| Форум -> Technical information -> Pump Station Design Requirements | Pump Station Design Requirements |
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| Engineer | Дата: 24.10.2017, в 13:11 | Сообщение №1 | 
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   | | Pump Station Configurations |
| | | Engineer | Дата: 24.10.2017, в 13:11 | Сообщение №2 |
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| Pump Station Terminology
The pump stations to be constructed as part of the Program are categorized into three general types:
C-P Standard Pump Stations
Program Pump Stations
Large Capacity Pump Stations |
| | | Engineer | Дата: 24.10.2017, в 13:12 | Сообщение №3 |
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| C-P Standard Pump Stations
In these Design Requirements, a C-P standard pump station is defined as one with two or three constant or variable speed pumps installed. All C-P standard pump stations shall be designed as submersible pump stations and shall have a minimum of two rail-mounted pumps (one duty pump and one standby pump) or three rail-mounted pumps (two duty pumps and one standby pump). They shall conform to C-P Standard Specifications and Details.
The C-P standard pump stations have been split into two groups. Type I pump stations are duplex and triplex stations that have electrical and controls equipment in a field panel. Type II pump stations are triplex stations that have electrical and controls equipment in an electrical building.
Standard pump stations shall also incorporate standby power generation as described in these requirements.
Program Pump Stations
In these Design Requirements, a Program pump station is defined as one with all of the following features:
Four, six, or eight pumps
Less than or equal to 500 horsepower (hp) per pump
Less than 50-foot wet well depth, measured from grade to the top of the bottom slab of the wet well
Capacity of 50,000 gallons per minute (gpm) or less
A minimum of four, variable speed pumps are required for these stations. Firm capacity of pump stations is defined as the capacity of the station with the largest capacity pump out of service.
All Program pump stations shall be designed as variable speed submersible pump stations using rail-mounted pumps with permanently mounted pump base and discharge pipe.
Pump stations shall be designed with an even number of pumps, including duty and standby pumps. The required number of pumps shall be based on the ratio of peak wet weather to average dry weather flows. Also, with one pump running at minimum speed, a minimum velocity of 2 feet per second (fps) in the forcemain shall be the goal, but not a requirement.
For Program pump stations with four or more pumps, the Engineer shall use a two- compartment wet well to facilitate maintenance. Compartments shall be capable of being isolated from each other with sluice gates, electrically operable from a concrete slab at or abovegrade.
Large Capacity Pump Stations
In these Design Requirements, a large capacity pump station is defined as one with at least one of the following features:
A firm capacity in excess of 50,000 gpm
Wet well in excess of 50 feet deep
More than 8 pumps
More than 500 hp per pump
The Engineer shall provide dual wet well compartments for all large capacity pump stations. Also, submersible pump stations shall be used if possible for all large capacity pump stations. Wet well/dry well pump stations may be used for large capacity pump stations if agreed to by the Louisiana Department of Public Works (DPW) and Project Manager.
Design of a large capacity submersible or wet well/dry well pump station is not specifically covered under these standards and shall be based on project-specific evaluations supplemented by applicable portions of these requirements. |
| | | Engineer | Дата: 24.10.2017, в 13:15 | Сообщение №4 |
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| Site Layout
Planning and design shall specifically address the visual impact on the neighborhood; access to the site for normal service trucks; clearance/separation from property lines and adjacent facilities; potential odor impacts; and site security.
The pump station shall be oriented according to prevailing wind direction so as to minimize hydrogen sulfide gases entering control building intake grills or electrical panels whenever possible. If main electrical and control panels shall be installed outside, they shall be out of direct sunlight and located in weather-proof enclosures.
Equipment shall be oriented to minimize sound transmission to the adjacent neighborhood. Sources of sound, such as the engine generator, building air intake louvers, and odor control fans shall be located to direct noise away from the adjacent neighborhood, or so that the
pump station building blocks sound transmission to the neighborhood. Other noise control provisions, such as high mass walls may be considered if necessary.
For single-lot sites, the pump station shall be positioned centrally on the lot or so as to maximize separation between neighboring structures, within the clearance guidelines described below.
The Engineer may prepare a preliminary site layout plan. The plan shall be submitted for review and approval prior to the 30% design completion date. If required by the Project Definition, the preliminary site plan will be submitted as part of a formal 15% submittal.
The preliminary site plan shall include, at a minimum, the following information:
Dimensions between structures
Distances from structures to property lines
Location of all underground piping and utilities, both existing and proposed
Location of overhead obstructions, such as power lines or trees
Limits of paving
Existing ground elevations
Location of fencing and gates |
| | | Engineer | Дата: 24.10.2017, в 13:16 | Сообщение №5 |
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| Clearances
The site design shall include the following clearances:
At least 30 feet from all sides of the structure to the property lines, where space is readily available.
At least 20 feet from the structure to property lines on at least two sides, when available land is limited.
Wet well tops extending 8 to 12 inches above the finished grade without berming up to top slab elevation.
Minimum setback distances from all property lines shall be as governed by ordinances. Particular attention shall be paid to the clearances required in National Fire Protection Association (NFPA) 30 between the generator base-mounted fuel tank and property lines or the edge of public rights of way.
Intrusion Protection/Fencing
Site security shall be provided by a full-perimeter intruder resistant fence, including one 12-foot-wide, inward-opening, double-leaf swing gate secured with chain and keyed padlock. The fence shall be a 6-foot high wooden fence in accordance with C-P Standard Details. Other security measures will be considered on a case-by-case basis, if special conditions or requirements dictate.
Access Requirements
The site security fence and entrance gate shall be placed far enough from the street to allow maintenance vehicles to be off the main roadway when the operator stops to unlock the gate.
Access roadway shall be concrete pavement and width shall be 12 feet. Turnout radius (inside) shall be at least 50 feet, or long enough to prevent truck or crane wheel overrun from the pavement. For Program pump stations, access roadway shall allow for trucks or cranes (20 ton mobile crane) to turn around and to safely enter the main roadway from the turnaround points. Curbs on access road shall not be required.
The site shall be reliably accessible during a 25-year flood event.
Operation and Maintenance Considerations
The pump station, including all mechanical and electrical equipment, shall be designed to withstand and operate during a 100-year flood event, including wave action.
