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Category: Calculation

How To Calculate Sonic Velocity

Rifka Aisyah

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

How to Check if a Horizontal Pipe Carrying Liquid is Full

Rifka Aisyah

In this post I want to share how to check if a horizontal pipe carrying liquid is full or partially full. We can use the following criteria to check:

  • The pipe is full if: Q/d5 ≥ 10.2
  • The pipe is partially full if: Q/d5 < 10.2

For partially full pipe, we need to do partially full flow analysis as follows.

x = ln (Q/d2.5)

Then we calculate height of liquid in the pipe using the following equation:

H/D = 0.446 + 0.272x + 0.0397x2 – 0.0153x3 – 0.003575x4 Read More

Step-by-Step Methods on Nongeometric Scale-up for Liquid Agitation

Rifka Aisyah

This post would be quite long since agitation scale-up involved trials and evaluation of the parameters. This post is based on Handbook of Chemical Engineering Calculations Fourth Edition by Nicholas P. Chopey.

To understand better about how to scale-up nongeometric liquid agitator, I will use an example. We will make one change at a time to understand its effect.

The example is below:

A process involving water-like liquid must be scaled up from an agitated 18-in diameter, 15-gallon pilot-scale reactor to a 120-in diameter, 7000-gal large scale reactor.

The pilot scale has a 18-in straight side and the large-scale reactor will have a 168-in straight side. Both reactors have ASME dished heads on the top and bottom.

Successful process performance was obtained in the pilot scale with two 6.0-in diameter pitched-blade turbines operating at 350 rpm. It is proposed that the large-scale reactor use hydrofoil impellers instead of pitched-blade turbines, for improved liquid motion.

Each pitched-blade turbine has a turbulent power number of 1.37 and each hydrofoil has a power number of 0.3.

Past scale-up experiences with similar processes, but with geometrically similar tanks, were successful when impeller tip speed was held constant. Read More

How to Estimate Hydrate Inhibitor to Depress Hydrate Formation

Rifka Aisyah

In previous post, I shared what is hydrate formation and primary conditions promoting hydrate formation. Quick review, hydrate in natural gas system is a physical combination of water and other small molecules to produce a solid which has an ice-like appearance. Hydrate should be control because it will cause several problems. The problems include restriction in flowlines, causing physical damage to chokes and instrumentation. One method to control hydrate formation is to inject hydrate inhibitor into production stream.

Read more: Hydrate Prediction using Pressure-Temperature Correlation Read More

Sizing Horizontal Three Phase Separator

Rifka Aisyah

In this post I want to share how to size horizontal three phase separator. The steps used in this post were from Surface Production Operations by Ken Arnold & Maurice Steward. You can learn the details and equations used from the book. In the end of this post, I share free spreadsheet on how to size horizontal three phase separator.

The calculation used in the spreadsheet in for preliminary calculation only. As for fabrication, you may need to discuss more with related vendors and EPC constructors.

Required Data for Horizontal Three Phase Separator Sizing

To size horizontal three phase separator, we need the following data:

  • Oil rate, water rate, and gas rate
  • Operating pressure and operating temperature
  • Properties (density, viscosity) of oil and gas, respectively
  • Retention time of oil and water, respectively
  • Droplet size of liquid and oil to be removed

Read More

How To Estimate Vessel Weight

Rifka Aisyah

Estimating vessel weight is not usual daily task of a process engineer. However, I found it useful to know how to estimate vessel weight, when we need to estimate vessel cost. In other chance, civil engineer also asks about vessel weight to design the equipment foundation.

To better estimate vessel weight, we need to understand vessel weight components. Those are weight of the shell, the weight of the heads, and the weight of internals, nozzles, pedestals, and skirts. Read More

Inert Gas Consumption for Tank Blanketing Calculator

Rifka Aisyah

In this post I want to share calculator to estimate inert gas consumption for tank blanketing. Please be noted that the result is average inert gas consumption. For peak consumption, please check my previous post.

I think this is the second time I created calculator. I am quite satisfied with the results because I used plugins.

I hope you find this post useful.

Inert Gas Consumption for Tank Blanketing

Rifka Aisyah 1 Comment

Inert gas is used to blanket certain fixed-roof tanks for safety. Nitrogen is a common inert gas used for the purpose. In addition to safety of storage tank, the benefit of tank blanketing includes improved product quality and equipment life cycle.

Why nitrogen is commonly used in tank blanketing?

Nitrogen has inert properties, wide availability, and relatively low cost at any economic efficiency. Other gases, such as carbon dioxide or argon, are also sometimes used for certain application.

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I Tried Using Aioflo Pipe Sizing and Flow Calculation

Rifka Aisyah 1 Comment

In this post, I want to share with you my experience using Aioflo Pipe Sizing and Flow Calculation. I found this software when searching for Uconeer professional unit conversion program.

Katmar Software developed many engineering software, one of them is Aioflo Pipe Flow Calculator. Aioflo can calculate pipe sizes, flowrate, and pressure drops for liquids and gases. This is a screenshot of the software.

Screenshot of Aioflow Pipe Size and Flow Calculation
Screenshot of Aioflow Pipe Size and Flow Calculation

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How To Estimate Optimum Insulation Thickness

Rifka Aisyah Leave a comment

In previous post I shared how to estimate insulation thickness for both flat surface and cylindrical surface. In this post I want to share how to estimate optimum insulation thickness.

The total annual cost of insulation is the sum of the cost of heat energy lost and fixed cost. A plot of cost vs insulation thickness will determine the most economical insulation thickness. A dimensionless factor can be used to calculate insulation thickness, depending on the ratio of insulation thickness to pipe diameter in the following equation:

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