www . refrigerationandaircon . co . za RACA Journal I January 2024 27
Feature
“ There could be a set of pumps running full blast all day long regardless of the load , with the only thing changing being that the valve opens and closes and water either goes through the coil , or bypasses back to the chiller – a highly energy-inefficient system .”
This is not to say that the accuracy of the valve is not important in large systems . Rather , it is simply to understand when selecting a valve the factors that make up the valve ’ s accuracy . The factors that make one valve more accurate than another include construction of the valve , complexity of internal components and higher engineered designs .
The preciseness of the valve is therefore key : it could be a needless expense to buy an extremely precise and more expensive control valve when a less precise one could have done the job just as well . Consequently , it is important to determine the margin of error that a system can endure while still being efficient .
Finally , it is important to narrow down valve selection by taking a look at the heat transfer fluids – such as water – that will be involved in the cooling process system :
• What is the source of the fluid ?
• What is the target water temperature ?
• To what degree does the system need to be cooled down ?
• What is the temperature of the water when it is introduced into the system ?
• Is the water clean ?
• Is the water going to be treated before it reaches the valve ?
These questions will also determine the material of construction selected for the cooling system and valves , based on the strength needed in the system ( pressure and temperature rating ); the internal and external environment of the system ( open or closed ); and the resistance to corrosion or erosion of the fluid being used to cool the system .
THE CRUCIAL ROLE OF PIPES AND VALVES Pipes are used to transport refrigerant , water and air between the various components of the system , while valves are used to regulate the flow of these fluids . Their proper functioning is critical to the efficient operation of an HVAC system .
Valves play a crucial role in regulating the pressure range in HVAC systems and protecting the actuators from letting the pressure reach its maximum level . There are different types of valves used in HVAC , including butterfly valve , gate valve , check valve , air-vent valve , motorised on / off valve and pressure independent balancing control valve .
There are several common problems that can occur with pipes and valves in HVAC systems . Here are some of them :
• Leaking : Leaks in pipes can cause significant damage to an HVAC system .
• Corrosion : Mineralisation , tarnish and wearing will corrode the parts inside your valves over time .
• Clogging : Clogging is a common problem with valves in HVAC systems . It can be caused by dirt , debris or mineral buildup .
• Freezing : Pipes and valves can freeze in cold weather conditions , which can cause significant damage to an HVAC system .
• Pressure problems : Pressure problems can occur when the pressure range in an HVAC system is not regulated properly .
Consequently , maintenance of valves and pipes in an HVAC system is crucial to ensure the efficient operation of the system . Here are some general tips on how to maintain your valves and pipes :
• Clean all valves : Cleaning valves is one of the simplest methods to extend their life . One can use a soft brush or cloth to remove any dirt or debris that may have accumulated on the valve .
• Clean dirt and debris from pipes : In addition , vent pipes should be protected to prevent the entrance of rainwater , which would inhibit valve operation .
• Check for leaks : Leaks in pipes can cause significant damage to an HVAC system . One should check for leaks regularly and repair them as soon as possible .
• Replace damaged parts : When noticing any damaged parts , such as a damaged pipe or cracked valve body , one should replace them immediately .
• Assess valves regularly : Valves should be examined and checked on a regular basis . This will help with identifying any potential issues before they become major problems .
• Perform routine shutdown maintenance : Mineralisation , tarnish and wearing will corrode the parts inside your valves over time . To prevent this , you should perform routine shutdown maintenance on your valves .
• Lubricate valves : Valves need lubrication to reduce friction and wear on the valve components , thereby extending their lifespan .
CONTROL VALVES IN AN HVAC SYSTEM Valves are part of the most essential components in an HVAC system , whether cooling water pumps , fan coil units , air handling units or water chillers , in order to control the flow of air , gas and water .
www . refrigerationandaircon . co . za RACA Journal I January 2024 27