The site layout shall address access and setting of vehicles that will lift out submersible pumps, the engine generator, or other equipment and to allow easy access to fuel the generator if a diesel engine is used. Site size, facility locations, clearance areas, overhead utilities, and orientation of hatches shall be coordinated with the setting position and lifting capacity of a maintenance crane.
Paving into the site and around the inside of the site shall be Portland cement concrete of sufficient design and thickness for anticipated loads.
Portland cement concrete pavement with minimum drainage slopes shall be provided around the pump station, piping, valves, electrical buildings, or control panels. The pavement shall be wide enough for proper mobility of the appropriate vehicle, but not less than 12 feet. In areas that are not accessible to vehicular traffic, concrete shall extend a minimum of 4 feet from all structures and control panel bases. To minimize grounds maintenance and such items as grass and weed cutting, the remaining area inside of the perimeter fencing shall be covered with 4 inches of crushed limestone with geotextile fabric.
Pipe bollards shall be shown on the drawings around the pump station for protection of equipment and the generator fuel tank.
Landscaping
Pump station site designs need to be safe and simple. Aesthetically, they shall blend into the surrounding landscape. All disturbed areas not paved or covered with limestone (outside the fenced area) shall be covered by sod.
Grading and Drainage
Pump station sites shall be graded so that surface water does not drain into the wet well, meter vault, or valve vault. Slopes shall not be greater than 1 foot vertical to 6 feet horizontal. Storm water shall be collected in pipes or swales, for discharge or retention
onsite in accordance with local requirements. The Engineer is responsible for investigating all local storm water issues and incorporating specific requirements into the project design.
All sites greater than one acre shall be analyzed to determine existing drainage patterns and to identify receiving outfalls or structures. The existing patterns must be adhered to and the receiving outfalls shall be upgraded to accommodate any increased flow for which they were not designed to accept. If this is not practical or is cost prohibitive, detention may be required. If the site is located on an outfall (stream, canal, ditch, and so forth) and the upstream watershed is 10 times greater than the site area being developed, no analysis is required.
Pump Wash Down Facility
Each Program pump station with four or more pumps shall contain a three-sided walled (6 feet high) pump wash down facility. It shall be sized to accommodate the largest pump, with a 3 feet clearance around the pump. The facility shall consist of a minimum 12-inch reinforced, sealed concrete slab with concrete masonry unit (CMU) walls with an epoxy coating. The slab shall be sloped to the rear wall with a 6-inch valved drain, which shall terminate in the pump station wet well. |
| | | Engineer | Дата: 24.10.2017, в 13:17 | Сообщение №6 |
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| Pump Station Hydraulics
Design Flows
All pump stations shall be designed to carry the estimated design wet weather flow, from the area ultimately contributing to the pump station, by the corresponding sanitary sewer system. The Project Manager will provide the hydraulic design criteria. The Engineer is responsible for submitting written requests to the Project Manager for additional information.
Peak wet weather hydraulic design for existing sewers and pump stations shall be based on the flow data provided by the Project Manager. The Project Manager will furnish the
Engineer with the following design flows as part of the Project Definition:
Average day dry weather flow rate (ADWF)
Peak wet weather design flow rate (PWWF)
The minimum flow condition is not provided to the Engineer, since the InfoWorks model does not include minimum flows. The Engineer must determine the minimum flow condition.
If the discharge forcemain is not part of the design scope of work or is part of the Suburban Transportation Network (STN) forcemain system, the Project Manager will furnish the following additional information:
Corresponding boundary system curves
Pump hydraulic design point
A form showing the standard information to be provided by the Project Manager to the Engineer is included in Attachment A. |
| | | Engineer | Дата: 24.10.2017, в 13:17 | Сообщение №7 |
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| Design Criteria
The following design criteria shall be considered for hydraulic design:
Hazen-Williams C-values shall be as defined further in this document.
Hydraulic Institute Engineering Data Book, or other recognized reference for hydraulic data, shall be used for fitting and valve velocity head K-factors.
The velocity of the pump suction line (where provided) shall be between 3 to 5 fps and shall be within pump manufacturer’s recommendations.
The velocity of the pump discharge piping shall be generally 5 to 10 fps at design peak wet weather flow. Pipe velocities shall be a minimum of 2 fps with one pump operating at minimum speed, if practical.
Net positive suction head (NPSH) calculations shall be provided by the Engineer, at design and boundary conditions. The NPSH available, as calculated by the Engineer, shall be compared to the NPSH required by the pump manufacturer. The calculated
NPSH available shall be a minimum of five feet greater than the NPSH required at design and boundary conditions.
For submersible pump stations, a minimum of two feet shall be added to the manufacturer recommended minimum submergence requirements.
The receiving sewer shall have sufficient capacity to accept the peak discharge rate from the proposed forcemain while not surcharging (i.e., the HGL in the receiving sewer shall be beneath the pipe’s crown). Surcharging of receiving sewers is not allowed. This data will be provided to the Engineer by the Project Manager.
Pump stations, including sumps and baffle walls, shall be hydraulically designed per the latest version of the Hydraulic Institute Standards and the recommendations of the ITT/Flgyt Corporation for submersible pumps.
Engineers shall obtain a certification from the pump manufacturer that the pumps will perform in the designed pump station layout.
For pump stations with capacities greater than 10 million gallons per day (mgd) (7,000 gpm), the pump station and sump shall be modeled with a physical hydraulic model to confirm hydraulic design. Modeling goals and objectives shall be submitted to the Project Manager for review prior to model development. |
| | | Engineer | Дата: 24.10.2017, в 13:22 | Сообщение №8 |
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| Wet Well Volume and Level Controls
Types of Level Controls
The primary device for pump station level measurement for Program pump stations and for Type II C-P standard pump stations shall be a bubbler tube/captive air system. Captive air systems are to be provided for Type I C-P standard pump stations, and shall be as shown in the C-P standards. Captive air systems shall use optical float switches to provide HIGH- HIGH and LOW-LOW alarm and back up pump control.
