The Importance of Soil Erosion Control Measures

Soil erosion control is the process of minimizing the potential for soil erosion. Erosion control measures have proven to reduce erosion potential by stabilizing exposed soil and reducing surface runoff flow velocity. 

Erosion and sediment control measures are classified into two categories:

1. Temporary control measures

2. Permanent control measures

Temporary soil erosion control measures are created to control soil erosion during the construction phase. Once the project has been completed and permanent measures have been installed, the temporary measures are completely removed.

Permanent soil erosion control measures are incorporated into the overall design to address long-term post-construction erosion and sediment control. Soil erosion control measures and stormwater management practices are thoroughly reviewed in our PE Civil exam review courses. 

Erosion Control Methods:

Source control of runoff flow

The primary goal of source control is to protect exposed earth surfaces from the erosive energy of rain splash and surface runoff flow. Cover is the most effective erosion control method for preventing soil erosion. Cover includes top soiling in conjunction with one or more of the following methods: seeding, mulching, hydroseeding, sodding, erosion control blankets, turf reinforcement matting (TRM), riprap, gabion mat, aggregate cover, and paving.

Runoff control during project work

During the construction of a project, it is not possible to provide surface cover for all disturbed areas. Runoff control methods, such as slope surface modification and slope gradient reduction, are employed to prevent soil erosion. 

Bio-engineering methods

Revegetation of exposed soil with grass and plant growth on topsoil is the main bio-engineering soil erosion control method. This method is a permanent soil erosion control measure that uses the roots, stems, and leaves of vegetation to reduce the potential for soil erosion. 

Bio-engineering involves the introduction of foliage that decreases the impact of rain, leading to infiltration of rainwater into the soil and resulting in anchoring the soil with root systems. As the plants grow, the bio-engineered erosion control system continues to strengthen. Bio-engineering methods provide a simple and cost-effective measure for controlling long-term erosion problems.

Terracing

Terracing prevents and reduces erosion caused by surface runoff by decreasing the incline and length of hillside slopes. Terracing is a land shaping method in which earth embankments and ridges are redesigned for the interception of runoff water, which in turn channels it into a specific direction and outlet. Terraces can be classified by two types: bench and broad base terraces. The bench terrace is the oldest form of terrace and is used to reduce land slope; broad base terraces are used to control and retain surface water on sloping land. 

Vegetated waterways 

Vegetated waterways protect soil against the erosive forces of runoff from sloping lands. These waterways absorb the destructive energy, which causes channel erosion and gully formation. Depending on the climate and functional requirements, waterways can have cross sections in parabolic, trapezoidal, and triangular forms.

Contouring

Contouring involves the tillage and planting of crops on the same elevation or "contour." Water is restrained between the contours, which moderates water erosion and increases soil moisture. With stable soils, contouring leads to reduced soil loss. 

Soil erosion is an important topic to understand for the PE Civil exam. Our PE Civil review courses thoroughly discuss soil erosion and the methods used to prevent it.

Effects of Air Pollution on the Environment

Air pollution occurs when harmful gases, dust, or smoke enters the atmosphere and has a negative impact on plants, animals, and/or humans. Air pollution is the deadliest form of pollution, killing millions of people each year. The World Health Organization reports that more than 92% of the world's population lives where air pollution exceeds safe limits. Among all other pollutants, air pollution has proven to be a major concern throughout the world. Air pollution and its impact on the environment creates an increasing demand for environmental engineers with their PE license. 

Air Pollution Hazards

Air pollution hazards are thoroughly discussed in our PE Environmental review courses. 

Air pollution can cause many problems including: 

1. Acid Rain

2. Eutrophication

3. Haze

4. Negative Effects on Wildlife

5. Ozone Depletion

6. Crop and Forest Damage

7. Global Climate Change

Acid Rain

Acid rain is formed when sulfur dioxide and nitrogen oxide in the atmosphere is mixed with rainwater as a weak sulfuric and nitric acid. Acid rain can damage crops, plants, and aquatic life and is even capable of damaging structures. 

Eutrophication

Eutrophication is a condition created by using excessive fertilizers and pesticides that drain into bodies of water. Nutrients, such as nitrogen, stimulate blooms of algae, which in turn endangers aquatic life.

Haze

Haze is formed when sunlight encounters suspended pollutant particles in the air. Haze obstructs our vision, clarity, color, texture, and form of what we visualize in the real world. 

Negative Effects on Wildlife

Like humans, wild animals are also developing health problems as they are exposed to toxic air. Air toxins contribute to birth defects, reproductive failure, and disease in wild animals and aquatic ecosystems.

