04 Battery Room Standard 41-644

Document Classification: CONFIDENTIAL

STANDARD

Title:

STANDARD FOR BATTERY ROOMS

Unique Identifier:

TST41-644

Document Type:

STANDARD

Revision:

0

Effective date:

JUNE 2007

Total pages:

19

Review date:

JUNE 2012

COMPILED BY

FUNCTIONAL RESP.

AUTHORIZED BY

…................................. BN JONGA TECHNOLOGY & SUPPORT -DC

…........................... A DE LA GUERRE M&C MANAGER

…................................. N KLEYNHANS PMC MANAGER

DATE:….......................

DATE:….......................

DATE:….......................

CONTENTS

PAGE

Foreword ........................................................................ .................................................................................................................................................... .............................................................................. ..33 33 1. Purpose ................................................................................. .................................................................................................................................................. .................................................................33 33 2. Applicability ............................................................... ........................................................................................................................................... .............................................................................. ..33 33 3. Normative references ......................................................................... ............................................................................................................................. ....................................................33 33 4. Definitions and abbreviations ......................................................................... ................................................................................................................. ........................................33 33 4.1 Definitions………………………………………………………………………………… Definitions…………………………………………………………………………………………………………2 ………………………2 4.2 Abbreviations………………………………………………………… Abbreviations……………………………………………………………………………………………………..2 …………………………………………..2 5. Requirements ........................................................................ ......................................................................................................................................... .................................................................33 33 5.1 General……………………………………………………………………………………… General……………………………………………………………………………………………………………2 ……………………2 5.2 Civil Requirements……………………………………………………………………………………………… 3 5.3 Electrical Requirements……………………………………………………………………………… R equirements…………………………………………………………………………………………8 …………8 5.4 Safety and Maintenance…………………………………………………………………………… Maintenance………………………………………………………………………………………...9 …………...9 6. Revision Information ........................................................................... ........................................................................................................................... ................................................1212 1212 7. Authorisation .......................................................................... ....................................................................................................................................... .............................................................1212 1212 Annexures Annexure A .............................................................................................................................................. ..............................................................................................................................................1313 1313 Annexure B .............................................................................................................................................. ..............................................................................................................................................1515 1515 Annexure C.1 ................................................................................................................................ ........................................................................................................................................... ...........1616 1616 Note: Concerns queries and comments on this document should be referred to the compiler When downloaded from Transmission database, this document is uncontrolled, responsibility lies with the user to ensure that it is the authorised version.

When downloaded from the EDC website, this document is uncontrolled and the responsibility rests with the user to ensure it is in line with the authorised version on the website. website. Note: This document has not been through the EDC processes prior to authorisation.


Unique Identifier: Revision: Page:

TST41-644 0 2 4 of 19

Note: Concerns queries and comments on this document should be referred to the compiler When downloaded from Transmission database, this document is uncontrolled, responsibility lies with the user to ensure that it is the authorised version



TST41-644 0 3 4 of 19

Foreword This document is derived from: NWG 7014: Rev 0; Design guide for battery rooms - 1990 – Leon Drotsché

1. Purpose The purpose of this standard is to assist design engineers in the design of battery rooms that will house stationary, vented lead acid and nickel cadmium batteries.

2. Applicability This standard is applicable to battery rooms at all Transmission substations.

3. Normative References The following documents contain provisions that, through reference in the text, constitute requirements of this standard. At the time of publication, the editions indicated were valid. All standards and specifications are subject to revision, and parties to agreements based on this standard are encouraged to investigate the possibility of applying the most recent editions of the documents listed below. Information on currently valid national and international standards and specifications can be obtained from the Information Centre at Megawatt Park. Standard for maintenance of DC systems . Procedure for maintenance of DC systems.

4. Definitions and Abbreviations 4.1. Definitions 4.1.1. Type ‘e’: Equipment that does not produce arcs sparks, or dangerous surface temperatures in normal service, and which has been provided with certain additional protective features in order to increase its safety to a level that is suitable for use in potentially explosive atmospheres.

4.2. Abbreviations 4.2 .1. BVR: Basic Ventilation Rate 4.2.2. RVR: Recommended Ventilation Rate 4.2.3. OHSACT: Occupational Health and Safety Act

5. Requirements 5.1. General i)

Battery rooms shall provide easy access for batteries and battery stands. In addition, battery rooms shall be dry, well lit, well ventilated and protected against the ingress of dust and foreign matter.

ii ) Only flat or stepped single row single tier, double row single tier ,three row centre terraced and four row centre terraced wooden stands (normally ordered from the battery manufacturer at the time the batteries are ordered) shall be used.




