API · ASME · DIN · EN standard industrial valves
Silent Check Valves
Silent check valves stop reverse flow before it can accelerate: a spring-assisted disc travels a short stroke and seats quietly, avoiding the slam and water hammer of conventional swing checks — the behaviour that gives the type its name. US executions align with MSS SP-126 for steel in-line spring-assisted centre-guided checks; European water-works executions are designed to EN 12334 with EN 1092 flanges and EN 12266-1 acceptance, and wafer axial-flow bodies follow API 594 face-to-face. Typical class coverage runs DN50-DN600 (2"-24") at PN10-PN40 / ANSI Class 125-300 in cast iron, ductile iron, WCB carbon steel or CF8M stainless; end connections are confirmed per execution at RFQ; a representative ductile-iron water execution covers DN50-DN400 PN10/16/25 from -10 C to 110 C on water/glycol. Opening starts near 0.5 psi differential with full opening around 1.0 psi on light-spring designs, soft seats give bubble-tight shutoff, and the streamlined short-stroke trim keeps head loss low with quick seat replacement. Spring closure makes the type orientation-forgiving (except downward gravity flow), adds a small pressure-drop penalty versus gravity tilting discs, and the disc travel helps shed seat debris. Selection turns on size versus line velocity, pressure class, end connection, seat material and media temperature.
Part of the Check Valves family
Last updated: 2026-10
Family specifications
| size range | DN50-DN600 (2in-24in) |
|---|---|
| pressure class | PN10-PN40 / ANSI Class 125-300 |
| body materials | cast iron, ductile iron, WCB carbon steel, CF8M stainless |
| testing standards | Pressure acceptance on the referenced EN executions is seat testing at 1.1 times rated pressure and body testing at 1.5 times, per EN 12266-1. |
| face to face | Wafer-style axial-flow silent checks are dimensioned to API 594 face-to-face so they fit between mating flanges without pipe changes. |
| closing mechanism | Closure is spring-assisted: the spring drives the disc onto the seat before reverse flow can accelerate, which is what removes the slam and water-hammer behaviour of swing, tilting-disc and double-door checks. |
| opening differential | Typical opening behaviour for spring silent checks is a start of opening at roughly 0.5 psi differential with full opening around 1.0 psi, so the valve responds to low forward flow without chattering. |
| cracking pressure by design | Cracking pressure depends on the closing design: gravity-closed tilting-disc checks open near 0.5 psi, while spring-loaded executions typically need about 5 psi, with adjustable springs available on some models. |
| standards mss sp126 | In the US frame, silent check valves are covered by MSS SP-126 for steel in-line spring-assisted centre-guided check valves. |
| standards en frame | In the European water-works frame the same family is designed to EN 12334, with flange drilling to EN 1092 (PN10/16/25); wafer executions follow API 594 face-to-face and DIN-flanged executions MSS SP-125 short-globe face-to-face. |
| size class envelope | A representative ductile-iron flanged execution covers DN50-DN400 at PN10/16/25; the tenant catalogue band (DN50-DN600, PN10-PN40 / ANSI 125-300) spans multiple OEM envelopes rather than one. |
| temperature envelope | The epoxy-coated ductile-iron water execution is rated for water and glycol mixtures from -10 C to 110 C; higher-temperature service moves to steel bodies and metal seats. |
| trim materials | In the referenced ductile-iron execution the body is GJS-500-7, seat and disc are stainless steel 1.4308, the closing spring is 1.4301, seals are EPDM and internal/external surfaces carry fusion-bonded epoxy coating. |
| seat options | Seat selection spans soft seats for bubble-tight shutoff and metal seats for durability and high temperature tolerance, soft-seat temperature limits follow the elastomer rather than the body. |
| media scope | Spring silent checks serve liquid, gas and steam service; the referenced water-works executions are limited to clean neutral liquids such as water and glycol mixtures. |
| orientation | Installation is flexible across horizontal and vertical lines; the spring, not gravity, returns the disc, so orientation does not change closing behaviour. |
| orientation limit | The one orientation caveat is gravity: on vertical lines with upward flow spring checks work in any orientation, but a check valve cannot close reliably against downward gravity flow. |
| head loss design | Head loss is controlled by a streamlined internal contour plus a light disc on a short stroke, and the same fast-closing spring design is what mitigates slamming. |
| spring drag dp | The spring adds a modest pressure-drop penalty compared with a gravity tilting disc, which is the trade for predictable spring-determined closure timing. |
| self cleaning | Disc travel under spring action helps dislodge debris from the seat area, so spring checks tolerate moderate solids better than gravity-tilted designs. |
| maintainability | The seat is designed for quick trim replacement in line, reducing turnaround when the seat erodes. |
| compact wafer savings | Wafer-body silent checks sandwich between standard flanges and save up to roughly 80 percent of the space and weight of a flanged swing check, cutting support load on large lines. |
| outlet butterfly mounting | On sizes up to and including DN200 the referenced design allows a butterfly valve to be mounted directly at the silent check valve outlet without adapter pieces. |
| peer threaded style sizes | Threaded Style available in sizes 1/2"-2" |
| peer wafer style sizes | Wafer Style available in sizes 2"-10" |
| peer globe style sizes | Globe Style available in sizes 2 1/2 ”- 42” |
| peer clean water scope | Ideal for clean water service - contact factory for other service |
| peer lead free certification | NSF 372 Certified Lead-Free - Globe Style |
| peer drinking water certification | NSF 61 Certified for Drinking Water - Globe Style |
| peer fm approval wafer | FM Approved Wafer Style - 2" to 10" |
| peer mss sp125 conformance | Meets MSS-SP 125 |
| peer seating construction | Precision metal-to-metal seating |
| peer disc guidance | Double guided disc - prevents vibrations and wear |
| peer resilient seat option | Resilient Seat - available for zero leakage |
| peer spring cycle rating | Heavy Duty Spring is tested for over 100,000 cycles |
| peer center guided design | center guided single disc and stainless to stainless seating with special stainless steel spring control to insure positive, noiseless opening and closing. |
| peer flange class fit | Rated to both 125 lb. And 250 lb. Flange class |
| peer activation dp | Activated at 1/4 to 1/2 psi |
| peer flow area design | Designed with larger-than-pipe-size flow area for low pressure loss with maximum efficiency. |
| peer service liquid only | Intended for liquid service only. |
| peer bolt circle fit | Fits both 250# Class bolt circle and 125# Class bolt circle. |
| peer globe style size range | Made in fourteen standard sizes: 2-1/2′′ through 30′′ |
| peer butterfly mating execution | 2-1/2′′ through 10′′ valves mate to wafer-style butterfly valves without use of spool pieces or other adapters. |
| peer companion flange drilling | Specify drillings to meet either 125/150 lb. or 250/300 lb. companion flanges. |
| peer spring closure sequence | When the pump stops and the flow ceases, the force of the spring will automatically close the disc prior to flow reversal. This creates a positive shutoff against flow reversal and minimizes system surges and water hammer. |
| peer disc opening trigger | When the pump starts and the downstream flow creates the required pressure drop in the forward direction, the disc will automatically open. |
Scope & source notes
| cracking pressure | Cracking pressure: DFT states its silent checks start opening at ~0.5 psi differential (full open ~1.0 psi), while the industry-reference tilting-disc frame lists ~5 psi for spring-loaded executions - opening threshold depends on spring sizing and design family, not a single industry value. |
|---|---|
| face to face framing | Face-to-face framing: wafer axial-flow executions follow API 594 while the referenced EN ductile-iron execution follows MSS SP-125 short-globe dimensions - standard depends on body execution, not on the silent-check type. |
Ordering & documentation
Documents
Ask for the documentation set with the inquiry — typical items (material certificates, test reports to the listed inspection standard, dimensional drawings) are confirmed and supplied with the quotation.
Quotation
Send the medium, temperature, pressure, size and connection for a quotation-ready inquiry. Lead time, MOQ and price are confirmed at quotation, together with the documents to be supplied with the order.
Sample & supply
Supply terms, order quantities and lead time are agreed per order — state the destination country and required schedule with the inquiry.
Storage & shipping
Store valves with seats and seals protected from UV, ozone and deformation, and keep end-face protectors on until installation; storage limits and shipping arrangements for the selected materials are confirmed at quotation.
Frequently asked questions
What sizes and pressure ratings are available for silent check valves?
The published size range is DN50-DN600 (2in-24in), and the published pressure ratings are PN10-PN40 / ANSI Class 125-300. Availability of a specific size and rating is confirmed at quotation.
What materials are silent check valves available in?
The published specification lists body materials: cast iron, ductile iron, WCB carbon steel, CF8M stainless. Material availability for a specific size and rating is confirmed at quotation.
What should a quotation inquiry for silent check valves include?
The governing standard and class, nominal size, body and seat materials, the service medium with temperature, and the destination — anything missing is confirmed during quotation.
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