NFPA 20-2019 Handbook

VIP专享

阿拉丁 2024-09-16 22 108.44MB 1043 页 18星币

侵权投诉

Sixth Edition

Edited by

Chad R.W. Duy, P.E.

Senior Fire Protection Engineer, NFPA

Janna E. Shapiro

Fire Protection Engineer, NFPA

With the complete text of the following:

2019 edition of NFPA® 20, Standard for the Installation of Stationary Pumps for Fire Protection

2016 edition of NFPA® 14, Standard for the Installation of Standpipe and Hose Systems

2019 edition of NFPA® 291, Recommended Practice for Fire Flow Testing and Marking of Hydrants

2019 edition of NFPA® 24, Standard for the Installation of Private Fire Service Mains and Their Appurtenances

Stationary Fire Pumps and

Standpipe Systems Handbook

NATIONAL FIRE PROTECTION ASSOCIATION

The leading information and knowledge resource on fire, electrical and related hazards

BK-NFPA-20HB19-180214-FM.indd 1 08/11/18 12:07 PM

Copyright 2018 National Fire Protection Association (NFPA®). Licensed, by agreement, for individual use and download on 12/18/2018 to New Haven University Of. No other reproduction or transmission in any form permitted

without written permission of NFPA®. For inquiries or to report unauthorized use, contact licensing@nfpa.org. This NFCSS All Access subscription expires on September 30, 2019.

{7d1cf25d-f130-43e0-8b7f-041dc4ddd530}

Find

To nd a word or term in the PDF:

1. Select Find under the Edit menu or use the keyboard shortcut: CTRL + F for PC; COMMAND + F for Mac.

2. Type a word or term in the Find box. To specify Whole words only or Case-sensitive, use the drop-down arrow

to the right of the Find box and toggle these criteria on or o.

The found term will be highlighted in the text. To go to other occurrences of the term, use the previous and next

buttons that appear beside the Find box.

Advanced Search

Use the drop-down arrow to the right of the Find box and select Open Full Search. Additional search options are

available by selecting Show More Options at the bottom of the pane. Options in the advanced search window

include matching the exact word or phrase, matching only some of the words, and stemming (see below).

Stemming nds words that contain part (the stem) of a specied search word. For example, a search for

the word opening would nd instances of open, opened, opens, and openly. Wildcard characters (* or ?)

are not permitted in stemming searches. Stemming isn’t available if either Whole words only or

Case-sensitive is selected.

Links

Links to other sections of the document are colored red. When you click on a link and are directed to another

page, use the following keyboard shortcut to return to the original page: ALT + <left arrow> for PC;

COMMAND + <left arrow> for Mac.

PDF Navigation Tips

without written permission of NFPA®. For inquiries or to report unauthorized use, contact licensing@nfpa.org. This NFCSS All Access subscription expires on September 30, 2019.

{7d1cf25d-f130-43e0-8b7f-041dc4ddd530}

The 2019 edition of the Stationary Fire Pumps and Standpipe Systems Handbook contains the complete

mandatory text of the 2019 edition of NFPA 20, Standard for the Installation of Stationary Pumps for Fire

Protection, and the 2016 edition of NFPA 14, Standard for the Installation of Standpipe and Hose Systems,

as well as expert commentary to assist users in their understanding and application of the standards.

In addition to the commentary text, this edition of the handbook also offers a number of helpful fea-

tures, which are described below.

2019 Stationary Fire Pumps and Standpipe Systems Handbook

312 Part I•NFPA 20•Chapter 10 Electric-Drive Controllers and Accessories

10.4 Components

10.4.1* Voltage Surge Arrester.

A.10.4.1 Operation of the surge arrester should not cause either the isolating switch or the cir-

cuit breaker to open. Arresters in ANSI/IEEE C62.11, IEEE Standard for Metal-Oxide Surge

Arresters for Alternating Current Power Circuits (>1 kV), are normally zinc-oxide without gaps.

The “gaps” referred to in A.10.4.1 are common when using the silicon-carbide (Si-C) types of surge

arresters referred to in 10.4.1.1. A surge voltage of sufficient magnitude arcs across the gap and the Si-C

semiconductor element absorbs the surge energy. Once the voltage decays sufficiently or at the next

zero crossing of the current, the arc extinguishes and prevents any further leakage or follow-on current.

This allows the Si-C element to cool down and be ready for the next surge, spike, or transient event.

10.4.1.1 Unless the requirements of 10.4.1.3 or 10.4.1.4 are met, a voltage surge arrester

complying with ANSI/IEEE C62.1, IEEE Standard for Gapped Silicon-Carbide Surge Arrest-

ers for AC Power Circuits, or ANSI/IEEE C62.11, IEEE Standard for Metal-Oxide Surge

Arresters for Alternating Current Power Circuits (>1 kV), shall be installed from each phase

to ground. (See 10.3.3.3.)