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iii) Battery rooms shall provide for possible future expansion / refurbishment, therefore it shall be located at the end of the building. Battery rooms shall be situated as near to the associated loads and rectifier equipment as possible. vi)

Every endeavour shall be made to ensure that the battery room is situated on the coolest side of the building.

v)

Separate battery rooms shall be provided for batteries with different types of electrolyte, i.e. nickel cadmium and lead-acid batteries shall not be installed in the same room. Two or more batteries with the same type of electrolyte may be installed in the same room but on separate battery stands. An access passage at least one metre wide to all battery rows and a minimum of one metre between rows of battery stands shall be provided. Only single row or stepped double row single tier battery stands may be positioned against a wall. The step shall be such that the top of the cell plates of the back row is exposed. The minimum distance between any battery terminal and the nearest water supply point shall be two metres.

ix) Rows of battery stands shall be positioned such that they do not jeopardize or obstruct the doorway. x)

Wherever possible the stands shall be positioned perpendicular to the entrance wall. The battery arrangements shall comply with the layout drawing, showing the positioning of the different batteries.

5.2. Civil Requirements 5.2.1. Floors Construction i)

Expansion joints shall be avoided.

ii)

When the battery room is located at ground level, the floor shall comprise a concrete surface bed laid on compacted earth. When the battery room is situated above ground level, the floor shall comprise a reinforced concrete slab.

iii)

Due to the mass of the batteries the floor shall be absolutely stable. Subsidence of the floor at points of load shall not take place, as this will cause settling and tilting of the batteries with consequent straining of the battery connection.

iv) The floor shall be given a uniform fall, end to end, of not less than 1:200, by applying a cement screed to the concrete. The lower end being that where the tapped water supply is located. Across this lower end of the floor, a white glazed fire clay block channel or epoxy lined concrete channel shall be provided, sloping towards the outlet. This outlet shall discharge into a PVC drainpipe that shall be built through the external wall of the battery room, and shall lead to a dedicated drainage system, designed and installed to prevent contamination of groundwater. v)

To prevent fluid discharge from the battery room, a lip of at least 25 mm shall be placed on the inside of the door entrance. Alternatively a water channel, complete with a non-corrosive grid cover, shall be installed along the wall.

5.2.2 Floor Protection i)

In lead-acid battery rooms, the electrolyte shall be sulfuric acid (H2SO4).

ii)

As concrete is highly vulnerable to corrosion by this acid, the floor shall be given a protective coating of acid-resistant, non-skid ceramic floor tiles or an approved acid-resistant epoxy coating applied in accordance with the manufacturer’s specifications.




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iii) The electrolyte used in nickel cadmium batteries is a solution of potassium hydroxide (KOH), in water. In certain cases, small quantities of lithium hydroxide (LiOH) are also included in the solution. iv) This fluid will not corrode concrete or brickwork, but if left for any length of time in direct contact with these materials, it will form a white encrustation of potassium carbonate (K2CO3). This encrustation however is relatively harmless and can easily be dissolved and removed with cold water. v)

For nickel cadmium battery rooms therefore, corrosion resistance flooring materials are not technical requirements and they cannot be justified economically.

5.2.3. Walls Walls shall be continuous from floor to ceiling and be securely anchored. The walls of lead acid or nickel cadmium battery rooms shall be protected against electrolyte splashes, by applying an approved lightcoloured, acid resistant enamel paint.

5.2.4. Windows Windows shall not be provided in battery rooms. Where windows have been installed in older rooms, they shall be suitably blanked off to prevent ingress of sunlight

5.2.5. Ceilings i)

The ceilings shall be flat preferably and be at least 2, 5 m above floor-level.

ii)

Being considerably lighter than air, the hydrogen given off during battery charging will rise and accumulate under the high points of ceilings and overhead structures. All such high points shall be vented to the atmosphere. Special attention shall be paid to this ventilation when ceiling beams have to be used.

iii) Skylights and false ceilings shall not be used. iv) Ceilings shall be given the same paint treatment as walls (see 5.2.2).

