Detail reason for using reducer in vertical & horizontal

First of all please take some time and read the "Training" article about "Fittings"
Go to the buttons at the top of the Home page of this web site.
Click on "Training"
Scroll down to Section I, C Fittings
Part way down the page you will see "Reducers"

Your questions:
This is Karthik,
I am aware of the use of reducers in vertical & horizontal pump piping.
I have consulted with all my Senior Eng regarding this. but I am not able to get a exact reason. My Question is, do we use a reducer to avoid cavitation in the pump. I want to know in detail the reason of using the reducer & how does it work in both horizontal & vertical piping.
Please, can anyone help me?

First of all the main reason there is a reducer in a pump suction line or a pump discharge line is because the pipe line size is different from the pump nozzle size.
The process engineer determines what line size is required for all lines to perform the function of the process. This is true for both the suction and the discharge lines for pumps.
The Pump Engineer specifies and purchases a pump that will perform the function of the process. Due to the nature of the pump, the suction and discharge nozzles almost always (95% of the time) turn out to be one or more sizes smaller than the connecting line sizes. You may ask why don't they buy a bigger pump? Or at least a pump with a bigger nozzle? Well it is pure economics. The bigger pump or the pump with bigger nozzles cost extra money and probably will not perform properly or be cost effective.

So what do we have? We have a pipe line (specified by the process engineer) and a pump (specified by the pump engineer) which needs to be connected. The piping is done by a responsible, well trained, and experienced piping designer. It is the piper's job to know what to do and do it right.

The detailed reason for having the reducer is that good pipers know that to change line size you must use a reducer.

Now, how do you install a reducer?
Vertical lines:
It is okay to use a concentric or an eccentric reducer (flow up or flow down) in vertical lines. You should choose an eccentric reducer when you want to keep one side of the pipe "flat" such as against a wall or group of supports.

Horizontal lines (not at pumps):
It is normal (and recommended) to use eccentric reducers (with the flat side down) for line size changes in horizontal lines on pipe racks. This allows for the different sized piping to have better contact with the pipe supports.

Pump suction piping:
If the pump has a top suction nozzle then you should use a concentric reducer to make the line size change. You should also make the line size change a minimum distance form the pump suction nozzle.

If the pump has an end suction nozzle or a side suction nozzle, then you must arrange the piping so the reducer is top flat and a minimum distance from the pump suction nozzle. The reason for the top flat is this. If the reducer is installed with the flat side down then a "vapor trap" is created by the change in diameter. This space allows bubbles to collect and leads to cavitation.

Now back to your questions. No you do not use a reducer to avoid cavitation of the pump. You use the reducer to change line size. You use the correct installation (orientation) of the reducer in a pump suction line to avoid cavitation of the pump.

Here is some help that was posted on the old pipingdesigners forum.

“In piping there is a reason for everything”
M. J. (Mike) Garofalo

Mike Garofalo was the Manager of Piping Engineering and Design at Fluor Corporation’s Southern California Division from mid 1954 till 1980. He did more for the piping profession in that company than anyone I know of. He was a visionary, a leader and a teacher.

One of the most important things that Mike did during his early years was to keep in touch with all the jobs and all the pipers. He would make a weekly “walk-around” through all the projects and talk to some of the piping people. He would not talk to every piper every week, (there were just too many) but he would randomly stop and talk to a few pipers on each job.

There are a lot of stories that could be told about him but I want to talk about his words, “In piping there is a reason for everything.” I first heard these words sometime in the late 1950’s when I was working on a project as a young piping designer. This was during the time when the other 3D design models were being built. We used wood and plastic for the structures and equipment, and we used brass wire with specific sized rubber sleeves for the pipe. We cast all of our own valves and soldered them to the brass wire. The pipers did allthe model piping.


There came a time when the model board I was working on was about 90% complete and Mike showed up for his weekly walk-around. On this particular day he stopped at my table and looked over my work. He greeted me and I, shaking in my boots, greeted him in response. He then proceeded to point to a specific line and ask, “Why did you route that line that way?” Needless to say I was a bit flustered and my response was “I don’t know”.

Now Mike was a full head taller than me and out weighed me by at least 150 pounds. He was Italian and looked stern. After my answer he turned red and I swear I saw steam come out his ears. I was sure that I had just made a classic career-ending mistake. But no, he proceeded to pull up a drafting stool and sit down beside me. He lowered his voice and taught me my most valuable piping lesson.