Ozone Depletion

Ozone is a gas that is present in the earth's upper atmosphere, the stratosphere. Ozone forms a layer that protects life on Earth from the sun's harmful ultraviolet (UV) rays. Ozone is gradually being destroyed due to ozone-depleting substances being released into the atmosphere. The thinning of the protective ozone layer is causing higher amounts of UV radiation to reach the earth, leading to more cases of skin cancer, cataracts, and impaired immune systems. UV rays also damage crops and lead to reduced yields. 

Crop and Forest Damage

Air pollution damages crops and trees in many ways. Air pollution reduces growth and the survivability of plant seedlings and increases plant susceptibility to disease, pests, and other environmental stresses, such as harsh weather. 

Global Climate Change

The earth's atmosphere is a delicate balance of naturally occurring gases that trap excessive heat from the sun. This greenhouse effect protects and maintains a stable temperature on the planet. Throughout time, humans have disturbed this natural balance by producing greenhouse gases, including carbon dioxide and methane. Thus, the earth's atmosphere is trapping more of the sun's heat, leading to the average temperature to rise. This phenomenon is known as "global warming." Global warming has significant impacts on human health, agriculture, water resources, forests, wildlife, and coastal areas. 

Air pollution and its potential impacts on the environment are fully reviewed in our PE Environmental refresher course.

Introduction to Basics of Boiler Components for Mechanical Engineers

The most important components of boilers include fuel oil systems, super heaters, and ash removal systems. As a mechanical engineer, it is extremely critical to understand the various components of boilers. Heat transfer is an important topic for undergraduate mechanical engineers preparing to take the FE Mechanical exam to understand. Heat transfer is thoroughly reviewed in our FE Mechanical exam review course. 

Table of Contents

1. Fuel Oil System

2. Super Heaters

3. Ash Removal

4. Common Types of Boilers for Engineering Applications

1. Fuel Oil System

Oil-fired boilers may use a light grade oil, typically diesel, or a heavier grade residual oil that is often referred to as "Bunker Fuel." Light oils have a low viscosity and do not require pre-heating. They are pumped from the storage tank to the burner, which is equipped with an atomizing tip that sprays the oil into the furnace in the form of a fine mist. The mist mixes very rapidly with the combustion air, ensuring efficient and clean furnace operation. Heavy residual fuel oils are viscous and require pre-heating for proper atomization. The most commonly used residual fuels are typically more viscous. The temperature required to achieve optimal atomization may differ between fuels.

2. Super Heaters

Steam leaving the boiler is routed through the super heater element, which is located in a high-temperature zone of the furnace. The moisture quickly evaporates because the steam is no longer in contact with the water in the drum. The actual difference between the saturation temperature and the actual steam temperature is called the degree of superheat. Although superheating does add additional energy to the steam, the primary objective is to provide a margin of safety by ensuring that the steam does not immediately begin to condense prior to giving up its superheat energy component. Super heaters are commonly used in water tube boilers. The nature of the process determines whether a super heater is required; a super heater is not generally used unless there is a specific need.

3. Ash Removal 

Environmental legislation in most jurisdictions imposes strict constraints on particulate emissions. Therefore, removing entrained fly ash is usually a mandatory requirement on solid-fuel boilers. For large boilers, electrostatic precipitators, bag houses, and scrubbers are widely used. One of the most common methods employed on small to medium sized boilers is the multi-cyclone grit arrester; it has low capital costs and a degree of efficiency that will satisfy all but the most stringent requirements. Understanding boiler components and heat transfer mechanisms is critical for the FE Mechanical exam. Our FE Mechanical exam review course thoroughly covers the topics of heat exchangers, boiling, and condensation. 

4. Common Types of Boilers for Engineering Applications 

(i) Fire tube boilers: 

Fire tube boilers have the advantage of relatively low capital and operating costs. These types of boilers are predominantly used in industries and processes that have modest steam demands at low to medium pressure. Physical size constraints impose limits on operating pressure and because of their large mass, fire tube boilers are not well suited to large, rapid changes in steam loads. 

(ii) Water Tube Boilers 

The water circulation through the tubes of a water tube boiler follows a defined path. This process ensures that a relatively small quantity of water will be rapidly distributed by heat, which results in an efficient operation. Water tube boilers can be brought up to working pressure much more quickly than fire tube equivalents.

Measuring Instruments and Their Performance Characteristics

Table of Contents

1. Introduction

2. Static Calibration

3. Linearity

4. Static Sensitivity

5. Repeatability Error

6. Hysteresis-Threshold Resolution

1. Introduction

Measuring instruments are used to measure a quantity. When choosing an instrument, the static calibration and static performance of an instrument must be considered. Our PE Electrical exam review course thoroughly covers what to consider when selecting instruments for a given job.