A bubbler system shall be provided for stations with three or more pumps with an electrical/control building with dual air compressors, each mounted on its own receiver. The air compressors and associated bubbler tube controls shall be housed in a control panel and shall be located in the pump building. Bubbler systems shall use pressure switches on the bubbler tubes as the secondary control method for backup of the Programmable Logic Controls (PLC)-operated pump control system. Since pressure switches are discrete devices, they shall be used to indicate LOW-LOW or HIGH_HIGH levels, as well as intermediate levels, if desired. Pumps shall operate automatically, based upon the water level in the wet well. Normal pump operation will be controlled by the PLC-based control system, but the pressure switches will provide the backup pump control in the event of a PLC failure. For pump stations with two or more wet wells, provide one bubbler panel with two bubbler tubes, one to each wet well, and locate the bubbler control panel in the electrical/control building. The bubbler tubes shall be provided with a valve on each tube to the bubbler panel. A connection with a shut off valve will be added upstream for connection to the air pump for startup.
Level Control Settings and Wet Well Volume
The peak wet well elevation shall be maintained at one foot below the lowest inlet pipe invert discharging into the wet well for influent pipes less than 25 inches. Therefore, this maximum elevation shall be used to determine the LEAD PUMP ON elevation for a two- pump station, or the last LAG PUMP ON elevation for a three-pump or more station. The wet well high-level alarm shall be maintained at the lowest inlet pipe invert discharging into the wet well. Upon approval from the Project Manager, and based upon a case-by-case analysis, the high water level may be allowed to back up into the pump station influent sewer, for influent sewers greater than 29 inches, at a maximum depth of 0.5D above the sewer invert where it enters the wet well, where D is the inside diameter of the influent sewer.
The operating depth for LEAD PUMP ON level controls for pump stations with three or more pumps shall be based on the minimum allowed cycle times between pump starts, accounting for the incrementally reduced pumping capacities. Pump cycle times shall be calculated assuming one pump out of service.
A minimum of 1.5 feet shall be provided between incremental PUMP ON and PUMP OFF elevations. |
| | | Engineer | Дата: 24.10.2017, в 13:23 | Сообщение №9 |
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| Wet Well Volume for Variable Speed Pumping
The pumping range in the wet well with variable speed pumps shall be a minimum of
1.5 feet per firm pump. For instance, if there are four installed pumps, the pumping range will be 1.5 feet x 3 pumps = 4.5 feet. Therefore, the ALL PUMPS OFF elevation for variable speed pumps shall be below the ALL PUMPS ON elevation by 1.5 times the number of firm pumps (in feet).
Wet Well Volume for Constant Speed Pumping
These requirements only apply to C-P standard pump stations.
The PUMP OFF elevation shall be determined using the following equation:
Where Ve is the effective pumping volume in cubic feet, and Aw is the wet well cross sectional area in square feet. The effective pumping volume may be estimated as follows:
Where Q is the design wet weather flow rate in gallons per minute, Ve is the effective pumping volume in cubic feet, and tmin is the minimum time interval in minutes allowed in one pumping cycle. Minimum cycle time (tmin) is calculated as follows:
The time within one pumping cycle shall be limited in order to prevent motor insulation failure due to overheating. When a motor starts, the inrush current may be significantly higher than normal operating current, resulting in significant heat generation. Hence frequent motor starts do not give the motor adequate time to “cool down” between starts. The Engineer shall also refer to NEMA standards.
Pump cycle times shall generally be per the manufacturer’s recommendation, or limited to a minimum cycle time of 15 minutes (at design flow), per “Ten State Standards”, in the absence of a manufacturer’s recommendation.
For cycle times less than 15 minutes at design flow, the Engineer shall obtain written verification from the pump and motor manufacturer that cycle time is acceptable. Pump cycle times shall not exceed manufacturer recommendations and NEMA standards.
Wet well storage volume shall be such that detention time is less than 30 minutes at dry weather flow, per “Ten State Standards”, to minimize septic conditions and odor generation. For low flow conditions, controls shall cycle the pumps at a minimum of once every 30 minutes. For pump stations where 30 minute detention time cannot be achieved in combination with the minimum pump cycle time, the Engineer shall notify the Project Manager. |
| | | Engineer | Дата: 24.10.2017, в 13:25 | Сообщение №10 |
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| The magnitude of surge pressure is a function of the following:
Change in the velocity of flow
Density of the fluid
Speed of the pressure wave within the fluid and piping system
The speed or velocity of the pressure wave is a function of the following factors:
Pipeline material
Pipeline wall thickness
Pipeline diameter
Specific gravity and bulk modulus of the fluid being pumped
The magnitude of surge pressure for a given change in velocity is expressed by the Joukowsky Equation, for instantaneous change or stoppage of flow, or:
The Joukowsky Equation shall only be used for a preliminary estimate of the surge potential of the system. The equation is limited in that it will only accurately represent surge pressure head changes for single pipes with near-instantaneous flow velocity changes. In more complex situations, such as pumping stations or pipe networks, this equation tends to predict excessive pressures.
Whenever the pressure class of the forcemain would have to be increased due to the effects of surge or cavitation, the Engineer shall use a computer model capable of performing transient analysis to perform a more detailed assessment of surge potential. This often provides a lesser, but more accurate, design pressure. It also provides insight into potential problems, such as minimum and negative pressures within a pipeline. Accurate design pressures may allow the Engineer to specify less costly materials while still maintaining an appropriate safety factor.
Wet Wells
Configurations
For C-P standard pump stations, circular wet well configurations with a minimum inside diameter of 8 feet or maximum of 12 feet may be used for non-compartmentalized wet wells. Floor bottoms shall be sloped toward pump inlets to minimize grit accumulation. Compartmentalized wet wells shall have a rectangular configuration.
If the C-P standard precast concrete wet well with integral precast concrete valve vault detail is desired for use on a site with limited available land, the Engineer must get special permission from the Project Manager and the C-P. If this detail is used, the Engineer must design the integral valve vault for cantilever, with no support from the wet well below.
Wet wells shall be accessed directly and only from outside atmospheric areas.
Compartmentalized Wet Wells
Wet well compartments are required for Program pump stations or large capacity pump stations with four or more pumps. Wet well compartments essentially divide the well into separate, isolatable chambers with electrically operated, fabricated stainless steel slide gates in accordance with AWWA C561. These compartments allow maintenance or cleaning of the wet wells, submersible pump base flange repair, or the replacement of guide rails or guide cables without bypassing the pump station.
