CHW Installations

System Explanation

A lot of heat is generated in many buildings, especially in Commercial Buildings (office buildings, Hospitals, etc.), Manufacturing facilities and Date Centres. Think about the people, equipment, computers and hardware in those buildings, these need moderate temperatures for optimal performance in reliability, so that heat must be handled. To handle this heat HVAC (Heating, Ventilation and Air Conditioning) systems are designed.

While residential buildings and smaller commercial buildings are often cooled using air-cooled equipment, CHW systems are typically the engineer’s preferred choice for larger buildings.

In Data Centres for example, Data centres use a lot of power, which translates into heat. The more equipment that's packed into a facility, the greater the heat generated.

Chilled water systems remove heat from buildings by transferring it from the air and into cold water through piping. In a complex and continuous process, water circulates through chilled water loops, absorbs the heat from the air, and returns heated water to the chiller for refrigerant to rechill it.

Please note that the below is a simplified system to understand how the CHW plant works. This system consists of:

• Chiller
• Cooling Tower
• Pumps
• CRAC units (Computer Room Air Conditioning)

The Chiller is the producer of CHW on the system.

• Evaporator:

• This is where the CHW is produced.
• The CHWF leaves the evaporator normally at 6°C - 8°C degrees. The temperature will depend on the purpose for which it is being used and as per project specifications.
• The pump pumps the CHW through the risers or dog boxes to the CRAC units.
• The CHWR comes back to the evaporator at a temperature of 12°C -14°C degrees.

• Compressor:

• This is where the refrigeration cycle happens.
• The heat within the CHWR is carried away by the refrigerant and sent into the condenser.
• Check on videos for the refrigeration cycles if you are interested in learning about the process.

• Condenser:

• This is where the heat of the building, the CHWR, is collected and dumped to the cooling tower.
• The pipe leaving the condenser is called - Condense Water Flow and it leaves at about 35°C.

• In the Cooling tower:

The cooling tower is usually located up on the roof and is the destination for the unwanted heat in the building.

The Condenser Water Flow enters the cooling tower, and it is sprayed into the air stream, and that spray runs in the inside of the cooling tower, and it is collected at the bottom.

Explaining it in steps:

• The Condenser Water Flow enters the cooling tower through the spray nozzles inside the tower.
• The spray nozzles spray the warm water evenly over the fill.
• Water passes down the fill whilst air passes upwards.
• As the water travels through the fill, some of it evaporates, which causes the remaining water to be cooled.
• The cool water that did not evaporate falls into the collection basin due to gravity, whilst the air, continues its path upwards, through the drift eliminator, through the axial fan then exits at through the top of the tower.

https://www.youtube.com/watch?v=sWJCWDpY9is

In that process, the sprayed water, the one we mentioned leaves the condenser at 35°C, will lose some of the heat and will be collected at the bottom of the tower, and the air leaving the tower will be mixed with the sprayed water leaving the cooling tower at a much higher temperature.

Once the cooling tower has loose about 7 °C degrees, in the cooling process, it is collected back to the Condenser. Condenser Water Return.

It is important to understand that these are 2 independent systems, the Condense Water System and the Chilled Water system, these are not mixed at any time in the Chiller.

CRAC Units

• Used to monitor and maintain: Temperature, Air Distribution and Humidity.
• The CRAC units have heat exchangers inside which are connected to Chilled Water Systems to remove the heat.
• CRAC units help prevent low humidity and water vapor from forming. Low humidity can cause static electricity buildup, which can damage electronics, and water vapor buildup, which can cause short circuits and corrode equipment.
• They have filters inside to remove the dust from the room as well as a fan to circulate and distribute the air.

Pipe Materials

The most common type of pipe used for chilled water are:

Carbon Steel Pipe (Black Steel Pipe)

• Carbon steel pipes are the most popular type of chilled water pipe.
• The term “carbon steel pipe” refers to a steel pipe that contains higher content of carbon.
• Due to the sheer black hue of the carbon steel surface, it is usually referred to as black steel pipes.
• Carbon steel pipes or black steel pipes are not galvanized which means that they rust.

