Iron Relief Valves | McMaster-Carr

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	Body Material Body Material

Iron

	For Use With For Use With

	Pipe Size Pipe Size

	Inlet Pipe Size Inlet Pipe Size

	Valve Function Valve Function

Pressure Relief

Pressure Regulation

Back-Pressure Regulation

	Maximum Pressure Maximum Pressure

1,000 to 1,999 psi

2,000 to 3,499 psi

	Valve Type Valve Type

Pop Safety

Relief

Pressure Regulator

Back-Pressure Regulator

	Maximum Inlet Pressure Maximum Inlet Pressure

Less than 500 psi

	Maximum Temperature Maximum Temperature

Less than 250° F

300° to 399° F

400° to 499° F

	Set Pressure Set Pressure

	Maximum Flow Rate Maximum Flow Rate

	Set Pressure Configuration Set Pressure Configuration

Nonadjustable

Adjustable

	Outlet Pipe Size Outlet Pipe Size

	Relief Port Pipe Size Relief Port Pipe Size

	Total Number of Ports Total Number of Ports

	Connection Connection

	Inlet Thread Type Inlet Thread Type

NPT

	Actuation Actuation

Pressure

	DFARS (Defense Acquisition Regulations Supplement) DFARS (Defense Acquisition Regulations Supplement)

DFARS Specialty Metals
COTS-Exempt

	Number of Ports Number of Ports

	Minimum Temperature Minimum Temperature

-49° to -25° F

-24° to 0° F

Greater than 0° F

	RoHS (Restriction of Hazardous Substances) RoHS (Restriction of Hazardous Substances)

RoHS Compliant with
Exemptions

RoHS Compliant

	REACH (Registration, Evaluation, Authorization and Restriction of Chemicals) REACH (Registration, Evaluation, Authorization and Restriction of Chemicals)

REACH Compliant

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65 Products

About Pressure-Relief Valves

For Use With: Air, Inert Gas
Temperature Range: -20° to 406° F

Commonly used with high-volume blowers, compressors, and air-powered conveyors, these valves quickly relieve a large amount of air in systems with a pipe size of 2 or greater. They spring fully open at the set pressure and remain open until the system pressure is restored below the set pressure. Attach a drain line to the threaded relief port for remote discharge. Valves have a cast iron body to absorb vibration for reduced noise and wear in your pipeline.

For technical drawings and 3-D models, click on a part number.

Inlet			Relief Port
Pipe Size	Location	Maximum Pressure, psi	Pipe Size	Location	Temperature Range, ° F	Overall Ht.	Test Mechanism	Valve Type	Choose a Set Pressure, psi		Each
NPT Male Inlet and NPT Female Relief Port
Cast Iron Body—Bronze Seal
2	Bottom	60	2	Side	-20° to 406°	7"	T-Handle	Pop Safety	2, 4, 6, 8, 10, 12, 14	0000000	0000000
2 1/2	Bottom	60	2 1/2	Side	-20° to 406°	8"	T-Handle	Pop Safety	2, 4, 6, 8, 10, 12, 14	0000000	000000
3	Bottom	60	3	Side	-20° to 406°	9"	T-Handle	Pop Safety	2, 4, 6, 8, 10, 12, 14	0000000	000000

Large-Diameter Remote-Discharge ASME-Code
Fast-Acting Pressure-Relief Valves for Air and Inert Gas

For Use With: Air, Inert Gas
Specifications Met: ASME BPVC.VIII
Temperature Range: -20° to 406° F

These valves meet ASME Code Section VIII for use with air and inert gas pressure vessels. Commonly used with high-volume blowers, compressors, and air-powered conveyors, they quickly relieve a large amount of air in systems with a pipe size of 2 or greater. They spring fully open at the set pressure and remain open until the system pressure is restored below the set pressure. Attach a drain line to the threaded relief port for remote discharge. Valves have a cast iron body to absorb vibration for reduced noise and wear in your pipeline.

For technical drawings and 3-D models, click on a part number.

