Spirax Sarco 25P pilot-operated pressure-reducing valve, ½” - 5”, is a self-acting pilot-operated pressure-reducing valve. An external pressure-sensing line detects downstream pressure, adjusts the main valve opening, and maintains stable pressure. The valve can close when there is no downstream demand. The main valve features a single seat and a hardened alloy valve plug. The valve body is made of ductile iron or cast steel, and the pilot valve is bolted directly to the main valve.

Available Models

Model	SKU
1/2” 25P SG Blue	6090328
3/4” 25P SG Blue	6090331
1” 25P SG Blue	6090334
1 1/4” 25P SG Blue	6090337
1 1/2” 25P SG Blue	6090340
2” 25P SG Blue	6090343

Downstream Pressure Range

• Yellow spring: 0.2 bar g - 2.1 bar g

• Blue spring: 1.4 bar g - 7.0 bar g

• Red spring: 5.6 bar g - 14.0 bar g

Size and Pipe Connections

• ½” - 2”: BSPT threaded connection (BS21)

• ½” - 4”: PN16 and PN25 flanges (ductile iron), PN40 flanges (cast steel)

• 5”: PN16 and PN25 flanges (ductile iron)

• Contact Spirax Sarco for other connection sizes.

Weight

Size	Weight (cast iron) (kg)
1/2”	10.8 (threaded), 11.4 (flanged)
3/4”	10.2 (threaded), 12.2 (flanged)
1”	13.6 (threaded), 16 (flanged)
1 1/4”	16 (threaded), 18.8 (flanged)
1 1/2”	15.8 (threaded), 20.4 (flanged)
2”	26 (threaded), 31.2 (flanged)
2 1/2”	62.4 (flanged)
3”	74.6 (flanged)
4”	112.2 (flanged)
5”	132 (flanged)

Materials

No.	Component	Material
1	Valve body	Ductile iron QT400 - 18
2	Bonnet	Ductile iron QT400 - 18
3	Bonnet bolts	Steel SAEJ429 Grs
4	Main valve plug	Stainless steel AISI 420
5	Main valve seat (1/2” - 2”)	Stainless steel AISI 420
5	Main valve seat (2 1/2” - 5”)	Stainless steel AISI 304
6	Main valve seat gasket	Copper
7	Valve return spring	Stainless steel AISI 302
8	Strainer screen	Stainless steel AISI 304
9	Valve stem	Stainless steel AISI 304
10	Valve stem sleeve (1/2” - 2”)	Brass
10	Valve stem sleeve (2 1/2” - 5”)	Steel
11	Bonnet gasket	Asbestos-free material
12	Spring guide	Steel SAEJ995
13	Nut (1/2” - 2”)	Brass
13	Nut (2 1/2” - 5”)	Steel
14	Pressure-balancing tube	Stainless steel AISI 304
15	Diaphragm top cover	Ductile iron QT400 - 18
16	Valve stem bushing	Stainless steel AISI 304
17	Diaphragm bottom cover (1/2” - 2”)	Brass
17	Diaphragm bottom cover (2 1/2” - 5”)	Cast iron
18	Pushrod guide (1/2” - 2”)	Brass
18	Pushrod guide (2 1/2” - 5”)	Stainless steel
19	Diaphragm plate	Ductile iron QT400 - 18
20	Diaphragm plate pushrod	Stainless steel AISI 304
21	Nut (2 1/2” - 5”)	Steel
22	Main diaphragm (1/2” - 3”)	Phosphor bronze
22	Main diaphragm (4” - 5”)	Stainless steel
23	Sleeve	Stainless steel AISI 304
24	Short tube and damping orifice	12L14
25	External tubing assembly	Stainless steel ASTM B280
26	Plug	Steel 12L14
27	Connecting bolts	Steel SAE1060
28	Adjusting screw (1/2” - 2”)	Brass
28	Adjusting screw (2 1/2” - 5”)	Stainless steel
43	Pilot valve spring	Copper, asbestos-free
44	Locknut	Steel
45	Washer	Stainless steel AISI 304
46	Diaphragm top cover	Ductile iron QT400 - 18
47	Spring plate	Stainless steel ASTM B283
48	Diaphragm bottom cover	Brass SAE1010
49	Pilot valve spring	Steel SAE1010
50	Diaphragm plate	Ductile iron QT400 - 18
51	Diaphragm	Phosphor bronze AISI 302
60	Pilot valve gasket	Graphite/asbestos AISI 302
61	Pilot valve mounting nut	Steel SAE J 429 Grs
62	Diaphragm chamber nut	Steel / 1 - 18x1” SAE J429 Grs

Installation

Install the pressure-reducing valve in a horizontal pipeline with a bypass and isolation valves. Install a steam trap and strainer upstream of the valve. Provide a straight pipe section of at least 10 pipe diameters upstream and downstream of the downstream pressure-sensing line.

Flow Capacity

Size	Cv
1/2”	3.4
3/4”	6.5
1”	10.5
1 1/4”	14
1 1/2”	20
2”	35
2 1/2”	56
3”	74
4”	115
5”	123

Typical Applications

25P provides accurate and reliable pressure reduction, reducing steam from high pressure to the equipment’s effective operating range and helping prevent equipment damage.