The dividing wall between wet well compartments shall extend to the top of the wet well, so that when the gate is closed the wet well being dewatered and potentially accessed is maintained dry and not subjected to gases from the adjacent wet well. This will serve to protect workers entering the dewatered wet well. A fabricated stainless steel slide gate is to be located in the dividing wall for hydraulic balancing when the wet well is compartmentalized.
A common influent chamber is required. All influent pipes will flow into this common chamber and the flow will split from there, through electrically operated, fabricated stainless steel slide gates, to the two wet well compartments.
At a minimum, wet wells (if odor control is not provided) shall be designed for passive gravity ventilation with a gooseneck vent pipe and equipped with non-corroding insect screens. Vent rates shall not create more than 1 inch of static pressure or vacuum to be applied to the structure at peak pump station design flow. Vent opening (bottom of gooseneck) shall be at least two feet above the 100-year flood elevation.
Concrete fillets shall be provided per Hydraulic Institute Standards to prevent solids build up in the influent chamber of the wet well and around the pumps.
The wet well hydraulic entrance with baffle shall be designed to minimize turbulence, air entrainment, and potential hydrogen sulfide gas release. |
| | | Engineer | Дата: 24.10.2017, в 13:25 | Сообщение №11 |
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| Geotechnical Coordination
At least one boring shall be located below the foundation of the pump station with a diameter, length, or width less than 20 feet. At least two borings shall be located below pump stations with diameter, length, or width greater than or equal to 20 feet. Depth of borings shall be extended at least 20 feet below the planned foundation base; actual depth is to be determined by the Engineer and their geotechnical engineer. The seismic site specific soil classification shall be provided by the registered professional geotechnical engineer preparing the soil investigation report in accordance with ASCE 7-05. Unless indicated by special site considerations, evaluation of soil corrosivity is not required.
Construction Type
For circular submersible pump stations with wet well inside diameters less than 12 feet, pre- cast, coated concrete pipe sections (conforming to fabrication and tolerance requirements of ASTM C478) may be used for caisson or conventional construction, instead of cast-in-place type concrete.
If the C-P standard precast concrete wet well with integral precast concrete valve vault detail is used, the Engineer is to design the integral valve vault for cantilever, with no support from the wet well below.
Wet wells shall incorporate an epoxy coating applied to the interior surface of the concrete, whether of precast or cast-in-place construction, in accordance with Section 822 of the C-P standards. Coating shall cover interior concrete surfaces of the wet well wall(s) and underside of the roof slab. Joints of precast sections shall be provided with a positive seal (see manholes in Conveyance Requirements). Construction joints of cast-in-place construction shall utilize a minimum 6-inch by 3/8-inch PVC waterstop. Detailing shall indicate a continuous seal.
Structural Design Criteria for Program Pump Stations
Structural designs shall be in accordance with the applicable codes and standards, including ACI 350.
Below-grade structures shall be designed to withstand external horizontal loads imposed by saturated lateral earth pressures with ground water at finished grade or at the 100-year flood elevation, whichever is higher, while empty, and internal hydrostatic loads while pump station is full of water with no external earth pressures. Lateral earth pressures shall provide for surcharge due to adjacent truck or crane loads. Where pump station consists of dual wet well compartments (cells), the common wall between the cells shall be designed for full hydrostatic load on one side while the other cell is empty.
The top slab of a submersible pump station shall support the dead load of the slab, plus a uniform live load of 250 per square foot (psf). The slab shall also support a concentrated live load at any location equal to the weight of the single largest submersible pump to be installed in the station. The facility design shall preclude vehicles from driving onto the top slab.
Buoyancy
A buoyancy analysis shall be performed to determine if additional restraint is required to prevent wet well flotation when the wet well is dewatered. The buoyancy analysis shall follow the recommendations of ACI 350.4R, Design Considerations for Environmental Engineering Concrete Structures, and as noted herein. The pump station and all ancillary below grade structures shall be designed to resist buoyancy due to groundwater at finished grade or the 100-year flood elevation, whichever is higher. The use of flap (hydrostatic relief) valves in the walls or pressure relief valves in the floor slab will not be an acceptable approach. The weight of items such as mechanical and electrical equipment, water weight, baffle walls, fillets, grout fill, shall not be considered in resistance against buoyant forces, since these are either temporary or may change in the future.
Note that special precautions may be required to prevent the possibility of flotation during the construction of the wet well.
Access Hatches
Hatches shall be gasketed to prevent rainwater from entering the pump station and designed for a uniform load of 250 psf. The frame and cover plate shall be fabricated from extruded aluminum trough flange with continuous anchor flange around the perimeter and aluminum checker plate or be constructed of 316 stainless steel. All aluminum embedded in concrete shall be coated with a bituminous paint. The frame and cover plate shall be equipped with all Type 316 stainless steel hardware and accessories, including lift assist mechanisms. Lifting mechanism shall consist of stainless steel compression lift springs enclosed in telescoping vertical housing or stainless steel torsion lift springs. The access hatch shall be provided with a hasp and recessed, keyed padlock locking system. Due to potential vandalism, a standard integral snap lock system shall not be used.
Pump access hatches (minimum 4 feet x 6 feet) shall be sized to provide standard or manufacturer’s recommended clearance on all sides of the pump as it is being removed. Sizing and placement of the hatch shall be in accordance with the pump manufacturer’s minimum recommendations and hatches shall be provided by the pump. Safety hatches shall be provided. Access hatches for maintenance of pumps and influent chamber shall be 4 feet wide x 6 feet long.
Handrails
Two-rail type handrails shall be provided where required by OSHA and shall be designed to sustain concentrated and uniform loads as prescribed in the IBC.
Aluminum handrails are acceptable. Carbon steel handrails are not acceptable, regardless of surface treatments they might receive.
Grating
Foot traffic grating shall be aluminum press-locked or swage-locked, rectangular, bar-type with manufacturer’s standard slip resistant surface. I-bar type grating will not be acceptable. Seat angles or support beams shall be aluminum, except for supports embedded in concrete, which shall be Type 316 stainless steel.
Light and heavy vehicle traffic grating shall be galvanized steel heavy-welded or press- locked, rectangular, crossbar type. Seat angles or support beams shall be galvanized steel, except for supports embedded in concrete, which shall be Type 316 stainless steel.