Inlet			Relief Port
Pipe Size	Location	Maximum Pressure, psi	Pipe Size	Location	Overall Ht.	Test Mechanism	Valve Type	Choose a Set Pressure, psi		Each
NPT Male Inlet and NPT Female Relief Port
Cast Iron Body—Bronze Seal
2	Bottom	60	2	Side	7"	T-Handle	Pop Safety	16, 18, 20, 22, 24, 26, 28, 30, 32, 34, 36, 38, 40, 42, 44, 46, 48, 50, 52, 54, 56, 58, 60	0000000	0000000
2 1/2	Bottom	60	2 1/2	Side	8"	T-Handle	Pop Safety	16, 18, 20, 22, 24, 26, 28, 30, 32, 34, 36, 38, 40, 42, 44, 46, 48, 50, 52, 54, 56, 58, 60	0000000	000000
3	Bottom	60	3	Side	9"	T-Handle	Pop Safety	16, 18, 20, 22, 24, 26, 28, 30, 32, 34, 36, 38, 40, 42, 44, 46, 48, 50, 52, 54, 56, 58, 60	0000000	000000

Vibration-Damping Pressure-Regulating Valves for Water, Oil, Air, and Inert Gas

For Use With: Water, Oil, Air, Inert Gas
Temperature Range: See Table

A cast iron body absorbs vibration from pressure changes to reduce wear and noise in your pipeline. These valves automatically reduce a high, variable inlet pressure to a lower, stable outlet pressure. Adjust the outlet pressure within the range.

Internal strainers trap debris.

For technical drawings and 3-D models, click on a part number.

Inlet			Outlet
Pipe Size	Location	Max. Pressure, psi	Pipe Size	Location	Temperature Range	End-to-End Lg.	Choose an Outlet Pressure Range, psi		Each
NPT Female
Cast Iron Body—Buna-N Diaphragm and Seal with Internal Strainer
1/4	Side	200	1/4	Side	32° to 180° F	3"	2 to 25, 20 to 60	0000000	0000000
3/8	Side	200	3/8	Side	32° to 180° F	3 7/8"	2 to 30, 20 to 70, 40 to 110, 90 to 150	0000000	000000
1/2	Side	200	1/2	Side	32° to 180° F	4 1/2"	10 to 50, 2 to 30, 30 to 125, 50 to 125	0000000	000000
3/4	Side	200	3/4	Side	32° to 180° F	5 1/8"	10 to 35, 105 to 125, 2 to 20, 30 to 75, 50 to 110	0000000	000000
1	Side	200	1	Side	32° to 180° F	5 7/8"	10 to 45, 2 to 20, 20 to 60, 55 to 100, 90 to 125	0000000	000000
1 1/4	Side	200	1 1/4	Side	32° to 180° F	6 3/4"	10 to 30, 2 to 15, 20 to 50, 45 to 100, 90 to 150	0000000	000000
1 1/2	Side	200	1 1/2	Side	32° to 180° F	6 3/4"	10 to 30, 2 to 15, 20 to 50, 45 to 100, 90 to 125	0000000	000000
2	Side	200	2	Side	32° to 180° F	9 1/4"	10 to 60, 2 to 20, 20 to 100, 90 to 125	0000000	000000
Cast Iron Body—Fluoroelastomer Diaphragm and 420 Stainless Steel Seal
3/8	Side	250	3/8	Side	32° to 300° F	4 1/4"	0 to 10, 10 to 50, 100 to 200, 40 to 100	0000000	000000
1/2	Side	250	1/2	Side	32° to 300° F	3 5/8"	0 to 10, 10 to 50, 100 to 200, 40 to 100	0000000	000000
3/4	Side	250	3/4	Side	32° to 300° F	3 5/8"	0 to 10, 10 to 50, 100 to 200, 40 to 100	0000000	000000
1	Side	250	1	Side	32° to 300° F	4 1/2"	0 to 10, 10 to 30, 30 to 50, 40 to 85	0000000	000000
2	Side	250	2	Side	32° to 300° F	6 1/2"	0 to 10, 10 to 30, 30 to 50, 40 to 85	0000000	000000

Pressure-Regulating Valves for Steam

For Use With: Steam
Temperature Range: -20° to 400° F

Automatically reduce a high, variable inlet pressure in your steam system to a lower, stable outlet pressure. Adjust the outlet pressure within the range. These valves have a cast iron body that absorbs vibration from pressure changes to reduce wear and noise in your pipeline.

Internal strainers trap debris.

For technical drawings and 3-D models, click on a part number.

