DB eample | estimate the size of chemical plant

db example
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DB (Dia inch) is a concept that every mechatronic engineer at a chemical plant should keep in mind.

It can be used not only for daily construction estimates, but also for a wide range of owner engineering, such as estimates for large projects at the plant construction level and periodic renewal plans for equipment.

It is very important for the owner-engineer who needs an urgent estimate.

Please estimate as soon as possible

In such a case, I will introduce a specific example of an estimate using a DB as a way of thinking to estimate without panicking.

Chemical plant DB (Dia inch)

Let’s look at a concrete example of DB for chemical plant piping

DB(Dia inch) of outdoor tank

The piping around the outdoor tank is about 200DB .

The route around the outdoor tank is pretty easy .

The route and shape of the piping varies depending on the location,

Consider an outdoor tank as a simple case.

Outside tank circumference (Dia inch) db

200DB around outdoor tank

pump suction

Try counting the DB in the pump suction line.

Pump Suction (Dia inch)

Consider 4 elbows and 4 flanges.

The piping between the outdoor tank and the pump is assumed to have a diameter of 50A and a length of about 10m .

The DB of this plumbing is 32DB .

(4 elbows x 2 + 4 flanges x 2) x (50A/25A) = 32DB

pump header

Let’s count the DB in the pump header.

Pump header (Dia inch)

Consider two tees, one elbow, one reducer, and four flanges.

The pipe diameter is 50A.

The DB of this piping is 42DB .

(1 piece of cheese x 3 + 4 elbows x 2 + 1 reducer x 2 + 4 flanges x 2) x (50A/25A) = 42DB


Check your circulation as well.

Circulation (Dia inch)

The DB of this piping is 40DB .

(6 elbows x 2 + 4 flanges x 2) x (50A/25A) = 40DB

pump discharge

This is OK with the same idea as circulation.

It is 40DB per one.

This way of thinking is also very effective in DB calculations for plants.

Since we focus only on the piping “around the device” , we do not consider the long-distance piping to another device.

Be careful here.

Summary calculation

Summarize the calculations above.

  • Pump suction 32DB
  • Pump header 42DB
  • circulation 40DB
  • Pump discharge 80DB (2)

Taking this sum

32 + 42 + 40 + 80 = 194DB

Rounding a little, 200DB is considered as the DB around the outdoor tank.

DB of outdoor tank

200DB minimum

In-factory DB (Dia inch)

The piping around the equipment in the factory is also about 200DB .

The same concept can be applied inside the factory as for outdoor tanks.

1 pipe 40DB

Let’s take a look at a single pipe base in the same way as the example of the outdoor tank.

40DB per 50A pipe 

All of the pump suction, pump header, circulation, and pump discharge were almost 40DB .

With the same idea as this, let’s take a look at 40 DB per pipe.

Piping between devices

The piping between devices is considered at 50A, 10DB per 5m .

The idea is the same as the pump suction of an outdoor tank.

Below is a reprinted drawing of the pump suction port.

Between devices (Dia inch)

Piping between devices is based on the idea of ​​”passing through the empty space in the factory” .

We will connect 1 pipe 5m as a unit.

The welding DB required for connection is as follows.

  • Flanged connection 4DB
  • Connected by welding 2DB

In order to pass the piping through the empty space in the factory, you have to change the route with an elbow .

There are about 3 elbows in one 50A pipe.

4 flange connections + 2 reroutes x 3 = 10DB

connection nozzle

There is a limit to the number of nozzles that can be connected to one device.

Let’s say 8 here .

Assuming that one pipe is connected to one nozzle, using the above idea,

40+10 = 50DB

is the piping DB per nozzle.

For a device with 8 nozzles,

50 × 8 = 400DB

can be calculated as

Think of this value as the minimum piping configuration DB.

There are more complicated examples in real life, but we’ll correct that later.

DB of batch chemical plant equipment

400DB minimum

1 process DB (Dia inch)

Approximately 2,000 DB per process in a batch chemical plant .

Let’s introduce the way of thinking.

1 process equipment

A batch-type chemical plant uses about five units per process .

A tank, heat exchanger, and pump are incorporated as standard equipment for one process .

Now the number of devices is 3 .

In the case of distillation, the number of heat exchangers is increased from one to two, and one to four receiving tanks are added.

Assuming a minimum of 3 and a maximum of 8 (3+1+4), the number of devices per process should be about 5.

Summary calculation

Let’s put all the above information together and do the math.

  • 1 tank 400DB
  • 5 units per process

400 × 5 = 2,000DB

DB per batch chemical plant process

2,000DB minimum

DB (Dia inch) of one plant

Approximately 20,000 to 40,000 DB per batch chemical plant .

If you follow the calculations so far, the idea is simple.

It means that there are 10 to 20 processes.


A batch-type chemical plant can have at most five “reactions” .

3 responses on average .

If you include the pre-processing and post-processing processes here, there will be about 9 at the process level.

filter drying

If there is special equipment such as filtration and drying, consider each of these as equivalent to one process .

Filtration is one process and drying is one process.


In addition to filtration and drying, there are various types of equipment in batch chemical plants.

  • filter
  • hopper
  • water tank
  • Heat exchanger

The number of connecting pipes for each one is small, but there are about 2 to 10 processes when stacked.

There is a lot of variation here.

Summary calculation

Let’s put all the above information together and do the math.

