Product Overview

Spirax Sarco DRV7 direct acting pressure reducing valve regulates fluid pressure without requiring external power supplies or pilot controls. Installed in industrial distribution lines, this unit reduces fluctuating upstream pressures to maintain constant downstream set points across steam, compressed air, gas, and intermittent liquid installations. The assembly utilizes an SG iron (ductile iron) body rated PN25, a single-seat configuration, and a stainless steel bellows seal on the stem to eliminate routine gland packing maintenance.

Actuation relies on downstream pressure piped directly to an elastomer diaphragm actuator opposing a calibrated control spring. Balanced internal construction stabilizes the valve against inlet pressure variations: DN15 and DN20 sizes employ a plug-balanced trim, whereas sizes DN25 through DN100 incorporate an AISI 316L stainless steel balancing bellows. A soft-seated variant, designated DRV7G, features a Nitrile rubber seat insert for gas and air duties demanding tight shut-off up to 90 °C.

Key Features

• Direct acting, self-powered design requires no auxiliary pneumatic or electrical supply.
• Maintenance-free stem sealing with stainless steel bellows prevents media leakage without gland tightening.
• Pressure-balanced trim ensures stable downstream control despite upstream pressure fluctuations (plug balanced for DN15–DN20, bellows balanced for DN25–DN100).
• Six interchangeable actuator and spring combinations accommodate downstream control ranges from 0.1 bar to 20 bar.
• Nitrile soft-seated DRV7G option offers tight shut-off for air and gas applications up to 90 °C, with a recommended maximum 10:1 turndown ratio.
• Nitrile diaphragm variant (suffix N) available for oil service; standard fabric-reinforced EPDM diaphragm handles steam and water duties.
• High flow capacities with maximum Kvs ratings up to 145 on DN100 flanged units.

Technical Specifications

Specification Parameter	Value / Range
Body Design Conditions	PN25
Body Sizes (Flanged)	DN15, DN20, DN25, DN32, DN40, DN50, DN65, DN80, DN100
Body Sizes (Screwed)	1/2”, 3/4”, 1”, 1 1/4”, 1 1/2”, 2” BSP (BS 21 parallel) or NPT
Standard Flange Connections	EN 1092 PN16, EN 1092 PN25
Optional Flange Connections	ASME 150, JIS
Maximum Design Pressure (PMA)	25 bar g @ 100 °C (25 bar g @ 120 °C)
Maximum Design Temperature (TMA) - DRV7	300 °C @ 17.5 bar g
Maximum Design Temperature (TMA) - DRV7G	90 °C @ 25 bar g
Minimum Design Temperature	0 °C
Maximum Operating Temperature (TMO) - DRV7	300 °C @ 17.5 bar g
Maximum Operating Temperature (TMO) - DRV7G	90 °C @ 25 bar g
Minimum Operating Temperature	0 °C (consult manufacturer for lower temperatures)
Maximum Saturated Steam Operating Pressure	22 bar g
Maximum Differential Pressure (DN15–DN50)	25 bar
Maximum Differential Pressure (DN65–DN100)	20 bar
Cold Hydraulic Test Pressure (Bare Body)	38 bar g
Hydraulic Test Pressure (Internals Fitted)	Maximum 25 bar g
Continuous Working Temp - EPDM Diaphragm	125 °C maximum
Continuous Working Temp - Nitrile Diaphragm	90 °C maximum

Flow Capacities (Kvs Values)

Nominal Size	DN15	DN20	DN25	DN32	DN40	DN50	DN65	DN80	DN100
Maximum Kvs	3.4	6.5	11.4	16.4	24	40	58	92	145

Note: Cv (UK) = Kvs × 0.963; Cv (US) = Kvs × 1.156. Kvs values represent full capacities and should be utilized for sizing downstream safety relief valves.

Applications

• Saturated steam distribution networks and process heating equipment (a WS4 or WS4-3 water seal pot must be installed in the sensing line when handling steam).
• Industrial compressed air distribution lines and dry gas supply systems.
• Non-hazardous and inert industrial gases demanding precise, self-acting pressure regulation.
• Mineral and synthetic oil supply systems (specifying the Nitrile diaphragm suffix N).
• Intermittent liquid supply lines (liquid duties are restricted to intermittent duty; continuous recirculation such as pump bypass is prohibited to avoid cavitation damage).