Surge arresters are provided in controllers to prevent power line surges from damaging components in

the controller and/or rendering them inoperable. Typical failures due to a power line surge are burnouts

of indicating lamps and dielectric breakdowns of the magnetic contactor holding coil.

10.4.1.2 The surge arrester shall be rated to suppress voltage surges above line voltage.

Even when the surge arrester is rated above line voltage as required by this section, there will be some

amount of increase of the voltage during a surge; no arrester can perfectly clamp excess voltage. How-

ever, properly rated devices should limit damage to the equipment. Some controller designs have a

high “voltage withstand” capability to provide the most reliability against surges.

10.4.1.3 The requirements of 10.4.1.1 and 10.4.1.2 shall not apply to controllers rated in

excess of 600 V. (See Section 10.6.)

The typical voltages involved are 2300 V ac or higher. These controllers are required to meet a minimum

basic insulation level (BIL) so that they are immune to normal surges, switching spikes, and transients.

10.4.1.4 The requirements of 10.4.1.1 and 10.4.1.2 shall not apply where the controller can

withstand without damage a 10 kV impulse in accordance with ANSI/IEEE C62.41, IEEE

Recommended Practice for Surge Voltages in Low-Voltage AC Power Circuits, or where the

controller is listed to withstand surges and impulses in accordance with ANSI/UL 1449, Stan-

dard for Surge Protective Devices.

The reference to ANSI/UL 1449, Standard for Surge Protective Devices, was added as an alternative to the

10 kV (10,000 volt) impulse test provision because it is an ANSI standard and readily available to test to

at the approval agencies.

BK-NFPA-20HB19-180214-Part1_Chp10.indd 312 02/11/18 6:12 PM

Commentary text, which is printed in black

and shaded in yellow, is intended to assist

users in understanding and applying NFPA

20 and NFPA 14.

Mandatory text and nonmandatory annex

text from the standards are printed in

black with shading to indicate where text

has changed from the previous edition of

the standard.

Features of the Stationary Fire Pumps and

Standpipe Systems Handbook, 2019 Edition

Section 4.20 • Relief Valves for Centrifugal Pumps 117

Stationary Fire Pumps and Standpipe Systems Handbook 2019

valve is required by the standard to be installed is when the diesel engine is turning faster

than normal, and since this is a relatively rare event, it is permitted for the discharge from

the pressure relief valve to be piped back to the suction side of the pump.

4.20.1.1* Pressure relief valves shall be used only where specifically permitted by this

standard.

The use of a main pressure relief valve to trim excess pressure is considered to

be poor design and should be avoided. Several methods are available to cope

with excessive pressures, such as the following:

1. A break tank

2. A variable speed pressure-limiting control device (see 11.2.4.3)

3. Other pressure-regulating devices downstream of the fire pump discharge

control valve

A.4.20.1.1 In situations where the required system pressure is close

to the pressure rating of the system components and the water supply

pressure varies signicantly over time, to eliminate system overpres-

surization, it might be necessary to use one of the following:

(1) A tank between the water supply and the pump suction, in lieu

of directly connecting to the water supply piping

(2) A variable speed pressure limiting control device

4.20.1.2 Where a diesel engine re pump is installed and where a total of 121 percent of

the net rated shutoff (churn) pressure plus the maximum static suction pressure, adjusted for

elevation, exceeds the pressure for which the system components are rated, a pressure relief

valve shall be installed.

Pumps that create pressures less than the pressure rating of the fire protection system compo-

nents [typically 175 psi (12.1 bar)] at 110 percent of rated speed do not need a pressure relief valve.

The sample calculation that follows illustrates the procedure used to determine if a pressure relief

valve is needed.

The plans for a diesel engine–driven centrifugal pump

do not show the installation of a pressure relief valve. Is

this omission permitted?

ANSWER: Yes, this is acceptable in some installations. The

pressure relief valve requirement on diesel engine–driven

pumps is intended to prevent the piping from overpressur-

ization if the fire pump malfunctions and runs at a higher

speed than anticipated. If 121 percent of the pump’s churn

pressure is added to the maximum static pressure of the

water supply, and the total does not exceed the maximum

working pressure of the system components, a pressure

relief valve is not required.

ASK THE AHJ

FAQ

Does NFPA 20 permit the installation of main pressure relief valves in electric fire pump systems?

No section in this standard specifically permits the use of a main pressure relief valve on an electric fire

pump, except where a variable speed driver is used. Variable speed drivers are required to default to con-

stant rated speed operation in the event the variable speed driver fails. If operating at constant rated speed

can result in system overpressurization, a pressure relief valve is required. The pressure relief valve setting

must be above the set pressure of the variable speed driver.