Galvanized Carbon Steel Pipe

• When a layer of zinc is applied to carbon steel or black steel pipes, they are oxidized and then become corrosion resistant.
• The pipe requirements are the same as before, except they are now coated.
• Compared to carbon steel pipes, galvanized carbon steel pipes are more expensive. They can be easily differentiated from carbon steel pipes by their silver colour appearance.

Stainless Steel Pipe

• For chilled water, stainless steel pipes are hardly used.
• They are substantially more expensive than carbon steel pipes, both galvanized and ungalvanized. For hot water systems, stainless steel pipes are far more commonly employed.
• The corrosion resistance of stainless-steel pipes is even better than that of galvanized carbon steel pipes.

HDPE Pipe

• HDPE (high-density polyethene) chilled water pipe.
• Pre-insulated HDPE chilled water pipes have a high-density polyethene carrier pipe. - Polyethene could be totally recycled and has no harmful effects on the environment. - HDPE has a 50-year life expectancy.
• Whereas classic carbon steel pipes are welded together, modern HDPE chilled water pipelines are put together like Legos.
• Basically, two HDPE pipes are hung together with spacing for the socket.
• Next, you insert the pipes into a connector and use heating equipment to fuse the two together.



Clamps and Brackets

Supports

Normally the CHW pipe is supported by M11s.

Note: manufacturers will provide with charts, as there are standard pipe Mupros and M11 dimensions for different type of pipe sizes.

Brackets

It is important to choose the right bracketry for each system. There can be many and varied causes for pipe failure, but one common cause is poor selection and installation of bracketing. Issues such as the below, are common factors which can lead to failure: - Using brackets of dissimilar metals - Placing a bracket too close to a change in direction

The most common bracketry type that is used in nearly every project is the Unistrut type. Unistrut brackets are versatile and widely used in many different industries and applications where strong and reliable structural support is needed.

What are Unistrut Brackets?

• Unistrut brackets are made from durable materials such as stainless steel, galvanized steel, and aluminium.
• They are designed to work with the channel system, which consists of a series of metal channels with alternating slots and holes.
• The slots and holes enable the brackets to be quickly and easily attached to the channels.
• The brackets are used to provide support, stability, and reinforcement to the channels.
• They are designed to accommodate various loads and pressures and are engineered to withstand harsh environmental conditions.
• They are also adjustable, allowing them to fit different sizes of channels, pipes, or conduits.

Unistrut Website: https://www.unistrut.co.uk/

Types of Unistrut Brackets Brackets come in a variety of types, including:

• Standard brackets: These are the most common type of Unistrut brackets. They are designed to fit the standard Unistrut channels and are used for general-purpose applications.
• •Angular brackets: These brackets are used when the channels need to be installed at an angle. They are designed to fit snugly against the channels, providing support and stability.
• Flat brackets: These brackets are used when the channels need to be mounted parallel to a surface. They are designed to sit flush against the surface, providing a secure and stable mounting point.
• U & Z-shaped brackets: These brackets are designed to fit around a channel or pipe, providing support on two sides.
• T-shaped brackets: These brackets are used when the channels need to be mounted perpendicular to each other. They provide a secure and stable mounting point for the channels.

Bracketry separation requirements for CHW pipe system

The separation requirements depend on pipework material, temperature, and pipe size. But as general rule, we can use the chart below to identify the correct amount of brackets have been installed.

Brackets are used at every bend and every Xm as per the below:

Components

Low point drains and High point AAVs

Vents and Drains are required in piping systems to meet the Process, Construction, Testing, and Commissioning requirements.

• These are basically small tapping connections from the main pipes having a total length limited to 300 mm.
• These connections are with an isolation valve or without.
• Even though vents and drains are small connections in the piping system and are very often missed or neglected, they are very important and must be provided. Installing vents and drains after the pipe has been installed results in additional costs and an extended schedule.