5.2.6. Doors i)

The battery room door shall have the applicable fire and security rating and shall be not less than 800 mm wide and 2000 mm high. The door shall have one leaf that opens outwards.

ii)

For small substations and small communication stations, a door of 800 mm wide (min) and 2000 mm high shall be used.

iii)

The inside surfaces of the door shall be protected by an approved light-coloured, acid resistant paint.

iv)

All fittings for these doors shall be subject to Eskom’s approval.

5.2.7. Fire Resistance Ratings 5.2.7.1. Battery rooms that are part of attached to or within another building, shall comply with the following: i)

Walls and ceilings shall have a fire resistance rating of not less than one hour.

ii) Floors of battery rooms shall have a fire resistance rating of not less than one hour where such battery rooms are located above other defined fire zones, for example, rooms, compartments, etc.




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5.2.7.2. Exceptions: i) Any exterior wall of a battery room that is more than 15 m from a potential fire zone will not be required to have a one hour fire resistance rating. ii) The wall shall however, be of a non-combustible construction. 5.2.7.3. Any duct, pipe, conduit, cable or other equipment that penetrates a wall, floor or ceiling, having a fire resistance rating, shall be fire stopped with a fire resistant material such that the fire resistance of the wall, floor or ceiling will not be negatively affected.

5.2.8. Plumbing i)

A laboratory type sink of glazed fire clay shall also be installed at the lower end of the floor, preferably the door side of the battery room. This sink shall be the large rectangular type preferably with draining boards on either side, and an acid resistant laboratory receiver beneath.

ii)

The sink shall be provided with a supply of suitable running water and controlled by an elbow action mixer tap. Discharge from the sink and from the laboratory receiver shall be into the white-glazed fire clay block channel referred to in 5.2.1.1 d).

iii)

An industrial safety shower, in addition to eye wash facilities shall be located in the vicinity of the normal water supply (sink) and shall not obstruct the door exit.

iv)

Where there is not enough space for civil extensions to accommodate an industrial emergency shower, it shall be located outside the battery room next to the door. The shower drain shall be connected to the battery room drain system.

v) At sites where only low water pressure is available a booster pump shall be installed to achieve 3(three) bar water pressure.

5.2.9. Cable Entry Facilities 5.2.9.1. Where the cable entry is through the floor, the following shall be adhered to: i)

The cable opening shall be adjacent to the wall and stands where applicable.

ii)

PVC or cement cable pipes curved to the bending radius of the cable shall be cast into the floor in such a way that the entry of the cables into the battery room is perpendicular to the floor.

iii) To prevent fluids or foreign matter from entering the pipe, its upper end shall project at least 50mm above the finished floor surface. 5.2.9.2 For any other form of cable entry, the following shall be adhered to: i)

These cable entries shall be either vertically from the floor above, if applicable or horizontally (at a satisfactory height) through one of the battery room walls.

ii)

A separate entry, as near as possible to the battery terminals, shall be provided for each battery bank.

iii) These entries shall be kept sealed with vermiculite or equivalent material, to prevent hydrogen transfer before and after installation of the cables.




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5.2.10 Ventilation 5.2.10.1. General i)

Battery rooms shall be so positioned and designed that they are subjected to only very slight changes in temperature.

ii)

The nominal temperature in the battery room shall be 25 °C and the temperature shall be kept as close to this as possible. If the temperature exceeds 35 °C, special consideration shall be given to controlling the air temperature. Air used for ventilating battery rooms shall not exceed 25 °C. Batte ry rooms shall be positioned on the coolest side of the complex.

iii)

Where a powered room ventilator cannot be used, a wall mounted axial type extract fan with back draught dampers shall be used. The fan shall be mounted as high as possible in the wall, but not below the level of the light fittings.

iv)

In very large battery rooms with deep roof beams, especially where cross flow between inlets and outlets is difficult to achieve (for example, when inlets and outlets must be in the same wall), the extract system shall include a duct with several intake points made available at high level.

v)

Hydrogen gas from battery rooms shall be extracted or ventilated to a safe area, i.e. outdoors or to an area where the gas will always dissipate into the atmosphere without possible danger of the gas accumulating in any part of that area.

vi)

Where it is necessary to provide ventilation ducts to discharge hydrogen gas to a safe area, such ducting shall comply with the above requirements.

vii) The ducting shall be protected with a one-hour fire rated material or plaster. Fire rating however will only be required if the ducting passes through intermediate rooms or potential fire zones. viii) In applications where there is complete dependence on forced ventilation, it is recommended that redundancy be provided in the extract fans, with suitable non-return dampers and a means of monitoring operation so that, in the event of failure of the operating fan, the stand-by unit can be switched on. ix) Where both supply and extract powered systems are provided, they shall be selected to ensure that there will, under normal conditions, be a slight negative pressure in the battery room. x)

