Rectifiers / Battery Chargers Condition Assessment

This article is about Rectifiers Battery Chargers condition assessment and Maintenance. Here we discussed Rectifiers Battery Chargers Basic with industrial rectifier circuit. We mentioned rectifier industrial applications, can be used in industry and IT field.

Rectifiers / Battery Chargers Condition Assessment Guidelines

  1. Introduction
    1.1 General
    1.2 Purpose and Intended Users
    1.3 Scope
  2. References.
  3. Definitions
  4. Safety Measures
  5. Instructions
  6. Pre- Assessment Activities (Desk Review)
  7. Actual Condition Assessment Activities (Condition of Rectifier Components)
  8. RCCA Criteria

1 Introduction Rectifiers / Battery Chargers

1.1 General

Plant, substation, I.T., or communications Rectifiers/Battery Chargers are crucial devices that supply conditioned power to critical loads, such as communication equipment, DCSs, emergency lighting and dc medical electronic loads. These equipments require condition assessment to ensure continuity of power to critical loads, thus avoid the catastrophic failures that could affect the company central business.

If rectifiers/battery chargers cannot supply needed conditioned power, plant dc critical loads will shut down and will not be able to energize protection devices and safety loads, such as communication and dc medical equipment. 

1.2 Purpose and Intended Users

The purpose of this Best Practice is to provide guidance to conduct a survey supporting the assessment of the condition of rectifiers/chargers. The document will include the list of items to be inspected and how the information can be used to detect potential problems and establish an upgrading plan for existing rectifiers/chargers. The main points to be surveyed will be gathered in a checklist form to make the data collection fast and easy. The intended users may include engineers and technicians working in the field of UPS and DC Systems, or people who are involved in repair of dc power electronics based systems, whether as supporting engineers or power electronics equipment maintenance.

1.3 Scope

This document is designed to surveying and assessing rectifiers/battery chargers, namely rectifiers /chargers Condition Assessment (RCCA). The article provides guidelines to assign a Failure Risk Score (FRS) utilizing the steps mentioned in this article. The RCCA method is applicable for industrial as well as IT type rectifiers /battery chargers.

The RCCA may be requested by operating department once a rectifier/charger reaches 15 years of age or has undertaken a major operational incident.This article in conjunction with “Guidelines for Minor and Major Preventive Maintenance (PM) of UPS Systems”; the rectifier/charger section.

2. References Rectifiers / Battery Chargers

International Standards should be followed for best Practice.

3. Definitions

Rectifier/Battery Charger: Power electronics device that converts mains ac to dc 
ac: alternate current
dc: direct current
Electrical measurement: Electrical output at specified point

4. Safety Measures during Checking Rectifiers / Battery Chargers

Rectifiers/battery chargers contain high voltage, thus only qualified/certified technicians should do any physical activities with the equipment. Hence, make sure that he following safety equipment is provided especially if there are batteries in the room:

 Use adequately insulated tools.
 Be cautious when working on rectifier/charger since they represent electric shock hazard.
 Ensure the rectifier/charger and battery rooms’ ventilation systems are operational and rooms’ temperature is maintained at 25°C.
 Do not wear metallic object such as jewelry.

5. Rectifier / Charger maintenance practices Instructions

This guide is not intended to define rectifier / charger maintenance practices. Guidance and recommendations herein are based on industry standards and practices. However, equipment and situations vary greatly, and sound engineering and management judgment must be exercised when applying these diagnostics.

All available information must be considered, for example, manufacturers’ and rectifiers/chargers experts’ recommendations, unusual operating conditions, and personal experience with the equipment in conjunction with this document. The condition assessment has two steps, pre-assessment activities and actual assessment activities.

Both steps determine the Failure Risk Score and help in determining the condition of a certain rectifier/battery charger. The pre-assessment is mainly to do with a non measurement or light assessment where it will focus on desk review, age, local support and visual inspection. Actual assessments will me much more involved in deeper assessment of the rectifier / charger.

Basic Circuit of rectifier / charger.

Basic Circuit of rectifier / charger.

 

6. Pre- Assessment Activities (Desk Review)

It is the responsibility of the condition assessment leader to make sure that all the following documents are available: 

 Rectifier/Charger design and Construction Drawings
 Electrical one line diagram of the Rectifier/Charger and the entire system
 All Preventive Maintenance records

 Previous conditions assessment studies
 Start-up procedures
 Commissioning/FAT data if available

The RCCA (Rectifier / Charger Condition Assessment) team leader will make sure that all the information has been reviewed and all documents are available. Pre-assessment will focus on the following:
1. Desk Review
2. Visual Inspection
3. Age
4. Local Support

1 – Desk Review

Desk review is the first essential step in conducting condition assessment where all plant available data as well as commissioning/PM data could tell if the PM was conducted on a timely manner. The method here is not to evaluate the PM, instead the score will be assigned on the availably of the data which means that PM was conducted on a timely manner.

Results of deck review are applied to Table 1 to arrive at an appropriate Condition Score.

Table 1 – Desk Review Scoring

2 – Visual Inspection

Visual inspection is the major milestone to conducting the RCCA. Rectifier/Charger as well as Rectifier / Charger room, enclosures are among many factors that can be checked visually. The Rectifier / Charger shall be in good condition even if it has been in service for many years. Visual inspection will also include using thermo vision in things does not appear normal or neat. Results of visual inspection are applied to Table 2 to arrive at an appropriate Condition Score.

Table 2 – Visual Inspection Scoring

3 – Age

The Rectifier/Charger is designed for 20~25 years life time and is expected to serve its design lifetime.

4 – Local Support

Local support is among the important scores as the unavailability in local support could jeopardize the importance of a Rectifier/Charger. The Rectifier/Charger is intended to provide critical power during emergency and local support should always be available and instantaneous.

rectifier industrial application

7. Actual Condition Assessment Activities (Condition of UPS Components)

Application of rectifier/battery charger section of “UPS PM”, is required to be able to estimate the condition of the consumable spare parts that affect the integrity of rectifier/charger operation. Examples of these spares are the dc filter capacitors, the dc smoothing choke, the ventilation fans, the automatic circuit breakers, and the tripping units.

All these parts are consumable and are replaced upon failure or bad condition (for example: exceeding ±10% tolerance). However; it is not industry practice to check the condition of the switching components and smoothing devices such as rectifier SCRs, PCBs, and circuit breakers/fuses. These components are always replaceable upon failure and the only concern is the availability of the spare parts for those components.

Also, the time of delivery should be examined during this RCCA exercise. Table 5 summarizes survey questioner to predict condition of the rectifier/charger internal components along with corresponding scoring, as follows.

Table 5 – Survey Questionnaire

  1. Are spare parts available?
  2. Are the available spare parts complete or limited
  3. Are these original equipment spare parts new or refurbished?
  4. How many years will these parts be available?
  5. Is there a minimum quantity of parts required to process an order? Specify.
  6. What is the average delivery time for non-stocked spare parts?
  7. Is there an existing spare parts agreement with Saudi Aramco?
  8. Is there a factory-built direct replacement/retrofit for the equipment?
  9. Please provide contact information (name or position, complete address, telephone number, fax number and e-mail)

8. Rectifier / Charger Condition Assessment Criteria

Sum all scores from both assessment activities of the condition assessment. If result <= 50%, then Rectifier/Charger condition requires attention immediately; whilst replacement consideration is sought. Otherwise, the Rectifier/Charger system should be looked after closely to clear all alarms effectively.

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