Att A - Steam Systems Design Manual 05012024.pdf

VA

U.S. Department of Veterans Affairs Office of Construction & Facilities Management

Steam, Heating Hot Water, and Outside Distribution Systems design manual May 1, 2024

Volume 1

STEAM BOILERS

(Steam Generating Systems)

Steam, Heating Hot Water, and Outside Distribution Systems Design Manual

May 1, 2024

Steam Boilers Volume 1 / Page 15

6.4 Condensate

6.4.1 To avoid flashing, the steam condensate gravity return system shall not contain connections between high pressure gravity returns or medium pressure gravity returns with the low-pressure gravity or vacuum return lines. Provide a flash tank, where all gravity returns will reduce pressure and temperature. From the flash tank, the low-pressure gravity return shall flow into the condensate receiver of the condensate return pump. Adjust the elevation of the flash tank elevation to ensure gravity flow into the condensate receiver.

6.4.2 Condensate Storage Tank shall be sized to accommodate surges without overflow. The tank shall be sized for 20 minutes minimum storage to overflow at peak plant output requirements. The A/E must review the condensate handling systems in all buildings to determine if any unusual situations will require a larger condensate storage tank in the boiler plant. Consideration should be given to sizing the tank for future loads.

6.5 Water Treatment Equipment

6.5.1 “Zero Hardness” water must be supplied for boiler makeup.

6.5.2 Water Treatment shall be provided if alkalinity in the makeup water exceeds 50 ppm.

The design engineer must obtain a current analysis of the water supply and determine the type of treatment which is necessary. The design engineer must determine if the treated water will cause any substantial corrosion problems and recommend preventative methods.

6.5.3 Life cycle cost studies must be performed to evaluate which type of water treatment equipment will be applied (ion-exchange softener, dealkalizer, reverse osmosis, other systems) as proven successful with local water conditions.

6.5.4 Softeners shall be dual tower to ensure supply during regeneration. Softener size for each tower will be based on 50% condensate return at peak steam loads. Provide connection points for adding capacity through the use of rental equipment in emergency situations.

6.5.5 Bulk brine storage shall be used where possible to avoid material handling if not possible salt storage space adjacent to water softener and dealkalizer. The area should be accessible using fork truck for transport of bulk salt and a lift table provided for loading bags of salt into the tanks.

6.5.6 Boiler Plant Chemical Feed Systems

6.5.6.1 For each chemical used, provide a separate continuous feed system (metering pump) for each boiler or injection point.

6.5.6.2 System shall utilize premixed chemicals in bulk storage tanks with containment, and multiple metering pumps for injection into the system to eliminate the need for mixing and handling of the chemicals.

6.5.6.3 Provide sample coolers and sample points on feedwater, Hot water header supply and return and in the system as directed by the chemical treatment vendor.

6.6 Steam Traps:

Note: Fixed orifice steam traps with no operating mechanism are prohibited due to the small diameter orifices that become plugged with dirt and cause the trap to fail shut. This will cause build-up of condensate in the steam main and dangerous water hammer may occur.