By Colin Foreman
A new report has shown that even on low rise projects, hoists are a cost-effective alternative to using the stairs. They also make moving around site safer and quicker. But while there are big savings to be made in high wage economies such as the USA, do these savings apply to the lower wage economies of the Middle East?
Riding a hoist is cheaper and easier than taking the stairs|~|ALM036a-pic2body.jpg|~||~|Passenger hoists are cost-effective even when constructing low-rise buildings, according to a detailed new study by hoist manufacturer Alimak.
According to the report, leaving workers to climb stairs can be a false economy. There are substantial savings in time - and hence money - if site workers do not need to waste valuable minutes taking the stairs every time they return to ground level.
The newly-published report examines the time and cost of transporting people and materials for a range of building heights.
Typical break-even points for installing a hoist can be fewer than 50 workers for an eight-storey building and about 20 people on a 15-storey structure over the course of a year. Installation of a passenger hoist can even be an economic proposition on a three-storey site, particularly if there is no need for a full-time operator.
Using a hoist also brings many less quantifiable health, safety and time benefits, including greater productivity and a reduction in the time taken off because of injuries.
Costs of vertical transportation of site labour were calculated based on an Alimak Scando FC 28/37 TD rack and pinion goods/passenger hoist spending 50 weeks on site. Savings would be even greater for the new Scando 650 hoist, Alimak believes. Hire rates were put at 3% of the new/replacement cost.
The report calculates that the total cost of installing and operating the hoist ranges from about US $126 000 for a three-storey building to US $158 000 for one 15 storeys high. These figures conservatively assume that there would be a full-time operator, costing US $50 000 for the period. Some sites would need only part-time manned operation of the hoist or may not require an operator at all, which would dramatically lower the break-even point.
Typically each worker will make a total of eight trips a day to or from their place of work, including arriving, leaving and three breaks. Speed for walking up the stairs varies according to the number of floors to be climbed but reasonable assumptions can be made - from 50 seconds a floor for lower buildings to 70 seconds on a more tiring higher climb, allowing time to rest at the end.
Every person on a three-storey building can save over six minutes a day if they ride in a hoist instead of taking the stairs, the report found. Taking the hoist, a workman would travel an average of 6m at 39m per minute, typically taking just nine seconds to reach the destination.
Total journey time using a hoist would be just 54 seconds, allowing a 45 second wait before the nine second ride. Walking up the stairs would take 50 seconds a floor – a total of 1.67 minutes. Using a hoist for the eight trips in a day therefore saves 6.16 minutes a day for each person.
The savings are even more dramatic for an eight-storey building. Walking up the stairs is more tiring, taking 60 seconds a floor including a short rest before starting work. This gives a total time of 4.5 minutes for an average journey of 4.5 floors. In contrast the time spent travelling by hoist would be just 1.35 minutes allowing a one minute wait for its arrival. This saves over 25 minutes for every person over the course of a day. Not surprisingly, the contrast is even greater on a 15 storey structure, giving a daily saving of almost an hour per person.
Cost savings will depend on an individual contractor’s rates but the report assumes US $30 per hour. Using this rate, taking the stairs costs US $770 more per person than using a hoist during a 50 week period on a three-storey building. Costs rise to US $3 150 for an eight-storey building and US $7 460 where the structure is 15 storeys high.
Multiplying these values up by the number of workers gives the total cost of the extra time spent if they have to rely on the stairs. Not surprisingly, it is economical to run a hoist with fewer than 25 workers on a 15 storey structure. But less obviously, the hoist often proves to be cost-effective on lower buildings. Using the stairs on an eight storey building costs U$ 3 150 per person over a 50 week period. This equates to US $157 500 for 50 people, which more than justifies the US$139 529 cost of installing and operating a hoist.
Time lost on the stairs costs US$77 000 a year for a three storey building with 100 people on site. Installation of an unmanned hoist is just US$76,124 for the 50 week period. This gives a saving even without taking into account the other benefits of carrying goods and labourers to their place of work.
Less time spent on the stairs can readily translate into a reduction in the overall contract period, bringing further cost savings. Workers will be less tired, so productivity is also likely to be higher. Improved site conditions can be expected to lead to a reduction in the amount of remedial work needed.
There may also be savings in on-site overheads such as site supervision. Reductions in workers’ compensations and time off for injuries can also result, providing further benefits from the investment.||**||