Wet Well Specialties
All guide rails, chains, anchor bolts, and other fasteners and hardware within the wet well shall be Type 316 stainless steel.
No permanent ladders or rungs are to be installed. No handrails or intermediate landings are to be installed inside the wet well. |
| | | Engineer | Дата: 24.10.2017, в 13:27 | Сообщение №12 |
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| Wall Construction
Wall construction shall be masonry bearing wall construction. Masonry may be decorative CMU, brick veneer on CMU back up, or brick/block cavity wall construction. Cast-in-place or precast concrete is allowed only where buildings do not require insulated walls. Concrete walls shall be aesthetically enhanced by use of rustication or formliners.
Roof Structure and Roofing Materials
All roofs shall have a minimum positive slope of ½ inch per foot for drainage to roof drains or roof scuppers. Gutters and downspouts are not allowed.
Roof penetrations shall be minimized or eliminated, where possible.
Roof construction shall be one of the following types:
Metal deck on structural beams.
Metal deck on steel bar joist.
Steel roof truss.
Light-gauge steel truss.
Pre-cast concrete hollow core slabs
Pre-engineered wood truss.
Roofing materials shall be rated for minimum UL I-90 wind uplift and use one of the following, as appropriate, for the roof structure construction:
Standing seam metal roof (preferred by C-P)
40-year architectural grade asphalt shingles (if approved by C-P).
Fully adhered or mechanically attached elastomeric single-ply membrane (if approved by C-P).
Energy and Insulation
Building shall be cooled only and not heated. Exposed insulation is not permitted.
Finishes
Exterior walls shall be coated with water repellent and sacrificial anti-graffiti coating.
Exterior eave overhangs shall be constructed of low maintenance materials such as metal soffit panels.
Interior wall surfaces shall be painted with semi gloss enamel for increased light reflectance.
Security
All louver openings shall be covered with anti-burglar bars.
Windows are not allowed. Doors shall not have any installed windows or panels.
Building Access
Doors and Hardware
Personnel doors and frames shall be of hot dip galvanized steel construction. Where security is a concern, stainless steel frames and doors shall be used.
For access to electrical buildings or rooms for the installation or removal of MCCs or control panels, doors shall be hot dip galvanized steel overhead coiling doors of sufficient height for equipment to pass through vertically.
Access doors shall meet the requirements of the IBC. All hardware shall meet BHMA standards.
Hinges shall be ball bearing, extra heavy weight, stainless steel finish, meeting BHMA 156.1 standards. Exterior hinges shall include a non-removable pin.
Locks and latches shall be lever–handled, mortise locks meeting BHMA 156.13, series 1000, grade 1 with stainless steel lock case and finish and non-ferrous or corrosion resistant working parts.
All active leaves of doors shall be equipped with closers. Exterior doors shall be equipped with door stops. Provide hold-open devices at doors used for moving equipment.
All exterior doors shall be fully weather-stripped and provided with thresholds.
Louvers
All louvers shall be factory finished, storm-proof, aluminum construction. Where operating louvers are required, a combination-type louver is recommended.
Confined Space Entry
All designs shall consider the provisions stipulated within OSHA and other regulatory agency requirements to protect operational and maintenance personnel from potential hazards in pump stations. In general, wet wells will not be regularly entered by maintenance personnel. |
| | | Engineer | Дата: 24.10.2017, в 13:30 | Сообщение №13 |
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| Pump Removal Systems
Only Type 316 stainless steel link chain shall be used to lift submersible pumps out of wet wells.
Pump stations with large submersible pumps that exceed the weight capacity of the C-P’s portable lifting equipment (10 tons) will require permanent hoisting systems for pump removal and replacement. The Engineer shall consult with the Project Manager regarding approved systems for pump removal and handling. Pump/motor combinations that weigh more than 10 tons shall have permanently installed bridge cranes for equipment removal, meeting the requirements stated below.
Pump Guide System
Dual Type 316 stainless steel guide rail systems shall be used for guiding submersible pumps to/from their anchorage/hydraulic connection points.
Guide rail supports shall be installed not more than 20 feet on center, with 10 feet preferred, all in accordance with the manufacturer’s recommendations. Guide rails and supports shall be Type 316 stainless steel. Non-sparking components shall be specified for discharge connections. |
| | | Engineer | Дата: 24.10.2017, в 13:31 | Сообщение №14 |
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| Backflow Preventer
For Program pump stations, a reduced-pressure principle backflow preventer per C-P Standard Details for the required water supply source shall be located adjacent to the water meter with a minimum of one 1-½ inch diameter hose bibb on the exterior, supported by a pipe bollard, and 1-½ inch hose bibbs located onsite as necessary for pump wash down and wet well wash down. The backflow preventer shall be located on the water supply immediately as the line arrives onsite, and shall be mounted abovegrade in an appropriate, DPW-approved standard enclosure. The area shall be appropriately landscaped. Note that backflow preventers have a drain that operates periodically – this shall be taken into account in the design. The Engineer shall verify that adequate potable water pressure exists at the site, and that the need for potable water booster pumps is not required.
Provisions for Bypassing
For Program and large capacity pump stations, an abovegrade flanged connection, force main size, shall be provided to receive a DPW-supplied header. It shall be located downstream of the individual pump isolation valves to permit connection of a dewatering pump discharge during wet well maintenance. This will allow temporary pumps to be located in the influent chamber and to discharge to the forcemain so the pump station can be taken out of service.
For C-P standard pump stations, C-P Standard Details include a connection in the valve vault on the discharge of the pump station for bypassing purposes. An immediate upstream manhole or chamber on the influent sewer, within 30 feet of the wet well, shall also be provided to serve as the dewatering pump suction well.
Odor Control
The need for odor control will be identified in the Project Definition. The Engineer shall design biotowers for odor control for all pump stations where odor control is required, except those that pump only wet weather peak flows. Since biotowers need continuous operation, carbon canisters shall be used for pump stations that only pump peak wet weather flow. Wet wells shall have a minimum of six air changes per hour. At least two fans shall be installed. One or more towers shall be provided. Odor control scrubber connections shall be based upon site-specific requirements and condition.
For biotowers with a recirculation system, an air gap shall be provided per the detail entitled “Odor Control System Piping Detail” shown below. The air gap must be provided to meet the requirements of the Louisiana Department of Health and Hospitals. For biotowers without a recirculation system, the air gap is not required (see figure Odor Control System Piping Detail below).
