meeting the requirements of nfpa 820

Standards

Certification

Education & Training

Publishing

Conferences & Exhibits

Meeting the

Requirements

of NFPA 820:

The Standard for Fire Protection in WW

Treatment and Collection Facilities

2016 ISA Water / Wastewater and Automatic Controls Symposium

August 2-4, 2016 – Orlando, Florida, USA

Speaker: Paul J. McGuire, P.E.

2016 ISA WWAC Symposium

Aug 2-4, 2016 – Orlando, Florida, USA 2

Presenter: Paul McGuire, P.E.

• Senior project engineer for NEORSD for 10 years

• I&C engineer for the District’s three

wastewater plants and collection system.

• 30 years I & C experience in various industries

• BSEET degree from Cleveland State University

• Registered professional engineer - State of Ohio

• Senior member of ISA

• Contact: [email protected]



NEORSD Overview

• Three activated sludge WWTPs serving 1 million people

in Cleveland and 61 surrounding communities

• Combined average daily treatment – 240 MG

• Collection system with 280 miles of interceptors and

relief sewers, pump stations, CSO storage tunnels, . .

• Stormwater management



Presentation Outline

• NFPA 820 overview

• What are NEC classified areas?

• Where are classified areas located?

• Using NFPA 820 tables

• Fire protection measures

• Alarms and ventilation

• Lessons learned



NFPA 820

• www.nfpa.org – Available for sale

– Free viewer

http://www.nfpa.org/



NFPA 820 - Overview

• Purpose:

–Provide fire & explosion protection

for life, property, continuation of

operations, and environmental

protection

–Reduce or eliminate the effects of fire

or explosion



NFPA 820 - Overview

• Applies to:

–New construction

–Additions or modifications to existing

facilities

• Owner to perform risk assessment



NFPA 820 - Overview

• Retroactive?

– Does not normally apply to facilities

constructed before effective date of standard

(1995)

– AHJ (Authority Having Jurisdiction)

CAN apply standard retroactively if

unacceptable degree of risk determined

– Retroactive requirements can be modified if

AHJ considers requirements impractical and

“reasonable degree of safety” provided



NFPA 820 - Overview

• Guidance/Requirements Document

–1990 – Recommended Practice

–1995 – Became a Standard

–2016 – Current Edition

• Next edition open for public input



NFPA 820 Contents - Chapters

– Chap. 1– Administration

– Chap. 2 – Referenced Standards

– Chap. 3 – Definitions

– Chap. 4 – Collection Systems

– Chap. 5 – WW - Liquid Stream Treatment

– Chap. 6 – WW - Solids Treatment

– Chap. 7 – Fire/Explosion Prevention/Protection

– Chap. 8 – Materials of Construction

– Chap. 9 – Ventilation

– Chap. 10 – Administrative Controls


Aug 2-4, 2016 – Orlando, Florida, USA

NFPA 820 Contents - Annexes

• Annex A – Explanatory Material

• Annex B – Wastewater Treatment Process

Overview

• Annex C – Collection System Materials of

Construction

• Annex D – Chemical/Fuel – Fire & Explosion

Hazards

• Annex E – Informational References

–(NFPA, UL, ISA, 10 States, etc.)

11



NFPA 820 Contents – Annex A

12

Classified Areas for

Anaerobic Digester

From NFPA 820, 2016 ed. Figure A.6.2(a)



NFPA 70

Guide to determine NEC classified

(hazardous) areas

What is Class 1, Division 1, Group D?

13



NFPA 70 - Article 500

• Class

– Class I – Flammable Gases/Vapors

– Class II – Combustible Dusts

– Class III – Ignitable Fibers

14




• Division*

–Division 1 – Gas/vapor always present or

can exist under normal conditions

–Division 2 – Gas/vapor present under

abnormal conditions only (leak, accident)

15

• NEC also recognizes international format Zone 0, Zone 1, Zone 2

for Class I areas. See NEC, Article 505




• Group – Group A – Acetylene

– Group B – Hydrogen, . . .

– Group C – Ethylene, . . .

– Group D – Methane, Gasoline, . . .

– Group E – Metal Dusts

– Group F – Coal Dust, . . .

– Group G* – Grain, Wood, Fibers, . . .

16

* Class II, Div 1 or Div 2, Group G for dried sludge dust



NFPA 820

• Wastewater Treatment/Collection Systems

– Most common area classifications

– Class I, Div 1 or Div 2, Group D

– Unclassified

– Less common

– Class II, Div 1 or Div 2, Group G (dried

sludge)

17



NFPA 820

• Sanitary Sewer (NNV) – Div. 1

• Combined Sewer (NNV) – Div. 1

• Storm Sewer (NNV) – Div. 2

• WW Pump Station Wet Well

– < 12 air changes – Div. 1

– 12 air changes – Div. 2

18 NNV – Not normally ventilated

Collection System Locations (Partial List)



NFPA 820

• CLASSIFIED

–HEADWORKS (BAR SCREENS)

–GRIT REMOVAL

– (PRE-AERATION)

–PRIMARY SETTLING

–ODOR CONTROL

19

Primary Settling Tank

Liquid Stream Treatment



• UNCLASSIFIED

–AERATION TANKS/TRICKLING FILTERS

–SECONDARY & FINAL SETTLING TANKS

– (FILTRATION)

–DISINFECTION

–PLANT EFFLUENT

20

Trickling Filter

NFPA 820

Liquid Stream Treatment



NFPA 820

Solids Treatment

• CLASSIFIED

–SLUDGE HANDLING

–SLUDGE THICKENING

–SLUDGE CAKE STORAGE (< 6 a.c.*)

–SLUDGE CAKE CONVEYANCE (< 6 a.c.)

