Triple Duty Valve Purpose
Triple duty valves combine three different types of valves typically on the discharge side of a hydronic pump system – a shut-off valve, check valve, and balancing/throttling valve – into one. Combining these valves can save space in crowded mechanical rooms, by far the triple duty valve’s most significant advantage.
Additionally, using a multi-purpose triple duty valve often provides substantial cost savings. Rather than paying for three individual valves, you’re only paying for one. That leads to dramatically reduced installation times, further reducing costs. Triple duty valves are a great economical choice.
How a Triple Duty Valve Works
There are components within a triple duty valve that allow it to function in the same way as three separate valves.
System Shut-Off
Positive shut-off, allowing isolation of the pump from the rest of the system, is available from both disc- and ball-style triple duty valves. If your triple duty valve has a ball, a concealed ball with a hole through the middle rotates to open or close the valve. Likewise, a triple duty valve disc will pivot and approach the seat with a “cam” action that results in high seating pressure. Thus, tight flow shut-off is possible even when using metal seats and disks.
Backflow Prevention
The check valve portion of a triple duty valve prevents backflow and gravity circulation in pumping systems by only allowing the flow of fluids in one direction, preventing damage to the pump and unwanted heat transfer through the system. In addition, many triple duty valves have a non-slam check valve, which provides quiet operation.
Flow Rate Maintenance
The balancing or throttling valve function sets the system flow rate within a triple duty valve, optimizing system operating efficiency and providing precise flow with a maximum control range. Most triple duty valves have a pre-set balance and memory stop to reset the valve in the correct position after shut-off.
Examples of the Internal Mechanisms on Triple Duty Valves
Triple Duty Valve Common Problems
Improper Mounting
Although triple duty valves can be mounted vertically or horizontally, they cannot be utilized with the stem/handle pointing downward or upside down. Additionally, they cannot be used in a fully open position and must be closed approximately 15% to operate correctly.
Improper Placement Within a System
Triple duty valves must be mounted a sufficient distance from the pump’s discharge to ensure proper operation. Failure to adhere to this minimum distance can result in premature failure of the check valve assembly and erroneous gauge pressure drop readings across the valve. Conversely, mounting a triple duty valve too close to the pump will result in “chattering” of the check valve assembly, causing premature failure of the springs and/or the flapper itself.
Leaks
Triple duty valves rarely require any routine maintenance. Still, it is beneficial to check for leaks at the packing nut or bonnet gasket area while regularly maintaining a hydronic system. In addition, it is possible to replace internal components on most triple duty valves, such as the stem packing, disc, or nameplate.
Identifying Triple Duty Valves
Many pump manufacturers offer triple duty valves as a pump system accessory. Each has its own name for these multi-function valves, but they all serve the same purpose by replacing at least three valves – a shut-off valve, check valve, and balancing/throttling valve.
Triple Duty Valves by Manufacturer
Armstrong Flo-Trex Valves
Armstrong Flo-Trex Valves are multi-function pump fittings for Armstrong commercial pumps. They are available in cast iron or ductile iron and with grooved, flanged, or threaded connections. When used together, Flo-Trex Valves and Suction Guides can eliminate up to nine different components from a pump system installation.
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Taco Multi-Purpose Valves
Taco Multi-Purpose valves offer performance and convenience with low pressure drops and a replaceable stem seal packing even under full system pressure. The Plus Two Multi-Purpose Valve is ductile iron with stainless steel and bronze fitted construction to provide years of trouble-free service. It is available in sizes ranging from 1-1/2" through 14", with flanged connections (1-1/2", 2", and 2-1/2" units are threaded connections).
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Bell & Gossett Triple Duty Valves
Bell & Gossett Triple Duty Valves combine three valves into one: a calibrated balance valve, a spring-loaded check valve, and an isolation/shut-off valve to provide all of the functions usually required on the discharge side of hydronic pump systems.
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Grundfos Combination Valves
Grundfos Combination Valves combine three valves in one: shut–off, balancing, and check. Fitted between the discharge pipe and the discharge flange of a Grundfos pump, Combination Valves are an economical and space-saving choice.