Materials of Construction

Item	Part Name	Size Range / Option	Material	Material Standard
1	Body	DN15 to DN50	SG iron	DIN 1693 GGG 40.3
1	Body	DN65 to DN100	SG iron	ENG JS 400-18-LT
2	Bonnet	All sizes	SG iron	DIN 1693 GGG 40.3
3	Valve seat	All sizes	Stainless steel	BS 970 431 S29
4	Seat gasket	DN15	Stainless steel	-
4	Seat gasket	DN20 and DN25	Mild steel	-
4	Seat gasket	DN32 to DN50	Reinforced exfoliated graphite	-
5	Valve head	DRV7	Stainless steel	BS 970 431 S29
5	Valve head	DRV7G (soft seated)	Stainless steel / Nitrile	BS 970 431 S29
6	Valve head screw	DN15 and DN20	Stainless steel	BS 6105 A2
7	Valve head seal	All sizes	Thermoplastic	Arlon 1555
8	Bush	DN15 and DN20	Stainless steel	BS 970 431 S29
9	Bush (part of 10)	DN25 to DN100	Stainless steel	BS 970 431 S29
10	Balancing bellows assy	DN25 to DN100	Stainless steel	AISI 316L
11	Balancing bellows gasket	DN25 to DN100	Reinforced exfoliated graphite	-
12	Bonnet gasket	All sizes	Reinforced exfoliated graphite	-
13	Bonnet nuts	All sizes	Steel	DIN 267 Pt13 Gr. 8
14	Bonnet studs	DN15 to DN40 (M10)	Steel	DIN 267 Pt13 Gr. 8.8
14	Bonnet studs	DN50 and DN65 (M12)	Steel	DIN 267 Pt13 Gr. 8.8
14	Bonnet studs	DN80 and DN100 (M16)	Steel	DIN 267 Pt13 Gr. 8.8
15	Pillars	All sizes	Steel zinc plated	BS 970 230 M07
16	Pillar nuts	All sizes	Steel zinc plated	BS 3693 Gr. 8
17	Spring adjuster	All sizes	Cast iron zinc plated	DIN 1691 GG25
18	Control spring	All sizes	Chrome vanadium	-
19	Bush (part of 20)	All sizes	PTFE / steel composite	-
20	Sealing bellows assy	All sizes	Stainless steel	AISI 316L
21	Sealing bellows gasket	DN15 and DN20	Stainless steel ‘S’ type	-
21	Sealing bellows gasket	DN25 to DN100	Reinforced exfoliated graphite	-
22	Clamp nut	DN25 to DN100	Steel zinc plated	BS 970 230 M07
25	Lock-nut	DN32 to DN50	Steel zinc plated	BS 970 230 M07
25	Lock-nut	DN15–DN25, DN65–DN100	Steel zinc plated	BS 3692 Gr. 8
26	Spring plate	All sizes	Steel zinc plated	BS 1449 Pt1 HR14
27	Needle bearing	All sizes	Steel	-
28	Setting nut	All sizes	Steel zinc plated	BS 970 230 M07
29	Bearing plate	DN32 to DN50	Steel zinc plated	BS 1449 Pt1 HR14
30	Circlip	DN32 to DN50	Steel zinc plated	-
31	Mounting plate	DN25 to DN50	Steel zinc plated	BS 1449 Pt1 HR14
32	Actuator housing	Types 1(N) to 4(N)	Steel	DIN 1514 St W24
32	Actuator housing	Type 5(N)	Steel	BS EN 10025 S355 J2G3
33	Housing screws	Types 1(N) and 2(N)	Steel zinc plated	BS 3692 Gr. 5.6
33	Housing screws	Types 3(N), 4(N), 5(N)	Steel zinc plated	BS 3692 Gr. 8.8
34	Housing nuts	Types 1(N) and 2(N)	Steel zinc plated	BS 3692 Gr. 5
34	Housing nuts	Types 3(N), 4(N), 5(N)	Steel zinc plated	BS 3692 Gr. 8
35	Diaphragm	Standard	EPDM fabric reinforced	-
35	Diaphragm	Suffix ‘N’	Nitrile fabric reinforced	-
36	Hex. bolt	All sizes	Stainless steel	BS 6105 A2
37	Sealing washer	All sizes	Fibre	-
38	Diaphragm clamp	All sizes	Stainless steel	ASTM A351 CF8M
39	Piston	All sizes	Carbon steel zinc plated	BS 1449 Pt1 HR14
40	Spindle	All sizes	Carbon steel zinc plated	BS 970 230 M07
41	Mounting nuts	All sizes	Steel zinc plated	BS 3692 Gr. 8
42	Coupling	All sizes	Steel zinc plated	-
43	Thread insert	DN15 and DN20	Stainless steel	DTD 734
44	Self-locking nut	DN25 to DN100	Stainless steel	BS 6105 A2