Valves
Inlet			Outlet						Repair Kits
Pipe Size	Location	Max. Pressure, psi	Pipe Size	Location	End-to-End Lg.	Choose an Outlet Pressure Range, psi		Each		Each
NPT Female
Cast Iron Body—Bronze Diaphragm and 420 Stainless Steel Seal
1/2	Side	250	1/2	Side	3 5/8"	0 to 10, 10 to 50, 40 to 100, 100 to 200	0000000	0000000	0000000	000000
3/4	Side	250	3/4	Side	3 5/8"	0 to 10, 10 to 50, 40 to 100, 100 to 200	0000000	000000	0000000	00000
1	Side	250	1	Side	4 1/2"	0 to 10, 10 to 30, 30 to 50, 40 to 85	0000000	000000	0000000	000000
1 1/4	Side	250	1 1/4	Side	4 1/2"	0 to 10, 10 to 30, 30 to 50, 40 to 85	0000000	000000	0000000	000000
1 1/2	Side	250	1 1/2	Side	6 1/2"	0 to 10, 10 to 30, 30 to 50, 40 to 85	0000000	000000	0000000	000000
2	Side	250	2	Side	6 1/2"	0 to 10, 10 to 30, 30 to 50, 40 to 85	0000000	000000	0000000	000000
Cast Iron Body—Bronze Diaphragm and PTFE Seal with Internal Strainer
1/4	Side	150	1/4	Side	3"	2 to 25, 20 to 60, 30 to 100	0000000	000000	000000	00
3/8	Side	150	3/8	Side	3 7/8"	2 to 30, 20 to 70, 40 to 110, 90 to 150	0000000	000000	000000	00
1/2	Side	150	1/2	Side	4 1/2"	2 to 30, 10 to 50, 30 to 125, 50 to 150	0000000	000000	0000000	000000
3/4	Side	150	3/4	Side	5 1/8"	2 to 20, 10 to 35, 30 to 75, 50 to 110, 105 to 150	0000000	000000	0000000	000000
1	Side	150	1	Side	5 7/8"	2 to 20, 10 to 45, 20 to 60, 55 to 100, 90 to 150	0000000	000000	0000000	000000
1 1/4	Side	150	1 1/4	Side	6 3/4"	2 to 15, 10 to 30, 20 to 50, 45 to 100, 90 to 150	0000000	000000	0000000	000000
1 1/2	Side	150	1 1/2	Side	6 3/4"	2 to 15, 10 to 30, 20 to 50, 45 to 100, 90 to 150	0000000	000000	0000000	000000
2	Side	150	2	Side	9 1/4"	2 to 20, 10 to 60, 20 to 100, 90 to 150	0000000	000000	0000000	000000

High-Accuracy Pressure-Regulating Valves for Steam

For Use With: Steam
Temperature Range: 40° to 450° F

Control steam line pressure with ±1 psi accuracy. These valves automatically reduce a high, variable inlet pressure to a lower, stable outlet pressure. Adjust the outlet pressure within the range. Valves have a cast iron body that absorbs vibration from pressure changes to reduce wear and noise in your pipeline. They meet ANSI/FCI 70-2 Class IV for tight shut-off (max. leakage rate of 0.01%). Install 1/4 NPT male pipe (not included) between the control valve and your downstream steam line.

Repair kits (sold separately) include replacement seals, diaphragm, spring, and spring assembly.

For technical drawings and 3-D models, click on a part number.

Valves
Inlet			Outlet					Repair Kits
Pipe Size	Location	Max. Pressure, psi	Pipe Size	Location	Choose an Outlet Pressure Range, psi		Each		Each
NPT Female
Cast Iron Body—301 Stainless Steel Diaphragm and 420 Stainless Steel Seal
1/2	Side	250	1/2	Side	3 to 20, 5 to 50, 10 to 100, 20 to 150	0000000	000000000	0000000	0000000
3/4	Side	250	3/4	Side	3 to 20, 5 to 50, 10 to 100, 20 to 150	0000000	00000000	0000000	000000
1	Side	250	1	Side	3 to 20, 5 to 50, 10 to 100, 20 to 150	0000000	00000000	0000000	000000
1 1/4	Side	250	1 1/4	Side	3 to 20, 5 to 50, 10 to 100, 20 to 150	0000000	00000000	0000000	000000
1 1/2	Side	250	1 1/2	Side	3 to 20, 5 to 50, 10 to 100, 20 to 150	0000000	00000000	0000000	000000
2	Side	250	2	Side	3 to 20, 5 to 50, 10 to 100, 20 to 150	0000000	00000000	0000000	00000000

Back-Pressure-Regulating Valves for Water and Oil

For Use With: Water, Oil
Temperature Range: -40° to 200° F

Commonly used as bypass lines after centrifugal, reciprocating, and rotary pumps, these valves obstruct flow to maintain sufficient operating pressure in your system. If the system pressure exceeds the set pressure, they exhaust through the threaded relief port. Adjust the set pressure within the range. Valves have a cast iron body that absorbs vibration from pressure changes to reduce wear and noise in your pipeline.

