Practical Condition Monitoring for Preventive Maintenance
Practical Condition Monitoring for Preventive Maintenance
Torbjörn Idhammar, IDCON INC
This article will touch on elements of practical condition monitoring
Condition monitoring (CM) is not a life-extending activity. Life-extending activities are things such as lubrication, alignment, balancing and operating procedures.
It’s very important to keep this very basic fact clear in all communications within your plant; otherwise, too little importance may be placed on the planning and scheduling of corrective work orders originated in condition monitoring.
Condition monitoring only provides information on failures before there is a breakdown. You can do it with inspection tools – vibration monitors, infrared temperature guns, pressure gauges, volt meters and others. You can also execute practical condition monitoring subjectively by looking, listening, feeling and smelling (let’s avoid tasting, shall we?).
This article is dedicated to the somewhat lost skill of subjective (look, listen, feel, smell) inspections.
These days, we tend to rely more and more on technology. Computers are great, but they can be awfully bad at interpreting machine condition.
For example, how do we get a computer to:
find a loose bolt for a reasonable cost before there is mechanical looseness?
see dirt buildup on an electrical motor before heat increases?
find a recently plugged breather on a gearbox?
find the location of a leak in a pneumatic system?
pinpoint a problem with a photocell that is knocked out of alignment?
These problems could somehow be found accurately with a computer, but a properly trained person would only need about 10 seconds to see the problems.
How well is your plant doing with mechanical, instrumentation and electrical inspections? While articles often talk about the management systems needed, I’d like to list some basic examples in order to rediscover the subjective inspection methods.
Regardless of whether you’re doing inspections with handheld computers or a paper system, can trend data or not, or have key performance indicators or not, you won’t be successful unless your people can do quality inspections on equipment. Here are the examples:
Example 1: AC motor temperature
If your inspectors look at motor temperature, do they take the time to think about the significance of a hot temperature on the coupling side of the motor vs. a hot temperature at the center of the motor? A hot temperature in the center often means a damaged winding or an overload situation, while a hot temperature at the coupling side of the motor means a bearing problem of some kind.
Example 2: Couplings
Are couplings and the equipment attached to the coupling operated to breakdown mode, or are problems found before a breakdown occurs? All couplings that can cause a breakdown costing more than a few hundred dollars should have an inspection lid so the coupling element, bolts and keyways can be checked easily. (The cost of inspection would be, at maximum, $100 per year.) Preferably, the inspection should be done with a stroboscope while the equipment is running (see Figure 1).
Figure 1. A coupling can be inspected on-the-run with a stroboscope. Note that this plant has followed OSHA 1942 regulations for guard safety.
Example 3: Heat exchanger sacrificial anode
The basic function of a sacrificial anode is to protect surrounding material. A common use is to place a plug in a heat exchanger’s cast iron shell (Figure 3). The anode is usually made of zinc and will slowly corrode instead of the iron shell.
The phenomenon is called galvanic corrosion. How would you inspect the zinc plug before it starts to leak in a critical application? Drill a small hole to a shallow depth in the center of the zinc plug. A small leak will be visible in the center of the plug well before it is time to change it.
Figure 2. Inspections of zinc anodes in a heat exchanger are simplified by drilling a small hole. When the anode wears away, a small leak will develop so that the need for replacement can be detected earlier.
Example 4: Pump packing
Pump packing replacements turn into emergencies in some plants because the wrong mind-set is in play. If it doesn’t leak more than the recommended one to two drops per second, it’s usually not examined. Why not change the mind-set? Make sure packing is changed when there is only one-eighth of an inch of takeup left in the packing (Figure 2)?
Figure 3. Change the pump packing when there is one-eighth of an inch of takeup left in the packing.
The Numbers
IDCON recently collected information on how work requests were initiated in a large process plant. We collected all work requests over seven months and analyzed how the work was found.
The data showed that close to 70 percent of all problems found from condition monitoring were picked up subjectively by operators and mechanics through detailed look, listen, feel and smell inspections.
Many problems wouldn’t have been found if it wasn’t for vibration analysis, infrared technology and oil analysis.
But the data makes you wonder if we don’t underutilize subjective inspections. They are a very powerful and cost-effective maintenance tool.
Torbjörn Idhammar
Torbjörn Idhammar is the president and CEO of IDCON INC., a Reliability and Maintenance Management Consulting Firm. Tor’s responsibilities include training IDCON consultants, product development, sales, and marketing. He gives advice to IDCON’s multi-site and international clients to ensure outcomes and deliverables are met.
Probably 80% of all testing. performed in electrical power systems is related to the verification of insulation quality. This Cadick Corporation Technical Bulletin briefly describes the fundamental concepts of insulation testing including – insulation behavior, types of tests, and some test procedures. For more detailed information, refer to the bibliography at the end of the paper.
