November 14, 2016

By: Bruce Ellis

It’s fall and for some, still warm – but it won’t be long until another heating season begins. Some facilities are already seeing the restart of boilers, and so, I’ve decided to address a cold weather issue that often arises with industrial steam and water boilers this time of year: they don’t start. Is there anything worse than a service call at 3 AM in January when the temperatures outside drop to -20°C? Once you have eliminated each component in your boiler as a possible culprit to boiler failure and it comes down to a check valve sticking open or closed in your system, it’s time for a replacement.

Each boiler is unique in the way it is designed and your choice in replacement will be somewhat dependent on the specifications your system requires. Whether you have a liquid, gas or steam boiler, this introduction to DFT Inc.’s three most common check valves for HVAC service is sure to get you warmed up to a replacement valve.

Note: DFT also manufactures check valves for use in large industrial boiler systems. A complete guide can be found here.

BASIC CHECK VALVE

This proven check valve is suitable for a wide range of applications and is extremely versatile due to its ability to work at various pressures and temperatures. The Basic Check Valve can be made in different grades of stainless steel and is available from ¼” – 2 1/2” line sizes. The basic check can be used in installations requiring a CWP of 450-6,000 psi. DFT also manufactures the Basic Check with higher cracking pressures, from 2-40 psi. While the Basic Check is versatile, be sure to reference DFT Inc.’s full Catalogue for certain restrictions.

SCV CHECK VALVE

The most common check valve for use in steam applications, the SCV is also commonly used with liquid and gas. It uses the same trim as the Basic Check, in a durable body made of either 316 stainless steel, Alloy 20 or Hastelloy alloys with either FNPT or socket end welds. DFT SCV’s are available for ½”-3” pipe sizes and either 750 or 3,600 CWP. The SCV-R (Restrictor Check) is designed for higher cracking pressures than the standard SCV check valve. For a more simplified and flanged version of the SCV check valve, available in ASME Class 150 and 300, see DFT’s DLC check valve.

FBC CHECK VALVE

If you have an existing system with limited space – check this little space-saver out. The FBC “insert wafer” check valve is designed to be installed between two flanges and uses the same proven technology as the Basic Check valve. Though small, the FBC is made to last with stainless steel construction and a well-protected spring, not to mention the FBC can withstand temperatures up to 232°C (450°F). The FBC check valve works with schedule 40 pipe in the most common sizes 1”-4”, pressure class 150/300.

DFT Check Valves Used Extensively in HVAC

The simplicity and durability of DFT Valves has been proven since the original design dates back to the 1940’s and remains unchanged to this day. The non-slam, spring-assisted design prevents  reverse flow and virtually eliminates water hammer in your system. All of DFT’s check valves are capable of water-tight shutoff, are easy to maintain, can be installed in any direction and are built to last. Our distributors and end-users tell us that “they last too long” and regularly comment on their unsurpassed design and efficiency. If you would like to learn more about DFT check valves for industrial steam, water or HVAC, let us know, we’re here to help.

Additional Resources

Design for Flexibility: Key Considerations to Make When Designing Fluid or Gas Flow Systems

DFT Check Valve Success Studies

Check Valve Application Data Sheet