Sewer Flow Metering Design Specifications & Guidelines

Meter Services Operations & Maintenance
Sewer Flow Metering Design Specifications &
Guidelines, Installation, O&M and Inspection Agreement
Date: September 2002 (Rev. 12/2015)

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Sewer Flow Metering Design Specifications & Guidelines, Installation, O&M and Inspection Agreement

Table of Contents

Section

Page

A. Scope................................................................................................................................1

B. Purpose and Principles of Operation................................................................................1

C. Agreements and Ownership of Flowmeter Installations..................................................2

D. Flow meter and Sampling Unit Design and Installation ..................................................2

1. Gravity Flow – Parshall Flume and Ultrasonic Flowmeter .......................................3

2. Pressurized Flow – Magnetic or Ultrasonic Tube Flowmeter ...................................5

E. Flow meter Installation Maintenance and Calibration.....................................................8

1. Maintenance Records.................................................................................................9

2. Calibration Check and Report....................................................................................9

Attachments

Attachment A - Summary of Sewer/Groundwater Meter Installation Steps, System Establishment Checklist, Document Requirements, and Process Flow Chart
Attachment B - Typical Manufacturers for Parshall Flume, Magnetic and Ultrasonic Tube Flowmeters
Attachment C - Sample Surveying Service Scopes Attachment D - Design Example Calculations Attachment E - Typical Flowmeter Installation Drawings Attachment F - Sample Specifications for various Flowmeter Systems
Section 02722 Precast Reinforced Concrete Flowmeter Vaults Section 06600 Fiberglass Reinforced Plastic Fabrications Section 10990 Miscellaneous Specialties Section 13400 Instrumentation Attachment G - Calibration & Maintenance Record Forms Attachment H - Sewer Flowmeter Installation /Inspection Agreement Attachment I - Sewer Flowmeter Installation /Inspection Request

Sewer Flowmeter & Sampling System Design Guidelines
A. Scope
The purpose of this manual is to provide the JEA’s customers the means of obtaining accurate sewer discharge flow data, and to provide the JEA with the means for sampling sewer discharge flows. Standardization of installations provides the JEA with accurate flow rates for billing purposes and a more efficient method of sampling industrial sewer discharges.
All items and issues discussed in the manual should be carefully reviewed, considered, and fulfilled in order to ensure a proper operating flow monitoring station.
JEA has many different types of customers that discharge into JEA’s sewer system. Some of the customers are residential and some are commercial/industrial facilities. In order to cover the wide range of JEA customers, this manual has been adapted accordingly. This manual has been developed to address sites that only require a sewer flow meter installation, and for those sites that require a sewer flow meter installation along with a sampling unit.
This manual provides guidelines for different types of sewer discharge systems: Open and Closed Systems. While this manual suggests the use of magnetic flow meter for pressurized/closed system, and Parshall flume/ultrasonic level sensor installations for open channel flow applications, special cases may arise where different types of installations that are more site specific, and more suitable may be allowable. This manual addresses “standard” installations only. However, the principles and basis for design and installation of the flow monitoring stations presented in this manual shall be used as guideline for unique site installations.
B. Purpose and Principles of Operation
Open Channel (Gravity Flow) The operation of an ultrasonic level sensor is based on the Doppler principle that there is an apparent change in frequency of sound or radio waves as a function of motion. The level sensor consists of a transducer and a transmitter. The transducer sends a continuous ultrasonic pulse into the liquid stream. When the transmitted frequency is reflected back to the transducer from a suspended particle moving in the stream, the apparent frequency change will be proportional to the velocity of the moving liquid. The transmitter measures the differences between the transmitter and the reflected frequencies and transmits an output signal linearly proportional to the liquid flow.

