Caleffi 519 User Manual

CALEFFI

www.caleffi.com

38482.03

Adjustable differential pressure by-pass valve with graduated scale

519 Series

Function

The differential pressure by-pass valve is used in systems with a fixed speed circulating pump supplying several zones controlled by two way zone valves. This valve ensures that the head pressure of the pump is proportional to the number of two way valves being closed. It will bypass the differential pressure created by the pump as the zone valves close, thus eliminating water hammer noise.

Product range

Code 519502A By-pass with flow up to 9 gpm. Size 3/4" MNPT

union inlet x 3/4" MNPT union outlet

Code 519599A By-pass with flow up to 9 gpm. Size 3/4" Sweat

union inlet x 3/4" Sweat union outlet

Code 519600A By-pass with flow up to 40 gpm Size 1" FNPT

inlet x 1" MNPT union outlet

Code 519609A By-pass with flow up to 40 gpm Size 1” Female

NPT x 1” sweat outlet

Code 519700A By-pass with flow up to 45 gpm Size 1 1/4" FNPT

inlet x 1 1/4" MNPT union outlet

Code 519709A By-pass with flow up to 45 gpm Size 1 1/4" FNPT

inlet x 1 1/4" Sweat union outlet

Technical characteristics

Materials

Body: brass Valve plug: brass Valve plug gasket: EPDM O-Ring seals: EPDM Union seals: asbestos free NBR Control knob: ABS Spring: stainless steel

Performance

Suitable fluids: water, glycol solutions Max percentage of glycol: 30% Temperature range: 32–230°F (0–110°C) Maximum working pressure: 150 psi (10 bar) Flow rates: 3/4” flow up to 9 gpm

1” flow up to 40 gpm

1 1/4” flow up to 45 gpm

Setting range: 1 - 6 m w.g. (2 - 10 psi)

SAFETY INSTRUCTION

This safety alert symbol will be used in this manual to draw attention to safety related instructions. When used, the safety alert symbol means ATTENTION! BECOME ALERT!

YOUR SAFETY IS INVOLVED! FAILURE TO FOLLOW THESE INSTRUCTIONS MAY RESULT IN A SAFETY HAZARD.

Flow rate G

∆p

NOMINAL

Pump curve

∆p constant on the circuit

Circuit resistance curve with two-way valves partially open

Circuit resistance curve with two-way valves fully open

∆G

50% 100%

Two-way

TOTAL LOAD

mH2O

1 2 3 4 5 6

PARTIAL LOAD

mH2O

1 2 3 4 5 6

CAUTION: All work must be performed by qualified personnel trained in the proper application, installation, and maintenance of systems in accordance with all applicable codes and ordinances.

Operating principle

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System operation

O = open C = close

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CAUTION: Over-tightening and breakage can occur with the use of Teflon pipe joint compounds. Teflon®provides lubricity so that care must be exercised not to over-tighten joints. Failure to follow these instructions could result in property damage and /or personal injury.

WARNING: System fluids are under pressure or temperature can be hazardous. Be sure the pressure has been reduced to zero and the system temperature is below 100°F (38°C). Failure to follow these instructions could result in property damage and/or personal injury.

When the spring (1) compression is adjusted using the control knob (2), the force balance acting on the valve plug (3) changes, thus modifying the threshold pressure value

of the valve. The valve plug opens, activating the by-pass circuit, only when it is subjected to a differential pressure sufficient to generate a thrust greater than the thrust exerted by the spring. This allows the flow discharge through the outlet (4), limiting the difference in pressure between the two points in the system where the valve is fitted.

The job of the differential pressure by-pass valve is to maintain the

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pump operating point as close as possible to its nominal value (point A on the graph shown below). If the by-pass valve is not used, when the flow rate in the circuit decreases due to partial closure of the twoway zone valves, the head loss in the circuit increases, point B. The by-pass valve, set to the nominal head value of the pump, limits the increase in pressure, by-passing the flow rate ∆G. This behavior is guaranteed at any closing condition of the system twoway zone valves. In fact, once the position of the valve control knob has been established, the threshold pressure value is more or less constant as the discharge flow rate varies (see hydraulic characteristic diagrams). A proper valve sizing must guarantee a sufficient flow rate by-pass to keep the pump at its nominal operating point in all system operating conditions, for example when the first zone valves are closed.

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