Zdenek Coubal, President of STROS, left a message at the 2013 Bauma China exhibition.
1. Introduction
STROS is the Czech Republic's largest manufacturer of construction hoists, serving customers worldwide. It ships three systems weekly. Eight skyscrapers in Russia's major construction project, "Moscow City," are currently under construction or have been completed using STROS hoists. These hoists can lift heights exceeding 300 meters and withstand wind speeds of up to 20 meters per second, ensuring their safety. Nord Drive Systems has partnered with STROS and has been its sole drive supplier for over 15 years.
STROS specializes in rack and pinion mast lifts, which enhance working height and allow for rapid installation. The gearbox output shaft features a gear secured by a rack that meshes with a guide rod. This robust drive system can withstand extreme environmental conditions for extended periods. Besides construction equipment rental and construction companies, STROS frequently supports power plants, industrial plants, and offshore facilities. Their completed projects span beyond the Arctic Circle and into harsh tropical climates. The NOV series personnel and material lifts offer maximum lifting speeds of up to 100 meters per minute and a load capacity of 3200 kilograms.
2. Moscow City Construction Project
The tallest elevator to date stands on the construction site of "Moscow City." This complex includes several high-rise buildings, eight of which are equipped with STROS elevators. One of these elevators is also used in the "Mercury City" building, currently the tallest building in Europe at 340 meters. The NOV2032 elevator has a lifting height of 350 meters, a load capacity of 2 tons, and a speed of 70 meters per minute. It features a control panel for operators to select floors and offers a level of comfort comparable to standard elevators in apartment buildings. The drive unit consists of three helical bevel geared motors with external braking resistors. "The motors are also equipped with electro-disc brakes that can be manually released," said Zdenek Coubal, President of STROS. "This is a customized solution from STROS Drive Systems. It reflects our collaborative spirit: whatever new challenges we encounter, STROS always provides consultation and testing, and develops solutions." The control cabinet, equipped with a lifting function, uses a frequency converter to control these three motors. It features soft start, stop, and high leveling accuracy. "We maintain a very close working relationship with construction companies," Coubal said. "They have indicated that our technology can save them time and costs."
3 Patented safety devices
The STROS engineering team designed a mechanical device to safely stop the lifting cage in case of malfunction. Once the predetermined descent speed is exceeded, the safety device trips, and then the lifting cage is gradually brought to a stop via a rack and pinion mechanism. This centrifugal mechanical device is individually configured for each model. STROS's safety device has received international accreditation from TÜV SÜD, the leading German technical testing authority.
4. Collaboration with Nord
Nord's partnership with STROS, serving as its sole drive supplier, began in 1997. At that time, STROS's predecessor first proposed expanding into the international market. Nord's subsidiary in the Czech Republic, NORDPoháncíTechnika,sro, convinced management in the first pilot project. Nord provided STROS with the reliable, long-lasting products it needed. Even so, for STROS, the most important factor in choosing Nord was its service capabilities, even in remote areas. Coubal said, "Nord truly lives up to its reputation as a one-stop supplier. They recommend optimal solutions for a wide range of applications in our daily operations. For example, we are not limited to standard gearboxes. These units need to be assembled correctly according to requirements. When we need them, Nord can also customize drives for us, providing reinforced bearings or special gearbox materials, or drives that meet ATEX and NEC standards for refinery applications."
5 Higher requirements
Initially, STROS used only geared motors. Since manufacturers at the time only produced relatively slow lifts, starting and stopping at speeds of 40 m/min could be easily controlled via a motor switch. However, as the customer base grew, so did the number of projects. STROS began manufacturing lifts for increasingly taller buildings. Therefore, the lift cages had to operate faster to reduce waiting times. Newer models are rated for speeds of 55 to 100 m/min and can be equipped with variable frequency drives. In addition to geared motors, STROS also offers control cabinet inverters to control motor speed and ensure precise braking. Advanced positioning and safety features, such as STO and SS1 functions, meet SIL3 safety level requirements.
6. Another type: Special permanent elevator
The 2008 construction industry downturn severely impacted suppliers like STROS. To survive, the company sought applications for its technology, venturing beyond construction hoists into permanent elevators for buildings, chimneys, and technical equipment. This new area now constitutes a significant portion of STROS's projects. For example, the company built a 150-meter-high permanent elevator for a chimney at the Siekierki power plant in Warsaw, Poland. This NOV514 elevator has a load capacity of 500 kg and a rated speed of 46 m/min. It is also equipped with a frequency converter to ensure soft start and braking, and features POSICON position control. The company subsequently secured a second project contract to build a 200-meter-high elevator for another chimney in the same factory.
7 Conclusions
If the hoist malfunctions, the entire construction site will be paralyzed. Therefore, the drive system must not fail under any circumstances. Nord designed three independently operating drives for STROS lifting equipment to prevent valuable downtime. Reflecting on Nord's 15 years as its sole drive supplier, STROS President Coubal said, "Nord's technology is reliable and its service is excellent." So what's the future? "Based on trends in the US, Canada, and Russia, we anticipate a growing demand for higher-performance drives and inverters due to increasing lifting cages, load capacities, and speeds. We are prepared to meet the challenges."