Those pump stations that are in service on a continuous basis shall use biotower technology.
Design Criteria
Minimum Empty Bed Contact Time (EBCT) – 15 seconds
Hydrogen sulfide (H2S) inlet design conditions
Average concentration 10 parts per million on a volume basis (ppmv)
Maximum concentration 200 ppmv
Removal efficiency – 99 percent minimum
Those pump stations that are to be used for wet weather flow events only shall use activated carbon technology.
Design Criteria
Maximum superficial velocity – 55 feet per minute (fpm)
H2S inlet conditions
Average concentration 10 ppmv
Maximum concentration 200 ppmv
Removal efficiency – 99 percent minimum
Note: At some sites with more than one station, one of the stations may operate continuously while the other(s) only operates in wet weather conditions. In this case, biotower technology may be used for both stations.
Odor Ducts
Fiberglass (FRP) shall be used abovegrade.
Penetrations through concrete shall be Type 316 stainless steel
Buried duct work shall be high density polyethylene (HDPE) and shall have drainage provisions
Pigging Facilities
Pigging facilities will not be provided at pump stations for launching pipe pigs; however, the pump station’s bypass connection shall be arranged to allow the connection of a pig launcher. If this is not feasible, buried and plugged branches shall be provided so that these facilities can be installed in the future.
Pipe Finishes
Exposed interior and exterior piping shall be painted with an industrial-grade alkyd enamel with a primer coat, plus two finish coats per DPW standards.
Piping and pumps in wet wells shall be coated with high solids content epoxy per DPW standards.
Pump Station Layout
Attachment B includes two drawings for a typical Program pump station.
Ventilating and Air Conditioning Requirements
Design Standards
Ventilating and air conditioning (A/C) systems shall be designed in accordance with all codes. Ventilation with odor control shall be provided for wet wells where specifically required by the Project Manager. Cooling loads shall be calculated using ASHRAE methods. Ventilation systems shall be coordinated with odor control systems where both are used.
Area Classifications
Wet wells shall be classified as Class I, Division I, Group D areas, unless modified by ventilation, per NFPA 820. Electrical and control buildings and valve and meter vault spaces shall be located in non-classified areas per NFPA 820.
Motor Control Housing
MCC and instrumentation shall be housed in a separate air-conditioned electrical/control building. Field-mounted exterior panels may be used only for C-P standard pump stations. If VFDs are allowed in a field-mounted panel, the panel shall be air-conditioned.
Air Conditioning
Heating shall not be provided. Heat pumps are not allowed.
Any control building shall be equipped with moisture and condensation control; however, humidity levels shall not be specifically controlled in the building. The preferred design is a properly sized unit(s) (minimum two units at 50 percent capacity each) that runs continuously to keep the air moving and to provide adequate level of dehumidification through the cooling cycles. The heating, ventilating, and air conditioning (HVAC) units shall be wall mounted package units, if possible. Large units, if required, shall have an indoor evaporator and outdoor condenser mounted at grade level. Window units are not acceptable. Portions of the unit that contact high humidity and potentially corrosive atmospheres shall be coated with corrosion-resistant material. The protective coating shall be factory-applied and provided by the unit manufacturer. |
| | | Engineer | Дата: 24.10.2017, в 13:33 | Сообщение №15 |
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| Electrical Requirements
General
The electrical design for power distribution to the individual pump stations will be undertaken by the serving electrical utility, under a separate contract, and not addressed in these design requirements. However, issues of coordination with the serving utility are addressed.
The pump stations have areas classified under NFPA 820, Standard for Fire Protection in Wastewater Treatment and Collection Facilities, and NFPA 70, National Electric Code, as Class 1, Division 1 and Class 1, Division 2 hazardous areas and unclassified areas. All materials and electrical design applications shall meet the requirements of the area classification in which it is installed.
The typical pump station, from an electrical load perspective, consists of electrical service, power distribution, standby generation and automatic load transfer, pump controls, pumps, wet well level monitoring, ventilation and odor control fans, electrical protection components, and lighting.
The electrical design requirements for pump stations include the following elements:
Electrical Service Equipment
Power Distribution Equipment
Branch Circuits
Motor Control Equipment
Conduit System
Conductors
Junction Boxes and Enclosures
Lighting
Grounding
Transient Voltage Surge Suppression
Primary criteria for the design of the electrical system are that it is safe, meets capacity requirements, is reliable, provides desirable operational control and ease of maintenance, and is economically reasonable. The following sections are a discussion of the individual electrical system elements as it relates to the aforementioned primary design requirements.
Codes
National Electrical Code 2011 Edition
National Fire Protection Association 820
ANSI/IEEE Standard 141 for Motor Control Equipment
IEEE Standard 142 for Grounding
IEEE C62 for application of Transient Voltage Surge Suppression
National Safety Fire Protection Code
Electrical Service Equipment
The local electrical utility, as discussed above, shall provide electric service at 480 V, 3-phase for pump stations with pumps from 5 hp to 500 hp. If 480 V, 3-phase power is not available, 240 V, 3-phase may be used for converted loads of 100 hp or less. There may be cases where only single phase power is available. In these cases, phase converters or a new 3-phase service will be required. While 3-phase power is preferred, DPW shall decide which option, 3-phase power or phase converters, is to be used. Cost estimates for bringing 3-phase power to the pump station shall be received from the electrical utility to assist DPW in their decision making. The electrical engineer shall be responsible for coordination of all pump station power requirements with the serving electrical utility and obtain the associated approvals and cost estimates. The program has arranged dedicated points of contact with each electric utility, each of them are familiar with the program and have been charged with providing support.
It is anticipated that the utility will distribute power to pump stations with an underground service lateral to the electrical service equipment provided under these projects. The electrical service equipment shall consist of a utility conductor landing section, metering section, and a main breaker. All of these devices will be designed based on the serving utility’s service requirements. |
| | | Engineer | Дата: 24.10.2017, в 13:34 | Сообщение №16 |
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| Electrical Design, Power Distribution, and Motor Control Requirements
C-P Standard Pump Stations
C-P standard pump stations include pump stations with two pumps (duplex) and three pumps (triplex). Duplex pump stations are smaller pump stations that include one duty and one stand by pump. Duplex and triplex stations are defined as Type I and Type II pump stations in Section 805 of the DPW standard specifications.
