Inline Relief Valves

Pneu-Hydro bar stock relief valves remain bubble-tight up to cracking pressure. They reseal at less than 10% drop from cracking pressure in lower ranges, and less than 5% at higher ranges.

Cracking pressure is reliable, repeatable and easily set by an internal adjustment, which is tamper-proof once the valve is installed in the system. An O-ring seals the poppet while a metallic stop bears the spring load. This simple design provides crisp settings and long life. The standard valve is constructed of 316 stainless steel for strength and durability in the most corrosive applications.

Specifications

Operating pressure ranges
401 series	50 to 3,000 psid
402 series	3,000 to 10,000 psid
Operating temperature ranges
Buna-N seals	-40° to 250°F (-40° to 121°C)
Viton seals	-20° to 450°F (-29° to 232°C)

Ordering Information

Model Number	Pipe Size	Length	Hex	Cv	Pressure Range	Dash #
401F4Q-^1,2	1/4 NPT Female	3	15/16	.6	50 – 250 psid	-1
401F6Q-^1,2	3/8 NPT Female	4-1/4	1-3/8	1.3	250 – 600 psid	-2
401F8Q-^1,2	1/2 NPT Female	4-39/64	1-3/8	1.3	500 – 1,750 psid	-3
401M4Q-^1,2	1/4 NPT Male	3-1/2	15/16	.6	1,500 – 3,000 psid	-4
402F4Q-²	1/4 NPT Female	4-1/2	1-3/8	.6	3,000 – 10,000 psid	N/A
402F8Q-²	1/2 NPT Female	4-43/64	1-3/8	.6	3,000 – 10,000 psid	N/A

¹Dash number for desired pressure range must be inserted.
²Buna-N is standard elastomer and requires no code. For Viton, insert “V”. Consult factory for other materials.

For example, Model No. 401F4Q-2V specifies an inline relief valve with 1/4 NPT female ports, Viton O-rings, and a 250 – 600 psid range.

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