The characteristics of measuring instruments can be classified into the following categories:

1)Static performance characteristics

2)Dynamic performance characteristics

2. Static Calibration

Static calibration refers to the procedure where an input is constant or a variable is applied to an instrument. Instruments are manufactured based on the property of irreversibility or directionality. This implies that change in an input quantity will cause a corresponding change in the output. A calibration standard must be at least ten times more accurate than the instrument to be calibrated.

Static performance characteristics include the linearity performance of the instrument, static sensitivity of the instrument, repeatability of the same results, hysteresis resolution, and the readability of the results. 

Static performance characteristics influence data acquisition if the instruments are not properly calibrated prior to the measurement. Understanding quality control and quality assurance procedures for handling equipment is essential for the PE exam.

3. Linearity

If the relationship between the output and input can be expressed by the equation Q0= P + RQ1, where P and R are constants, then the instrument is considered linear. Linearity is never fully achieved in real-world situations, and the deviations from the ideal are referred to as linearity tolerances. For example, 3% independent linearity means that the output will remain within the values set by two parallel lines spaced ± 3% of the full-scale output from the idealized line. If the input-output relationship is not linear for an instrument, it may still be approximated to a linear form when it is used over a very restrictive range. 

4. Static Sensitivity

Static sensitivity can be defined as the slope of a calibration curve. 

Sensitivity = Q0/Q1

Sensitivity influences the input parameters of an instrument. The sensitivity factor can also be referred to as sensitivity drift or scale factor drift. 

5. Repeatability Error 

When an instrument is used to measure the same or an identical input many times and at different time intervals, the output is never the same; it deviates from the recorded values. This deviation from the ideal value is referred to as repeatability error.

6. Hysteresis-Threshold Resolution

When testing an instrument for repeatability, it is often noted that the input-out value does not coincide with the inputs, which are continuously ascending and descending values. This occurs because of hysteresis, which is caused by internal friction, sliding, external friction, and free play mechanisms. Hysteresis can be eliminated by taking readings corresponding to the ascending and descending values of the input and calculating their arithmetic mean.

Professional engineers who work with measurements and instrumentation should understand calibration procedures of various instruments for proper data acquisition.

Importance of Quality Control and Quality Assurance Procedures

Table of Contents

1. Productivity and Quality Control Plan Implementation

2. Project Quality Management Plan for Construction Projects

3. Disadvantages of Inappropriate Quality Control Procedures

Productivity and Quality Control Plan Implementation

In order to enhance client satisfaction during a construction project, the project must meet the expected quality. This expected quality can be ensured through quality assurance and quality control activities. The quality control process confirms that the project outcome meets the client's standards. The quality assurance process checks the quality plan and quality control process to confirm that quality standards are implemented on the project site. To improve the quality construction of the project, understanding project requirements and standards is essential. This is usually done by a team outside of the project construction team, and the goal of this practice is to maintain quality standards, eliminate practices that are not appropriate and share best practices for quality assurance in the organization and with the project construction team. The project quality plan should be part of the project construction management plan. The quality control plan defines how quality should be handled throughout the duration of the project. Quality and safety are the main concerns for project completion. In large construction projects, management assigns an individual department for quality assurance and safety to ensure the standards of the project; in small projects, the project manager is responsible for quality assurance. Construction productivity and quality control procedures and testing methods are important for PE exam preparation. 

Project Quality Management Plan for Construction Projects

The success of any project has two key factors: one is the completion of the project on schedule as per the contract document and the quality of the project as per department standards. A failed project cannot lead to achieving business goals, and moreover, it leads to losses. Proper project planning is the first step for the success of the project. The plan describes the number of phases in the project and the list of construction activities to be carried out in each phase. Individual responsibility of each project phase, the duration of the project and the overall project budget are also included in the project plan. Generally, there are four steps in construction project management. The steps are planning, executing, monitoring and quality assurance. Each and every step of project management should contain a document within itself. These four steps help to increase productivity and quality as per the client's requirements. The team should evaluate the overall project on a regular basis to validate the quality standards of the project. The responsibility of the project engineer is to ensure that quality control is implemented effectively. It is best to have professional engineer exam certified candidates in charge for better productivity and overall quality.

Disadvantages of Inappropriate Quality Control Procedures

Overlooking the quality control procedures of a project incurs additional expenses and project delays. Having to rework increases the maintenance and opportunity costs. Structural elements that are not built according to quality assurance standards have the potential to collapse at any time, which could lead to injuries and death. Professional engineers ensure the quality of the project the first time around. Project quantity takeoffs and scheduling costs should be recapped through a PE exam review course. The project team should maintain good communication with the client. When the project is completed, the essential support and technical arrangements should be given to the client. After completing the project, the project document should be finalized, and the final report of the project should be prepared. If the organization follows a quality management process, completing new projects is not a major ordeal.