Meeting the Requirements of NFPA 820:

Transcription

1 Meeting the Requirements of NFPA 820: The Standard for Fire Protection in WW Treatment and Collection Facilities Standards Certification Education & Training Publishing Conferences & Exhibits Speaker: Paul J. McGuire, P.E ISA Water / Wastewater and Automatic Controls Symposium August 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: mcguirep@neorsd.org 2

3 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 3

4 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 4

5 NFPA Available for sale Free viewer 5

6 NFPA Overview Purpose: Provide fire & explosion protection for life, property, continuation of operations, and environmental protection Reduce or eliminate the effects of fire or explosion 6

7 NFPA Overview Applies to: New construction Additions or modifications to existing facilities Owner to perform risk assessment 7

8 NFPA 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 8

9 NFPA Overview Guidance/Requirements Document 1990 Recommended Practice 1995 Became a Standard 2016 Current Edition Next edition open for public input 9

10 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 10

11 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

12 NFPA 820 Contents Annex A Classified Areas for Anaerobic Digester From NFPA 820, 2016 ed. Figure A.6.2(a) 12

13 NFPA 70 Guide to determine NEC classified (hazardous) areas What is Class 1, Division 1, Group D? 13

14 NFPA 70 - Article 500 Class Class I Flammable Gases/Vapors Class II Combustible Dusts Class III Ignitable Fibers 14

15 NFPA 70 - Article 500 Division* Division 1 Gas/vapor always present or can exist under normal conditions Division 2 Gas/vapor present under abnormal conditions only (leak, accident) NEC also recognizes international format Zone 0, Zone 1, Zone 2 for Class I areas. See NEC, Article

16 NFPA 70 - Article 500 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,... * Class II, Div 1 or Div 2, Group G for dried sludge dust 16

17 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

18 NFPA 820 Collection System Locations (Partial List) Sanitary Sewer (NNV) Div. 1 Combined Sewer (NNV) Div. 1 Storm Sewer (NNV) Div. 2 WW Pump Station Wet Well < 12 air changes Div air changes Div. 2 NNV Not normally ventilated 18

19 NFPA 820 Liquid Stream Treatment CLASSIFIED HEADWORKS (BAR SCREENS) GRIT REMOVAL (PRE-AERATION) PRIMARY SETTLING ODOR CONTROL Primary Settling Tank 19

20 NFPA 820 Liquid Stream Treatment UNCLASSIFIED AERATION TANKS/TRICKLING FILTERS SECONDARY & FINAL SETTLING TANKS (FILTRATION) DISINFECTION PLANT EFFLUENT Trickling Filter 20

21 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 *a.c. air changes 21

22 NFPA 820 Solids Treatment UNCLASSIFIED SLUDGE DEWATERING (CENTRIFUGE) SLUDGE CAKE STORAGE (> 6 a.c.) SLUDGE CAKE CONVEYANCE (> 6 a.c.) SLUDGE CAKE INCINERATION SKIMMINGS INCINERATION Centrifuge 22

23 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

24 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

25 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

26 NEC Area Classifications 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

27 NEC Area Classifications From NFPA 820, 2016 ed. Figure A.5.2 Primary Sedimentation Tank (Not Enclosed) 27

28 NEC Area Classifications 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

29 NFPA 820 Table Liquid Stream Treatment (6 pages total) 29

30 NFPA 820 Table Liquid Treatment Location 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 30

31 NFPA 820 Table Liquid Treatment Is space enclosed or not? VENTILATION KEY: A - < 12 a.c. 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 31

32 NFPA 820 Table Liquid Treatment For new facility design VENTILATION KEY: A - < 12 a.c. 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 32

33 NFPA 820 Table Liquid Treatment For existing facility VENTILATION KEY: A - < 12 a.c. 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 33

34 NFPA 820 Table Liquid Treatment VENTILATION KEY: A - < 12 a.c. 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 34

35 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

36 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, H 2 S, low O 2 ) 36

37 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

38 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

39 Summary Why follow NFPA 820? Photo source: Cleveland State University, Michael Schwartz Library,

40 Thank You Questions? Paul McGuire, P.E