What is the Difference Between Orifice and Reducer?

or⋅i⋅fice [awr-uh-fis, or-] -noun

an opening or aperture, as of a tube or pipe; a mouthlike opening or hole; mouth; vent.

Orifice Plate -

From Wikipedia, the free encyclopedia

Flat-plate, sharp-edge orifice

An orifice plate is a device used to measure the rate of fluid flow. It uses the same principle as a Venturi nozzle, namely Bernoulli's principle which says that there is a relationship between the pressure of the fluid and the velocity of the fluid. When the velocity increases, the pressure decreases and vice versa.

An orifice plate is basically a thin plate with a hole in the middle. It is usually placed in a pipe in which fluid flows. As fluid flows through the pipe, it has a certain velocity and a certain pressure. When the fluid reaches the orifice plate, with the hole in the middle, the fluid is forced to converge to go through the small hole; the point of maximum convergence actually occurs shortly downstream of the physical orifice, at the so-called vena contracta point (see drawing to the right). As it does so, the velocity and the pressure changes. Beyond the vena contracta, the fluid expands and the velocity and pressure change once again. By measuring the difference in fluid pressure between the normal pipe section and at the vena contracta, the volumetric and mass flow rates can be obtained from Bernoulli's equation.

Orifice Plates are normally the responsibility of and purchased by the Instrument/Control Systems Engineering group. The Orifice plates are shipped to the job site and installed by the field piping installation contractor.

http://www.emersonprocess.com/daniel/Products/Gas/Orifice/Plates/Ds_sheets/Orifice%20Plates%20563KB.pdf

Orifice Flanges -

Orifice Flanges are normally purchased by the Piping Engineering and Design group. They are normally shipped to the pipe fabrication shop.

http://www.thermocouple.co.uk/Downloads/FM-CR_FLGA.pdf

and

http://www.imperialco.net/flange/flange.html

Orifice Run -

Orifice Runs are normally horizontal. However there are sometimes when the runs can be in the vertical. Vertical runs are very rare and require the complete approval of the Process Engineer and the Instrument Engineer.

Orifice Runs require very specific up-stream and down-stream lengths.

The up-stream should be 20 diameters of straight run with no obstructions (Thermal Wells, etc). This distance may be reduced with the approval of the Instrument for various reasons. These reasons may include the configuration of In-plane elbows and the distance between the Ells.

The down-stream run should be a minimum of 5 diameters of straight run before any obstruction or elbow.

An FO (including all the items above) will also have the Flow transmitter, one or more Flow indicators (Dials) and a Flow Control Valve. This is all part of a complete Loop which is alive and self adjusts the flow.

A Restriction Orifice (RO) is just a plate (or other device) with a fixed hole which cuts down the flow through the pipe.

Orifice and Restriction Orifice #2

The question:

What is the use of orifice? What is the difference between orifice & restriction orifice?

My answer:

Because you gave us only limited information we are left to guess what you are talking about. I think you are talking about Process Plant Piping design and the use and purpose of the different types of the object called an "Orifice".

First: the definition of the word "orifice": ": an opening (as a vent, mouth, or hole) through which something may pass"

Second: The term "Orifice" is used in two ways in the Piping profession. There is the "Orifice Meter" and the "Restriction Orifice" both of which I feel you are asking about.

The "Orifice Meter" is a method of measuring the floe in a pipe line. It is made up of the following elements:

• An upstream run (length) of pipe. This run of pipe needs to be select pipe with a very smooth bore and 10 to 20 diameters in length.
• A downstream run of pipe. This run of pipe needs to be select pipe with a very smooth bore and a minimum of 5 diameters in length.
• A pair of "Orifice Flanges". These flanges mated face to face and are specially made with "Flange Taps". In the space between these flanges will be a gasket, the orifice plate and a second gasket.
• The "Orifice Plate". The Orifice Plate is normally flat and tends to block the flow in the line except for the "orifice" (or hole) normally in the center of the plate. The "Hole" on the orifice plate is not always round and is not always in the center. The hole will sometimes have square profile, a tapered profile or a rounded profile.
• The "Flange Taps". The flange taps (two each in the upstream and downstream flange) are holes drilled 180 degrees apart through the flange between the bolts from the outside diameter of the flange through to the inside diameter of the flange. External piping, valves and instruments are connected to these taps to take continuous readings. This all becomes part of a more extensive and complex "Control Loop".

The purpose of an Orifice Meter is to measure the flow in the specific pipe. It is done (both in liquid and cases) by reading the pressure differential (upstream and downstream) of the plate. This "Flow" rate can then be used to do other "work" in a control loop of a process system.

The "Restriction Orifice" is a method to "govern the amount of flow of a liquid or gas in a pipe. It is composed of some kind of a blockage or plug in the line with a pre-determined hole size drilled in it. There is no specific upstream or downstream run involved. It is just a flow restriction. Unless it is removed and replaced with another plug with a different hole it is not adjustable. If you must have an adjustable feature to the restriction then you need to use a Globe Valve or a Needle Valve.

Reducers, Concentric vs. Eccentric

The questions:

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 an 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?

My answer:

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 they don't 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.

99% of the time you are pumping a fluid that will contain vapor (water w/air or hydrocarbon liquid w/gaseous hydrocarbon, etc) which will form bubbles in the high point of lines. The bottom flat reducer in the horizontal at a pump suction nozzle forms a trapped high point for the build-up of a vapor pocket. This is BAD, therefore you must place the reducer in the top flat position for all liquids. The 1% time that you pump "Slurry" you should place the reducer in the bottom flat position so there is not a build-up of the solids contained in the fluid.

Reducer Wall Schedule

The Question:

"For reducers, if the branch size requires a different schedule than the main size, example: 3X1.5 reducer, main requires SCH40, branch requires SCH80, the process engineer asks to use a reducer of SCH80/SCH80."

My answer:

First of all, unless the Company is very different than the normal EP&C Company the Process Engineer has nothing to do with the proper wall schedule selection. The Project Piping Material Engineer and the applicable Piping Code (ASME B31.3, etc.) will determine pipe wall thickness.

Second, if the wall thickness is not the same with the mating pipe, fitting or flange then the one with the thicker wall will need to be taper bored to insure a full penetration weld and compliance with the applicable piping Code. This adds extra time and cost to the fabrication process.

Third, if there is a failure of a piping component during operations after the plant start-up the Process Engineer is not the one who will be blamed and maybe lose his (or her) job.

Forth, reducers should be spec'd with the proper wall schedule to match the pipe wall schedule of that size. Based on that I think your 3" x 1-1/2" reducer should be 3" (Sch 40) x 1-1/2" (Sch 80) and again the process engineer has no say in the matter. Before you say that "You cannot buy reducers that way" I suggest you check with one or more piping material suppliers and see what they say.

Fifth, (this may be just a slip in terminology) A reducer is not a branch fitting and does not have branch size. A reducer description in CADWorx (or any other CAD system) should be related to "Large End" and "Small End" only.