By: Joseph Sanchez
According to the U.S. Dept. of Labor, many workplaces contain spaces considered “confined” because their configurations hinder the activities of employees who must enter, work in, and exit them. A confined space has limited or restricted means for entry or exit, and it is not designed for continuous employee occupancy. Confined spaces include, but are not limited to underground vaults, tanks, storage bins, such as those used in wastewater pumping applications.
OSHA uses the term “permit-required confined space,” to describe a confined space that has one or more of the following characteristics: contains or has the potential to contain a hazardous atmosphere; contains a material that has the potential to engulf an entrant; has walls that converge inward or floors that slope downward and taper into a smaller area which could trap or asphyxiate an entrant; or contains any other recognized safety or health hazard, such as unguarded machinery, exposed live wires, or heat stress.
The greatest danger facing the person entering a confined space is a lack of oxygen. Several breaths of an atmosphere holding less than 6 percent oxygen can disable in seconds and can kill in minutes. Either the volume percent of oxygen can be too little (less than 19.5) or other gases (such as carbon monoxide) in the confined space may interfere with the body’s uptake of an otherwise sufficient supply. Oxygen deficiency can also debilitate sensors: Thus, a space with very low oxygen levels can’t be tested for combustible gases since standard instruments for this purpose require oxygen to function. (The sensor actually attempts to ignite a sample of the atmosphere and can’t do so when the fuel/oxygen ratio is too high.)
Not only is it dangerous to operate in a confined space, but it is also costly and time consuming for municipalities to maintain according to Metropolitan Industries Service Manager Mike Schiazzano. He says a permitted confined space needs a minimum three-man crew with the following safety gear; two multi function gas monitors, tripod with safety retrieval line, safety harness, a fresh air blower, a fresh air tank with airline, respirator and escape pack. Training the crew to use all safety gear along with the retrieval equipment procedures is also an added requirement. He adds by eliminating the need to enter or work in a confined space a municipality can save time and money.
Solutions to Confined Space Applications
Above-grade applications eliminate the danger, costs and manpower issues associated with confined space applications. Installations typically consist of a small control and generator building installed next to wells below grade containing pumps. The pumps are easily accessible and can be easily removed and installed without entering well using guide rails.
Costs and labor to maintain such an installation are minimal. Given that it is above grade and anything below grade is accessible from above, typically one person can operate the entire station reducing operating costs. Also further reducing cost is the elimination of the equipment and safety apparatuses associated with confined space entry.
Metropolitan Industries, Inc. specializes in the design and manufacture of above grade, lift station/control packages and recently completed two such jobs in Merrillville, Ind. that eliminated previous confined space applications.
Broadfield Lift Station
Working with Robinson Engineering and Contractor Hasse Construction, Metropolitan Industries, Inc. supplied a triplex, component lift station complete with a prefabricated building that houses the controls, valves and generator.
The triplex concrete lift station uses three, 50 HP, rated for a total 1442 gallons per minute (GPM) at 89.2 feet of total dynamic head (TDH). One submersible level transducer and four level switches control on, off, override and alarm levels in side the basin. Access hatches, a pump removal lift out system and guide rails allow easy access to pumps for maintenance without having to enter the 32’ basin.
To eliminate confined space entry, all controls, valves and a back up generator were housed in a prefabricated building measuring 19’ 3’’ long by 13’ 6’’ wide by 11’ tall building. The building itself was divided into two sections, one side for the controls and valves and the other side dedicated to just the generator.
On the control/valve side of the building, a triplex control panel with programmable logic controller and touch screen operator interface controls the system. The discharge pipe and valve assembly are located above grade inside the building for easy access.
The generator side of the building houses a Caterpillar 125kW, 3-Phase natural gas generator complete with accessories. A 400 amp automatic transfer switch allows for transfer to the generator during power outages.
Other features of the building include an HVAC system for climate control, high water alarm with dialer and battery back up, lighting and smoke detectors.
John Wood School Lift Station
The John Wood School Lift Station is another example of an above-ground application that eliminates confined space applications. This application called for a duplex component lift station again with a prefabricated control, valve and generator building. The duplex concrete lift station uses two 40HP submersible pumps, rated for a total 700 GPM at 113’ TDH. One submersible level transducer and four level switches control on, off, override and alarm levels in side the basin. Two lift-out hydraulic sealing flange assemblies allow pump removal for maintenance and repair without entering the sump.
Just as the last example, all controls, valves and a back up generator were housed in a prefabricated building but this one measured 18’ long by 13’ 6’’ wide by 9’ tall. The building as well was divided into two sections, one side for the variable speed controls and valves and the other side dedicated to just the natural gas Caterpillar generator inside.
Other feature of the building include an HVAC system for climate control, high water alarm with dialer and battery back up, lighting and smoke detectors.
Above grade applications eliminate the dangers and costs associated with confined space procedures. Towns and villages save money by eliminating the special safety gear and reducing the personnel required by OSHA on a service call. Municipalities will save time by eliminating the requirement of obtaining a “confined space permit” that designates what is to be done, when and by whom. No longer will the local fire and police departments need to be involved as sometimes the permits dictate. As demonstrated a “permitted confined space” requires special handling, equipment and a fair amount of extra time and work if all the rules are followed. Eliminate these hurdles with an above grade application.