How to Replace Any Safety or Relief Valve
Brand doesn’t matter. Specifications do. Use this guide to collect the right information from your existing valve and find the correct replacement — regardless of who made the original.
Send Us Your Nameplate Configure a ReplacementThe Universal Truth About Safety Valves
Safety and relief valves are commoditized by specifications, not brand. A Kunkle, Apollo, Watts, Consolidated, or Crosby valve can be replaced by any manufacturer’s valve — as long as the critical specifications match or exceed the original. This is true across ASME Section I, Section IV, and Section VIII applications.
The challenge is knowing which specifications matter and where to find them on your existing valve. This guide walks you through exactly that.
3 Steps to Find Your Replacement
Collect Your Nameplate Data
Photograph the nameplate or record the key specifications listed below. If the nameplate is damaged or illegible, note the manufacturer’s name and any visible markings.
Check the 8 Specifications That Must Match
Use the checklist below to verify you have all the data needed for a code-compliant replacement. Pay special attention to specs NOT on the nameplate.
Get Your Replacement
Use our configurator, browse the shop, or send us your specs for a cross-reference. We’ll match the right Aquatrol valve to your application.
What’s on the Nameplate (and What Isn’t)
ASME and National Board standards require specific markings on every safety valve nameplate. But several critical replacement specs are not stamped on the nameplate — and missing them can result in a non-compliant installation or operational problems.
Replacement Specification Checklist
| ☐ | Specification | Why It Must Match | Where to Find It | Imperial / Metric |
|---|---|---|---|---|
| ☐ | ASME Code Section | Legal compliance requirement. Section I (fired boilers), Section IV (low-pressure heating), or Section VIII (unfired pressure vessels). Determines which code stamp the replacement must carry (V, HV, or UV). | Nameplate — code stamp symbol | — |
| ☐ | Set Pressure | Must not exceed the vessel’s Maximum Allowable Working Pressure (MAWP). Operating pressure is typically 10% below set pressure. | Nameplate — stamped in PSI | psig / kPag / barg |
| ☐ | Rated Capacity | Replacement must meet or exceed original capacity. Under-sizing is a code violation; over-sizing is acceptable. | Nameplate — rated in lbs/hr, SCFM, or GPM | lbs/hr & Nm³/hr SCFM & LPM GPM & kg/hr |
| ☐ | Valve Series | Identifies the valve design family and determines body material, internal construction, and available configurations. Sometimes listed as “Model” on other manufacturers’ nameplates. | Nameplate — model/series number | — |
| ☐ | Inlet Size & Type | Physical fit — must match existing pipe connections. Common types: NPT threaded, flanged (150#, 300#, 600#), tri-clamp (sanitary). | Nameplate + physical measurement | inches / DN (mm) |
| ☐ | Outlet Size & Type | Must match discharge piping. Outlet is often larger than inlet per code requirements. | Nameplate + physical measurement | inches / DN (mm) |
| ☐ | Service Medium | Steam, air/gas, or liquid service. Determines valve internals, seat design, and capacity calculation method. | Nameplate or system documentation | — |
| ☐ | Orifice Size | Determines flow capacity. Designated by standardized letter codes (D, E, F, G, H, J, K, L, M, N, P, Q, R, T). Larger orifice = higher capacity. | Nameplate — letter code | — |
The following specs are not stamped on most nameplates but are just as important for a correct replacement. Missing any of these can result in operational failures, compliance issues, or safety hazards.
Hidden Specs — Must Be Verified Separately
| ☐ | Specification | Why It’s Critical | How to Determine |
|---|---|---|---|
| ☐ | Seating Material | Determines seal tightness and media compatibility. A soft seat (PTFE, Buna-N, Viton) provides a tighter seal than metal-to-metal. If the original valve had a soft seat and the replacement has metal-to-metal, it may weep at operating pressure. Seat material must also be compatible with the process fluid — especially important in chemical, food/beverage, and pharmaceutical applications. | Disassemble the valve, check the original spec sheet, or contact us for guidance based on application. |
| ☐ | Cap Type / Lever | Valves come in three configurations: lift lever (open handle for manual testing), packed lever (sealed handle for hazardous/outdoor service), or closed cap (no lever — tamper-resistant). Your facility’s test procedures likely reference a specific lever type. Matching the wrong cap type can mean non-compliance with your testing protocol. | Visual inspection of the existing valve. Check your maintenance/test procedures for lever requirements. |
| ☐ | Flange Configuration | If the original valve uses non-standard or manufacturer-specific flange dimensions, the replacement must match the bolt pattern and face dimensions — or you’ll need an adapter or custom flange. | Measure bolt circle, number of bolts, flange OD, and face finish. We manufacture custom flanges to match competitor dimensions. |
Pressure & Capacity Unit Conversions
Safety valve specifications are expressed in different units depending on your region. Use these conversion tables when working with international equipment or ordering from overseas suppliers.
