Behind the Walls: Valves in Building Systems

Commercial buildings are all around us, but unless we pay close attention during their construction, we have no concept of the multitude of fluid arteries hidden within the walls of masonry, glass, and metal. Those pipelines carry everything from water to critical gases, and the buildings couldn’t function without them.

The common denominator among buildings is water—all commercial buildings contain piping systems carrying many combinations of the hydrogen/oxygen compound in the form of potable water, wastewater, hot water, grey water, and fire protection.

SAFE FROM FIRE

From a building’s survival standpoint, fire protection systems may be the most important of the water systems. Fire systems in buildings are almost universally fed and filled with clean water. For these systems to be effective, they must be reliable, have sufficient pressure, and be conveniently located throughout the structure. Two primary systems deliver this combustion-quenching liquid: sprinkler systems and hose connections.

The sprinklers are usually installed in the ceiling of each floor. These systems are designed to automatically energize in case of a fire. Hose connections, which are called standpipes, exist at various locations in a multistory building and are designed to extend the reach of a fire department’s hose without having to drag hoses up into tall buildings.

Design and installation of fire sprinkler systems, including valving, is directed by the National Fire Protection Association (NFPA) document 13, Standard for the Installation of Sprinkler Systems. Additional NFPA standards cover different aspects of fire protection piping.

The two water arteries of sprinkler and standpipe lines have to have sufficient water pressure to provide the necessary flow to fight a fire. For low-rise structures, the piping pressures are nominal, usually, less than 100 psi, so many different materials of construction will suffice. However, ductile iron and bronze are the materials of choice because of their low cost and ease of manufacture.

In general, city water supplies are in the 40–100 psi range, which is sufficient for fighting fires in most low-rise buildings. But what happens when the building is higher than that? To answer that question, we need a little refresher on physics and gravity.

Each foot of height provides or consumes .43 psi of pressure, so an average pressure loss for a 12-foot floor is about 5.16 psi. For this reason, pumps have to be used to energize the lines and provide the minimum sprinkler operating system. Where these pumps are placed depends on the height of the building. In the case of very tall, high-rise buildings, pumps and related piping move into the 300–600 psi working pressure range. This higher pressure requires higher-rated piping components, including valves. In many older buildings, a water tank has been located on the rooftop to provide immediate water pressure for most floors. However, the water tank first has to be filled via a pumping system.

CLEAN WATER

While fire protection water may be the most vital water in a building’s piping system for safety reasons, the buildings could not function without potable water. Clean water is used for drinking, restroom facilities, and a host of other building needs. Piping for these systems follows the general tenants of firefighting piping, in that iron and bronze are used, and pressures are moderate. Both firefighting piping and water piping predominately use grooved mechanical connections on their pipes, valves, and fittings. These mechanical joints, as they are sometimes called, have some flexibility, as well as the ability to adjust for small miscalculations in piping alignment. In areas that are earthquake-prone, the grooved piping also handles the shakes and sways so that pipes don’t break.

LOW-LEAD REQUIREMENTS

When a building’s water system is connected with the city water supply, contamination is always a concern. The clean water in the mains can be at risk if contaminated or non-potable water in the building’s water system is drawn back into the main. To prevent this, plumbing engineers resort to backflow prevention technology. These devices are usually made up of valves in series, including two check valves. The devices ensure that any downstream overpressure or upstream vacuum will not draw unwanted water back into the clean water stream. Nearly every plumbing code requires the use of such devices.

Although water systems are the main focus of general commercial piping, they are not the only fluid plumbing engineers must focus upon. The heating, ventilating and air conditioning (HVAC) side of buildings has its own complex piping system and valves.

The oldest HVAC fluid is steam, which has been used in heating systems for over 100 years and is still very popular in the northeast. Direct steam heating uses low-pressure steam provided by an in-house boiler or purchased from a municipality. The steam is piped throughout the building and regulated into radiators to disseminate the heat.

If steam is generated on-site, the boiler and associated equipment is valve intensive. These boiler systems are treated just like their big brothers at the power plant so high-temperature steel valves and piping are normally used. Class 300 steel valves are very popular in this type of application.

As an alternative to steam heat, many facilities use hot-water climate control systems. The lower-than-boiling-point hot water systems require a much less robust piping system than what is used for steam. Elastomer-seated ball valves and rubber-lined butterfly valves are often used in this service, with bronze and iron the material of choice.

For large-scale commercial and industrial air conditioning systems, a central chilling unit often is employed. These central units distribute chilled water at about 40°F (4°C) to each desired location. An additional line returns the warmed water to the chiller to be re-chilled and used again. Valves for chiller applications are mainly quarter-turn types, with the butterfly valve being the first choice of HVAC piping engineers. A large central facility such as those found on college campuses or in medical complexes could contain miles of piping and hundreds of valves.

HEALTH CARE FACILITIES

Some of the more critical piping systems in buildings are found in the walls of hospitals and medical facilities. These buildings use numerous fluids and gases that all must be safely and securely handled. The NFPA 99 document, Health Care Facilities Code, is the guiding document for hospital and health care center piping systems.

