Steam Pressure Reducing Station | PRS |Pressure Reducing Station

THERMODYNE Enhancing Energy Efficiency

THERMODYNE Enhancing Energy Efficiency

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In process industries, steam is usually generated at a high pressure (standard pressure being 10.5/14/17.5 Kg/cm2 or more)

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The required pressure for process heating is lesser, ranging from 2 to 6 Kg/cm2 in most of the industries.

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For this, the pressure of the steam generated has to be reduced as per the process requirements.

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This is done through a steam pressure reducing station. It is a set of valves, properly sized, to suit the flow and pressure requirements of the user.

STEAM PRS

THERMODYNE Enhancing Energy Efficiency

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This is done through a steam pressure reducing station. It is a set of valves, properly sized to suit the flow and pressure requirements of the user.

Courtesy: Forbes Marshall

STEAM PRS

THERMODYNE Enhancing Energy Efficiency

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In order to design a Pressure reducing station to suit the client’s requirements, we need to know the following parameters from the client about his process: ◦ Flow of steam required through the PRS, in Kg/hr ◦ Inlet pressure of steam available at PRS, in Kg/cm2

◦ Outlet pressure of steam required after the PRS, in Kg/cm2

Based on the above inputs, sizing of various valves is done as explained in the following slides

STEAM PRS

THERMODYNE Enhancing Energy Efficiency

â—Ś The size of inlet line to the PRS has to be selected as per the following table:

For example, for a steam flow of 1500 Kg/hr at a pressure of 8 Kg/cm2, the line size must be 65 mm. So the inlet valve for PRS should be selected as 65 mm size

STEAM PRS

THERMODYNE Enhancing Energy Efficiency

◦ The moisture separator at the inlet to the PRS shall be as per the inlet line size selected as above. ◦ After the inlet valve, steam strainer also would be of the same size as the steam flow and pressure through the strainer also is same. ◦ The by-pass line and by-pass steam valve would be of the same size as the inlet valve. The steam pressure and flow through the by-pass line is same as the inlet parameters.

STEAM PRS

◦ Steam PRV is selected as per this chart.

Example ◦ To select a PRV for

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 Flow rate of 2000 Kg/hr  Inlet steam pressure of 10 Kg/cm2  Outlet steam pressure of 6 Kg/cm2 On the Upstream pressure line, select 10 Go upwards, where this curve cuts the horizontal line of 6 bar downstream pressure.

From this intersection point, drop a line vertically downwards to reach the required flow rate (2000 Kg/hr).

On the horizontal line, select the required valve size to match the required flow.

As per the chart, 40 NB PRV would be selected for our defined parameters

THERMODYNE Enhancing Energy Efficiency

STEAM PRS

This chart may vary as per the PRV manufacturer. Please refer the manufacturer’s recommendations for right selection

THERMODYNE Enhancing Energy Efficiency

â—Ś The size of outlet line from the PRS has to be selected as per the following table:

For example, for a steam flow of 2000 Kg/hr reduced to 6 Kg/cm2, the line size must be 80 mm.

So the outlet valve & line from PRS, after the PRV should be selected as 80 mm size

STEAM PRS

THERMODYNE Enhancing Energy Efficiency

Following additional accessories are also apart of the PRS:

◦ Pressure gauge with isolation valve & syphon - 1 each at inlet & outlet of PRS to monitor the inlet & outlet steam pressures. ◦ Steam safety valve, suitably sized, at the outlet of PRS ◦ Steam trap assembly at the inlet of PRS, to remove the condensate in the inlet line ◦ All pipes & pipe fittings like flanges, bends & reducers etc. must be selected as per the selected valves to finalize the PRS. All drawings & designs must be approved from the statutory authority (IBR) before fabrication. Fabrication of PRS has to be done by approved welders as per the requirements of IBR and final inspection is must for legal compliance.

STEAM PRS

THERMODYNE Enhancing Energy Efficiency

STEAM PRS

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