Pressure Conversions
| From | To | Multiply By | Example |
|---|---|---|---|
| psig | kPag | 6.895 | 150 psig = 1,034 kPag |
| psig | barg | 0.06895 | 150 psig = 10.34 barg |
| kPag | psig | 0.1450 | 1,034 kPag = 150 psig |
| barg | psig | 14.504 | 10.34 barg = 150 psig |
| barg | kPag | 100 | 10.34 barg = 1,034 kPag |
Capacity / Flow Rate Conversions
| Measurement | Imperial Unit | Metric Unit | Conversion |
|---|---|---|---|
| Steam capacity | lbs/hr | kg/hr | 1 lb/hr = 0.4536 kg/hr |
| Air/gas volume flow | SCFM | Nm³/hr | 1 SCFM = 1.699 Nm³/hr |
| Liquid flow | GPM (US) | LPM | 1 GPM = 3.785 LPM |
| Pipe size | inches (NPS) | DN (mm) | 1″ = DN25, 1.5″ = DN40, 2″ = DN50 |
Common Pipe Size Reference
| NPS (inches) | DN (mm) | NPS (inches) | DN (mm) |
|---|---|---|---|
| 1/4″ | DN8 | 1-1/2″ | DN40 |
| 3/8″ | DN10 | 2″ | DN50 |
| 1/2″ | DN15 | 2-1/2″ | DN65 |
| 3/4″ | DN20 | 3″ | DN80 |
| 1″ | DN25 | 4″ | DN100 |
Common Reasons for Valve Replacement
Scheduled / Preventive
- NBIC-mandated testing intervals — Varies by jurisdiction, pressure, and application. Many jurisdictions require annual pop testing.
- 5-year replacement cycles — Required by IIAR Bulletin 109, ANSI/IIAR 2, and many facility insurance policies.
- Insurance recertification — Your insurer may require valve replacement or recertification on a defined schedule. If a valve fails a bench test, it must be replaced.
- Inspector findings — Annual boiler or pressure vessel inspections frequently flag aging or non-compliant safety valves.
Reactive / Failure
- Valve discharges and won’t reseat — Often caused by seat damage, debris, or operating too close to set pressure.
- Visible leaking, dripping, or weeping — Indicates seal failure. Especially common when soft seats degrade over time.
- Failed pop test — Valve doesn’t open at set pressure during bench or field testing. Must be replaced immediately.
- Physical damage — Cracks, dents, corrosion, frozen/stuck lever. Any physical compromise disqualifies the valve from service.
Who’s Involved in the Replacement Process
Safety valve replacement typically involves multiple people. Information must transfer cleanly between whoever discovers the problem and whoever places the order:
- Maintenance technician discovers the issue — takes a photo of the nameplate or records the data.
- Technician or supervisor brings the valve (or the data) to purchasing, or looks up the replacement themselves.
- Purchasing places the order based on the specs provided.
- Technician or contractor installs the replacement.
Frequently Asked Questions
Can I replace a Kunkle / Apollo / Watts valve with an Aquatrol?
Yes, in nearly all cases. Safety valves are interchangeable across manufacturers as long as the ASME code stamp, set pressure, capacity, connections, service medium, and materials match. We cross-reference Kunkle, Apollo, Watts, Consolidated, and other brands to Aquatrol equivalents daily. See our Kunkle replacement guide.
What if my nameplate is illegible or missing?
Record whatever you can read, photograph the valve from multiple angles, and measure the inlet and outlet connections. We can often identify the valve series from physical characteristics and help you determine the right replacement specs from there.
Does the replacement capacity need to match exactly?
The replacement capacity must meet or exceed the original. Over-sizing is acceptable and common; under-sizing is a code violation. If you’re unsure about capacity requirements, provide the vessel data (MAWP, volume) and we can help calculate the required relieving capacity.
What’s the difference between a lift lever, packed lever, and closed cap?
A lift lever has an open handle for manual field testing — pull the lever to verify the valve opens. A packed lever has a sealed lever for outdoor or hazardous environments where you need testing capability but want environmental protection. A closed cap has no lever at all — it’s tamper-resistant and used where manual testing isn’t required or must be prevented. Your facility’s test procedures will typically specify which type is required.
What if my valve has a non-standard flange?
Some manufacturers use proprietary or non-standard flange dimensions. We can machine custom flanges to match your existing bolt pattern and face dimensions, so you can install an Aquatrol replacement without modifying your piping. Contact us with your flange measurements for a quote.
Do I need to match the seating material?
You should. If the original valve had a soft seat (PTFE, Buna, Viton) and the replacement has metal-to-metal, it may weep or leak at operating pressure. Conversely, if the original was metal-to-metal and operated fine, a soft seat upgrade may improve performance. The key is knowing what you’re replacing and whether the seat material is compatible with your process fluid.
How do I convert between PSI and metric pressure units?
Multiply PSI by 6.895 to get kPa, or by 0.06895 to get bar. See our full conversion tables above. We list our capacity charts in both imperial and metric units.
Need Help Finding Your Replacement?
Send us a photo of your valve nameplate and we’ll identify the right Aquatrol replacement — usually within one business day. We cross-reference all major manufacturers.
Send Us Your Nameplate Configure a Valve Now