Downstream Pressure Ranges and Actuator Selection

Range Code	Valve Designation	Actuator Type	Spring Colour	Downstream Pressure Range	Actuator PN Rating
1	DRV7(G)B1(N)	1 or 1N	Yellow	0.1 to 0.6 bar (DN32–50: 0.15–0.6 bar; DN65–100: 0.3–0.6 bar)	PN2.5
2	DRV7(G)B2(N)	2 or 2N	Yellow	0.2 to 1.2 bar (DN65–100: 0.4–1.2 bar)	PN2.5
3	DRV7(G)B3(N)	3 or 3N	Blue	0.8 to 2.5 bar	PN6.0
4	DRV7(G)B4(N)	4 or 4N	Blue	2.0 to 5.0 bar	PN16.0
5	DRV7(G)B5(N)	5 or 5N	Blue	4.5 to 10.0 bar	PN25.0
6	DRV7(G)B6(N)	5 or 5N	Red	8.0 to 20.0 bar	PN25.0

Dimensions and Weights

Face-to-Face and Overall Envelope Dimensions (mm)

Size	Flange PN25 (A1)	Flange ASME 150 (A1)	Screwed (A2)	Screwed Center (E)	Act. 1 (B)	Act. 2 (B)	Act. 3 (B)	Act. 4 (B)	Act. 5/6 (B)
DN15	130	127	88	38	537	511	426	426	411
DN20	150	143	102	38	537	511	426	426	411
DN25	160	153	134	51	546	520	435	435	420
DN32	180	176	144	51	608	582	497	497	482
DN40	200	198	150	62	608	582	497	497	482
DN50	230	229	180	71	611	585	500	500	485
DN65	290	295	-	-	633	607	522	522	507
DN80	310	314	-	-	639	613	528	528	513
DN100	350	350	-	-	744	718	633	633	618

Actuator housing diameters (C): Type 1 = 305 mm; Type 2 = 250 mm; Type 3 = 208 mm; Type 4 = 168 mm; Types 5 & 6 = 143 mm.

Component Weights (kg)

Valve Size	DN15	DN20	DN25	DN32	DN40	DN50	DN65	DN80	DN100
Flanged Body (Yellow Spring)	10.8	11.8	14.0	18.8	20.4	23.0	31.7	38.2	53.9
Flanged Body (Blue Spring)	10.8	11.8	14.0	18.8	20.4	23.0	31.7	38.2	53.9
Flanged Body (Red Spring)	11.8	12.8	15.0	20.2	21.8	24.4	33.5	40.0	56.5
Screwed Body Weight Reduction	-1.7	-2.2	-2.2	-3.6	-3.9	-5.5	-	-	-

Actuator Type	1 or 1N	2 or 2N	3 or 3N	4 or 4N	5 or 5N
Actuator Weight (kg)	12.3	6.5	3.9	2.5	2.6

Note: Total unit weight equals the valve body assembly weight plus the actuator weight.

Installation Guidelines

• Position the valve in a horizontal pipe run with the directional arrow on the body pointing in the direction of fluid flow.
• For steam services or media operating above 125 °C, mount the valve vertically downwards with the actuator below the pipework. A WS4 series water seal pot must be installed in the downstream pressure sensing line.
• For operating temperatures below 125 °C, mounting vertically upwards or vertically downwards is permitted.
• Route an 8 mm outer diameter copper or stainless steel sensing line between the actuator coupling and the downstream main. Position the sensing tap at least 1 meter or 15 pipe diameters away from the valve or flow disturbances.
• Protect the valve inlet by flushing system piping prior to commissioning and installing a pipeline strainer. For steam and air lines, mount the strainer on its side to avoid condensate collection.
• In steam lines, fit an upstream separator with a float steam trap, upstream and downstream isolating valves, and pressure gauges on both sides.
• Install an appropriately sized downstream safety valve discharging to a safe location to protect downstream equipment against full DRV capacity in the open position.
• Charge the WS4 / WS4-3 water seal pot with soft water before startup. Open upstream isolation valves gradually to avoid waterhammer.

Commissioning and Maintenance

Before servicing, isolate the valve, vent pipeline pressure to zero, and rotate spring adjuster (17) to release spring compression fully. Never rotate setting nut (28) without loosening lock-nut (25), as doing so twists and destroys the stem sealing bellows.

Downstream set point adjustment is achieved using an open-ended spanner (17 mm A/F for sizes up to DN50; 24 mm A/F for DN65 to DN100). Rotating the spring adjuster compresses the control spring to increase downstream pressure, while relaxing tension reduces set pressure.

