Pressure reducing orifice plates

In summary, the conversation discusses the problem of calculating the flow rate and pressure after two pressure reducing orifice plates in series, using seawater as the medium. The input pressure and orifice diameters are known, but the overall flow rate and pressure after the orifice plates are unknown. The conversation also mentions the design for a minimum flow rate for an oil cooler downstream and the potential changes in flow rate and pressure if the supply pressure is reduced. The solution may involve an iterative equation and reference to orifice plate calculation methods.
  • #1
clint84
2
0
Hi,

I would like to know how would i be able to solve a problem involving two (2) pressure reducing orifice plates in series with seawater as medium.

I know the orifice diameters, the supply pressure, but i don't know the overall flowrate, and pressure after the orifice plates.

The Ship's firemain which is the source of pressure = 9 bar, has a branch which is connected to an
Oil cooler downstream. Downstream from the oil cooler the pipe discharge into the sea (3m below waterline). The total length of branch pipe is 10m and the supply point is 5 m above the discharge point, with the discharge point being 3 m below waterline.

If I know the pressure but don't know the pressure drops or flowrate, is it possible to solve for the flowrate and pressure after the multiple orifice plates by hand?

I'm guessing this would be an iterative equation because the pressure drop over the orifice plates will be dependent on velocity - which i don't know, and K, which is dependent on Reynold's number and also related to velocity. Is there a method to solving this problem?

The only standards i find are on flowrate measuring orifice plates which are not the same as pressure reducing orifices.

Any help would be much appreciated

Cheers

Clint
 
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  • #2
The oil cooler will require a minimum flow and so you must design for that, with a safety margin.
You know your input pressure, outlet head, pipe sizes and the pressure drop across the oil cooler at that design flow.
The two orifice plates will have to each drop half the remaining pressure.
 
  • #3
I already know the minimum flow into the oil cooler, but what if i wanted to calculate/estimate the resultant flowrate from reducing supply pressure from 9 bar down to 6, 4, and 2, keeping orifice plate dimensions constant?

The orifice plates in series at the moment are designed for a specific supply pressure and design flowrate into oil cooler. I want to know how the flowrate and pressure drop over the orifices will change if i deviate from the design supply pressure, i.e. supply pressure is reduced significantly
 

FAQ: Pressure reducing orifice plates

1. What is a pressure reducing orifice plate?

A pressure reducing orifice plate is a type of flow control device that is inserted into a pipeline to reduce the pressure of a fluid or gas passing through it. It typically consists of a thin metal plate with a precisely sized hole in the center, which creates a restriction in the flow and causes a drop in pressure.

2. How does a pressure reducing orifice plate work?

When a fluid or gas passes through the orifice plate, the restriction in the flow causes an increase in velocity. This increase in velocity results in a decrease in pressure, in accordance with Bernoulli's principle. The size of the orifice hole and the properties of the fluid or gas determine the amount of pressure drop.

3. What are the advantages of using a pressure reducing orifice plate?

One of the main advantages of using a pressure reducing orifice plate is its simplicity and low cost compared to other flow control devices. It also has a relatively low maintenance requirement and can handle a wide range of fluid or gas flow rates. Additionally, it can be easily installed or removed from a pipeline without disrupting the flow.

4. What factors should be considered when selecting a pressure reducing orifice plate?

The size of the orifice hole, the type of fluid or gas being transported, and the desired pressure drop are all important factors to consider when selecting a pressure reducing orifice plate. The material and thickness of the plate should also be chosen based on the properties of the fluid or gas and the operating conditions of the pipeline.

5. What are the potential limitations or drawbacks of using a pressure reducing orifice plate?

One potential limitation of using a pressure reducing orifice plate is that it can cause a significant energy loss, as the pressure drop across the plate results in a decrease in available energy for the fluid or gas. This can also lead to increased turbulence and erosion in the pipeline. Additionally, the orifice plate may not be suitable for controlling very low flow rates or for fluids or gases with high viscosity or particulate matter.

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