Author: anderthalbAdmin

Avoidance of Common Mistakes during Failure Analyses and Misinterpretation of Lab Results – Part 1: Sampling

Frank Udo Leidich

For a proper failure analysis or root cause analysis (RCA) a great deal of data and evidence-based information is needed. Within this context, various types of samples from different locations need to be taken for chemical and/or metallurgical examination. Therefore, proper and correct sampling, without alteration of the composition or contamination of the samples, is of utmost importance. Unfortunately, this is often not practiced correctly and so the risk of incorrect conclusions is high. This article is intended to help personnel obtain these samples in a proper manner and avoid common and repeated mistakes.

PPCHEM^® 2021, 23(3), 108–119

Update on Predicting RIHT Using the UNB-CNER CANDU-6 PHT System Model

Olga Y. Palazhchenko, William G. Cook, Alex L. Martin, and Jennifer Lennox

Reduced heat transfer in CANDU steam generators has safety consequences such as lower margins to fuel dryout due to higher reactor inlet header temperature (RIHT). To identify methods to maintain the RIHT within operational margins, it is necessary to model the effect of thermal degradation mechanisms on boiler heat transfer.

A comprehensive steam generator heat transfer and fouling add-on has been developed at the University of New Brunswick, Canada, and previously benchmarked using historic data from Point Lepreau Nuclear Generation Station. The one-dimensional, steady-state heat transfer code mechanistically predicts the effect of primary-side fouling, and semi-empirically models the effects of divider plate leakage and secondary-side fouling. This paper presents the most recent predictive modelling, where simulations of post-refurbishment operation (2012–2042) were conducted based on the benchmarked mechanisms. The predictive simulations inform the timeline for mitigating strategies such as a primary-side clean during the plant’s operating lifetime.

PPCHEM^® 2021, 23(3), 122–131

IAPWS Seventh Meeting of the European HRSG Forum (EHF2021)
Highlights and Press Release

Barry Dooley and Bob Anderson

The seventh annual IAPWS European HRSG Forum was held on the 18th and 20th May 2021 as a virtual event. It was chaired by Barry Dooley of Structural Integrity and Bob Anderson of Competitive Power Resources. EHF2021 attracted 90 participants from 17 countries and included 55 users.

EHF is supported by the International Association for the Properties of Water and Steam (IAPWS) and is held in association with the Australasian Boiler and HRSG Users Group
(ABHUG) and the US HRSG Forum (HF). The 2021 EHF had two sponsors: Trace Analysis and Swan Analytical Instruments. The conference was organized by PPCHEM AG.

PPCHEM^® 2021, 23(3), 132–133

ATP Testing – A Real Time Monitoring of Microbiological Growth in the Cooling Water Systems of Power Plants

Kiran Diwakar, Rajendra K. Saini, Upain Kumar Arora, Janakiraman Pattabhiraman, and Gopi Kanta Nayak

In power plants, the warm environment of recirculating cooling systems is ideal for the growth of microorganisms. As microorganism communities grow in cooling systems, they can attach to tubes, pipe walls, and cooling tower fills, and form biofilms. Uncontrollable biological growth causes fouling, loss of heat exchange capacity, equipment failure, and energy wastage.

Due to the large volume of a cooling system with a flow rate of 60000–75000m3·h–1 (500 MW plus unit) and the diverse types of bacteria, spores, and algae, no one chemical can kill everything. There must be proper selection of a biocide, adequate contact time, and real time monitoring techniques to allow control of biological problems.

The best solution for any system is the fast and early detection of biological contamination, and the setting up of proactive actions and subsequent corrective treatments. For the measurement of microbiological counts, we can use culture tests like the heterotrophic plate count (HPC) method. However, these culture tests only measure culturable organisms while adenosine triphosphate (ATP) testing measures all microorganisms within a sample. There are two types of ATP – intracellular ATP contained within living biological cells and extracellular ATP located outside of biological cells, which has been released from dead or stressed organisms.

