Steam trap function

Are the control valve and steam trap functioning correctly ... 

Steam traps are automatic mechanisms that remove low heat-content air and condensate from the steam delivery system. The lack of steam traps or use of traps that fail to function properly leads to a gradual decline in heat-transfer efficiency, waterlogged heat exchangers, and water hammer (which may in turn result in ruptured pipes). When adequate maintenance of steam traps is neglected, this ultimately leads to a serious overall loss of operating efficiency. There are various types of steam traps, each designed for a specific function. Some common variations are discussed in the following sections. 

All supply line steam traps, to ensure that they are functioning. 

A simplified cyclic test (Mitchell method followed by cyclic propylene steaming) has been proposed which addresses the redox aging of the metal, but not the non-uniform laydown and age distribution of metals on the catalyst. Under actual FCC conditions, the penetration and age profile of the metals will influence the efficiency of the catalyst metal trapping function [23,39,40] and consequently catalyst activity and selectivity. 

Steam-heated calandrias with process boiling temperature less than 100°C can present control problems, especially at reduced rates and during start-up. In most such cases, low-pressure steam is used for heating. Control is usually achieved by throttling the entering steam in order to reduce the pressure at which it is condensed. At reduced rates this often results in steam pressures less than atmospheric or less than the steam condensate return system pressure. The steam is usually removed through steam traps which require a positive pressure differential to fiinction. In order for the trap to function, steam condensate floods part of the steam chamber imtil the steam pressure is sufficient to operate the trap. This leads to poor control and all the problems associated with condensate flooding. 

The best steam trap will not function correctly if the piping to and from it is not properly designed and installed. Many factors are important and some will be discussed. 

Figure 13.1 The function of a steam trap is to minimize condensate back-up and to preserve the condensate seai.

The steam trap neither aids nor retards condensate drainage, unless it is mechanically malfunctioning, meaning it is sticking either open or closed. Also, replacing the steam trap with a condensate drum and LRC also neither retards nor aids drainage. Condensate drainage is a function of system hydraulics, as discussed in subsequent sections. 

Figure 7.6 Abnormally functioning steam trap shown on the left side (courtesy of FUR Systems, Inc.).

FCC catalyst development to reduce the effect of vanadium has been aimed at reduction of vanadium mobility the application of special ingredients in the catalyst which function as metal scavengers or metal catchers. In the past (2, 10) transport experiments were used to show that during steam-aging, intraparticle transfer of vanadium occurs and that migrating vanadium can be irreversibly sorbed by a metal trap such as sepiolite (2) in the form of a heat stable vanadate. 

Connect the safety valve ( C) and the safety trap (D) to the steam generator. In order for the system to function properly, the bottom of the glass tube that acts as the safety valve and pressure regulator must be below the water level in the steam generator. Usually a position 1 to 2 cm from the bottom of the flask is satisfactory. 

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