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Safety Valve vs Relief Valve (Differences based on API 521)

Sometimes terms can be confusing. Terms safety valve and relief valve are confusing too. So, to make it clear, let see the definition based on API 521.

Pressure relief valve is a generic term applied to relief valves, safety valves, and safety relief valves. It is designed to automatically reclose and prevent the flow of fluid.

Relief valve is a spring-loaded pressure relief valve actuated by the static pressure upstream of the valve. The valve opens normally in proportion to the pressure increase over the opening pressure. A relief valve is used primarily with incompressible fluids.

Safety relief valve is a spring-loaded pressure relief valve that may be used as either a safety or relief valve, depending on the application.

Safety valve is a spring-loaded pressure relief valve actuated by the static pressure upstream of the valve and characterized by rapid opening or pop action. A safety valve is normally used for compressible fluid.

Can you spot the differences?

Relief valve is used for liquid and open in proportion to the pressure increase, while safety valve is used for gas and open rapidly.


API 521 Pressure relieving and depressuring system


Typical Content of Feasibility Study

Many people visited my blog because they searched about feasibility study. I wrote a bit about the topic years ago. I wrote it when I involved in my second feasibility study project, which is bankable feasibility study for ferronickel smelter.

In this post I want to share you typical content of feasibility study. The content actually may be different from one another, depends on the topic. But, after I involved in two previous feasibility projects and current project, I learnt that there is similarity about the structure of the content.

I hope you find this post is useful. Read More

Job Description of Project Engineer – My Real Experience (Part 1)

When I was working in this company, I worked as project engineer for precommissioning activity. In the end I realized that the term precomissioning department was not suitable for us, but mechanical completion.

I want to share you some experience and what I actually did as project engineer in that project. For your information, the project was Senoro Gas Development Project. It is owned by Joint Operating Body of Pertamina & Medco EP. It is located at Senoro, Central Sulawesi.

The History Begin With… Read More

Cold-keeping system (

LNG Recirculation Requirement

In LNG receiving terminal, where LNG is pumped from LNG carrier to onshore LNG storage tank, we have to provide one line to intermittently circulate LNG through unloading lines. This is called LNG recirculation line or keep-cool line.  The function of this line is maintain cryogenic condition of the unloading line during holding mode. Unloading activity is conducting intermittently. Sometimes we need to wait for a week or even a month to the next LNG unloading. During this time, there is a possibility of increasing temperature in the line. To prevent that, we need to circulate LNG in unloading line. Read More

Typical Process Diagram for Small LNG Regasification (Part 2)

As mentioned in part 1, small LNG regasification facility typically consists of LNG unloading facility (which can be flexible hose or marine loading arm), LNG storage tank, LNG sendout pump, ambient air vaporizer, and metering. In part 1 we already discussed about LNG unloading facility and LNG storage tank. In this part I want to share the rest of them.

LNG Sendout Pump

LNG sendout pump is used to increase pressure of LNG before being sent to vaporizer. In LNG facility, there are two most common type of pump: submerged centrifugal pump and reciprocating pump.

Submerged centrifugal pump is used when LNG flowrate is high but the pressure in low to medium. Meanwhile reciprocating pump is used when the flow is low but the pressure is high. Read More

Typical Process Diagram for Small LNG Regasification (Part 1)

Today I want to share you Typical Process Diagram for Small LNG Regasification. For your information, small LNG regasification is very useful to be built in remote location where power supply is very limited.

Small LNG Regasification
Small LNG Regasification

Typically main equipments installed in Small LNG Regasification are unloading facility, LNG storage tank, LNG pump, natural draft ambient air vaporizer, and metering system. Read More

New Company

Hi, everyone! It’s been a long time since the last time I updated this blog. I want to share you a good news: I’ve resigned and got a new job. Yey!

The company which I am working for is EPC company especially for oil and gas project. Now I involve in gas development project in Senoro, Indonesia. Before I talk much about my work, I want to share you a few things about the process of deciding to resign.

See the whole things

Before you decide to take or not a new job, you need to see the whole project you’ve involved in. Don’t just see what is the latest project. In interview you may share about works or project you think the coolest, the most amazing, or the biggest. Sometimes, it does not help you or actually it does not fit for you (this is my real experience). If you have completed, for example, six projects, you need to analyze each of them and ask yourself: in what project I feel the most all out, which project I feel comfortable, learn the most, love the most, exciting the most…

Know your values

Money is consideration, but not the first one. I value creativity and freedom of thinking. I also value flexibility. You need to find what your values are and keep questioning: does the company you will be involved in appreciate your values?

Know your talents

This is the hardest one. Not everyone knows in which area they are good naturally. I suggest we need to keep doing exploring and analyzing ourselves in what kind of job we find easy for us to master and in what part we need to do extra effort. It’s good to have a job we love the most, fit with our talents, and appreciate your values. Have you find it?