BK-NFPA-20HB19-180214-Part1_Chp04.indd 117 11/3/18 1:58 PM

Frequently asked questions (FAQs)

are based on the most commonly

asked questions of the NFPA 20 and

NFPA 14 staff.

Ask the AHJ questions offer

snapshots of typical situations faced

by authorities having jurisdiction.

2019 Stationary Fire Pumps and Standpipe Systems Handbook

118 Part I•NFPA 20•Chapter 4 General Requirements

Prior to the 1996 edition, NFPA 20 required the installation of pressure relief valves for all diesel engine

fire pumps. This requirement was based on the assumption that, if engines ran too fast (a condition

known as overspeed), the fire protection system would be exposed to pressures in excess of the

pressure ratings of the system components. Because an overspeed shutdown device is required (see

11.2.4.4.1), the technical committee believes that a pressure relief valve is not needed on all diesel fire

pump installations.

A re pump rated for 1500 gpm (5677 L/min) and 100 psi (6.9 bar) at 1750 rpm has a shuto pressure

of 120 psi (8.3 bar). The shuto pressure produces 145 psi (10 bar) at 110 percent of rated speed. If a

maximum of 45 psi (3.1 bar) static pressure is available from the city water supply, the total pressure

when the pump is running at churn at 110 percent of rated speed is 190 psi (13.1bar).

Pressure increase at 110 percent of rated speed = 110%2 = 121%

120 psi (8.3 bar) × 1.21 = 145 psi (10 bar)

145 psi + 45 psi (10 bar + 3.1 bar) = 190 psi (13.1 bar)

In this case, a pressure relief valve (see Exhibit I.4.27) is needed if the re protection system com-

ponents are rated at 175 psi (12.1 bar). A pressure relief valve is not required if the re protection system

components are rated for 200 psi (13.8 bar) or higher.

CALCULATION EXAMPLE

EXHIBIT I.4.27 Pressure Relief

Valve with Waste Cone. (Courtesy

of JENSEN HUGHES, Inc.) Pressure relief valve

Discharge site cone

4.20.1.3 Where an electric variable speed pump or a diesel pressure limiting driver is

installed, and the maximum total discharge head adjusted for elevation with the pump operat-

ing at shutoff and rated speed exceeds the pressure rating of the system components, a pres-

sure relief valve shall be installed.

BK-NFPA-20HB19-180214-Part1_Chp04.indd 118 11/3/18 1:58 PM

Calculation Examples

illustrate important equations

and formulas.

Interactive PDF versions of the forms

featured in Part IV, Supplement 3 are

also available as “eForms” at

nfpa.org/20.

2019 Stationary Fire Pumps and Standpipe Systems Handbook

246 Part I•NFPA 20•Chapter 8 Positive Displacement Pumps

8.6.2.3 Bearings shall be in accordance with AGMA standards and applied for an L10 life of

15,000 hours.

8.6.2.4 For drive systems that include a gear case, the pump manufacturer shall provide a

complete mass elastic system torsional analysis to ensure there are no damaging stresses or

critical speeds within 25 percent above and below the operating speed of the pump(s) and

driver.

8.6.2.4.1 For variable speed drives, the analysis of 8.6.2.4 shall include all speeds down to 25

percent below the lowest operating speed obtainable with the variable speed drive.

8.6.3 Common Drivers.

8.6.3.1 A single driver shall be permitted to drive more than one positive displacement pump.

Paragraph 8.6.3.1 overrides the requirement in 4.7.4 and permits one motor/engine to drive multiple

pumps. The flow demands of a water mist fire protection system, combined with the low operat-

ing flow range of a positive displacement pump, commonly require that more than one pump be

driven off the same motor/engine driver. Manufacturers typically supply this arrangement in a preas-

sembled unit.

CLOSER LOOK

Torsional Vibration

Torsional vibration is the angular speed fluctuation of a rotating power train system. The fluctuations

are in response to torque pulsation from the driver, such as a diesel engine, or the load, such as a

positive displacement piston pump. Driveline components have inertia (mass) and store energy like

a spring when they twist (like elastic). When these components are assembled into a driveline sys-

tem, a unique “mass elastic system” is created that has unique resonant behavior. Resonance is also

referred to as natural frequency.

Think of resonant response as that of a tuning fork or wine glass to a vibration input. These simple

examples have a unique natural frequency which, when excited by a forcing function at that same

frequency, will generate high levels of vibration response. This can lead to damage or failure, such

as the shattering of the wine glass. The driveline will exhibit similar resonant behavior and must be

carefully designed so that frequency of the torque pulsations produced by the driver do not excite

any of the natural frequencies of the system when operating at any normal operating speed. The

rotational speed at which the pulsation frequency coincides with a natural frequency is referred to

a critical speed. Damage or failure to the driveline may result if the system is operating too close to a

critical speed.