High Point Vent (HPV):

A vent tapping installed at the highest elevated point of the Piping network. Purpose:

• Each plant with a piping system must be insured properly for quality of fabrication, Installation, and Sustaining in designed pressure. To test its sustainability complete piping system is pressure tested normally by filling water in the pipe.

• During the filling of water, it is mandatory to evacuate all air particles from the piping system for not letting pressure down while compressing the water. To fulfil this requirement, we need to provide a venting point at the highest location of the piping network.

• The high point vent helps to evacuate all air particles from the piping system so that no air bubble can form, and no pressure drop will be there because of uneven molecule distribution for compression.

Low Point Drain (LPD):

Drain tapping installed at the lowest point of a piping system. Low point drain also consists of a valve which generally called “Low point drain valve”. This is being used to empty the piping system after hydrotest. Purpose of Low Point drain:

• After flushing testing of the piping system, which is often done with water, it is important to drain all water from the pipe so that no rust can develop on the internal surface of the pipe and reduce its wall thickness.
• During draining of water after hydrotest this becomes a matter of fact that, “How to open low point drain?” because the direct opening of only LPD will create a vacuum in a piping system that may damage and destruct pipes.
• To avoid this disruption, it is mandatory to open a High point vent before opening the Low point drain. Doing so will release pressure inside the pipe and provide a way to enter the air in the pipe to maintain the same atmospheric pressure inside the pipe during draining.

How to identify these in a drawing

Ideally these should be added into the model during the coordination process but most of the times, that’s not the case and these are redlined on site.

We want to be able to have them in the model for several reasons:

• Make sure these are not missed.
• Ensure this are installed without creating additional clashes.
• Ensure access is provided to these.

Strainers

• Strainers are used to filter the water flowing through the pipeline. Strainers have wire mesh inside them that traps dirt in the water. These protect piping equipment from potential damage due to dirt by water.
• Strainers are integrated into heating and cooling systems to filter impurities from the circulating medium.
• Impurities consist of debris, packing and materials that enter the pipes during operation. Deposits of scale/rust or materials from the medium can become dislodged and subsequently flushed around the system. In district heating systems, deposits/materials can also be introduced from the supply network.
• The use of strainers in piping is before meters and control valves, to prevent impurities from damaging them or causing them to close. To determine when a filter requires cleaning, a pressure gauge can be mounted on each side of the filter to monitor the pressure drop. Note that district heating system providers often require strainers to be located before the consumption meter, to protect it against deposits/materials from the supply network, but also forbid the installation of pressure gauges near the meter.
• Furthermore, isolating valves should also be located as closely as possible on each side of the strainer, to minimise the amount of water that needs to be drained during cleaning.

Valves

Chilled water systems require valves to regulate water flow through the pipes and to ensure that the system runs efficiently.

If you want to know more about valves, I recommend you reading this document:

• Spirax Sarco – Pipelines Ancillaries:

https://www.spiraxsarco.com/learn-about-steam/pipeline-ancillaries/isolation-valves---linear-movement#:~:text=Isolating%20valve%20%2D%20A%20valve%20intended,between%20closed%20and%20fully%20open

Meters

Commercial and industrial businesses spend a great percentage of their building costs on creating hot and cold water and pumping it around their facility.

This infrastructure include chillers, cooling towers, pumps used for heating & cooling etc. Considering how much money is spent on this portion of the business, it is not surprising that there is an increased focus on determining the correct amount of water required to meet the needs of the business.

The purpose of this sections is that you have a general information of what do they do and where are these normally located in the CHW system.

• Water meter measures the volume of water as it passes through the meter.
• Flow meter measures the speed at which the water passes through the meter.
• Some flowmeters are meant to measure the fluid amount flowing inside them after a period of time (100 litres per minute, for instance). Other flowmeters are meant to count the total amount in litres of fluid that has gone through them (such as 100 litres).
• Manufacturer guidance should be followed when installing these, some typical requirements of installations are:
  • Requirements for straight pipe section
  • It must be installed horizontally on the pipe (the pipe tilt is less than 5).
  • During installation, the flowmeter axis should be concentric with the pipe axis and flow direction should be consistent.
• The meters output information on:
  • Total flow (l).
  • Flow rate (l/s).
  • Alarm conditions.

