Pipe plans

The plumbing distribution system for the Burj Dubai tower has needed considerable care at the design and installation stages. We take a look at the issues that had to be tackled.

ANALYSIS, MEP

The plumbing distribution system for the Burj Dubai tower has needed considerable care at the design and installation stages. We take a look at the issues that had to be tackled.

Providing the plumbing system for the Burj Dubai may sound at first like one of the more standard tasks to be undertaken on the project, but this is far from reality.

With drainage pipes that measure up to 600mm in diameter and working pressures of up to 30bar to deal with, the system being installed is no ordinary building plumbing network.

 

We�re using different solutions to those you would traditionally use to give a very reliable and robust system.

Add in the height of the main risers through which the primary pipes run and it becomes clear why the design of every segment of the system had to be overseen in minute detail.

Design guidelines

The length of pipe runs through the main riser meant that the system design has to consider the movement of the building as well as the natural expansion and contraction of both the pipes and building structure.

A specialist stress analysis subcontractor has been appointed under the MEP scope of works to study the pipe movements and advise on the positioning of expansion joints and guides. A stress calculation has been made for every single pipe and joint within the building's plumbing system.

We had a design from SOM and on-site the stress analysis consultant has checked the loads at all the anchors and guides, plus double-checked all the expansion and contraction elements within the building," stresses Hyder Consulting senior mechanical engineer Alastair Mitchell.

"We are trying to put effort into the detail. We've got plumbing risers that go straight up for almost 75 floors; stainless steel lines that operate at 30bar pressure...it's very unusual to take risers so high and we're all aware that we're doing something special and are putting extra effort into the engineering," adds Mitchell.

Rather than a conventional gravity support system, pipe guides and ball joints are installed at various building levels, thus enabling free movement of the pipework while accounting for seismic, building deflection, vibrations and acoustic requirements.

At high stress points within the system, such as the stanchion supporting the main chilled water line, the wall thickness of the pipes has been increased in accordance with the stress analysis results.

"We're having to use different solutions to those you would traditionally use in the construction industry to give a very reliable and robust system," explains Mitchell.

These include expansion compensators on the chilled water pipework that would normally be applied in the process oil and gas sector. "We're trying to do our best to implement best practices from the process and oil and gas industries on this site," adds Mitchell.

Special attention is being paid to the welding of pipe joints, with all welders having to pass an onsite test and certification process prior to being employed on the project.

We're not interested in [simply accepting] previous qualifications...nobody is allowed to carry out any welding work until they have been qualified for this job," confirms Mitchell.

This attention to welding detail is followed up with a non-destructive testing program, with an independent verification and testing consultant employed by Emaar carrying out the final checks.

In some areas 100% of the welds are checked and any that do not meet the standards will be cut out and redone.

"Some people in the building services industry are nervous of high pressures, but the equipment is available, you just need to have the confidence to us it and specify it correctly," assures Mitchell.

We've asked the [MEP] contractor to submit everything down to the nuts, bolts and gaskets being used, because if you use the wrong gasket when you're operating at 30bar it will just fly apart...everything becomes critical when you get to these higher pressures," he stresses.

System overview

The hot and cold water plumbing systems in the Burj Dubai tower and podium will generally operate under the principle of gravity. Water storage tanks are being installed within the main mechanical plantroom floors, which are located at approximately every 30 floors within the tower.

These tanks are fed by pumped transfer lines from the lower zones and distribute water downwards through the plumbing network in an umbrella effect. The height of the building will provide the necessary pressures via gravity for successful operation of the system.

"Only two pump sets are used to relay water to the highest level bulk tanks on level 136," explains Greg Sang, Emaar assistant director - projects.

The distribution pressures to hotel guestrooms, residential apartments and other parts of the building will be regulated via pressure reducing valves, which typically in turn feed local risers that serve eight to ten floors of the building," he adds.

A series of filtration units located within the basement of the building will filter all mains water from the Dubai Electricity and Water Authority (DEWA) mains before it is distributed around the tower.

DEWA mains water can reach [temperatures of] over 40°C in summer, so it is passed through heat exchangers that cool the water using a combination of condensate water from the air conditioning units and CHW (chilled water)," explains Sang.

Pipework considerations

The hot and cold water plumbing systems are split into many different zones in the podium and tower areas. The maximum size of distribution pipes within the tower are 200mm diameter fill-lines to storage tanks; maximum gravity or pumped distribution lines from tanks will generally be 100 or 150mm diameter.

The sizes of the drainage pipes however are much larger, with the maximum drainage line being a 600mm single-stack system in the podium. This reduces to 500mm and rises through the tower at the same diameter all the way to level 155.

Hot and cold water pumped supply and gravity systems are being constructed from a combination of stainless steel and PVC/CPVC plastics pipes. Stainless steel pipes are being used for all high pressure lines and PVC versions are used for low pressure lines that operate systems at below 5.5bar.

The main drainage stack that rises to level 155 is manufactured from ductile iron, with all the other local drainage connections and risers connecting to individual apartments being carried out in PVC.

Water conservation

A number of measures have been taken in the design of the system and product selection to ensure that water use is minimised.

The use of a single-stack drainage system means that grey and foul water are not separated, therefore no water reclamation is made from this system. However, once the building is operational, the condensate water will be reclaimed from the air conditioning system and routed to a central tank.

This will be used for the irrigation of the surrounding landscaping rather than using treated sewage effluent (TSE) water as is standard in the Middle East.

TSE will only be used for irrigation purposes when insufficient condensate water is available. A TSE connection from an off-site supply will supply this make-up water when insufficient condensate water is available.

The WC cisterns that are being installed within the building are generally the low water volume type. In addition, most taps will be the spray type and automatic infra-red control urinals will be installed in the public areas.

The contracts for several of these products are now being awarded, with Hans Grohe, for example, recently winning a contract to supply more than 5,000 Philippe Starck Axor Starck mixers for installation in the project.

RELATED LINKS: Supplying skywards services, Servicing the Burj, Going up..., Cool runnings, Tower power, Fire safety at height, Making initial preparations

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