points. Automatic air vents will be provided at all high points; the designer should minimize the number of exterior high points.

Piping within the M-Plant shall be standard 150 psi black steel schedule 40 with mineral fiber insulation and a PVC jacket. Piping outside the plant is to match the present base standard of a Logstor pre-insulated jacketed system with leak detection. Exterior mounting shall match existing base standard;

August 8, 2016 piping mounted wooden sleepers at grade with concrete hold-down blocks. Valves outside shall be provided with stems but not handles. All air vents shall be located indoors. The distribution will use the existing service “alley” between the series of building similar to 100 North Star Inn and Dormitory 105.

Building 97 and 98 are listed in the scope as “Option” buildings. They will be given a single branch line connecting to a point across the street from M-Plant. They shall terminate at valve and capped connections adjacent to their mechanical rooms.

Water movement is the primary protection against freezing. All potential dead ends are to be provided with small size circulation bypasses per the base standard detail.

Building Conversions

Buildings will be converted from the existing steam service to district heating hot water. Existing base standard system details are used as guiding principles for the conversion. Due to various differences among the buildings they generally do not fall exactly into the base standard details that have been provided.

Where possible, heating water will connect directly into the building heating water system. In older buildings, where the condition of the piping may be unknown the district water will be separated from the building heating with a plate and frame heat exchanger. Redundant heat exchangers will not be provided.

If the building heating system uses glycol a plate and frame heat exchanger will be provided. The minimum connection size will be 2 inches.

Domestic water will utilize district heating water as a heat source. Current code requires double wall heat exchangers in domestic water tanks heated by district heating water. New tanks will be required unless the contractor can show that the existing tank is code compliant. Base standard 200 liter stainless steel Smartline tanks will be specified.

Control Systems

M-Plant boiler conversions will be controlled by a modified Weithaupt control system that has been prepared on its manufacture for this conversion. This should be tied into the overall M-Plant control system.

A typical building has its controls for steam replaced by new Trend controls for the district heating water conversions. This is tied into the base-wide Trend system. Based on investigations all buildings affected by this scope already have the Trend base fiber backbone in the building. All building control work will be carried on the base-wide Trend network. Building 99 will be listed as an Option.