Skip to main content

Convert Composition Expressed in Weight Fraction to Mol Fraction

In this post, I want to share you a simple calculation that may be useful in the future of your process engineering career 😊. This post explains how to convert composition expressed in weight fraction to mol fraction.

Before we jump into the calculation method, let’s first understand that it is important to state the basis of percentage, whether it is expressed in weight basis, molar basis, or volume basis. The abbreviations w/w and v/v are used to designate weight basis and volume basis.

Let’s use examples on how to convert composition expressed in weight fraction to mol fraction.

In this example, we want to express in mol fraction a technical grade hydrochloric acid which has strength of 28% w/w. Read More

Basis of Material Balances

In this post, I want to share the basis of material balances. Material balances are the basis of design. The amount of raw materials needed and the amount of product produced will be determined by a material balance applied to the entire process. In each process unit, there will be specific stream flows and compositions.

Process design requires a solid understanding of material balance calculation.

As you may experience as a process engineer, material balances are always key to the process. In almost every project, material balance calculation is always required. It is because equipment design and sizing need material balances. Utility consumption calculation is also generated from material balance information. Read More

How Air-Diaphragm Pumps Work

Air-diaphragm pumps (double diaphragm pumps) are one type of positive displacement pump. Their main applications are to transfer fluid, low pressure spray, and other low-pressure applications requiring less than 120 psig. They do not meet either ANSI or API standards and are most often used because of their profitability and ability to run on compressed air.

Air-diaphragm valves
Air-diaphragm valves

Read More

Rotary valves

Get to Know About Rotary Valves

A rotary valve, also known as a rotary-motion valve, rotary airlocks, or rotary feeders, controls the flow of liquid or gas through the connected pipes by rotating one or more passageways in a transverse plug. The function of rotary valve is to meter the flow of granular bulk or powders. With small pressure loss, material enters the valve by a hopper or other inlets, processed by the valve rotor, and then deposited in discrete packets onto a conveyor system.

Purpose of Rotary Valves

The major purposes of rotary valves are:

  1. To offer an airlock (pressure seal) between two processes that are next to each other
  2. To provide solids metering (feeding)
  3. To provide a pressure seal and solids metering combined for feeding solids into a pneumatic conveying system.
Rotary valves
Rotary valves

Read More

Ball valve and Plug Valve

Differences between Ball Valves and Plug Valves

The flow of liquids and gases can be controlled using valves in a variety of settings. Valves come in a variety of types, functions, porting, durability, and control capabilities. On the other hand, plug valves and ball valves serve the same purpose. They both regulate the flow of gas or liquid using either a straightforward on/off function or a multipath function. So, what are the differences between those valves?

In this post, I want to share the differences between ball valves and plug valves in terms of body structure, function, application, and maintenance. And on the last post, we will learn how to choose the right one. Before we jump into the difference between those valves, let’s learn some basics about ball valves and plug valves.

What Are Ball Valves?

Ball valves are valves with an internal spherical disc. There is a port, or hole, in this disc. When the port and both ends of the valve are lined up, the valve is in the open position, enabling the medium to freely flow through it. When the port is perpendicular to the ends of the valve, the valve closes, and the medium flow stops. Read More

General Selection Guidelines of Rotary Pumps

In this post, I want to share to you general selection guidelines of rotary pumps.

Rotary pumps are positive displacement pumps. However, they are different from reciprocating pumps because they have relatively steady and non-pulsating flow. Rotary pumps are generally selected to handle very high viscosity fluid or if the flow rate is too low to be handled economically by other pumps.

There are several common applications of rotary pumps:

  • Transferring gasoline, fuel oil, diesel fuel into tanks or day tanks
  • Supplying fuel oil to burners
  • Running lubricant through the bearings of process machinery, turbines, reduction gears, and engines.

Before we jump into the general selection guidelines of rotary pumps, I think we need to understand several terms that related to rotary pumps, such as slip, volumetric efficiency, and mechanical efficiency, and of course several types of rotary pumps. Read More

Efficiencies of Centrifugal and Axial-Flow Compressors

In this post, I want to share the approximate efficiencies of centrifugal compressors and axial-flow compressors. We may have already heard about these terms: polytropic efficiency and isentropic (adiabatic) efficiency. What are those?

Polytropic efficiency is frequently used in compressor evaluation. It is frequently referred to as small stage efficiency. The polytropic process is a modification of the adiabatic process, involving an efficiency to represent actual conditions more closely. The performance of centrifugal compressors is frequently compared using the polytropic compression method.

On the other hand, isentropic (adiabatic) efficiency compares actual compression to an ideal compression (adiabatic) in which no heat is exchanged with the environment and no losses are produced (no viscosity and reversible). It is isentropic because it is adiabatic and reversible. The adiabatic process that compresses with the least amount of work is hence the isentropic process. Read More

How To Calculate Sonic Velocity

In this post I want to share how to calculate sonic velocity. Before we jump into the equation, let’s review about sonic velocity briefly.

Sonic velocity or critical velocity is the maximum velocity that can be attained by a compressible fluid. We usually use this parameter in sizing pipe, control valve, and flare.

Sonic velocity is a function the following parameters:

  • Ratio of specific heats in the gas (k or Cp/Cv)
  • Temperature
  • Molecular weight of the gas

The molecular weight is expressed in absolute temperature, therefore we will use temperature unit of oR or oK. Read More