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Closed Channel (Pressurized Flows) The operating principle of a magnetic flow meter is based on the electrical law (Faraday’s law of induction) that an electrical current is directly proportional to the velocity of the conductor. A magnetic flow meter uses the fluid, which passes through it as the conductor. Therefore, the electrical current produced is proportional to the fluid flow rate and can be used to indicate the flow rate.
Ultrasonic flow tube meter operates on the principle of transit time difference can also be used for pressurized/closed discharge system. An acoustic signal (ultrasonic) is transmitted from one sensor to another. The time (transit) that the signal requires to arrive at the receiver is then measured. According to the physical principles, the signal sent against the direction of flow requires longer to return than the signal in the direction of flow; therefore, the difference in the transit time is directly proportional the velocity of flow. The transmitter coverts the measured values supplied by the sensors into standardized output signals.
C. Agreements and Ownership of Flow Meter Installation for All Future
Installations
Ownership of the meter and associated piping includes, but not limited to, operation and maintenance of the meter and parts replacement associated with the meter. If the flow meter is installed on the property of the customer, JEA shall have the right to access the flow meter installation and perform meter reading for billing purposes. As referred to in Attachment I, the Agreement establishes access rights and installation agreements between JEA and the proposed customer.
Surveying services will have to be performed at each of the installation locations to acquire a layout of the existing site and accurate elevations of all existing piping associated with the customer’s sewer discharge system. A “sample” copy of a Surveying Scope of Services that may be used once a surveying consultant has been established has been illustrated in Attachment C.
D. Flow Meter and Sampling Unit Design and Installation
In order to minimize costs associated with rework and reengineering, JEA requires that all surveying and design work be performed and sealed by Florida registered professionals. A minimum of three (3) sets of detailed construction drawings for any proposed new or revised discharge flow measurement system shall be made for review and archiving purposes. These drawings shall indicate the relevant pipe slopes, elevations, locations, dimensions, types and locations of instrumentation, details of flow metering elements, the estimated flow range (minimum, maximum, and average), and details of upstream and downstream piping, structures and devices which could influence flow through the flow monitoring installation.
All Work shall be done in accordance with the latest edition of the JEA Water and Sewer Standards, Details, and Materials, and the attached specification sections.

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Manufacturer’s calculations, catalog cut sheets, and data sheets shall be included with the construction drawings for any equipment installed as part of the flow monitoring system. Complete rating data and meter sizing calculations shall be submitted for any engineered flow metering device.
New systems need to be calibrated before installation and prior to activating the flow monitoring installation. A calibration report must be prepared and submitted with a completion of construction notification. The initial calibration should be conducted in accordance with the requirements specified herein, according to the manufacturer’s recommendations, and using JEA’s calibration report forms (See Attachment G).
Some installation may not require an Industrial Pretreatment Sampling Unit (IPSU). The need for a sampling unit shall be established by JEA. Please refer to http://www.jea.com/business/services/industrialpre/permits.asp for details. All flow instrumentation shall be housed in the equipment storage box indicated on the figures. Space will be provided in the equipment storage box for a sampling unit, whether the unit is installed initially or in the future.
1. Gravity Flow – Parshall Flume and Ultrasonic Level Sensor
For systems that consist of gravity flow, a Parshall flume with an ultrasonic level sensor shall be installed into the system. The type of ultrasonic level sensor installed shall be as specified in the attached Specification Section 13400, Attachment F.
1.1 Sizing/Selection Guidelines for Parshall Flumes and Ultrasonic Level Sensors for Wastewater Applications
To ensure proper operation of the Parshall flume, there are a few guidelines that must be followed when selecting the size of the flume. The size of the flume will depend on the minimum and maximum flow rates that the system will encounter. The size of the flume required for the customer’s specific flow rate can be determined from Table 1 indicated on Figure 1 in Attachment D. The selection of the ultrasonic level sensor shall be based primarily on the specifications detailed in the attached Specification Section 13400.