Maximum Valve Lift Settings

Valve Size	Maximum Lift (mm)	Setting Nut Adjustment
DN15	4.00	2 turns, 4 flats
DN20	4.75	3 turns, 1 flat
DN25	6.25	4 turns, 1 flat
DN32	7.75	5 turns, 1 flat
DN40	9.00	6 turns
DN50	11.00	7 turns, 2 flats
DN65	12.25	8 turns, 1 flat
DN80	15.75	10 turns, 3 flats
DN100	19.50	13 turns

Recommended Tightening Torques

Component	Fastener / Item	Valve Size	Recommended Torque
Valve seat (3)	Seat	DN15	50 to 55 N·m
Valve seat (3)	Seat	DN20	105 to 110 N·m
Valve seat (3)	Seat	DN25	160 to 170 N·m
Valve seat (3)	Seat	DN32	100 to 110 N·m
Valve seat (3)	Seat	DN40	175 to 185 N·m
Valve seat (3)	Seat	DN50	165 to 175 N·m
Balancing bellows assy (10)	Threaded body	DN25	90 to 100 N·m
Balancing bellows assy (10)	Threaded body	DN32 and DN40	170 to 180 N·m
Balancing bellows assy (10)	Threaded body	DN50	220 to 230 N·m
Balancing to sealing bellows	Threaded junction	DN25 to DN100	2 to 3 N·m
Adaptor (23)	Adaptor body	DN25 to DN50	55 to 60 N·m
Clamp nut (22)	Nut	DN25 to DN50	40 to 45 N·m
Clamp nut (22)	Nut	DN65 to DN100	60 to 65 N·m
Bonnet nuts (13)	Stud nuts	DN15	15 to 20 N·m
Bonnet nuts (13)	Stud nuts	DN20	20 to 25 N·m
Bonnet nuts (13)	Stud nuts	DN25 to DN50	25 to 30 N·m
Bonnet nuts (13)	Stud nuts	DN65	40 to 45 N·m
Bonnet nuts (13)	Stud nuts	DN80	60 to 65 N·m
Bonnet nuts (13)	Stud nuts	DN100	50 to 55 N·m
Spindle guide bush (8)	Bush	DN15 and DN20	50 to 60 N·m
Pillar nuts (16)	Fastener	All sizes	25 to 35 N·m
Sealing bellows assy (20)	Bush	DN15 and DN20	175 to 185 N·m
Setting nut / lock-nut (28/25)	Nuts	All sizes	10 to 15 N·m
Actuator housing bolts (33/34)	Housing bolts	Types 1, 1N, 2, 2N	4.5 to 5.5 N·m
Actuator housing bolts (33/34)	Housing bolts	Types 3(N), 4(N), 5(N)	10.5 to 11.5 N·m
Diaphragm clamp bolt (36)	Bolt	All actuator types	23 to 27 N·m
Actuator mounting nuts (41)	Nuts	All actuator types	15 to 18 N·m

Spare Parts Kits

Kit Description	Sizes Available	Included Items in Kit
Coupling	All sizes	Coupling (A)
Diaphragm kit	All actuator types	Diaphragm (B) and fibre sealing washer (C)
Needle bearing	All sizes	Needle bearing assembly (D)
Control spring(s)	All sizes	Spring(s) (I)
Sealing bellows set	DN15 and DN20	Sealing bellows assembly (E), sealing bellows gasket (F), bonnet gasket (G)
Sealing bellows set	DN25 to DN100	Sealing bellows assembly (E), sealing bellows gasket (F), adaptor gasket (O on early DN25–50)
Seat / head set	DN15 and DN20	Valve seat (J), seat gasket (K), valve head (L), bonnet gasket (G), head seal (H)
Seat / head set	DN25 to DN50	Valve seat (J), seat gasket (K), head (L), self-locking nut (W), head seal (H), bonnet gasket (G)
Valve head set	DN65 to DN100	Valve head (L), self-locking nut (W), head seal (H), bonnet gasket (G), balancing bellows gasket (M)
Balancing bellows set	DN25 to DN50	Balancing bellows assy (N), balancing bellows gasket (M), bonnet gasket (G), head seal (H), nut (W), sealing bellows gasket (F), adaptor gasket (O)
Balancing bellows set	DN65 to DN100	Balancing bellows assy (N), balancing bellows gasket (M), bonnet gasket (G), self-locking nut (W), head seal (H)
Gasket set	DN15 and DN20	Sealing bellows gasket (F), bonnet gasket (G), seat gasket (K)
Gasket set	DN25 to DN50	Sealing bellows gasket (F), bonnet gasket (G), seat gasket (K), balancing bellows gasket (M), adaptor gasket (O)
Gasket set	DN65 to DN100	Sealing bellows gasket (F), bonnet gasket (G), balancing bellows gasket (M)