While the capacity of construction hoists has grown in recent years (a model like Alimak’s Scando 650 has a payload capacity of up to 3.2t) renters and manufacturers say the machines have not crossed over into the role filled by cranes. Each still has its own well-defined role to play, with hoists working on a different, not necessarily lesser, scale to cranes. While the massive building components are left to cranes to lumber to the top of a building, hoists shoot up and down a structure delivering seemingly countless loads for internal works.

Advances in technology now mean these seemingly countless movements can in fact be quantified. In 2008 a hoist broke manufacturer Alimak’s record for usage while operating on the prestigious Ropemaker building development in London. The Alimak Scando 650I 20/50 FC model hoist, the company’s latest model, was one of three purchased by UK hire company HTC Plant for the project. Data gathered by Alimak’s A3 remote monitoring system fitted to the hoist showed that in a one month period, the unit made 22,180 total starts, averaging 90 starts an hour, and in one day clocked up 1,000 starts. It travelled 286km (177miles) in the month, on average more than 10km each day, and on one day alone it travelled 12km. The hoist was actually moving 35% of the available time (not including loading and unloading). The hoist lifted to a height of 65m (213ft) over 15 floors, with the hoist moving at a speed of 54m/min.

Broadly speaking, there are three main types of construction hoist: passenger lifters, material lifters and the dual capability passenger/material models. There are two methods of lifting the car inside a tower frame fixed to the building structure. Either the car is moved up and down by pulleys on a tower frame, or it is driven up and down using an on-board electric motor that spins a pinion running in a vertical rack.

Construction hoists can be split into another two categories: manually operated and driverless, used when there is no need for a person to escort a load. A trend that has developed over the past decade is toward the driverless passenger models, which can be controlled by remote control. The latest models use new technology control systems which can reduce waiting times by storing all calls from the landings and sending the hoist that is logistically nearest to a landing to pick up passengers.

California-based crane company Bigge responded to demand from its tower crane customers last year and began renting and selling construction hoists. Bigge’s tower and hoist division manager Jesse Sullivan says the number of hoists needed on a job “depends on the floor space, total manpower and materials needed to support the job. A low rise might use a single car, while a high rise would need at least two cars to support the floor-to-floor activity.”

Hoist placement on the building is vital, considering the amount of time the machine will be on site, the need for easy access for loading at the base, and for a minimal impediment to movement on the site.

The hoist provider will be involved from early on in a project, helping identify on paper where the equipment will stand in relation to the building. As the hoist needs to be anchored to a solid concrete base, contractors usually work to fix the hoists in a position where the footings will serve a purpose after completion, such as for an elevator shaft base.

Once secured in position at the base, the construction hoist is a self-assembling unit. The unit has its own working platform with winch crane which is used to lift up sections of the tower, which in turn is tied to the main building. The tower-to-building connection is usually done working in unison with scaffolders, who build platforms at each level to which the frame for the hoist is tethered.

A team of three people are usually used to extend each segment of the hoist, with the team taking two to three days. Lease companies say this is done on weekends wherever possible, to avoid interfering with general construction work. The hoist crew return at the required intervals and the construction hoist climbs up in unison with the building. Hirers also return at set intervals to carry out maintenance and undertake safety checks. This happens around every six weeks, keeping inline with safety regulations.

While standard hoists available on the market come with set specifications regarding maximum heights, the reality is that the tower heights are only limited by the height of the buildings they are attached to. The units are able to continually add more segments to the tower and manufacturers can make modifications allowing hoists to reach greater heights.

Nowhere is this demonstrated better than in Dubai, where Alimak’s newly introduced high-speed Scando 650 FC-S construction hoist is providing access during construction of the skyscraper Ocean Heights 1 in the Dubai Marina.

The building will extend to 82 floors and reach 310m in height.

Contractor Arabtec Construction is using two of the hoist systems with dual cars. These cars move at 100m/min, with a 2,800kg payload capacity and 3.9m car length (full dimensions: 1.5m x 3.9m x 3.2m). The hoists are equipped with a frequency control drive system, which was designed to provide smoother stopping and starting. The hoists use no counterweight and can use the entire line of modules and additions available for the 650 range. Three frequency control motors drive the system through a high efficiency gearbox.

Construction is scheduled to be completed in 2010. The tower, which features unique curves and a twisting structure, is owned by DAMAC Properties Co and will consist of 672 apartments. It is the first phase of the two-building Ocean Heights complex. The second tower could have as many as 105 floors and be 460m (1,500ft) tall.

David Lawrence from UK hoist hiring company HTC Plant says he has witnessed major advances in hoists in recent years: “They are now designed to be much lighter and more durable, the capacity is continually getting bigger, newer doors work better, and I’d say they have easily doubled in speed in the past decade.

“The improvements in safety have been incredible. Nowadays if anything goes wrong, or a load is not positioned properly, you can’t move; they have self cut-out functions. This stops a lot of potentially dangerous situations.

“The biggest demand has always been for greater reliability, which has improved dramatically. The most common problems now come down to human error. That’s the guy getting out and not shutting the door properly on the 11th floor so when someone calls it down by remote it doesn’t move,” Lawrence says.

He says the next most common fault is caused by the hoist cables becoming snagged, which again comes down to human error.

The industry itself operates identically to that of tower cranes, broadly involving manufacturers, hirers and contractors. The similarities between the two, Lawrence says, is why HTC Plant, part of the PC Harrington Group, moved into hoists in January 2008, when it purchased Hewden Stuart’s construction hoist division.

Now HTC is looking to undertake a first in the industry by designing a new universal tower which will be compatible with hoists manufactured by different companies. Currently the various hoists roll up and down along towers and connectors of different shapes and sizes. The company has begun the process of creating a uniform kind of track for the hoists to run along and is in talks with manufacturers to see this developed.

“It’s a new area for us, but we’ve been amazed at the interest we have had in it from contractors. But at the end of the day, they want something that is reliable, that won’t break down. They’d like it brought on site when it is needed, supported throughout the process and then taken away at the end,” Lawrence added.

In the UK, the installation, maintenance, examination and operation of construction hoists is covered by BS 7212. In 2009, the Construction Plant-hire Association (CPA) is expected to deliver two new safety documents via its Construction Hoist Interest Group. Release of the first document is currently pending approval from the Health and Safety Executive.

The Best Practice Guide on Working at Height for Construction Hoists is expected to be released in April. Its main goal is to protect people from falling from the hoists and to mitigate the effect of a fall if it does occur. It will encourage the use of restraint systems rather than fall arrest systems, because fall arrest systems risk creating dangerous suspension trauma injuries. The CPA says its objective is to create an even playing field for safety across the industry, which until now has been served by a mishmash of safety plans devised by separate companies in the hoisting industry.

Late in 2009 the CPA plans to release a revised version of the Best Practice Guide for the Maintenance, Inspection and Thorough Examination of Construction Hoists. This will be similar to a best practice guide produced last year on tower cranes, with almost identical approaches shown in how to plan maintenance and undertake inspections. Both documents will be available free on the CPA website (http://www.cpa.uk.net).

On a global front, in 2007 the Transport Platform Working Group (TPWG) was convened in Milan, Italy, under the auspices of the International Powered Access Federation’s (IPAF) Mast Climbing Work Platform Committee. The group’s goal was to create an international standard to promote safety in the use of transport platforms. The process is ongoing, and a spokesperson for IPAF says the latest developments are taking place in coordination with the European Committee for Standardisation (CEN) TC10 committee.

“The IPAF TPWG is monitoring developments from TC10, in order not to risk drafting a duplicating standard,” a spokesperson said.