Virtually every room in a medical facility contains an oxygen source so the oxygen distribution system is extensive. The outlets are all fed from carefully designed distribution piping systems that are valve intensive. Because of its ability to support combustion, oxygen has to be carefully handled. It only takes a drop of oil and a spark in an oxygen line to cause a huge fire. For this reason, all valves and piping in oxygen lines have to be thoroughly cleaned and degreased before and after installation. The cleaning procedure is detailed in the Compressed Gas Association (CGA) document 4.1, Cleaning Equipment for Oxygen Service.

Most oxygen is stored on site in its cryogenic liquid state, which allows for more fluid in the same amount of space. Cryogenic compatible system piping is required for these applications. For valves, this usually means that the stems are extended so the packing will not freeze. Cryogenic ball valves also often require specially designed seats that will energize at the ultra-low temperatures. Other gases that require special piping systems include medical air and nitrous oxide.

Beyond gas piping, hospitals also have vacuum systems with outlets in most rooms. These require special vacuum piping systems. Vacuum piping and valves are usually cleaned prior to installation to remove any contaminants. All of these medical gas and vacuum systems use materials such as bronze and stainless steel, with quarter-turn valves being the valve type of choice.

Medical facilities also require the usual water and fire piping systems, although the requirements are tighter and more detailed. Additionally, many medical facilities require “pure water” for many processes. This is water that is free from particulate matters, minerals, bacteria, pyrogens, organic matters and dissolved gases, all of which can be found in common potable water. The pure water piping system requires cleaning similar to what is required for oxygen service. Many different materials are used for pure water piping including stainless steels, aluminum, polyvinyl chloride (PVC) and acylonitrile butadine styrene (ABS).

MANUFACTURING PLANTS

Manufacturing facilities and assembly plants have their own unique requirements for piping systems. Some of these on-site plants have all the piping complexity of a small-town utility company.

The usual fire and water systems are required and depending on the products and processes involved, these systems may need to be more robust than those found in general commercial structures. On-site industrial boilers are often required to meet hearty steam requirements.

A common need in manufacturing is compressed air for powering equipment. Compressed air lines are fed from compressors, which are usually mounted in the ceiling area with drops at convenient points throughout the facility. These lines require a multitude of low-pressure valves to close off different areas for safety or expansion purposes. The bronze gate valve is still the first choice for this service.

Plants that perform precision painting and finishing activities, such as automotive industry facilities, require clean, silicon-free air for spray painting. Even a minute amount of silicon in the paint mix can ruin the paint. Valves and piping used in this service must be specially prepared, with valves cleaned in accordance with MSS SP-140, Quality Standard for Preparation of Valves and Fittings for Silicone-Free Service.

Although usually not piped facility-wide, pressurized hydraulic fluid often is used when high energy is required. These piping systems operate at working pressures up to 10,000 psi, so piping and valves must be carefully chosen to handle the high pressures.

Although green has become a religion for some people and political groups, the principles of green design in most cases are based on common sense, especially when you define “green commercial plumbing systems” as those designed to save energy and materials. In fact the concepts of energy savings are old school. One of the best ways to green success is tapping into under- or unused energy sources. The most successful of these so far has been geothermal, where ground-source heat pumps use the earth as a heat source in winter and as a heat-sink in summer.

These systems are similar in concept to hot-water or chilled water systems in that they are considered hydronic systems, which means they use water to distribute or transfer heat through the piping system. An example of a green hydronic system besides geothermal would be using solar collectors to directly heat water in a piping system.

Geothermal systems require a quantity of piping, pumps and valving to function properly. High temperature is not an issue, and corrosion is minimal, so the popular water systems use piping materials of bronze, copper and PVC or chlorinated PVC, depending on the actual ground temperature. If size is an issue, butterfly valves are the best choice. For smaller diameter lines, ball valves or bronze gate valves work well. Control valves for this service are usually made of bronze.

Recycling, which traditionally meant collecting aluminum cans or scrap automobile, has been expanding into the reuse of water. This involves a separate piping system for grey water or reclaimed water, which is used for non-potable inside applications such as toilet flushing and outdoor applications such as landscaping. The two sources for this type of water are the drain lines of showers, washing machines and sinks, as well as the newest source, which is municipal or institution-wide grey water distribution systems.

Costs for creating dual water supply systems, potable and grey, are involved, but the increased plumbing system cost to the high-rise builder has been estimated at only 9%. Meanwhile, the addition of a second supply system means more pipe, valves and fittings.

CONCLUSION

When we consider the scope of piping systems in commercial buildings, we tend to think in terms of spigots and taps. But as this article has shown, from basic manual on-off valves to exotic HVAC control systems, those walls hide a lot more of the valve industry than what is needed for simply moving water through pipes. VM

GREG JOHNSON is president of United Valve (www.unitedvalve.com), Houston, and is a contributing editor to VALVE Magazine. He serves as chairman of VMA’s Education & Training Committee, is a member of the VMA Communications Committee and is president of the Manufacturers Standardization Society. Reach him at greg1950@unitedvalve.com.