Significance and Use

Corrosion products, in the form of particulate and dissolved metals, in the steam and water circuits of electricity generating plants are of great concern to power plant operators. Aside from indicating the extent of corrosion occurring in the plant, the presence of corrosion products has deleterious effects on plant integrity and efficiency. Deposited corrosion products provide sites at which chemicals, which are innocuous at low levels, may concentrate to corrosive levels and initiate under-deposit corrosion. Also, corrosion products in feedwater enter the steam generating components where deposition on heat transfer surfaces reduces the overall efficiency of the plant.

Most plants perform some type of corrosion product monitoring. The most common method is to sample for long time periods, up to several days, after which laboratory analysis of the collected sample gives the average corrosion product level over the collection time period. This methodology is referred to as integrated sampling. With the more frequent measurements in the on-line monitor, a time profile of corrosion product transport is obtained. Transient high corrosion product levels can be detected and measured, which cannot be accomplished with integrated sampling techniques. With this newly available data, plant operators may begin to correlate periods of high corrosion product levels with controllable plant operating events. In this way, operators may make more informed operational decisions with respect to corrosion product generation and transport.

1. Scope

1.1 This test method covers the operation, calibration, and data interpretation for an on-line corrosion product (metals) monitoring system. The monitoring system is based on x-ray fluorescence (XRF) analysis of metals contained on membrane filters (for suspended solids) or resin membranes (for ionic solids). Since the XRF detector is sensitive to a range of emission energy, this test method is applicable to simultaneous monitoring of the concentration levels of several metals including titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, mercury, lead, and others in a flowing sample. A detection limit below 1 ppb can be achieved for most metals.

1.2 This test method includes a description of the equipment comprising the on-line metals monitoring system, as well as, operational procedures and system specifications.

1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.

1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

2. Referenced Documents (purchase separately) The documents listed below are referenced within the subject standard but are not provided as part of the standard.

ASTM Standards

D1066 Practice for Sampling Steam

D1129 Terminology Relating to Water

D2777 Practice for Determination of Precision and Bias of Applicable Test Methods of Committee D19 on Water

D3370 Practices for Sampling Water from Closed Conduits

D3864 Guide for Continual On-Line Monitoring Systems for Water Analysis

D4453 Practice for Handling of High Purity Water Samples

D5540 Practice for Flow Control and Temperature Control for On-Line Water Sampling and Analysis

D6301 Practice for Collection of On-Line Composite Samples of Suspended Solids and Ionic Solids in Process Water

Keywords

corrosion products; metals; on-line monitoring; water quality; x-ray fluorescence; XRF; Automated procedures--water analysis; Corrosion--water environments; Dissolved elements (of water); Low-level particulates; Online monitoring (in water analysis); XRF (X-ray fluorescence)--water;

ICS Code

ICS Number Code 13.060.50 (Examination of water for chemical substances)

DOI: 10.1520/D6502-10

ASTM International is a member of CrossRef.

ASTM D6502