RokStories Automated Guided Vehicle Systems - a Hands off Approach to Removing Medical Waste
By Todd Williams
Medical waste management is perhaps the least desirable item that has to be dealt with by hospitals. It is also one of the most important functions a hospital has to address.
As modern hospitals have increased in size and patient capacity, the labor- intensive collection and disposal of waste have become more difficult and thus more expensive.
To meet this problem, various methods of waste collection have been tried to varying degrees of success. Of course, the methods of collection differ from facility to facility with most still relying on manual labor.

In an increasing number of hospitals, especially large facilities, the use of Automated Guided Vehicle Systems (AGVS) is becoming more and more popular. First introduced back in the late 1960’s as a labor-saving way of material handling in places as diverse as printing plants and automotive manufacturing, these robotic systems began to be adopted by hospitals as a way to distribute supplies and collect both medical waste and general trash.

According to Ed Schachinger, president of The Schachinger Group, a Fairfax, VA-based consulting firm specializing in materials handling and management including waste management, there are now approximately 30 hospitals in the US of some 300 to 350 hospitals worldwide that use AGV systems.

Typically, The Schachinger Group provides its hospital clients physical and economic feasibility studies followed by functional and space programming. It then designs and writes specifications for highly sophisticated materials and waste management systems including AGVS.

“We create the specifications and then a set of drawings. Vendors then bid on the system and we consult with the hospital as to which system is best suited for its needs,” Schachinger noted.

He said a 700-800-bed hospital needs between 35-45 AGVs while a 1,000-bed hospital needs over 50 vehicles.

AGVs are integrated robotic systems employing self-powered wheeled vehicles that pick up and deliver waste and materials on a pre-programmed, guided route, according to Bob Baker, Manager of Technical Services at The Schachinger Group.

The vehicles can follow a path of buried magnets, an eye-safe laser system that follows wall-mounted targets using triangulation to fix the position of the vehicle enabling it to follow a defined path, or a contour following system that knows the hospital layout and identifies landmarks to navigate. The vehicles generally stay within one-half to one-quarter inch of their planned route. Also the robot is in constant wireless communication with a central command station.

According to Baker, in most hospitals medical “red bag” waste is collected from patient rooms by hand, put into carts and transported to a central collection point for either on-site disposal of pick up for off-site disposal. This old way of doing things can cause a risk of contamination to surfaces such as elevator buttons and doors when the employee handling the waste touches these surfaces. Also, in large facilities the employee may have to push a cart a great distance to reach the final destination. Of course, the use of vertical chutes to drop red bags is unworkable and illegal because of the risk of contamination.

With AGV systems, bags are brought to a utility room on each patient floor where they are manually transferred to a collection point in specially designed carts to await robot pick-up. About two or three times a day the robotic vehicle arrives, picks up the waste loaded cart, and work its way to the main waste collection point. There the bags are hand sorted and either sent to an on-site autoclave or incinerator, or held for off-site pick-up and disposal, Baker explained.

“The AGVs are demand driven, not scheduled. Each vehicle will scan a bar code on the cart to insure that it is picking up medical waste and not something else. The waste is taken to its final destination where the cart is unloaded. The robot then drops off the dirty cart to a washing area for about three minutes. There it then picks up a clean cart and is off to its next assignment,” Baker said.

AGV systems normally send the robot with its now clean cart to an area where it does double duty by taking supplies or food back to the patient floors for distribution, and once again to bring waste back down, thus completing the cycle.

In the Cleveland (Ohio) Clinic’s Service Center, over 1,000 such carts are carried by 81 five-foot long AGVs, including waste carts, food carts, linen carts and heavy equipment carts. All the carts carry a radio frequency identification tag in order to ensure the right cart is going to the correct location on the proper robot. Also workers scan bar codes on the carts with hand-held devices to verify the proper delivery specifications for the material, noted Schachinger.

Dave Miano of Bostwick Design Partnership, Cleveland, project architect for the Cleveland Clinic Service Center construction job, said in just one day the robots travel over 1,000 miles on nearly 5,000 trips. The longest round trip from the Service Center through a tunnel to the hospital is nearly three-quarters of a mile long.

Schachinger called the robots “very efficient,” noting the entire system works on demand basis rather than a fixed schedule.

“Sometimes all 81 robots are out. But normally about 65 vehicles are online at any given time,” he added.

According to Baker, in all AGVSs the robots occasionally move offline to recharge their NiCad batteries. Termed “opportunity charging,” this process occurs after every 1,000-2,000 linear feet of travel. Most AGVs can take on several job assignments before recharging.

Baker explained that AGVs need monthly preventative maintenance including cleaning and inspecting the undercarriage and circuits as well as a battery change out for full cycle charging.

Another important part of the inspection is a check of the laser bumpers. These bumpers constantly scan the robot’s path for objects and people, ordering the AGV to immediately stop to avoid collisions. The detection field is 10-foot wide for full speed travel down to as narrow as 18 inches for elevators. Sensors also enable the robots to move around stationary objects. AGVs use their own, narrow elevators that are off limits to humans.

In the six-floor, 750-bed Greenville (South Carolina) Memorial Hospital, the 41 robots make use of narrow, dedicated AGV elevators that are devoid of all buttons, making them unable to be used by people.

According to Mike Bailey, Director of Environmental Services for the entire Greenville Health System, there has been an AGVS at Memorial Hospital since the late 1970s. This system is one of the two oldest hospital systems in the nation. When first installed, the robots operated by following a signal emitted from a buried wire line. When the system was upgraded several years ago it was changed to laser guided telemetry, Bailey said.

“The robots operate about three to four hours before recharging in 15 minutes. If a unit’s charge is totally depleted it may take up to 30 minutes to attain a full charge. Thirty two to 34 AGVs are operating at any given time in a 24-hour cycle. It is a very safe and reliable system,” Bailey added.

Bailey said Greenville’s AGVS cost about $10-$15 million to install and about $1 million per year to operate. Schachinger said a system including the vehicles, carts, elevators and cartwashers will range from around $1.4 million for a limited shuttle system moving a few hundred carts per day and running point to point between two or three locations to $16 million for a large installation moving about 4,000 carts a day.

“Generally,” Schachinger said, to do the same functions at the same levels of service the costs for a fully manual system will be about 60 percent of the costs for the AGV for elevators, carts, etcetera.”

He noted that when an AGVS is added to the project design at the programming and concept phases there is a greater opportunity for space savings equaling or exceeding the costs of the system.

For example, he explained that at the Cleveland Clinic a manual system that would have provided equal material handling service would have required 35,000 more square feet of space than with the AGVS.

Generally, Schachinger noted, the number of beds and the configuration of the facility will determine the cost. A 250-bed facility is usually the starting point for using an AGVS, he said.

Schachinger suggested that hospitals considering robotic material handling systems have a detailed materials handling study with a life cycle cost analysis done for the project.

These studies are particularly important when the hospital is contemplating installing the AGVS in an existing building.

“Can the building accept the system ‘as is?’ How much would be the cost for physical changes to the building?” he said.

Schachinger cited studies that show for more than 70 percent of the cases there might have been a significant financial saving with an AGV, but the existing building would not support the installation without significant and “deal breaking costs” and/or “operational compromises.

Although the cost of the system is extremely important, he added that there is a “quality benefit” derived from the use of robots.

“AGVs handle material better. They’re safer when dealing with medical waste. And they work 24 hours a day. They don’t take breaks or get injured lifting,” he added.

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