Type I Pump Stations
Type I pump stations include both duplex and triplex pump stations with the electrical and controls equipment in a field-mounted panel, including VFDs, if specified.
Duplex pump stations are generally 75 hp or smaller and are typically constant speed, unless VFDs are needed for hydraulic reasons. Duplex stations with pumps 50 hp or greater shall utilize a reduced voltage soft starter (RVSS), rather than a full voltage, non-reversing starter (FVNR). Sheet 805-09, Sheet 2 of 2 shall note whether or not the starter is FVNR or RVSS.
Triplex Type I pump stations are generally less than 75 hp per pump and have VFDs. The DPW Engineering Division has prepared a set of standard drawings and specifications that show electrical design requirements for Type I pump stations. The Engineer shall follow these requirements for detailed design of Type I pump stations. The following drawings shall be followed for electrical design:
The Engineer shall obtain copies of the standard drawings listed above for use in electrical design of the duplex pump stations. For triplex stations with a field-mounted panel, standard drawings include VFDs and automatic transfer switch (ATS) incorporated into the panel. In sizing the generator and other electrical equipment, the Engineer shall use the maximum allowable pump motor horsepower as the basis, per the process mechanical Engineer.
The Engineer is responsible for final design and stamping of Sheet 805-09, Sheet 2 of 2.
Note that all equipment shown on these drawings are furnished and installed by the contractor except the generator and Supervisory Control and Data Acquisition (SCADA) cellular modem/antenna, which are Owner-furnished equipment. ATS shall be sized by the Engineer and furnished by the contractor. |
| | | Engineer | Дата: 24.10.2017, в 13:34 | Сообщение №17 |
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| Type II Pump Stations
Type II pump stations include triplex pump stations with variable speed pumping in an electrical building. Triplex stations include two duty pumps and one standby pump, with motor horsepower up to 300 hp. Type II stations shall also be designed in accordance with C-P standard drawings and specifications. The following drawings shall be followed for electrical design: |
| | | Engineer | Дата: 24.10.2017, в 13:36 | Сообщение №18 |
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| Branch Circuits
The load on branch circuits that supply lighting and receptacles, where applicable, shall be limited to 80 percent of the rating of the branch circuit protective device, per Article 220-3 of the National Electrical Code (NEC), because lighting and receptacle loads shall be considered "continuous." Branch circuit breakers for instruments, instrumentation panels, and other accessories, where the exact load is unknown but small, shall be sized at 15 amps to allow installation of multiple conductors to be installed in the same conduit without the need for de-rating. In addition, these circuits may pass through an instrument panel and become No. 14 AWG (American wire gauge) control conductors.
A separate branch circuit shall be provided for each instrument and instrumentation panel. Branch circuits and branch circuit protective devices shall be rated at 15 amps unless a larger size is required to supply the load. The design shall make an effort to group circuits that perform a common function together within a panelboard (i.e., all lighting together, all receptacles together). In addition, three- and four-wire branch circuits shall be used wherever they are appropriate to minimize the amount of conduit that is required. These circuits shall be connected to adjacent circuit breakers in the panelboard. Where a common neutral is used for multi-wire branch circuits, the neutral size shall be increased to account for third-harmonic neutral current generated by non-linear loads such as computers and other similar devices. Extra space and spare breakers shall be provided in all 208/120 V panelboards.
A 110 V branch circuit shall be provided at each pump station for a convenience receptacle located in pump station control panel and in appropriate areas of the electrical building to help facilitate maintenance. Area classification shall be considered in locating convenience receptacles. Ground fault interruption shall be provided for all outlets at a pump station.
Branch circuits for pump power, controls, and alarm circuits entering the wet well shall be designed to provide strain relief for conductors suspended in the wet well and provide a demarcation box outside the wet well for transition to conductors suitable for the wet well environment. The demarcation box shall be located outside the wet well and associated hazardous classified areas. The example drawings provide detail of the preferred demarcation box and method of applying sealing fittings. Appropriate sealing fitting shall be used between the demarcation box and any panel.
Pump stations with four or more pumps of 200 hp or more shall have dual feed with tie- breakers with the loads equally divided between each half of the line-up. |
| | | Engineer | Дата: 24.10.2017, в 13:38 | Сообщение №19 |
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| As a general rule, no conductor, regardless of voltage, shall be spliced, but there are certain situations where splices and terminations may be required. Low-voltage power conductors in lighting and receptacle circuits may be spliced using UL-listed, insulated, twist-on spring connectors (wirenuts). Splices in conductors to process equipment, control elements, and instruments shall be made with approved compression-type connectors. Final terminations at motors and similar equipment, where removal of the equipment for maintenance can be expected, shall be made with approved bolted connections. Splices are not allowed in control and instrumentation circuit conductors. Where splices are required, they may be made on terminal strips in a junction box (terminal junction box). Control conductors and cables shall be terminated at box, lug-type terminal blocks rated at 600 V.
All conductors shall be identified by a system of unique numbers. The conductor numbers shall be arranged in two parts. The first part shall be a termination identifier consisting of a series of letters and numbers that uniquely keys the termination to its respective pump station, control enclosure or device, and terminal number. The second part of the conductor number shall be in parentheses and contain the unique termination identifier for the other end of that conductor.
The following is the format to use for single conductor wire tags. Tag information to the left refers to the termination point. Tag information in parenthesis refers to the point of origination.
Device Terminal Identifier No. (Equipment Tag No.*/Device Terminal Identifier No.)
* For wiring within a piece of equipment, control panel, junction box, etc., the Equipment Tag Number is not required, only the Device Identifier and Terminal Number from the point of origination is required.
Example: For a wire connected from terminal block 1 terminal 23 to relay CR1 terminal 9, the correct tag would be TB1-23(CR1-9) at the terminal block and CR1-9(TB1-23) at the relay.
Each conductor shall be identified at each termination point and at all accessible locations, such as handholes, manholes, pullboxes, etc. Conductor and cable tags shall be machine printed and of the heat shrink sleeve type.