“A complete mass elastic system torsional analysis” is an analytical computation that predicts the

dynamic response of a rotating power train system; it predicts critical speeds. Often referred to as a

torsional vibration analysis (TVA), it is exclusively concerned with the rotating degree of freedom and

disregards any lateral vibration (vibrations felt by the hand) or shaft whirl that may be present. This

is a tool the pump system designer can use to avoid designing a driveline that will run near a critical

speed. The mass elastic system model typically comprises lumped inertias connected by torsional

springs and damping elements. The data required to assemble the model is obtained from compo-

nent suppliers, measured in a lab, or estimated using an analytical solid model or finite element (FE)

model. The accuracy of the predicted response relies on the accuracy of the input data; care should

be taken to obtain the most accurate input information possible. Exhibit I.8.8 provides images of

damage that resulted from the rotating system being torsionally incompatible.

BK-NFPA-20HB19-180214-Part1_Chp08.indd 246 11/3/18 1:54 PM

Section 4.7 • Pumps, Drivers, and Controllers 75

Stationary Fire Pumps and Standpipe Systems Handbook 2019

4.7.7.2* Pressure relief valves and pressure-regulating devices in the re pump installation

shall not be used as a means to meet the requirements of 4.7.7.1.

The use of pressure relief valves is limited in this standard to the following situations:

• Constant speed diesel engine drivers where pressures developed can exceed the pressure rating

of system components if a 10 percent overspeed condition occurs.

• Variable speed drivers where pressures developed can exceed the pressure rating of system com-

ponents if a failure causes the driver to revert to rated speed.

A pump should never be deliberately oversized so that a pressure-regulating device is needed.

Pressure relief valves are maintenance intensive and should be incorporated into the design of a fire

pump system only when necessary and allowed by this standard. Pressure-reducing valves are not per-

mitted to be installed in the fire pump system piping. Where pump discharge pressures exceed 175

psi (12.1 bar), flanged cast-iron valves and fittings between the fire pump discharge flange and the

discharge isolation valve must be of extra heavy pattern. It is not the intent of 4.7.7.2 to limit the use

of pressure-reducing valves or pressure-regulating valves downstream of the discharge isolation valve.

The use of pressure-regulating valves downstream of the discharge isolation valve is covered in other

standards. In many cases, high-pressure output is needed to meet the design requirements of systems

installed in high-rise buildings and in standpipe systems in particular.

A.4.7.7.2 It is not the intent of this subsection to restrict the use of pressure-reducing valves

downstream of the discharge isolation valve for the purpose of meeting the requirements

of 4.7.7.

4.7.7.3 Variable Speed Pump.

4.7.7.3.1 Variable speed pumps, as dened in this standard, shall be acceptable to limit sys-

tem pressure.

Variable speed pumps control system pressure by changing the pump speed to prevent overpressur-

ization of the fire protection system. Using a variable speed pump can eliminate the need to use pres-

sure-regulating devices, such as pressure-reducing valves, in some system designs. A variable speed

pump can be used when high flow and high pressure are needed but, due to the nature of fire pump

For more information on pres-

sure control, see the feature

Controlling Excess Fire Pump

Pressures at the end of this

chapter.

DESIGN ALERT

EXHIBIT I.4.7 Check Valve

Listed for 300 psi (20.7 bar).

(Courtesy of JENSEN HUGHES,

Inc.)

BK-NFPA-20HB19-180214-Part1_Chp04.indd 75 11/3/18 1:56 PM

See More boxes indicate where

additional information can be

found in other sections of the

handbook.

Design Alert icons in the

margins alert users to points

of special interest.

Closer Look features provide

further information on select-

ed topics from the standards.

without written permission of NFPA®. For inquiries or to report unauthorized use, contact licensing@nfpa.org. This NFCSS All Access subscription expires on September 30, 2019.

{7d1cf25d-f130-43e0-8b7f-041dc4ddd530}

文档加载中……请稍候！
如果长时间未打开，您也可以点击刷新试试。

下载文档到电脑，查找使用更方便

亲，本站95%以上的标准规范都面向会员免费，办理VIP会员下载更省钱，平均每篇不到2元

立即下载

摘要：

The NFPA 20-2019 Handbook provides comprehensive guidance on the installation, maintenance, and testing of fire pumps and related equipment, serving as an essential resource for engineers, contractors, and facility managers. This edition includes the

展开>> 收起<<

NFPA 20-2019 Handbook.pdf

共1043页,预览4页

还剩页未读，继续阅读

声明：本文档系会员上传，若文档所含内容侵犯了您的版权或隐私，请立即通知，我们立即给予侵权申诉删除！

NFPA 20-2019 Handbook

相关推荐

开通VIP享超值会员特权

相关内容

热门标签

举报选择: