APCO CSC Silent Check Valve Wafer and Globe Style

Spring-loaded check valve that closes before flow reverses

The APCO CSC silent check valve is made by DeZURIK to mitigate water hammer by closing positively while there is still slight positive head on the inlet side. A stainless steel coil spring forces the plug onto the seat as the pump stops, so the disc is already closed when reverse flow would start, and the valve closes silently without regular maintenance.

The valve opens at roughly one quarter to one half psi (2 to 3 kPa). It is offered with a wafer body (model 300A, up to 10 in) or a globe body (model 600A, 3 to 42 in), so the range as a whole runs from 1 to 42 in (25 to 1100 mm), and the bulletin points to vertical turbine pump installations lifting water from a well to a reservoir, plus commercial and industrial HVAC, heating and condensate return lines.

CSC technical specification

Wafer style materials of construction

On globe style valves the plug seat ring, bushing retaining ring and plug ring screw are also 316 stainless steel, and the largest globe sizes use a ductile iron plug with a 316 stainless shaft (30 to 42 in) and a 17-7 PH spring is listed for 24 to 30 in. Contact the supplier for the exact trim of a 36 or 42 in valve.

How the design keeps head loss and wear low

The body contours are shaped for smooth flow and minimum loss, with a full cross-section at critical points larger than the matching pipe. The plug is center-guided at both ends by the shaft, and stainless bushing and shaft avoid electrolytic action between dissimilar metals, which supports a long service life.

Maintenance is simple. The seat and plug are hand replaceable in the field, and the bushing is held in place by the spring and a retaining ring so it can be removed easily. The resilient seat ring can be added later to convert a metal-seated valve to a resilient-seated one. The short face-to-face length saves space in equipment room piping layouts, and the valve can run silently in vertical flow up, flow down or horizontal positions.

Selection and ordering

The bulletin builds the code from style, size, model (300A or 600A), end connection, body material, then the seat and trim sequence. The printed example is CSC,10,600A,F1,DI,S2-M*, a 10 in globe style with flanged ASME 125/150 ends, ductile iron body, 316 stainless trim and metal seat.

Install the valve on the discharge side of the pump. With a silent check valve there, reverse flow toward the pump is eliminated, which is the main cause of water hammer, and the pump is protected. Typical drawings in the bulletin show a butterfly valve for isolation next to a wafer silent check valve downstream of vertical turbine pumps. Keep line velocity inside the recommended range, because very low flow lets the plug chatter against the spring.

Applications, standards and documents

Applicable standards listed include ASME B16.42 flat-faced flange drilling and FM 1230. As general engineering context, silent check valves of this kind appear on booster and transfer pump discharge lines, cooling water circuits and chilled water systems across Gulf buildings and plants, where closing speed matters as much as shutoff.

More check valves are listed under Check Valves. The bulletin 640 (04/2025) is attached with materials lists, Cv data and dimensions. Send the size, body style, end connection, body material, seat and temperature when requesting a quotation from Seven Star LLC.

Using the CSC in Oman and the GCC

Silent check valves are used in the region on pump discharge lines in water networks, booster stations, building water systems, district cooling and irrigation, wherever water hammer and slam must be kept low. Vertical turbine pumps drawing from wells and reservoirs are a typical application. The spring-assisted closure means the valve closes before the flow reverses, which protects pumps and pipework.

For seawater, brine or treated effluent, check the body, plug and spring materials against the water chemistry. Check the expected flow so the valve opens fully in normal service.

Where the valve replaces an existing check valve, send its face-to-face length and flange data so the new valve fits without pipe changes.

Information to send with an enquiry

• Size and model: wafer 300A or globe 600A
• Fluid, pressure and flow range
• Flange standard and materials
• Quantity