He said to me that “In piping there is a reason for everything. He told me that when you are about to route a line, place a valve or locate an instrument connection you must know why you are doing it and why you are doing it that specific way and why you are placing it there. If you don’t know why then you should look again. If you can not figure out why then you should ask one of the senior pipers.”

He went on to say “Today it was me that asked you this question, but what if it had been the Client?” He went on, “What do you think he or she would have thought? You see there is always a reason for routing a line a certain way or placing a valve in a certain place.” We talked for some time about this approach to piping and I have remembered it and used it throughout my career.

Reasons to consider:
- Functional: Check the P&ID for the function of this line valve, instrument or other item. It has a purpose and it may have some specific restrictions (do not pocket, slope, etc.)
- Mechanical: The limitations of the piping materials or the properties of the piping materials may have a baring on the assembly or configuration.
- Stress and flexibility: The routing must consider that lines expand or contract and they cause forces that can result in failure of the system.
- Fabrication/Installation: The ability to fabricate and install a piping system may seem like small thing but it needs to be considered.
- Operation: What does the operator need to do to operate valves and read instruments.
- Maintenance: What is required to maintain this piping system and the equipment around this specific area.
- Safety: Not thinking about the pipe routing may result in a situation that creates an unsafe work place.

It would have been good for all pipers to meet Mike. But sadly he is gone now. But you can all remember his words:
“In piping there is a reason for everything”



What does it take to be a good piper? To be a good piper you need knowledge (data and information), intelligence and wisdom. You see there is a big difference between these three. What’s the difference? Let’s start with all five terms.

Knowledge, n. the state of knowing, cognition // understanding. (Consisting of):
-Data, n. a known fact // the assumption which forms the basis for an inference or conclusion. Data plural of Datum (fact, facts).

-Information, n. the communication of news, knowledge etc. a fact or facts told or communicated // data fed to a machine

Intelligence, n. the ability to perceive logical relationships and use one's knowledge to solve problems and respond appropriately to novel situations.

Wisdom, n. the quality of being wise. Wise, adj. having the ability to make a right decision or judgment by applying intelligent thought to a wide range of and knowledge, with prudence

The above is very important to the piping designer in the performance of the day to day piping work. You need to make sure you have all the data and all the information. With this pool of knowledge you will hopefully have the intelligence to do the work right and the wisdom to get it when it is required.

A key issue here is:
Is All the Right Information Known?
And
Is All the Known Information Right?

I will give you an example where this applied. And in this example the answer to the first question was yes, but the answer to the second question turned out to be a big no.

My company accepted a small secondary “add-on” project from an existing client. I was assigned to this smaller project as the piping engineering lead. The client was in such a rush for this project that they had already purchased all the equipment. (From vendor “X”) We had to deal thru the client for all communications with vendor “X”. The equipment was already being manufactured. We needed all the information about the equipment including the shape, size, configuration, anchor bolt locations, piping connections, etc. Vendor “X” would not talk to us and said we should talk to the client.

We finally got both the client and vendor “X” to agree to a joint meeting. In this meeting we asked if vendor “X” had done there engineering drawings on a computer. They said they had and it turned out their system was compatible with the system we were using. We asked if their drawing were accurate and to scale. They said, “Of course!” Figuring we could save a lot of time I asked the client to have vendor “X” give us an electronic copy of the equipment files. Vendor “X” said “No problem.”

To make a long story short, we got the files. They were very detailed and we proceeded to use them. Structural got a copy and started on their work. Piping got a copy and started on their work. When we brought the two models together they did not match. The problem was that the electronic picture and the dimensions did not match. Somehow they (vendor “X”) had taken an electronic copy of the equipment from another (smaller) job and then overridden the dimensions to meet the needs of our project.

I had used poor judgement in not having the E-drawings checked. We had all the right E- drawings but not all of the E- drawings were right.

I hope you find this helpful

Rich Jones (and all other pipers)
I also have a copy of the book "Piping Guide"
It is the only book that you will find that promotes this (bottom flat) orientation for a reducer in a pump suction line. I have four or five other books that promote the top flat position I stated in my response above.
The "Piping Guide" can and should be credited with being 98% or 99% correct on most things but on this item (and only a few others I have found in the book) it is in error.
You and anyone else who has a copy of the "Piping Guide" should try to get a copy of the other piping design books and then compare before you take a rigid stand in favor of the "Piping Guide."