  • 1 process 2,000DB
  • 10 to 20 processes per plant

2,000 × 10-20 = 20,000-40,000DB

The size of this width will actually vary depending on the characteristics of the plant.

DB per batch chemical plant

About 20,000 to 40,000 DB

DB (Dia inch) and plant construction cost

Let’s analogize the relationship between DB and plant construction costs.

The number matching game element is large.

construction cost

If you are going to build one batch chemical plant, 4 billion yen is one guideline.

Even if you calculate by adding overhead expenses such as material costs and labor management costs to 1DB,

4 0,000 DB will cost about 400 million yen for plumbing work.

That’s a long way from $40 million.

This 5 billion yen includes various fields such as machinery, electricity, instrumentation, and civil engineering.

The mechanical work alone would cost about 1.2 billion yen.

The plumbing work alone is about 800 million yen .

Considering this, it seems that there are costs that cannot be determined by DB alone at the plant construction level.

The number of outdoor tanks, the number of pipes between the outdoor tank and the plant, the number of utility pipes, etc.

At the plant construction level, these elements alone will not fall below 100 million yen .

In addition, incidental equipment etc. that do not fit in the above simple calculation are also added.

Just think about plumbing

400 million yen for plant construction piping + 100 million yen for incidental piping = 500 million yen (1)

4 billion yen/5=800 million yen②

500 million yen ① < 800 million yen ②

relationship can be derived.

A quick calculation will show you how accurate it is.

I think that the approximate budget calculation using DB should be done like this.

extension and renovation

When expanding or renovating an already completed plant, such as introducing a new product, the general amount will be about 1 billion yen.

If the amount is higher than this, it can no longer be said to be a profitable investment.

It’s about 1/4 times the plant construction, so in terms of DB, it will be about 10,000 DB .

This agrees well with my experience.

What is the DB (Dia inch) of a nuclear power plant?

I heard that there are 25,000 welding points in a nuclear power plant .

I can’t tell if the 25,000 point points to “DB” .

It’s probably not the DB.

Assuming that it is DB, if the piping is properly considered at 500A, it is 500,000DB.

By assuming that “the nuclear power plant is 500,000 DB” , let’s practice estimating the scale of the nuclear power plant.

1 pipe

It is a calculation of 120 DB per 5m of one pipe of a nuclear power plant .

Details of the calculation are given below.

Piping is about 500A on average

Assume the average pipe diameter of a nuclear power plant is 500A .

I have never seen a nuclear power plant.

I’m guessing based on the literature.

The main piping should be cooling water, and it seems to be at least 400A.

Around the pump is about 1000A.

The expression 50B is more correct at this point ^ ^

It’s hard to estimate the average value, but let’s consider 500A .

The dimension is different from the average 50A of the batch factory (laughs)

Straight pipe

A straight pipe is basically 5m long.

The reason why it is 5m is because it is “the limit length that can be transported on the road”.

This is a major prerequisite for plumbing work.

One 5m means that you have to connect a pipe every 5m .

Welded connections are common in nuclear power plants .

Flange connections are often used in chemical plants due to the large number of extensions and alterations.

Welding is cheaper and has a longer life because the piping route does not change significantly at nuclear power plants .

20DB of 500A piping occurs every 5m .


Consider using 40DB for 5m at the fitting section of a nuclear power plant .

There will be overwhelmingly many elbows even in fitting .

Since the diameter is larger than that of a chemical plant, the number of bends is small and there is only about one elbow per 5m.

The face-to-face distance of a 500A 90° elbow is about 840mm, so 840 / 1000 x 5 = 4.32m

It’s 5m just by arranging 5 elbows.

5 elbows is quite a lot. Even one is too many.

Summary calculation

Summarize the above calculations.

  • Straight pipe 5m20DB
  • Elbow 5m40DB
  • Welding times 3 times

(20 + 40) x 3 = 180DB

Considering that the pipe diameter is large and the welding cannot be completed in one time, we are considering three-layer welding.

The result is 180DB every 5m .

nuclear size

Let’s consider the size of the nuclear power plant and verify the validity of the DB.

piping length

The result of the trial calculation is that the pipe length of the nuclear power plant is about 42 km .

  • 500,000DB
  • 180DB every 5m

Calculate from this information as follows.

500,000 / 180 × 5 /1000 = 14km

nuclear size

Let’s consider a nuclear power plant as a plant about 70m long and 30m high.

Spatial volume is 70×70×30=147,000m3.

Pipes account for only about 1% of this.

The pipe volume is 147,000×1% = 1,470m3.

If the pipe diameter is 500A, the cross-sectional area is 0.19m2

The number of meters of piping in the plant is

1,470 / 0.19 = 7.7km

About half of the 14 km will be piping inside the plant.

The rest is external connection piping such as utilities.


DB is a concept that is often talked about in plant construction, but not so much at the owner-engineering level.

Opportunities to work with plant engineering companies are expanding more and more, so there is no loss even if you know.

Also study the following books.

Related information

Related information

DB basic

Lang factor

0.6 power law


I explained a specific example of DB (dia inch).

Taking a chemical plant as an example, if we consider the outdoor tanks and the inside of the factory separately and accumulate them, one plant will have about 20,000 DB.

From here, it is possible to develop into plant construction and extension/renovation.

It is possible to make some analogies with other industries such as nuclear power plants.

Please feel free to post your worries, questions, and questions about the design, maintenance, and operation of chemical plants in the comments section. (The comment section is at the bottom of this article.)

*I will read all the comments and answer them seriously.