Generant Cryogenic Relief Valve, 1/4" MNPT, 10 to 350 PSI, -320 F
ABOUT THIS PART
Generant brass cryogenic relief valve, 1/4 in MNPT male, factory set and permanently locked. Nine set pressures from 10 to 350 psi (0.7 to 24.1 bar). $84.00, with three pressures on clearance from $39.00.
These are the relief valves fitted to N.B. Oler hydrocarbon systems and the ones we resupply to the people running them.
The short version
- Connection: 1/4 in MNPT male, port code 250B
- Orifice: 0.250 in (6.35 mm). The 1/2 in valve uses the same orifice and does not flow more
- Flow: 117 SCFM at a 250 psi (17.2 bar) setting, per 3P Certz engineering report ECR-250902-R0
- Full rated flow at 110 percent of set pressure. Back pressure to 10 percent has no effect on the setting
- Brass body, 302 stainless or 17-4PH spring, seal changes with set pressure
- Set pressure is factory locked and stamped on the valve. It is not adjustable
- Not ASME coded. If an inspector wants a stamp, see the Generant RVA in 1/2 in
- Cleaned and packaged for oxygen service, 100 percent factory tested, screened Dirt Guard poppet
Set pressures and price
| Set pressure | Price |
|---|---|
| 10 psi (0.7 bar) | $84.00 |
| 22 psi (1.5 bar) | $42.00, clearance |
| 50 psi (3.4 bar) | $84.00 |
| 100 psi (6.9 bar) | $84.00 |
| 150 psi (10.3 bar) | $42.00, clearance |
| 200 psi (13.8 bar) | $39.00, clearance |
| 250 psi (17.2 bar) | $84.00 |
| 300 psi (20.7 bar) | $84.00 |
| 350 psi (24.1 bar) | $84.00 |
The 22, 150 and 200 psi are being cleared from stock below our normal price. Same valve, same factory setting, same warranty. When they are gone the price returns to $84.00.
Pick the pressure for the location. Do not buy one and try to turn it.
How cold it goes depends on the set pressure
| Set pressure | Seal | Temperature range |
|---|---|---|
| 10 to 49 psi (0.7 to 3.4 bar) | Fluorosilicone | -85 F to 350 F (-65 C to 176 C) |
| 50 psi (3.4 bar) and above | PCTFE | -320 F to 165 F (-196 C to 74 C) |
So the 10 psi and the 22 psi are not -320 F (-196 C) valves, and the 50 psi and up do not reach 350 F (176 C). For genuinely cryogenic service order 50 psi or higher.
Which pressure goes where
| Location on a 20 LB system | Set pressure |
|---|---|
| Solvent vessel | 250 psi (17.2 bar) |
| Solvent vessel jacket | 100 psi (6.9 bar) |
| Chiller line and jacket inlets | 22 psi (1.5 bar) |
| Material column | 250 psi (17.2 bar) |
| Material column jacket | 100 psi (6.9 bar) |
| Color remediation column | 250 psi (17.2 bar) |
| Recovery vessel | 250 psi (17.2 bar) |
| Molecular sieve | 250 psi (17.2 bar) |
| CO2 supply | 350 psi (24.1 bar) |
| Manifold | Varies by build |
From 3P Certz Certificate of Conformance 3PC0930. Your build sheet governs.
When to replace, and what to keep on the shelf
| What the valve does | Replace at |
|---|---|
| Pops off constantly | 3 months |
| Just sees cold and discolors | 6 months |
| Neither of those | 12 months |
Discoloration means cold cycling, and a valve you have heard vent this month is a three month valve.
Spares, from our operators manual: 22 psi three plus one, 100 psi one plus one, 200 psi one plus one, 250 psi six plus one, 350 psi two plus one.
Before you order
- Match the number stamped on the valve you are replacing
- Below 50 psi (3.4 bar) you are buying a -85 F (-65 C) valve, not a -320 F (-196 C) valve
- Need an ASME stamp? Order the Generant RVA instead
- More detail: Cryogenic relief valve selection
Usually on the shelf and ships from Bend, Oregon. When a set pressure is out, figure one to two weeks.