Probably 80% of all testing. performed in electrical power systems is related to the verification of insulation quality. This Cadick Corporation Technical Bulletin briefly describes the fundamental concepts of insulation testing including – insulation behavior, types of tests, and some test procedures. For more detailed information, refer to the bibliography at the end of the paper.
When selecting pressure measurement transmitters, the first stage is whether to opt for a transducer or a transmitter. Although the terms are often confused, there are several differences between transducer and transmitter devices. A transducer creates a low-level electronic signal in response to changes in applied or differential pressure. As with transmitters, transducers feature an internal sensor that converts the applied force into an electrical signal, from which the measurement is derived.
When selecting pressure measurement transmitters, the first stage is whether to opt for a transducer or a transmitter. Although the terms are often confused, there are several differences between transducer and transmitter devices. A transducer creates a low-level electronic signal in response to changes in applied or differential pressure. As with transmitters, transducers feature an internal sensor that converts the applied force into an electrical signal, from which the measurement is derived.
The paper deals with the method of gearbox diagnostics fault detection, and shows that using: design, production technology, operational, change of condition (DPTOCC) factors analysis leads to the inference of gearbox diagnostic information. In the paper is a review of the current possibilities for using mathematical modeling and computer simulation for investigating the dynamic properties of gearbox systems. Computer simulation of dynamic behavior of gearboxes is a powerful tool for supporting gearbox diagnostic inference.
The paper deals with the method of gearbox diagnostics fault detection, and shows that using: design, production technology, operational, change of condition (DPTOCC) factors analysis leads to the inference of gearbox diagnostic information. In the paper is a review of the current possibilities for using mathematical modeling and computer simulation for investigating the dynamic properties of gearbox systems. Computer simulation of dynamic behavior of gearboxes is a powerful tool for supporting gearbox diagnostic inference.
In its simplest form, vibration can be considered to be the oscillation or repetitive motion of an object around an equilibrium position. The equilibrium position is the position the object will attain when the force acting on it is zero. This type of vibration is called "whole body motion", meaning that all parts of the body are moving together in the same direction at any point in time.
In its simplest form, vibration can be considered to be the oscillation or repetitive motion of an object around an equilibrium position. The equilibrium position is the position the object will attain when the force acting on it is zero. This type of vibration is called "whole body motion", meaning that all parts of the body are moving together in the same direction at any point in time.
As the infrared industry continues to develop, documentation will become more important and required. Infrared video recording and data logging creates a database, making the thermographer and the end user accountable for all items surveyed, thereby reducing the liability and improving the quality for both the end user and infrared thermographer.
As the infrared industry continues to develop, documentation will become more important and required. Infrared video recording and data logging creates a database, making the thermographer and the end user accountable for all items surveyed, thereby reducing the liability and improving the quality for both the end user and infrared thermographer.
During Academy of Infrared Training courses, we see many students who have purchased an infrared camera that is not suited for their intended use. These students have put their trust in a camera salesperson, and, many times, that salesperson was solely interested making a sale. Later, these students are disappointed to find out that the camera is not truly suited for their application. This article aims to help the camera buyer understand what basic camera specifications mean, and also help them determine what type of camera and options are suitable for their application. If you note your answers to questions throughout this article, by the end you should have a custom list of applicable specifications and options.
During Academy of Infrared Training courses, we see many students who have purchased an infrared camera that is not suited for their intended use. These students have put their trust in a camera salesperson, and, many times, that salesperson was solely interested making a sale. Later, these students are disappointed to find out that the camera is not truly suited for their application. This article aims to help the camera buyer understand what basic camera specifications mean, and also help them determine what type of camera and options are suitable for their application. If you note your answers to questions throughout this article, by the end you should have a custom list of applicable specifications and options.
The purpose of this paper is to introduce condition monitoring and reliability engineers to the principles of using ultrasound for the assessment of machine condition. Ultrasound can be a complimentary technology to vibration, thermography and lubrication monitoring. It must be emphasized that it is rarely successful as a stand alone technology for effective machine condition assessment and subsequent required maintenance planning. This paper concentrates on the use of airborne ultrasound as a complementary technique particularly for machinery that may be inaccessible due to guards or hazardous locations.
The purpose of this paper is to introduce condition monitoring and reliability engineers to the principles of using ultrasound for the assessment of machine condition. Ultrasound can be a complimentary technology to vibration, thermography and lubrication monitoring. It must be emphasized that it is rarely successful as a stand alone technology for effective machine condition assessment and subsequent required maintenance planning. This paper concentrates on the use of airborne ultrasound as a complementary technique particularly for machinery that may be inaccessible due to guards or hazardous locations.