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1.2 Design/Installation Guidelines for Parshall Flumes and Ultrasonic Level Sensors for Wastewater Applications
The system in which the Parshall flume is to be installed shall be evaluated before the procurement/construction process begins. Calculations and supporting data shall be designed by a Florida registered professional engineer concerning, but not limited to, the elevation of the incoming and out going lines of the flume vault, corresponding pipe slopes, flow ranges, head calculations, upstream and downstream analysis, and all other relevant calculations. Once all relevant analysis and calculations have been performed, refer to previous section (1.1) for the Parshall flume and ultrasonic level sensor selection criteria. The flume installation design shall be in accordance with the flume design illustrated by Figures 2 through 4 in Attachment E.
The flume shall be installed with the inlet approach section completely level. When the crest of the flume is greater than 6-inches above the channel bottom or invert of the incoming pipe, then a short sloping approach to the inlet of the flume with a slope no greater than 4:1 shall be provided. A long, straight run of pipe shall be provided upstream of the flume to ensure that turbulent flow is not passing through the flume. The piping downstream of the flume vault shall not have a slope greater than 2%. The flume shall be installed to allow for free flow discharge downstream of the flume throat. The installation of the flume shall also be in accordance with the manufacturer’s recommendations. The position of the flow level sensor shall be per the manufacturer’s recommendations.
All 4-inch and larger piping associated with the Parshall flume and flow level sensor installation shall be SDR 26 polyvinyl chloride (PVC). All other piping shall be as indicated on the attached figures. A sufficient number of guard posts, acceptable to JEA, shall be installed in order to protect the flow meter installation from any damage.
1.3 Instrumentation/Power Supply
In a typical flume system, the flow level sensing device is usually an ultrasonic level sensor; depending on the system requirements, another level sensor type may be more appropriate and will be considered. The ultrasonic level sensor shall have the capability of interfacing with a JEA required ISCO sampling unit so that flow-proportioning sampling may be performed, please refer to http://www.jea.com/business/services/industrialpre/permits.asp for details. Each installation shall be provided with a JEA standard flow read-out for the ultrasonic level sensor, as indicated in the attached Specification Section 13400, in Attachment F. The flow read-out/totalizer shall be mounted in an upright position at a location and height (five feet minimum) accessible to JEA personnel for meter reading purposes. An extra duplex outlet will be required. All other instrumentation shall be installed inside the equipment storage box. The source of the power supply for the instrumentation shall be coordinated with JEA and shall

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NOT be tied into a Ground Fault Interrupter (GFI) circuit. If the plant/facility will have continuing sewer discharge, limiting or full capacity, the power wiring shall be routed in a separate conduit to a properly sized uninterruptible power supply (UPS). The UPS shall provide the necessary power directly to the meter. Using a UPS in this configuration will ensure a steady-state “pure” power supply and lightning protection. Industrial grade electric power surge suppression device should be considered regardless to better protect the system in case of lightning strike. Surge suppressors should be installed in both the electronic module (4-20 ma) and power module of the metering system.
All electrical equipment and wiring installed in a confined space or exposed to vapor space of the public sewer shall be suitable for operation in hazardous locations, as specified in the current National Electrical Code. All electrical equipment shall be of explosion proof construction, or alternately may be certified to be intrinsically safe by a nationally recognized testing laboratory, such as Underwriters Laboratories, Inc.
1.4 Meter Bypass
Meter Bypass is not allowed in any Gravity Flow (Open Channel) Discharge System.
1.5 Meter Flow Totalization
The readout from the meter shall be able to display totalized flow volume in thousands of Gallons and flow rate in Gallons per Minute (GPM)
2. Pressurized Flow – Magnetic or Ultrasonic Flow Tube Meter
For systems that consist of pressurized flow, (i.e. pump station with a force main) a magnetic or ultrasonic flow tube meter shall be installed into the system. All sizing, selection, design, and installation of the magnetic flow meters shall be in accordance with the following guidelines and the manufacturer’s recommendations. The following illustrates the guidelines and installation requirements for selecting and installing the magnetic flow meters:
2.1. Sizing/Selection Guidelines for Magnetic and Ultrasonic Flow Tube Meters for Wastewater Applications
a. To ensure that the flow meter operates accurately, there are a few guidelines that must be followed when selecting the size of the flow meter. Magnetic flow meters should be selected to create a desired fluid velocity through the flow meter tube between 3 feet per second to 15 feet per second. However, the velocity shall be no less than 2 feet per second for abnormal flow conditions that are extremely below the average flow rate and no more than 20 feet per second for peak flow