Fans shall be selected to provide the required performance even when operating against normal system resistance, including dust-laden filters, as well as considering prevailing wind and any other detrimental effects. Generally speaking, axial or centrifugal fans are required in applications where the fans have to overcome filter resistance. Each application shall be checked to ensure that fan noise will not be a negative factor to the adjacent environment.

xi)

Air inlets, through which the necessary replacement air would enter the battery room, shall be fitted into one of the longitudinal walls and / or in the door, opposite the air outlets, in such a way that they are evenly distributed along the section of wall opposite the battery cells, to ensure that there is a cross ventilation system . They shall also be located as close to the floor as possible to ensure that the incoming fresh air passes around and over the battery cells.

xii) Air-bricks for ventilation are not recommended as they have shown that, unless a great number are used, the resulting ventilation will be negligible. Air-bricks, moreover, readily permit the entry of dust. xiii) The size of natural roof-ventilator required for each application depends on the height of the ventilator above the air-intake points, the effective difference between internal and external air temperatures, and the rate at which the air is to be extracted.




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xiv) For a very small battery room, the ventilator-louvre combination shall be selected and installed so that it will be capable of removing the air-hydrogen mixture from the room at a rate not less than, 250 x -7 3 10 P m /s, for example. xv) All battery rooms shall be naturally or forced ventilated by ensuring that the minimum amount of air exchanges takes place thereby rendering the battery room safe. This can be done by determining the amount of hydrogen given off by the cells during the end-of-charge phase where gassing is caused by overcharging. See annex B for the calculations. xvi) Battery rooms shall be provided with the following options wired to a central point: •

A remote operated facility for ventilation. . Some battery chargers have the facility to do this when they are switched to a higher charging rate. This option will not be used where the fan is required to function permanently.

•

A facility that can detect when the ventilation system fails or the filters are blocked. This shall be done by means of a pair of potential free contacts that would indicate when the system is abnormal, and can be used to inhibit the battery charger from switching to the higher charge mode or initiate an alarm on the charger.

5.2.10.2. Small battery rooms Small battery rooms are defined as those in which the sum of the products obtained by multiplying the nominal ampere hour capacity of each battery in the room by its number of cells is less than 6000. Whenever possible, such rooms shall be naturally ventilated with roof ventilators and louvred air inlets with filters in outside walls. In cases where such rooms have no outside walls and/or it is not practical to provide roof ventilation, a forced ventilation system shall be provided. 5.2.10.3. Large battery rooms i)

Large battery rooms are those containing battery installations having a total capacity, exceeding the limit imposed in item 5.2.9.2. All such rooms shall be force ventilated.

ii)

Where a central ventilation system is not supplied, the ventilation fan shall be powered from the same source as the battery charging equipment and controlled in such a way that maximum available ventilation is assured when batteries are on charge and gassing is likely.

iii) Where roof ventilation is fitted, the fans shall only be operational when a battery charger is selected to a higher charge mode, a feature fitted to all modern chargers. All fans shall be fitted with a “Fan fail” alarm and a normally open or normally closed potential free contact, to provide an alarm when the fan fails. iv)

Depending on building configuration and prevailing ambient conditions, any of the following systems are acceptable. For reasons of cost and overall reliability, the simplest system that meets basic requirements shall always be preferred. •

Powered roof ventilator with panel filters at the air inlets in at least one outside wall. This is a low cost system that provides filtration of replacement air. Filtered openings for replacement air shall be provided as remotely as possible from the extraction point, to encourage a through draught at high level. Disposable filters 600 x 600 x 50mm of 95% gravimetric efficiency or 2 minimum dust holding capacity of 1 300 g/m are recommended. Maximum velocity through panels 2 m/s. Doors shall be close fitting, and cable entry pipes and other openings (to other rooms or the outside) properly sealed to prevent ingress of unfiltered air that could also cause dust ingress.

•

Dust collector type fan-filter units may be used. Such units are relatively expensive but virtually maintenance free and can usually be justified where dust conditions are particularly severe as, for example, in the boiler house of coal-fired power station.



•


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Fan filter units as above with naturally ventilated roof ventilation. This system shall only be used when the battery room door exits to the outside of the building, i.e. the hydrogen shall not be forced into adjacent rooms.

5.3 Electrical Requirements 5.3.1. Fan Motors 5.3.1.1. When a special ventilation system is used to comply with 5.2.8 of this standard, the extraction fan shall comply with the relevant safety regulations and shall be subject to Eskom’s approval. 5.3.1.2. The preferred motors for these extraction fans shall be the single-phase squirrel-cage induction type and shall be suitable for direct-on-line starting. 5.3.1.3. They shall, moreover, be of the “increased safety” design commonly known as Class I Division II ‘non-sparking’ motors. ‘Non-sparking’ motors are acceptable for battery room applications as specified in SABS 0108- and are available in South Africa. A certificate is issued with each motor or batch of motors.

5.3.2. Artificial Lighting 5.3.2.1. General i)

The entire lighting installation within the battery room shall consist exclusively of type ‘e’ apparatus and luminaires.

ii) The basic difference between the type ‘e’ protection now required and the traditional type of protection using flameproof or explosion-proof enclosures that has been in use for many years, is as follows: •

In the traditional method of protection, it is assumed that an explosion may occur inside the enclosure, and the enclosure is therefore designed so that such an internal explosion cannot damage it or cause the ignition of the gas or vapour surrounding it.

•

In the type ‘e’ system however, flameproof and explosion-proof enclosures are not required because the equipment is instead designed in such a way that all possible sources of ignition, such as arcs, sparks and excessive surface temperatures, can be closely controlled. As a result of this, the statistical probability of an explosion occurring is reduced to an acceptably low level.

5.3.2.2. Main lighting installation i)

The main lighting installation in the battery room shall be supplied from the station’s 230/400 V a.c. auxiliary supply.

ii)

The installation shall consist of fluorescent luminaires only, type Ex’e’ class 1 Div 1 (T1 – T4). This form of lighting is favoured over mercury-vapour lighting for the reason that the latter, when subjected to dips in supply voltage, may go out and remain out for periods of up to ten minutes. Incandescent lighting is also considered unsuitable because of its relatively low lumen output and short service life, both of which factors give rise to excessive maintenance costs.

iii) The fluorescent fittings chosen shall preferably be installed on the ceiling, and shall provide sufficient light output to illuminate the tops of the batteries to a level not less than a maintained 100 lux, in accordance with the OHS Act for battery and charging equipment rooms. 5.3.2.3. Emergency lighting installation i)

The emergency lighting installation shall consist of incandescent luminaires type Ex’e’ (T1 – T4), with a standard two pin bayonet or screw type socket or fluorescent luminaires as in 5.3.2.2 and fitted with D.C. to A.C. converters. These units shall be supplied from the station battery using the normal d.c. distribution system.

ii) These luminaires shall be mounted on the ceiling only. Note: Concerns queries and comments on this document should be referred to the compiler When downloaded from Transmission database, this document is uncontrolled, responsibility lies with the user to ensure that it is the authorised version



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iii) The maintained level of emergency lighting required in this area shall be not less than 20 lux at floor level to enable employees to evacuate the workplace safely, in accordance with the OHS Act. 5.3.2.4. Luminaire positioning i)

The luminaires shall not be mounted directly over the battery stands.

ii)

The luminaires shall be positioned in parallel with the battery stands. This precaution will facilitate maintenance on the fittings, and will also minimize the obvious dangers of working over the cells.

iii)

No battery baks shall be installed directly under the luminarie.

5.3.3. Other Electrical Equipment 5.3.3.1. All light switches, power outlets, distribution boards, telephones and fan contactors (item 5.2.8.3), shall be mounted outside but still in close proximity to the battery room door. 5.3.3.2. These devices are not required to be explosion-proof, flameproof, or type ‘e’.

5.4. Safety and Maintenance 5.4.1. Maintenance and Protective Equipment All maintenance and protective equipment as specified in TST41-643 shall be provided.

5.4.2 Safety Signs The required safety signs are specified in table 1.




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Table 1 – Safety signs required for battery rooms Description of safety sign a.

b.

c.

d.

a.

A notice identifying the room as being a battery room. It clearly sets out the elementary first aid procedures in the case of eye and / or skin contact with an acid or alkali. A no-smoking prohibitive sign and corrosive substance warning sign are also posted on the notice. The notice also displays that unauthorized entry to the battery room is prohibited. This notice shows that open flames are prohibited inside the battery room. It also shows that an apron, eye protection and gloves shall be worn.

Required location of safety sign At the designated entrance to the battery room.

Eskom code and drawing number TG 1: 0.52/20380 Sheet 1

(See Annexure C.1)

On wall directly opposite the entrance to the battery room.

TG 2: 0.52/20380 Sheet 3

A notice indicating the location of the emergency shower.

Next to the emergency shower.

GA 20: 0.52/20381 Sheet 1

A notice indicating the location of the eyewash equipment.

Next to the eyewash equipment.

A notice showing that the drinking of water is prohibited (when applicable)

On wall above battery room sink or water container.

b.

(See Annexure C.2)

(See Annexure C.3)

GA 19: 0.52/20381 Sheet 2 (See Annexure C.4)

TG 3: 0.52/20381 Sheet 3 (See Annexure C.5)




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6. Revision Information Rev

Notes

Date

0

Original document NWG 7014- (Design for battery rooms)

1990

Leon Drotche 0

Renumbering, old number TRMASACN1

July 2007

7. Authorization This document has been seen and accepted by: Name

Designation

Tony Sheerin

M&C Applications Manager

Piet Jooste

Transmission Grids

Chico Ramgovind

Secondary Plant Manager(Central Grid)

Krish Govender

Secondary Plant Manager (Eastern Grid)

Rhulani Matshidza

Secondary Plant Manager(North East Grid)

Noxolo Sipunzi

Secondary Plant Manager(Western Grid)

Paul Grobler

Secondary Plant Manager (Northern Grid)

Johan Pieterse

Secondary Plant Manager (North West Grid)

Ian Worthington

Secondary Plant Manager (South Grid)

DC Work Group

Transmission National DC Working Group/Committee




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Annexure A (Informative)

Hydrogen Removal A1. Basic Principles When batteries are on charge, hydrogen bubbles are released and, due to the buoyancy, these bubbles rise rapidly in the air until they meet an obstruction such as the ceiling where they tend to accumulate. Compared with heavier gases, the hydrogen diffuses relatively quickly so that in due course it becomes evenly distributed under any obstruction. This process of molecular diffusion is greatly accelerated under conditions of air turbulence. The main purpose of ventilation is to keep the hydrogen concentration within safe limits. Ridge ventilators are particularly effective because they release some hydrogen to the outside before it is able to diffuse in the room. It should also be borne in mind that lightweight building elements such as ceiling tiles do not provide an effective barrier to hydrogen. Battery room walls shall therefore, be extended to roof sheeting height where there is a pitched roof over the battery room and the roof is provided with a ridge ventilator. The ventilation system is based on the assumption that the air that enters the battery room through the filters will mix with and adequately dilute the hydrogen gas discharged by the cells. The resulting airhydrogen mixture discharged by the cells will then be extracted from the room by the fans at a rate not less than that recommended in the tables (A3).

A2. Determination of Basic Ventilation Rate (BVR) If a battery in the room is on charge, such room will be considered sufficiently ventilated if its air hydrogen mixture is being extracted from it at a rate not less than that given by the following formula: BVR = q x t x d x s x P where q = volume of hydrogen in litres produced per second per ampere per cell -6

q = 126,7 x 10 l/s rated at 25 °C at sea level t = “thinning factor” = 100 / 3.8 % = 26,3 An air - hydrogen mixture can explode if the volume of hydrogen contained in the mixture equals or exceeds 3,8% of the total volume. d = “diffusion factor” that normally has a factor of 3,0. This factor provides against the possibility of the hydrogen being non-uniformly dispersed throughout the air in the room s = a general safety factor that, for stationary installations, is normally 2,5




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Annexure A (Continued) P = the sum of the product obtained by multiplying the number of cells in the largest battery in the room by the output current rating, in amperes, of the battery’s particular charger plus (+) the corresponding product obtained in respect of the second largest battery in the room. NOTE: When designing the ventilation system, the worst possible charging conditions (normally during commissioning) should be assumed. Such conditions would occur if, due to a charger fault, maximum rated charger current is forced through a fully charged battery. Basic ventilation rate (BVR) should be achieved at any prevailing conditions (i.e. blocked filters). Combining the above values into the original equation, it follows that the basic ventilation rate required for the battery room is: BVR = q x t x d x s x P

-6

= 126.7 x 10 x 26.3 x 3 x 2.5 -4

= 250 x 10 P litres/sec -7

3

= 250 x 10 P m /sec BVR is sufficient for safety purposes. However, to increase life expectancy of the cells, consideration should be given to ventilating the room to limit temperature rise to 5 °C above ambient. In a well-in sulated room, this can be achieved by supplying 10 to 15 air changes per hour.