With this information, you can tailor the system to match the water flow to the building demands. This is typically done through a BMS, but can also be done on smaller buildings that do not have a BMS.

https://www.youtube.com/watch?v=Cz3Fzktv-jw

Trace heating

In the cold winter months, pipes transporting liquid substances can become vulnerable to freezing temperatures and increased viscosity. Heat trace is most commonly used to protect pipes from freeze damage during winter conditions. These systems are most often used to keep water from freezing, as water in any process or facility is critical.

https://www.youtube.com/watch?v=40b6shKPRLA

Some real life site photos:

Insulation, Cladding and Labels

Insulation

Chilled water systems need adequate insulation so they can effectively execute cooling functions.

Reasons for insulation:

• Stops Condensation. Condensation causes mold and mildew, diminishes the cooling system’s efficiency and can lead to a malfunctioning or inefficient chilled water system. In addition, condensation on the pipes can create a significant health risk to the structure’s occupants.
• Prevents Heat gain.
• Protection against frozen pipes.

Phenolic blocks are normally installed around pipe clamps. This type of foam prevents the heat loss or gain through the pipe supports. It also prevents condensation.

• Phenolic pipe insulation blocks are specified on LTHW to CHW pipework with temperatures between 50°C to 110°C and are typically specified for internal rather than external environments.
• Phenolic materials have a number of other unique desirable qualities for insulation applications:
  • Thermal performance: Rigid phenolic foam offers outstanding insulating properties due to its very low thermal conductivity.
  • Fire performance: Phenolic has superior fire resistance, with a very low flame spread and very low levels of toxic gas emission. All phenolic foam is rated with an ASTM E84 25/50 Class A flame and smoke rating, meaning that flame and smoke spread will not exceed 25 feet and 50 feet, respectively, if the insulation ignites. Many phenolic foams do not burn at all when exposed to an E84 flame test, yielding a perfect 0/0 rating.

Cladding

Cladding protects the insulation material underneath against both mechanical damage and the penetration of moisture, oil, chemicals and other substances which can affect its functionality.

On outdoor installations, cladding also provides protection against UV rays, weathering, and an increased risk of corrosion. It is also easier to keep pipework clean if it has been equipped with an appropriate cladding.

This is of particular importance where not only an aesthetic finish, but also hygienic requirements play a role.

Labels

Every system in a commercial, residential, data center etc. building must be labelled. Pipe identification help:

• Identifying which types of pipework are installed.
• Identifying the flow direction of the fluid. This comes together with identifying the valves they need to shut off.
• Preventing mishaps by alerting workers, subcontractors, and first responders to potentially hazardous pipe contents at any stage of the project, especially during commissioning and when pipe repairs are required.
• It can be more efficient for maintenance crews to locate the pipes that require maintenance.

There are standards to follow when labelling pipes:

• Label text and colour code is correct. As per standard followed on site, which should be on the Project Specification documentation (BS 1710, ASME/ANSI 13 etc).
• Label is the correct size for pipe/tube. Different label sizes for different pipe diameters. This is standard.
• Label arrow is correctly indicating flow or vacuum direction.
• Label is in line with existing labels on adjacent services.
• Label is fitted at correct intervals as per the site specification.
• Label is fitted square, straight, and plumb.
• Label is fitted to be read from the best vantage point. Specially through access hatches.
• Labels are not fitted across welded or mechanical joints.
• Labels are fitted next to equipment, valves, strainers etc.

Pipe Installation Examples



Process for offering the system to the client

Pipework Snagging - QA issues

Snagging is a process completed at the end of the system installation, with the purpose of identifying any defects, mistakes or issues relating to the project.

Issues can occur due to poor craftsmanship, design, or installation.

