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Fail-Safe Position Selection of Control Valves (Part 2)

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In this post I want to share several examples of fail-safe position selection of control valves. I posted about this topic a long time ago. You can also check the post.

A control valve consists of valve body, trim, or stem, plug and seat, and an actuator. The valve body consists of an orifice through which the manipulated variable passes. The trim or stem is connected to the diaphragm and the valve plug that can be in the form of a ball, a disk, or a gate. The valve seat offers a tight seal for a valve shutoff position.

Schematic of control valve
Schematic of control valve

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How to Easily Estimate the Time Needed for the Vessel to Collapse

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In this post, I want to share to you how to easily estimate the time needed for the vessel to collapse. The equation involves several simple and basic equation, such as conservation principle and adiabatic compression equation. Let’s dig into the example.

There is a thermally insulated vessel initially at atmospheric pressure and partially filled with water. The vessel is fed with additional water at a constant flow rate of 2 m3/h. The air contained in the vessel headspace is compressed as the additional water is fed. The vessel can withstand a maximum pressure of 3 atm absolute. Read More

Applications of Globe Valves and Their Examples

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In this post, I want to share with you the applications of globe valves and their examples. Different from ball, plug, and gate valves, which are used to start and stop fluid flow in piping systems, globe valves are used to regulate flow. Globe valves usually should not be used for less than 20% opening for throttling, because it will increase the wear and load concentration on the seat and plug.

Application of Globe Valves for Control Valves Bypass

Typical application of globe valves is for control valves bypass. When control valve is taken out for maintenance purpose, a bypass globe valve provides continuous operation with some level of regulation. Read More

Applications of Butterfly Valves and Their Examples

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In this post I want to share with you the applications of butterfly valves and their examples. A butterfly valve can stop, regulate, and start the fluid flow. Due to its ninety-degree rotation of the handle and the disk, the valve is quickly and easily operated.

Butterfly valves offer many advantages over ball, gate, globe, and plug valves, such as lower cost, less weight, less space requirements, and lower maintenance cost. The maintenance cost is relatively low because of few moving parts.

Butterfly valves are usually selected for utility services and low pressure gas services, with pressure class 300 and lower.

Applications of Butterfly Valves and Their Examples
Applications of Butterfly Valves and Their Examples

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Application of ball valves and their examples

Applications of Ball Valves and Their Examples

Rifka Aisyah Leave a comment

In this post, I want to share with you the applications of ball valves and their examples. In my experience, many oil and gas projects use ball valves a lot. What are the advantages and disadvantages of using ball valves, and what are their applications?

Ball valves are frequently selected for process and aggressive services containing hydrocarbon oil and gas. Ball valves are used for on/off purposes only, not for flow control (throttling). Read More

Understanding Three Layers of Integrated Control and Safety Systems

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In this post, I want to share with you about three layers of integrated control and safety systems. The layers consist of Basic Process Control System (BPCS), alarm, and Safety Instrumented System (SIS). I heard about these terms of BPCS and SIS quite late in my career as process engineer. I hope those do not happen to you

Three layers of integrated control and safety systems
Three layers of integrated control and safety systems

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How to Calculate Partial Volume of Horizontal Vessel with Ellipsoidal Heads

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In this post, I want to share with you how to calculate partial volume of horizontal vessel with ellipsoidal heads. Basically, the horizontal vessel consists of cylinder and two heads. Thus, the total volume will be:

Total volume = volume of liquid in two heads + volume of liquid in cylinder
Total volume = 1/6 π K1 D3 + 1/4 π D2 L

Where:

K1 = 2 b/D

b, D, and L are function of vessel geometry. Please see figure below. Read More

Understanding Overpressure and Thermal Relief

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Thermal relief refers to automatic release of fluids or gases from a system to a specified level. Pressure relief systems are intended to prevent pressures in process equipment from increasing to the point where a mechanical failure or rupture might take place, automatically releasing any materials within.

What are causes of Overpressure?

There are several most common causes of overpressure.

Causes of overpressure
Causes of overpressure

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What is Convection and Its Problem Example

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In previous post we learned what is conduction and its example on heat loss through a pipe wall with insulation. In this post, I want to share what is convection and its problem example.

Convection is heat transfer between a solid and an adjacent fluids develops as a result of fluid molecular movement. Cold molecules replace hot molecules as they leave the solid surface. A thin layer or film next to the solid surface is where most of the resistance to this type of heat transfer occurs. Even though the bulk fluid flow is extremely turbulent, this layer still exists.

Convective heat transport is governed by Newton’s law of cooling.

Q = h ∙A∙ ∆T

Where:

Q = heat transfer (Btu/hr)

h = heat transfer coefficient [Btu/(hr∙ ft2∙oF)]

A = area (ft2)

∆T = temperature difference (oF)

Convective heat transfer is divided into two types, natural or free convection and forced convection. Read More

What is Conduction and Its Problem Example

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In this post I want to share what is conduction and its problem example.

In contrast to general molecular motion or mixing, conduction describes the rate of heat transfer through materials as a function of vibrations and interactions between nearby molecules. Conduction always applies to solids and rarely to fluids.

There are several fundamental equations for steady heat conduction through some basic solid shapes, neglecting conditions of border:

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