– (DIGESTERS)

–SKIMMINGS (SCUM)

–ODOR CONTROL SYSTEMS

21

*a.c. – air changes



• UNCLASSIFIED

–SLUDGE DEWATERING (CENTRIFUGE)

–SLUDGE CAKE STORAGE (> 6 a.c.)

–SLUDGE CAKE CONVEYANCE (> 6 a.c.)

–SLUDGE CAKE INCINERATION

–SKIMMINGS INCINERATION

22

Centrifuge

NFPA 820

Solids Treatment



NFPA 820

Why area classifications?

– Type of equipment protection

(e.g., explosion proof)

– Installation methods

(e.g., conduit seals)

– Should result in safe

working environment and

equipment protection 23



NEC Area Classifications

• Recommendations – Produce a set of classified area drawings

for your WW plants and collection facilities

–Plans & elevations

–Shading and cross hatching

–Don’t use color as a differentiator of areas

–Can be used for current and future projects

–Can see where classified areas may overlap

–Preferred over notes on drawings

24



Sample Classified Area Plan

• Recommendation – Produce a set of classified area drawings for

your WW plants and collection facilities

–Site plans

–Elevations

–Shading and cross hatching

–Can be used for current and future projects

– Preferred over notes on drawings

Cross-hatched area is Class 1, Div. 2

25




• What would you rather see?

– For a Primary Sedimentation Tank (Not

Enclosed) –

–“Interior of the tank from the minimum

operating water surface to the top of the

tank wall; envelope 0.46m (18 in.) above the

top of the tank and extending 0.46 m (18 in.)

beyond the exterior wall; envelope 0.46 m

(18 in.) above grade extending 3 m (10 ft.)

horizontally from the exterior tank walls”

OR

26




Primary Sedimentation Tank (Not Enclosed)

27

From NFPA 820, 2016 ed. Figure A.5.2




• Lessons learned

– Don’t assume area classifications are correct

– Check for rated area extending beyond tank or

structure

– Check that ventilation supply air is from an

unclassified area

– Don’t assume ventilation rates are sufficient

– Don’t assume ratings of electrical equip. are

correct (enclosures, exhaust fans, HVAC)

28



NFPA 820

Table 5.2.2

Liquid Stream

Treatment

(6 pages total)



NFPA 820

Table 5.2.2 – Liquid Treatment

30

VENTILATION KEY:

A - < 12 a.c. (air changes)

B - 12 a.c.

MATERIALS KEY:

NC - Noncombustible

LC - Limited-combustible

LFS - Low flame spread

FIRE PROTECTION MEASURES KEY:

FE - Portable fire extinguisher

CGD - Comb. Gas Detection System

H - Hydrant

Location



NFPA 820


31

VENTILATION KEY:

A - < 12 a.c.

B - 12 a.c.

MATERIALS KEY:

NC - Noncombustible






H - Hydrant

Is space enclosed or not?



NFPA 820


32

VENTILATION KEY:

A - < 12 a.c.

B - 12 a.c.

MATERIALS KEY:

NC - Noncombustible






H - Hydrant

For new facility design



NFPA 820


33

VENTILATION KEY:

A - < 12 a.c.

B - 12 a.c.

MATERIALS KEY:

NC - Noncombustible






H - Hydrant

For existing facility



NFPA 820


34

VENTILATION KEY:

A - < 12 a.c.

B - 12 a.c.

MATERIALS KEY:

NC - Noncombustible






H - Hydrant



Combustible Gas Detectors (CGD)

• Selection & placement by “qualified person”

• CGDs shall be provided with a backup power supply

• CGD required for fire protection shall be set to alarm

at 10% LEL

– Alarm level may be set higher if allowed by AHJ (Authority

Having Jurisdiction) and if lower setting would create

nuisance alarms

– Typical setpoints

– 20% LEL – Warning

– 40% LEL – Alarm

35



Combustible Gas Detector Installation

• Don’t count on mounting location advice from manuf.

• Lighter than air & heavier than air gases rule of thumb

– Careful what you wish for on lighter than air gases

– May end up with detector mounted where it can’t be maintained

– Use remote kit – sensor at high elevation, transmitter at eye level

• Heavier than air gases

– Watch out for flooding

– Recommend IR type combustible detector

• Recommend using smoke test

• Mount near source of combustible (e.g., natural gas

line)

• NFPA 820 is a fire protection standard so it does not

address or require toxic gas detectors (CO, H2S, low O2)

36



Alarm & Ventilation Requirements

(Chapters 7 & 9)

• Positive confirmation of air flow with flow monitor

(e.g. flow switch) when ventilation is used to reduce

area classification

– Run contact from blower motor won’t suffice

• Both supply and exhaust fans required

(with monitoring for both)

• Continuous ventilation required

when reducing area classification

• Ventilation system shall have means to accept power

from alternate source (e.g., portable generator)

• Alarm failure of primary source of ventilation power

37



Alarm & Ventilation Requirements

(Chapters 7 & 9)

• Visual & audible alarms for CGD & ventilation failure

– Within spaces

– Entrances to spaces (Remote location exception)

– Don’t forget warning signs

• Air changes based on 100% outside supply air

– Partial recirculation allowed when certain criteria met

• Lower air rates allowed (>= 50%) when five criteria

are met.

– Fifth criteria new to 2016 ed. (ventilation d/p)

• Air recirculation (up to 75%) allowed when certain

criteria met

38



Summary

Why follow NFPA 820?

39

Photo source: Cleveland State University, Michael Schwartz Library, 1953



Thank You

Questions?

Paul McGuire, P.E.

[email protected]

216-881-6600

40

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