Common root causes for issues:

• • Incorrect installation
• • Damage after installation
• • Manufacturing Defects
• • Missing Components
• • Material/Component failure
• • Design defect/lack of Desing
• • Shipping damage

Real examples of most common QA issues in the CHW pipe:

Pipework Expansion Design

When a pipework system is designed, consideration must be taken into thermal expansion and contraction.

• Thermal expansion normally happens in systems carrying hot water like: Steam Systems, Heating systems LTHW (Low Temperature Hot Water System), Domestic Water Services etc.
• Contraction is due to happen in pipework carrying cold water like CHW pipework.
• All piping materials expand and contract as a result of temperature change.
• Contraction: As the temperature decreases, pipes contract.
• Expansion: As the temperature increases, pipes expand.

Just to have an idea, the typical temperature range for some of the systems mentioned above:

• LTHW 50°C - 80°C.
• CHW 6°C - 12°C.

Effects of the above:

Contraction:

• When in ambient installation in hot dates in Ireland like in July/August, when the temperature is about at 24-26°C you get a Temperature difference (ΔT) of 18°C-20°C to the Flow temperature of 6 °C.
• If you have a very large run say as big 200 metres of pipe it contracts 50 mm. The likelihood of 'L' bend flexibility if anchored in the centre is highly possible. If Victaulic or similar couplings have been used, even better.
• If installed during Winter at say ΔT 5°C the contraction = 13 mm. If installed at the same temperature as the CHW Flow it is zero.
• In Ireland, the use of bellows in CHW is very, very rare. In the Middle East (or similar hot climates) with ambient temperatures to the late 40's and even hitting 50 °C turning on the CHW at 6°C is a different story.

Expansion:

• System to fail prematurely, resulting in unnecessary repairs and reliability concerns.
• The forces created by the thermal expansion can be large enough to cause pipe bowing and buckling, water hammer, dynamic forces displacements, damaged pumps, valves, pipe clamps and fixings and even fracturing of the pipe or damage to the steel or concrete structure of the building.
• For example, if a pipe in a LTHW system is constrained at both ends, stress will begin to build as the pipe expands. If the stress becomes too great, then the pipe will break, and the system may not deliver water needed.

https://www.walraven.com/en/how-to-guides/thermal-pipe-expansion/

Fortunately, the damaging effects of thermal expansion and contraction can be easily prevented by understanding how temperature change impacts piping and how to deflect stress on a piping system. These calculations are normally done by Structural Engineers where they asses where the stress will happen and how to balance it implementing some changings in the design.

The Structural Engineers should provide with:

• Calculations.
• Solutions recommendations.
• Technical Drawing design.

Construction Solutions:

• Anchors and guide brackets.
• Bellows.
• Skids & Slides.
• Spring Hangers.
• Flexible Connectors.
• Flexible Hoses.

Below an example on how the expansion design could be done:

• The first step is to take the pipe layouts of the area (pipes carrying hot water, these can be Steam, LTHW, Hot Water Services etc).
• A structural engineer will carry on with a study of the forces generated in the pipes.
• Based on that study, they will understand where the higher forces are generated.
• To ensure the pipe installation will be solid and stable without breaking, they will indicate the locations where bellows and anchor points are required.
  • The bellows will sustain pressure and prevent abrupt damage of a pipeline due to vibrations, impact, fluid thudding, etc. They absorb vibrations and mechanical shocks of the piping system.
  • The bellows prevent misalignment, angular deflection, axial travel, and sudden movement of mechanical equipment installed in piping systems.
  • The anchor points will control movement and stop a pipe from shifting in three dimensions (fixed anchor points). Directional anchor points will allow some movement, but they focus movement in one direction.
• There are many manufactures that can supply with the above but the engineer looking to procure these must select these that can handle the forces that will be generated in the pipes, those shown in the reported by the structural engineers. Sometimes the structural engineers also provide with specific bellows types to use on their reports.

In the example below we see:

• Either side of the below the recommendation is to install 2 guiding brackets at certain max separations from the bellow and from each other.
• These brackets are typical Unistrut brackets with a 40x40 profile.
• For the anchor point, a more robust bracket that can handle the forces generated with a guiding clamp is selected.