PMP & PUMP-TRAP APPLICATIONS CONDENSATE DRAINAGE • using Pump-Trap
PURPOSE:
For removing condensate from below steam heat transfer equipment when a modulating valve is used for control, and condensate discharge is elevated and/or pressurized, resulting in Stall condition.
OPERATION:
The Pressure Motive Pump (PMP) is used to overcome the stall condition that exists when steam feeding a single piece of heat transfer equipment is controlled by a modulating steam valve and steam pressure falls below system back pressure as the valve closes. A steam trap is required after the PMP to prevent the loss of live steam when the system is under positive pressure. Operating as a closed loop provides an energy-efficient system by eliminating the need to vent flash steam.
INSTALLATION GUIDELINES:
(see Figure 23)
• Proper installation and piping of the pump vent line is critical to ensure the system operates correctly. Follow guidelines or consult factory for additional information. • Maintain proper fill head above the top of the pump to ensure proper function of the pump and system. A suitably sized reservoir or oversized piping should be installed ahead of the pump for accumulation of condensate during the pump’s discharge cycle (i.e. when not filling). • The steam trap after the pump must be sized in conjunction with the pump to ensure proper function as a system. Improper sizing may result in reduced capacity leading to condensate back-up, poor heat transfer and potentially dangerous waterhammer. Consult appropriate sections of this catalog or the factory for guidelines regarding proper sizing of the pump-trap combination. • While a separator is appropriate for protection of the Regulator, it is not always required, as a properly sized drip leg with steam trap may be sufficient. It is recommended for systems where steam is known to be “wet” and the entrained moisture could affect valve performance and/or result in component damage. • Low-cracking pressure (1/4 PSI opening pressure) check valves should be installed after steam traps when discharging into condensate return lines. Check valves eliminate the possibility of condensate backing up through the steam trap into the system. • The thermostatic air vent installed on the heat exchanger promotes optimum heat transfer. The air vent improves heat-up times and overall heat transfer by expelling accumulated air on start-up. When properly sized and installed, the pump-trap combination can operate in sub-atmospheric (i.e. vacuum) conditions; therefore, a vacuum breaker should not be used.
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www.watsonmcdaniel.com •• Pottstown PA • USA • Tel: 610-495-5131
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