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HomeProductsPressure-reducing and desuperheating stations (PRDS)

Pressure-reducing and desuperheating stations (PRDS)



Designation and classification

Pressure-reducing and desuperheating stations (PRDS) and fast-response pressure-reducing and desuperheating stations (FPRDS) are used in power circuits for steam pressure reducing and steam desuperheating to preset parameters. Desuperheating stations (DS) provide only steam desuperheating, pressure-reducing stations (PRS) – only steam pressure reducing. PRDS are used for the boiler allurement fire, the reservation of steam bleeding from turbine in circuits of high and medium pressure power block, the steam removal in industrial bleedings, own needs of power stations. PRDS are also used when no other sources of preset parameters steam exist. FPRDS are used for removal of steam which is produced by a boiler or steam generator but not consumed by the turbine under start-up and variable modes of block. It is feed in the steam receiver or the auxiliary collector of power block. This steam is used for the supply reservation of the feed pump driving turbine and the blower, as well for the steam supply of heating up of intermediate superheat pipelines.
Stations manufactured by ROU Co. are arranged according to the following characteristics:
• By station’s designation (FRPRDS, PRDS, DS, PRS);
• By station’s capacity of superheated and reduced steam;
• By parameters of live and reduced steam.
Main technical characteristics of PRDS, DS and PRS and technical requirements for any type of station design should correspond with OST 1008.0026.006-79 “Pressure-reducing and desuperheating stations. General specifications”.
For order and in technical documentation stations should be named according the reference designation rules, stated in the example of station’s reference designations.

Examples of reference designations:

PRDS, 60 t/h capacity, superheated steam pressure 4,0 MPa, reduced steam pressure 1.5 MPa, live steam temperature 450˚ С, reduced steam temperature 300˚ С:

4,0 — 450
РОУ 60 —————
1,5 — 300

DS 30 t/h capacity, superheated steam pressure 3.15 МПа, live steam temperature 420˚ С, desuperheated steam temperature 300˚ С:

3,15 — 420
ОУ 30 —————
3,15 — 300

PRS 40 t/h capacity, superheated steam pressure 1.4 МПа, reduced steam pressure 0.6 МПа, live steam temperature 350˚ С:

1,4
PRS 40 ——— 350
0,6

Technical parameters needed for PRDS order:
• Capacity of the station – G, t/h (superheated or reduced steam)
• Live and reduced steam pressure – Р1 and Р2, MPa, (abs. orexc.)
• Superheated and reduced steam temperature – Т1 and Т2, ˚С
• Cooling water pressure – Рw, MPa, (abs. orexc.)
• Cooling water temperature – Тw, ˚С
Technical parameters needed for PRS order:
• Capacity of the station – G, t/h
• Live and reduced steam pressure – Р1 andР2, MPa, (abs. orexc.)
• Superheated steam temperature – Т, ˚С
Technical parameters needed for DS order:
• Capacity of the station – G, t/h (superheated or reduced steam)
• Pressure – Р, MPa, (abs. orexc.)
• Superheated and desuperheated steam temperature – Т1 andТ2, ˚С
• Cooling water pressure – Рw, MPa, (abs. orexc.)
• Cooling water temperature – Тw, ˚С

Other parameters (non-obligatory):
• Response time, sec.
• Desired electric actuators
• Explosion proof type
• Necessity and parameters of CMD&A
• Dimensional and installation values
Stations are supplied with all needed parts and elements according to specific delivery contract.
In the volume of supply the following elements can be added:
• Shutoff gate valve (on live steam line)
• The control valve (on live steam line) or control valve with combined functions of reducing and cooling (on live steam line)
• Desuperheater unit with water-steam nozzles Globe valves, control valves and check valves, which are installed on the cooling water injection line.
• The valves on the drainage lines
• Pressure safety valves (PSV) or pulse-relief devices (PRD) on the reduced steam line
• Control system
• The pipelines elements to connect all devices in a single unit
The performing plant project organization defines a specific composition of power valves, in agreement with the customer.

Technical requirements

1. Main technical characteristics of PRDS, DS and PRS and technical requirements for any type of station design should correspond with OST 108.026.06-79 “Pressure-reducing
and desuperheating stations” and IS 10-573-03 “Rules and regulations for design and safe operation if steam and hot water pipelines”.
2. Pressure-reducing and desuperheating stations designed for constant operation for the customer should provide stable operation conditions ranging from 40 to 100% of nominal capacity.
3. Preset value of reduced steam temperature should be 200 ˚С (293К) higher than saturation temperature
4. Discharge capacity of safety valves should be equal to total discharge capacity of fully opened steam and water control valves.
5. Pipelines should be installed with at least 1:500 incline pitch ratio in the direction of steam stream
6. Installation of the superheated steam pipeline and reduced steam pipeline should be carried out in such a way that pressure from the pipeline weight as well as its thermal expansion will not affect the valves.
7. Water used for steam desuperheating by its properties should be equal to the water used in high-pressure steam boilers according to rules and regulations of ROSTEHNADZOR.
8. Installation of thermal sensors should be carried out at least 5-6 m from the place of cooling water injection for PRDS and PRS and 10-12 m for DS.
9. Pulse-relief device can be installed in any section of the reduced steam pipeline no more than 1,5 m from the steam desuperheating unit, noise-dumper unit or throttle-control valve.
10. It is strictly prohibited to use the station with parameters, which are even slightly different from those stated in the manufacturer’s certificate.






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Barnaul, Russia, 656012