SPECIFICATIONS
▦ IN YOUR MANUAL
This part appears in the operator manual that ships with your system. The QR code there links to this page.
◈ REFERENCE FOR THIS PART
COMMON QUESTIONS
How do I know which set pressure I need?
Look at the valve already on your system and match the number stamped on it. You are replacing what is there, not sizing something new. If the stamp is unreadable, the fitment table on this page gives the standard pressure for each location on a 20 LB system, and your build sheet governs.
Which set pressure goes where on a 20 LB system?
250 psi (17.2 bar) on the solvent vessels, material columns, color remediation column, recovery vessel and molecular sieve. 100 psi (6.9 bar) on the solvent vessel and column jackets. 22 psi (1.5 bar) on the chiller line and jacket inlets. 350 psi (24.1 bar) on the CO2 supply. Manifold ratings vary by build. This comes from 3P Certz Certificate of Conformance 3PC0930.
Is the set pressure adjustable?
No. Every Generant CRV is factory preset and permanently locked, and permanently stamped with the part number and the setting. It cannot be altered or adjusted in the field. Order the pressure you need.
Is the 10 psi valve rated to -320 F (-196 C)?
No. At 10 to 49 psi (0.7 to 3.4 bar) the seal is Fluorosilicone and the rating is -85 F to 350 F, which is -65 C to 176 C. At 50 psi (3.4 bar) and above the seal is PCTFE and the rating is -320 F to 165 F, which is -196 C to 74 C. For genuinely cryogenic service use 50 psi (3.4 bar) or higher.
Does the 1/2 inch relief valve flow more than the 1/4 inch?
No. Both use a 0.250 inch (6.35 mm) orifice, so relieving capacity is the same. Choose by the port on your vessel, not by expected flow.
What flow rate does this valve relieve?
Our third party certification report, 3P Certz ECR-250902-R0, publishes 117 SCFM at a 250 psi (17.2 bar) setting through a 0.250 inch (6.35 mm) orifice. Actual capacity depends on the medium, the set pressure and the back pressure. Tell us the medium and the set pressure and we will run the number.
How often should a relief valve be replaced?
It depends on what it sees. A valve that pops off constantly should be replaced every 3 months. A valve that just sees cold and discolors is closer to 6 months. An ASME relief on a large vessel that rarely lifts goes 12 months. Discoloration means cold cycling, and a valve you have heard vent this month is a 3 month valve.
How many spares should I keep on the shelf?
From the N.B. Oler operators manual: 22 psi (1.5 bar), three plus one spare. 100 psi (6.9 bar), one plus one. 200 psi (13.8 bar), one plus one. 250 psi (17.2 bar), six plus one. 350 psi (24.1 bar), two plus one.
Is this an ASME coded relief valve?
No. This is the brass CRV. The ASME BPVC Section XIII coded and National Board stamped valve is the Generant RVA, which N.B. Oler offers in 1/2 inch at 22 and 100 psi (1.5 and 6.9 bar).
How accurate is the set pressure?
Per EN ISO 4126-1, plus or minus 5 percent at or below 28.90 psi (1.99 bar), plus or minus 1.45 psi (0.10 bar) from 29.00 to 48.30 psi (2.00 to 3.33 bar), and plus or minus 3 percent at or above 48.40 psi (3.34 bar).
Can I use it on liquid CO2, nitrogen or oxygen?
Yes, on liquid and vapor, provided the set pressure is 50 psi (3.4 bar) or above so the seal is PCTFE. Every valve is supplied cleaned and packaged for oxygen service.
Why are some pressures cheaper?
The 22, 150 and 200 psi are being cleared from stock below our normal price. Same valve, same factory setting, same warranty. When they are gone the price returns to $84.00.
What happens if the valve gets dirty?
Generant fits a screened Dirt Guard poppet specifically to tolerate particulate. Trash on the seat is the usual reason a relief valve in this service stops resealing, and the screen is there to delay that. It does not make the valve permanent.
What is the lead time?
Usually on the shelf and ships from Bend. When a set pressure is out, lead time is typically one to two weeks, and the longest we have ever seen is 12 weeks.