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Freeze Protection


Freeze Protection

Fig. 36: AF valves protect check valves and water lines.  At ship docking facilities, water mains are equipped with check valves at supply manifolds to prevent water from flowing back into the main.  When not in use, both manifolds and lines are susceptible to freezing.  The AF valves establish a bleed flow to prevent freezing, while minimizing water waste.

Any water line that might be exposed to freezing temperatures needs some type of freeze protection. Similarly, process equipment carrying water, such as pumps and valves, that may be subjected to freezing conditions should also be protected.

    One solution to the problem of protecting water lines is to simply drain the system before freezing conditions might occur. However, in many instances this is not practical. An alternative is to open a manual valve slightly to permit some flow to drain and hope the flow is enough to prevent freezing, without losing too much water. Usually this is not practical and can be expensive because it wastes water. Manual bleeding at the proper time is subject to human error, and often results in freeze damage. Further, scarcity of water in many parts of the country and potential waste also precludes this approach.

    Automatic drain valves provide another solution to freeze protection of water lines that are exposed to intermittent freezing temperatures. This approach is simple and inexpensive. One or more Ogontz Type F valves at appropriate points in the system provide the most economical way to protect water lines and other equipment from expensive freeze damage.

    In applications where auxiliary heating is not really required, or in the south where only occasional cold spells occur, an automatic bleeder/drain valve is the ideal solution. These valves are inexpensive, easily installed and the inherent fail-safe design provides reliable, unattended operation. The wax-filled thermal actuator used in F valves, Fig. 34, is the same fully self-contained, temperature-actuated device employed in other Ogontz valves.


Economic Considerations

FP/FPR Valve

Fig.34: Type F valve.  The thermal actuator inside the valve senses water temperature.  When the water temperature falls below 40F the valve opens, draining the line to prevent freezing.

The automatic bleeder/drain approach to freeze protection provides substantial savings compared to manually operated systems. Freezing conditions can seriously damage or temporarily immobilize valuable equipment. The resultant loss of equipment or production could mean staggering financial losses. In addition, the cost of water saved by automatic freeze protection is significant.

Comparing Manual and Automatic Bleeder Valves

Manually operated bleeder valves must be left cracked open when danger of freezing is eminent. This means that water is being wasted during the entire winter. Analyzing weather shows that many hours in the winter months present no danger of freezing water. For example, in the Middle Atlantic states, during winter, about 50% of the time the temperature is above 32F.

    With automatic bleeder valves, the water flow is established only as required by weather conditions and water temperature. That is why over 50% water savings were realized when Ogontz Type F valves were installed at a large industrial facility.

 In addition to protecting water lines, the automatic drain valve system provides protection to other equipment such as valves and pumps.

Using Automatic Bleeder Valves to Protect In-Line Equipment  

    When a ship in port replenishes its water supply, back flow preventers (check valves) are used to prevent water from surging back into the supply main, Fig. 36. At one of the largest naval bases in the world, freeze damage to the back flow preventers averaged about $150,000 a year. After installation of Ogontz automatic bleeder valves, system freeze-ups were eliminated, resulting in huge maintenance savings.  And, after many years of successful  operation,these automatic bleeder valves are still the primary method of protecting this equipment for both the U.S. Navy and Coast Guard.

    Another ideal application for automatic bleeder valves is on solar systems using water as the heat exchange medium. Usually, thermostatically-actuated solenoid  valves are employed for flow control, but the automatic bleeder valve serves as a reliable back-up device in the event of loss of power. This guarantees maximum protection for heat exchangers and piping.

F and AF Valve Installation Procedures

    Two basic types of automatic drain valves are available. The Type F valve has its thermal actuator inside the valve and responds only to water temperature. The thermal actuator in the Type AF valve is outside the valve body, making it sensitive to air temperatures, as well as water temperature.

    Since the F type valve has relatively small mass compared to the equipment it is protecting, it responds to temperature differentials faster than the rest of the system -- bleeding or draining the system only when a danger of freeze-up exists.

Type AF Valve

Fig.35: Type AF valveThe thermal actuator on this valve is outside the valve body on the cap.  Thus, the valve initially responds to ambient temperature.  Then, as the valve opens and water flows, the AF senses a combination of ambient and water temperatures.  If the valve senses no immediate danger of freezing, it will automatically close.  If it senses a danger of freeze-up, the valve will open to provide freeze protection.

    The AF valve, which is recommended for freeze protection in extreme climates, is actuated by two conditions. When no fluid is flowing through the pipe, the initial response is due to an ambient temperature drop and the valve begins to open. As water flows through the valve, a secondary response occurs. If the temperature of the water entering the valve is 10F or more above set point, the valve will throttle to the closed position.

    The choice of which type of F valve to use for a given application depends on several criteria. Generally, in severe climate areas where the ambient outdoor temperatures can drop quickly, the AF type is the safest choice. On the other hand, the F valve may be preferred to minimize water consumption, but thorough precautions must be taken to avoid any possibility of freeze-up at the valve's discharge.

Freeze Protection System Design   

Many applications are well suited for automatic drain valves including:

• Water piping
• Fire lines
• Condensate lines and steam headers
• Pumps
• Valves
• Cooling towers
• Heat exchanger coils
• Water-cooled compressors and engines
• Sprinkler systems
• Air scrubbers
• Ship supply lines
• Safety showers
• Any exposed water bearing equipment

Ogontz has developed an entire series of F type valves to meet the individual requirements of each application. Each type F valve has unique design features that give it special advantages in certain situations.

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