Junction Boxes and Enclosures
Junction boxes and pull boxes shall be provided to facilitate the combination of multiple circuits into a single conduit and the pulling of conductors and cables. Junction boxes shall be sized as required by the NEC to accommodate the conductors and cables being installed and conduits connected to them. They shall be constructed of a material suitable for the environment where they will be located. Small boxes shall be cast metal with suitable accessories for wet locations. Larger boxes located outside or in wet areas, shall be Type 316 stainless steel (316 SST) NEMA 4X rated. Boxes located in air conditioned areas shall have a NEMA 1 or 12 rating.
The term terminal junction box (TJB) shall be a term applied to junction boxes that contain terminal strips for the termination of control conductors, small power conductors, or instrumentation cables. They shall be constructed using a junction or pullbox that is suitable for the area where it is to be installed and contain terminal strips that are suitable for the conductors to be terminated. For C-P standard pump stations, a TJB detail is included in the standard drawings. For Program pump stations, a TJB detail is included in Attachment C.
Lighting
Site lighting shall be provided as directed by the DPW personnel for each specific site. Additional task lighting with a manual switch may need to be provided by maintenance personnel for some night repair activities. In addition, where switchgear enclosures are greater than 18 cubic feet, a switch controlled internal fluorescent light shall be provided.
Grounding
Electrical circuits, equipment, and equipment enclosures shall be bonded and grounded as required by Article 250 of the NEC. References to be used in designing grounding systems shall include the following:
NFPA 70–The National Electrical Code
IEEE Standard 142–IEEE Recommended Practices for Grounding of Industrial and Commercial Power Systems
A grounding electrode system shall be provided for all pump station site wiring systems as required by the NEC. The grounding electrode system shall be used for neutral grounding of the low-voltage power supply and the equipment ground conductors. Each power supply system shall be connected to a grounding electrode system meeting all requirements of NEC Article 250. Each item within the electrical system shall be bonded together by a bonding conductor sized in accordance with the requirements of the NEC. Grounding electrodes shall be 5/8-inch by 10-foot (minimum) copper-plated steel rod (copperweld or equal). |
| | | Engineer | Дата: 24.10.2017, в 13:39 | Сообщение №20 |
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| Transient Voltage Surge Suppression
Transient voltage surge suppressors (TVSS) shall be specified for the electrical distribution system including the main service, distribution, motor control equipment, and branch circuit panelboards per the recommendations of IEEE C62.41.1, C62.41.2, and C62.45 and compliant with UL 1449. The TVSS shall be designed for critical loads at service equipment (IEEE C62.41, Category C3/B3) or distribution panelboard (IEEE C62.41, Category C2/B3) locations. The TVSS equipment will limit the maximum clamp voltage line-to-line or phase- to-neutral per UL 1449 at 400 V for 208Y/120 3-phase and 120 V single-phase, and 800 V for 480Y/277 and 240 V 3-phase systems.
Standby Power Generator System
Generator Design
The pump station design shall include a standby power generator. The generator package will be purchased by the C-P, and provided to the pump station project as Owner-furnished Equipment. The Engineer shall include the Owner Furnished Products specification included in Attachment E with the specific generator product submittal included as a supplement to the Owner Furnished Products specification. The generator submittal will be provided by the Project Manager. The pump station construction contractor will install the generator and interconnecting conduit and conductors. The generator supplier will receive and store the equipment at a site in East Baton Rouge Parish, and make it available for pick up by the pump station construction contractor. The generator supplier will provide start up services as part of the generator supply contract.
Generator packages shall consist of a skid-mounted, diesel-engine-driven generator set with an integral double-wall sub-base fuel tank. The design generator size is listed in the Project Definition document. This size shall be verified during the design process by filling out the Electrical Load Estimate Sheet, included in Attachment F.
The generator package will include a sound/weather enclosure, a silencer for the engine, control panel, and a steel skid. A battery charger will be mounted on the skid and the engine will have a jacket water heater.
For C-P standard pump stations, an ATS will be included in the control panel in accordance with the C-P Standard Details. For automatic transfer control or ATS requirements for Program pump stations, see the example drawings referenced in Section 11.4 Power Distribution and Motor Control Requirements.
The generator shall be mounted outdoors on a concrete pad. If the generator is not located within a fenced pump station site, the generator shall be fenced by itself, with a minimum of 3-foot clearance between the generator and the fence and a gate of sufficient width to allow the entire generator package to be removed.
The Engineer’s responsibilities in regard to the generator include:
Locate the generator(s) on the pump station site.
If multiple generators are to be used for one pump station, include the Automatic Transfer Control System specification provided in Attachment G. This specification shall be modified by the Engineer as necessary for the specific pump station.
Provide distribution panel breakers, circuits, and raceways to the generator for the battery charger (115 V single-phase), the jacket water heater (115/230 V single-phase depending on generator size) and a duplex ground fault circuit interrupter (GFCI) receptacle inside the generator enclosure. For generators 750 kW and larger, with walk- in style weather and sound enclosures, provide a circuit to the distribution panel mounted in the enclosure.
Provide access platforms with stairway around the generator if the generator control panel is more than 6 feet abovegrade or the access door is more than 4 feet abovegrade.
Provide electrical load data to the PM to allow them to verify the generator sizing. Data shall include number of duty pumps, pump motor horsepower, motor voltage and phase, motor starting arrangement (across-the-line, soft start, variable frequency drive, etc.), and number and size of auxiliary loads such as lights, exhaust fans, heaters, sump pumps, odor scrubbing equipment, etc. The Electrical Load Estimate Sheet to be filled out by the Engineer is included in Attachment F. The Microsoft Excel version of the estimate sheet may be obtained from the PM.
Provide jacket heater 120 V receptacle (for 250 kW and smaller generators) and convenience receptacle. For larger generators, the size of the jacket water heater will be provided with the generator size.
Provide sealed engineering drawings of the generator installation for submission to the Louisiana State Fire Marshal for the generator-mounted fuel tank permit.
The PM will supply the designer with the following information:
Preliminary and final generator size and manufacturer’s data for the proposed equipment.
Verified generator size and manufacturer’s data for the proposed equipment after the designer provides electrical load data.
Location where the generator will be available for pick up by the installing contractor. This location is included in Attachment E.
Additional power distribution design requirements are specified in 11.4 Power Distribution and Motor Control Requirements. |
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