ASME PTC 12.1-2015 pdf download.Closed Feedwater Heaters.
1-1 GENERAL (a) For the purpose of this Code, a closed feedwater heater is a power plant heat exchanger designed to heat a given quantity of feedwater through a specified tem- perature range. The heating medium is steamor conden- sate at a specified temperature and pressure. In feedwater heaters, the feedwater and heating medium typically are routed through the tubes and shell, respec- tively. Feedwater heaters are typically designed to be configured in one of the following ways: (1) horizontal (2) vertical channel down (3) vertical channel up (4) duplex (two separate tube bundles in a single divided shell) (b) In some cases, more than one feedwater heater is required fora givenfeedwaterflow and extractionsteam source. Insuchinstances, the feedwaterheateris divided into two or three parallel heaters, which constitute a multiple string arrangement. The shell side of the heater may be constructed with one, two, or three independent zones and arranged in various combinations: (1) desuperheating zone (2) condensing zone (3) drain cooling zone Each zone is considered to be an independent heat transfer entity contained within the same shell. Extraction steam from the turbine is the heating medium in the desuperheating zone. Depending on the heater design, extraction steam from the turbine together with other possible energy sources such as incoming drains are the heating medium in the condens- ing zone. Condensate is the heating medium in the drain cooling zone.
1-2 OBJECT The object of this Code is to provide the procedures, direction, and guidance for determining the thermo- hydraulic performance of a closed feedwater heater. It can be utilized to verify contractual performance for a new heater or to calculate performance of an existing heater in comparison to the design point. The overall performance parameters utilized to accomplish this are the following: (a) terminal temperature difference (TTD), which is the difference between the saturation temperature cor- respondingto the steaminletpressure and the feedwater outlet temperature (b) drain cooler approach (DCA), which is the differ- ence between drain outlet temperature and feedwater inlet temperature (c) tube-side (feedwater) pressure loss through the heater (d) shell-side pressure loss through the desuperheat- ing zone (e) shell-side pressure loss through the drain cool- ing zone The Code methodology adjusts the manufacturer’s guaranteed performance parameters to the actual test conditions, for a comparison to as-tested performance.
3-1 ITEMS FOR AGREEMENT The parties to the test shall reach definitive agreement regarding the specific test objectives in Section 1. This agreement may be included in the form of a test proce- dure, protocol, or other written document. At a mini- mum, the following items shall be agreed upon prior to the test: (a) unit operating conditions during the test; specifi- cally onthe means to secure consistentinletsteam condi- tions and feedwaterflow and the method ofdetermining drain flow (b) data to be recorded, method and frequency of recording/archiving data, duration and number of test runs (c) full review of the allied system schematics to establish the total test boundaries, and the location of all measurement parameters (d) instrumentation to be utilized (temporary and/or installed) and any permitted alternatives (e) instrumentation accuracy and methods and fre- quency of calibration (f) determination of parameters not directly measured (g) fouling resistance to be used in computing design- adjusted TTD and DCA (h) method of testing and determining performance of multiple-string feedwater heaters (i) identification of any known damage or deficiency, e.g., plugged tubes (j) status of continuous vent operation during test (k) method of determining extraction steam enthalpy for cases where steam quality is less than 100% (see subsection 5-2) (l) shell liquid-level set point.ASME PTC 12.1 pdf download.