In one thermal power plant cooling water system of NTPC Ltd., India, this technique was demonstrated with successful results.

PPCHEM^® 2021, 23(3), 134–142

Ngati Tuwharetoa Geothermal Assets Ltd Reboiler Plant Water/Steam Chemistry Improvements to Resolve Ongoing Corrosion Issues and Prevent Future Tube Failures

David Addison, Nik Vandervegte, and Nellie J. Olsen

Since its commissioning in 2010, the Ngati Tuwharetoa Geothermal Assets Ltd Kawerau reboiler plant has suffered from major corrosion and plant failure issues. Corrosion-related failures which occurred due to water/steam chemistry issues and interactions with plant materials have led to premature complete replacement of the tube bundles.

In 2018 a major root cause analysis was undertaken into the failures that included a detailed chemical and metallurgical investigation and successfully identified the failure mechanisms. A number of simple chemical treatment changes, including hydrogen sulfide neutralisation, pH correction and the application of corrosion inhibiting film forming substances, were carried out to successfully mitigate ongoing corrosion of the plant and to significantly extend asset life.

PPCHEM^® 2021, 23(2), 56–72

A Novel Combination of CMIT/MIT with a New Non-biocide Dispersant in Cooling Tower Biofilm Control

Henk A. Jenner

Microbial biofilm communities are a significant problem in recirculating cooling water systems resulting in reduced heat transfer efficiency, and the risk of microbial influenced corrosion (MIC) and Legionella infection of operators. Most biocides are generally only effective in the control of microorganisms when in the water phase. A new dispersant was tested that is able to remove biofilms from their substrate, releasing the biofilm community into the water phase. This study investigated how the effectiveness of (chloro)methylisothiazolinone/methylisothiazolinone (CMIT/MIT) (non-oxidizing biocide) in a heavily fouled scale cooling tower model with condenser tubes could be improved by the new dispersant. Dosing tests with CMIT/MIT separately and combined with the new dispersant were performed with different CMIT/MIT concentrations. Microbial activity in both water samples and biofilm samples was measured by the analysis of adenosine triphosphate (ATP). Additionally, the biofilm mass in the transparent condenser tubes was visually inspected by photos. The new dispersant was shown to be effective in loosening the biofilm and the biocidal efficacy of CMIT/MIT was greatly increased due to this combination.

PPCHEM^® 2021, 23(2), 74–81

Online Analysis of Film Forming Amines

Harold Stansfield

Waltron has developed an online colorimeter for online analysis of film forming amines
(FFA). The design basis and development process are discussed. Data from beta testing and two working case studies are presented. The analyzer can monitor FFA-based products in a working range of 0–1 000 µg ⋅ L^–1, with an accuracy of ± 2 % of full scale or ± 5 µg ⋅ L^–1, with a lower detection limit of < 5 µg ⋅ L^–1 as FFA.

PPCHEM^® 2021, 23(2), 86–91

IAPWS Fourth International Conference on Film Forming Substances (FFS2021) Highlights and Press Release

Barry Dooley

The IAPWS Fourth International Conference on Film Forming Substances (FFS2021) was held on the 23rd and 25th March 2021 as a virtual event chaired by Barry Dooley of Structural Integrity Associates. FFS2021 was a unique conference on a narrow topic in cycle chemistry control of power plants and steam generating facilities. In 2021 the conference attracted a record number of 130 participants from 28 countries which included 41 plant operators/users and 27 people from the Film Forming Substances chemical suppliers.

The FFS conferences are developed and supported by the International Association for the Properties of Water and Steam (IAPWS), and the FFS2021 was organized by PPCHEM AG, publisher of the PPCHEM® Journal. Three sponsors supported FFS2021: Trace Analysis, Fineamin Swiss Water-Treatment Chemicals and Swan Analytical Instruments.

PPCHEM^® 2021, 23(2), 92–93