Steam Turbine Deposit Collector/Simulator

A simple inexpensive device located outside the turbine, for the collection of exfoliated oxides and deposits representative of deposition inside the turbine. The collected deposits are analyzed to predict deposition and corrosion inside the turbine, and to assess boiler carry-over and the effects of steam and water chemistry upsets.

The optional flow totalizer allows the average concentration of impurities to be determined.

Pressure range: subatmospheric to 3000 psig (20.6 MPa)

Temperature range: Up to 900ºF (482ºC)

Attachments: Welder or Swagelock connections

Collection Time: 1 to 14 days

Background

Turbine deposits can cause corrosion of blades, rotors, and discs, reduction of turbine efficiency and MW generating capacity, and malfunction of valves and seals. It is estimated that more than 50% of U.S. utility and industrial turbines have an accumulation of harmful deposits. It is almost impossible to evaluate turbine deposition without an expensive and time consuming turbine disassembly. When turbines are opened for inspection or due to forced outages, it may be too late to prevent damage. Without a chemical analysis of the deposits, evaluation of the sources of impurities is difficult.

The Deposit Collector/Simulator was developed by Jonas, Inc. to allow:

For many applications, Jonas, Inc. recommends the use of A/SA182-316/316LSS because of the material's resistance to corrosion and erosion. Other materials are available upon request.

• testing chemistry effects during commissioning of new and rebuilt units

• determination of the effects of water chemistry upsets on steam chemistry and deposition in LP turbines

• root cause analysis of copper and phosphate deposition in HP turbines leading to MW and efficiency losses

• collection of samples of exfoliated oxides which lead to solid particle erosion

• evaluation of composition and morphology, and determination of the time and type of operation when impurities are transported into the turbine

Background

A filter-like device (Figure 1) which simulates the turbine conditions governing deposition from superheated steam and can be installed anywhere in piping or a turbine. The Deposit Collector/Simulator is accessible during operation and its filter elements can be periodically replaced. The deposits are collected from superheated steam flowing through the Collector at approximately 40 lb/hr. The collection time depends on the concentration of impurities. Typically, the collection time is between 1 and 14 days. With the use of the Flow Totalizer, the approximate average concentration of impurities in steam can be determined.

Figure 1. Turbine Deposit Collector/Simulator

Deposit Analysis

An example of a deposit formed on the Collector Filters, and its SEM and elemental analysis by EDS are shown in Figure 2. After exposure to steam, the weight and chemical nature of the accumulated impurities are determined. The recommended analyses include EDS, optical and SEM microscopy, X-ray diffraction, and wet chemistry methods.

Figure 2. SEM and EDS Analysis of Impurities obtained in Deposit Collector/Simulator

Optional Flow Totalizer

Consists of a Flow Totalizer with LCD display and a Thermal Shutoff Valve. The steam is condensed and the Totalizer measures both the average flow rate and total flow over the length of the test. This data can then be used to determine the average concentration of impurities in the steam.