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conditions. The velocity through the magnetic flow meter generally should not be allowed outside of the desired velocity range for more than 5% of the total operating time of the system. The size of the magnetic flow meter required for the customer’s specific flow rate can be determined from the table of velocities based on flow rates as illustrated in Table 2 on Figure 1 in Attachment D.
b. Ultrasonic Flow Tubes Meter shall not be applied where discharge flow has gaseous content.
All other items involved in the selection of the magnetic flow meter should be as indicated in the attached Specification Section 13400, Attachment F.
2.2. Design/Installation Guidelines for Magnetic and Ultrasonic Flow Tube Meters for Wastewater Applications
The system in which the flow meter is to be installed shall be evaluated before the procurement/construction process begins. Calculations and supporting data shall be designed and performed by a State Registered Professional Engineer concerning, but not limited to, the elevation of the incoming and out going lines of the flow meter vault, flow meter sizing, flow ranges, and all other relevant calculations.
Once all relevant analysis and calculations have been performed, refer to previous section (2.1) for the flow meter selection criteria. The magnetic flow meter structure design shall be in accordance with the magnetic flow meter design illustrated by Figures 5 through 7 in Attachment E.
Magnetic or Ultrasonic Flow Tube meters shall not be installed immediately downstream of any mixing points in the system (i.e. any chemical addition, etc.) Any chemicals not fully mixed with the fluid can result in inaccurate readings. Flow disturbing piping obstructions located too near the magnetic flow meter inlet and outlet may add an additional 1 to 10% of uncertainty to the measured flow. The flow meter shall be installed with upstream and downstream pipe diameters of the flow meter per manufacturer’s recommendations. The meter shall be installed in a manner to provide sufficient space to facilitate calibration, in-line maintenance, or meter removal.
The meter shall also be installed to facilitate full flow within the flow meter at all times during flow recording. Meter orientation leading to non-full meter pipe, trapping gases, or resulting in material build-up on the electrodes severely degrades the meter accuracy, potentially costing the business owner extra in sewer bill.
Meter installed below ground level shall be properly insulated per NEMA 6P Standard or equivalent.

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The flow meter shall be electrically grounded properly per manufacturer’s requirements. Avoid locating the magnetic flow meter near heavy electrical induction equipment, as this may affect the performance of the meter. Orient the meter per manufacturer’s recommendations.

The corrosive and/or abrasive characteristics of the process liquid dictate the proper selection of the lining material and electrode construction. During installation of the flow meter, liner protectors shall be used to protect the flow meter liner. This will prevent damage to the flow meter liner during installation or due to over torqueing of the flange bolts during installation. The flange connections shall be torqued per the manufacturer’s installation specifications.

Flow meter installation shall be braced with proper weight and strength supporting structures strong enough to protect and hold up the meter in any field condition(s), above or below ground. All 4-inch and larger piping associated with the flow meter installation shall be restrained joint ductile iron pipe. All other piping shall be as indicated on the attached figures in Attachment E. The sump pump discharge shall be routed to the nearest JEA sewer manhole. If the nearest JEA sewer manhole is not a feasible option, the sump pump discharge line shall be routed to the upstream wetwell. A sufficient number of guard posts, acceptable to JEA, shall be installed in order to protect the flow meter installation from any damage.

2.3. Instrumentation/Power Supply

The magnetic or ultrasonic flow tube meter shall have the capability of interfacing

with ISCO sampling unit so that flow-proportioning sampling may be performed,

if an on-site sampling unit is required.

Please refer to

http://www.jea.com/business/services/industrialpre/permits.asp for details. Each

installation shall be provided with a JEA standard flow read-out for the magnetic

flow meter, as indicated in the attached Specification Section 13400 in

Attachment F. The flow read-out shall be mounted in a location accessible to

JEA personnel for meter reading purposes.

Driven-shield signal leads shall be used and routed between the transmitter and the meter through a dedicated 1-inch or 2-inch conduit, depending on wiring size. Each installation shall be provided with a flow read-out for the meter, as indicated in the attached Specification Section 13400, in Attachment F. The flow readout/totalizer for above ground installation shall be mounted in an upright position at a location and height (three feet minimum) accessible to JEA personnel for meter reading purposes. The remote flow read-out/totalizer for underground installation shall be mounted in an upright position at a location and height (five feet minimum) accessible to JEA personnel for meter reading purposes. An extra duplex outlet will be required. The source of the power supply for the instrumentation shall be coordinated with JEA and shall NOT be tied into a

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