A3. Recommended Ventilation Rates (RVR) for South African conditions Obviously the formula derived in A2 can apply only to battery rooms located in temperate regions at sea level. In order to provide ventilation data that can be used readily under typical South African conditions, the above formula has been expanded to produce the following table A1. Table A1 – Ventilation data for South African conditions Altitude above sealevel

Atmospheric pressure

metres

m bar

0 0 305 610 914 1219 1524 1829 2134 2438

1013 1013 977 942 908 875 843 812 781 752

Recommended ventilation rate (RVR) Battery room temperature °C 0 25 25 25 25 25 25 25 25 25

litres per sec 229.P.10 250.P.10 259.P.10 369.P.10 279.P.10 290.P.10 301.P.10 312.P.10 324.P.10 337.P.10

3

cumecs m /s 229.P.10 250.P.10 259.P.10 269.P.10 279.P.10 290.P.10 301.P.10 312.P.10 324.P.10 337.P.10




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Annexure B (Informative)

Ventilation to avoid hydrogen concentration in battery rooms NOTE: The following is an extract from BS 6133:1985 – Safe operation of lead-acid stationary cells and batteries. In order to be certain that the ventilation of the battery room is adequate to keep the average concentration of hydrogen gas in the room within safe limits, it is necessary to be able to calculate the rate of evolution of hydrogen. Hydrogen is evolved during a recharge or freshening charge of the battery when the voltage rises above 2.30V per cell. During this period when the cells are gassing freely, it is recommended that the concentration of hydrogen gas within the battery room is limited to an average of 1%, except in the immediate vicinity of the cell tops. This is only one quarter of the normally accepted safe limit of 4% hydrogen, but in view of the potential hazard with stationary batteries, this additional safety margin is fully justified. The following method may be used to calculate the ventilation requirements of a battery room. 26,8Ah input to a fully charged cell will liberate 8 g of oxygen and 1 g of hydrogen. 1 g of hydrogen occupies a volume of 12 l at 20 C and at a pressure of one standard atmosphere. Therefore 26,8Ah input will evolve 12 l of hydrogen. Therefore the volume of hydrogen evolved from a battery per hour: °

=

no of cells × ch arg e current × 12l

26.8 = no of cells × ch arg e current × 0.45l =

no of cells × ch arg e current × 0.00045m 3

The volume of hydrogen found by the above calculation can be expressed as a percentage of the total volume of the battery room, and from this, the number of changes of air per hour to keep the concentration of hydrogen below 1% can be calculated. Example Consider a battery of 100 cells, using a double tier, double row terraced arrangement, in a room with dimensions 4 m x 2 m x 3 m. Charge current = 17 A (finishing rate of charge for cell type used). 3 Volume of hydrogen evolved per hour = 120 x 17 x 0,00045 = 0,92m . 3 Total volume of room = 4 x 2 x 3 = 24 m . 3 Approximate value of battery and stand (i.e. volume of battery + 20 % for volume of stand) = 3 m . 3 Therefore volume of free air in room = 21 m . Therefore concentration of hydrogen gas after charging for 1h above 2,3V per cell (gassing potential) at 17 A with no ventilation would be: =

0.92 21

× 100% =

4.4%

Therefore to keep the concentration of hydrogen gas at a maximum of 1%, the air in the room will need changing

4.4 1

=

4.4 times per hour, or about five times per hour.

To allow for variations from the assumed values and contingencies, ventilation shall be arranged to change the air in the room six times per hour. NOTE: The effectiveness of a ventilation system can only be assessed by sampling gas concentrations under operational conditions.




TST41-644 0 16 4 of 19

Annexure C.1 Unauthorized entry prohibition No smoking allowed Warning of corrosive substances First aid procedure in case of burns, due to eye or skin contact with acid or alkali




TST41-644 0 17 4 of 19

Annexure C.2 No open flames allowed Hand and eye protection to be worn




TST41-644 0 18 4 of 19

Annexure C.3 Emergency Shower




TST41-644 0 19 4 of 19

Annexure C.4 Eyewash




TST41-644 0 20 4 of 19

Annexure C.5 Drinking of water is prohibited


04 Battery Room Standard 41-644

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