For technical drawings and 3-D models, click on a part number.

Inlet			Outlet		Relief Port
Pipe Size	Location	Max. Pressure, psi	Pipe Size	Location	Pipe Size	Location	End-to-End Lg.	Choose an Outlet Pressure Range, psi		Each
NPT Female
Cast Iron Body—Nickel Alloy Diaphragm and 303 Stainless Steel Seal
1/2	Side	400	1/2	Side	1/2	Bottom	2 7/8"	0 to 25, 5 to 50, 30 to 100, 75 to 175, 150 to 400	0000000	0000000
1 1/4	Side	400	1 1/4	Side	1 1/4	Bottom	4 1/4"	20 to 85, 40 to 125, 50 to 230, 175 to 380, 300 to 400	0000000	00000000
1 1/2	Side	400	1 1/2	Side	1 1/2	Bottom	5"	10 to 55, 30 to 100, 40 to 200, 125 to 300, 200 to 400	0000000	00000000
2	Side	400	2	Side	2	Bottom	5"	10 to 55, 30 to 100, 40 to 200, 125 to 300, 200 to 400	0000000	00000000

Pressure-Relief Hydraulic Valves

To set the pressure, unscrew the cap and turn the adjustment screw. Valves begin opening at the set pressure and fully open at about 10% over the set pressure. They begin closing as pressure drops and fully close when the system pressure is restored below the set pressure.

Iron valves absorb vibration to reduce noise and wear in the pipeline.

For technical drawings and 3-D models, click on a part number.

Iron

Inlet Connection		Relief Connection		O'all
Pipe Size	Dash Size	Pipe Size	Dash Size	Lg.	Wd.	Ht.	Temp. Range, °F	Choose a Set Pressure Range, psi		Each
NPT Female Inlet and NPT Female Relief Port
Iron Body
3/8	06	3/8	06	2 1/16"	1 3/8"	5 3/8"	-20° to 400°	3 to 10, 7 to 35, 30 to 100, 60 to 175, 150 to 350, 300 to 500	0000000	0000000
1/2	08	1/2	08	2 3/16"	1 7/16"	6 3/16"	-20° to 400°	3 to 10, 7 to 35, 30 to 100, 60 to 175, 150 to 350, 300 to 500	0000000	000000
3/4	12	3/4	12	2 11/16"	1 11/16"	6 15/16"	-20° to 400°	3 to 10, 7 to 35, 30 to 100, 60 to 175, 150 to 350, 300 to 500	0000000	000000
1	16	1	16	3 5/16"	2 1/16"	8 1/4"	-20° to 400°	3 to 10, 7 to 35, 30 to 100, 60 to 175, 150 to 350, 300 to 500	0000000	000000
1 1/4	20	1 1/4	20	3 13/16"	2 1/2"	9 9/16"	-20° to 400°	3 to 10, 7 to 35, 30 to 100, 60 to 175, 150 to 350, 300 to 500	0000000	000000
1 1/2	24	1 1/2	24	4 1/8"	2 7/8"	11 1/16"	-20° to 400°	3 to 10, 7 to 35, 30 to 100, 60 to 175, 150 to 350, 300 to 500	0000000	000000
2	32	2	32	4 5/8"	3 1/4"	13"	-20° to 400°	3 to 10, 7 to 35, 30 to 100, 60 to 175, 150 to 350, 250 to 600	0000000	000000

Pressure-Regulating Inline Hydraulic Valves

When input pressure varies, use these valves to maintain a consistent pressure. They are often placed after a directional-control valve and before an actuator, such as a cylinder. They have an indicator/gauge port for the inlet and one for the outlet so you can monitor that output pressure remains steady.

For technical drawings and 3-D models, click on a part number.

Inlet/Outlet Connection		Relief Connection		O'all
Pipe Size	Dash Size	Pipe Size	Dash Size	Lg.	Wd.	Ht.	Choose a Set Pressure Range, psi		Each
NPT Female Inlet and Relief Port
Cast Iron Body
3/4	12	1/4	04	5 7/8"	3 3/4"	7 1/8"	100 to 1000, 500 to 2000, 1000 to 3000	000000	0000000