Carson Ph., Mumford C. Hazardous Chemicals Handbook (Справочник по опасным химическим веществам)
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Table 12.13 Typical recommended transport velocities
Material, operation or industry Minimum transport velocity
(m/s) (ft/min)
Abrasive blasting 17.8–20.3 3500–4000
Aluminium dust, coarse 20.3 4000
Asbestos carding 15.2 3000
Bakelite moulding powder dust 12.7 2500
Barrel filling or dumping 17.8–20.3 3500–4000
Belt conveyors 17.8 3500
Bins and hoppers 17.8 3500
Brass turnings 20.3 4000
Bucket elevators 17.8 3500
Buffing and polishing
dry 15.2–17.8 3000–3500
sticky 17.8–22.9 3500–4500
Cast iron boring dust 20.3 4000
Ceramics
glaze spraying 12.7 2500
brushing 17.8 3500
fettling 17.8 3500
dry pan mixing 17.8 3500
dry press 17.8 3500
sagger filling 17.8 3500
Clay dust 17.8 3500
Coal (powdered) dust 20.3 4000
Cocoa dust 15.2 3000
Cork (ground) dust 12.7 2500
Cotton dust 15.2 3000
Crushers 15.2 3000
Flour dust 12.7 2500
Foundry, general 17.8 3500
sand mixer 17.8–20.3 3500–4000
shakeout 17.8–20.3 3500–4000
swing grinding booth exhaust 15.2 3000
tumbling mills 20.3–25.4 4000–5000
Grain dust 12.7–15.2 2500–3000
Grinding, general 17.8–22.9 3500–4500
portable hand grinding 17.8 3500
Jute
dust 12.7–15.2 2500–3000
lint 15.2 3000
dust shaker waste 16.3 3200
pickerstock 15.2 3000
Lead dust 20.3 4000
with small chips 25.4 5000
Leather dust 17.8 3500
Limestone dust 17.8 3500
Lint 10.2 2000
Magnesium dust, coarse 20.3 4000
Metal turnings 20.3–25.4 4000–5000
Packaging, weighing etc. 15.2 3000
downdraft grille 17.8 3500
Pharmaceutical coating pans 15.2 3000
Plastics dust (buffing) 19.0 3800
Plating 10.2 2000
Whatever the type of ventilation, air flow must be adequate to prevent particulate matter
settling in the ducting; typical transport velocities are given in Table 12.13.
PIPING ARRANGEMENTS 409
410 SAFETY BY DESIGN
Rubber dust
fine 12.7 2500
coarse 20.3 4000
Screens
cylindrical 17.8 3500
flat deck 17.8 3500
Silica dust 17.8–22.9 3500–4500
Soap dust 15.2 3000
Soapstone dust 17.8 3500
Soldering and tinning 12.7 2500
Spray painting 10.2 2000
Starch dust 15.2 3000
Stone cutting and finishing 17.8 3500
Tobacco dust 17.8 3500
Woodworking
wood flour, light dry sawdust and shavings 12.7 2500
heavy shavings, damp sawdust 17.8 3500
heavy wood chips, waste, green shavings 20.3 4000
hog waste 15.2 3000
Wool 15.2 3000
Zinc oxide fume 10.2 2000
Table 12.13 Cont’d
Material, operation or industry Minimum transport velocity
(m/s) (ft/min)
Fire protection
The installation of fixed fire protection depends on analysis of potential fire characteristics (see
Chapter 6). A summary of the factors is given in Table 12.14.
Table 12.14 Fire characteristics determining protection system design
• Types of combustibles, e.g. resulting in surface fires for which inerting or an inhibiting agent may be best, or deep-seated
combustion requiring a cooling agent, e.g. water.
• Relative importance of speed of detection.
• Degree of risk to personnel, e.g. toxic combustion or fire-fighting agent decomposition products.
• Indoors, indicative of a total flooding system; outdoors requiring assessment of exposure of nearby hazards, involvement
of other combustibles, wind effects and difficulty of extinguishment.
• Probability of fire spread, with a need for, e.g., fire walls, fire doors, fire stops.
• Requirement for detection and control, or detection and extinguishment.
• Any features which rule out specific extinguishing agents, or making other types preferable.
• Any advantages of a dual agent system, e.g. water and carbon dioxide.
• Inherent or possible explosion risks (e.g. static discharge associated with extinguishant discharge).
• Need for operation with personnel present.
• Need for rapid ‘knock-down’.
Activation may be automatic, by a detection system, or manual. The general requirements are
summarized in Table 12.15.
Table 12.15 General requirements for fixed fire extinguishing system
• Capability to control and extinguish the anticipated fire condition without outside assistance, unless planned for (dependent
on requisite spacing of discharge nozzles to cover all areas at risk, application rates, discharge times, quantities of
extinguishant available).
• Reliability, allowing for environmental features possibly detrimental to operation, e.g. corrosion, dust, tar.
• Agents must be compatible with the process, chemicals present (Chapter 7) and any other installed system.
• Potential toxicity of the agent, its thermal breakdown products, or products generated on contact with chemicals will
determine safety measures necessary (e.g. in occupied areas a ‘double-knock’ system, allowing evacuation time, may be
required.
• Visibility in the fire zone after extinguishant discharge, if manual fire-fighting is anticipated.
Installation and operation
Engineering specification and purchasing procedures are essential to ensure that all items are to
the design specification and to comply with company or national standards. During installation
the features to consider are foundations, selection of materials, fabrication, assembly, supports,
pressure testing, etc.
INSTALLATION AND OPERATION 411
13
Operating procedures
Safety is a management responsibility requiring an awareness of all relevant local legislation and
a strategy that comprises:
• A clear, widely-published statement of company policy on safety.
• Clear lines of responsibility identified for each level of management and the workforce to
enable the policy to be implemented.
• Company management systems and ‘safe systems of work’.
• Emergency procedures.
• Procedures for monitoring compliance with the policy and the safety performance.
In the UK these duties are imposed by the Health and Safety at Work etc. Act. Employees also
have a legal responsibility to cooperate with management by using designated protective devices
and not interfering with such apparatus.
An excellent framework for the management of occupational health and safety is provided by
OHSAS 18001:1999 which is compatible with ISO 9001: 1994. Key elements of the standard
addressed include
• Policy.
• Legislation.
• Hazard identification and risk assessment and risk control.
• Structure and responsibilities.
• Training, awareness and competence.
• Consultation and communication.
• Documentation.
• Documentation and data control.
• Operational control.
• Emergency preparedness and response.
• Performance measurement and monitoring.
• Accidents, incidents, non-conformances and corrective and preventative action.
• Records and their management
• Audits.
• Management review and continuous improvement.
Plant must be properly designed, installed, commissioned, operated and maintained. Depending
upon the risk, working procedures should be documented, e.g. as codes of practice. Consideration
of safety at the design stage was discussed in Chapter 12.
Commissioning
Commissioning embraces those activities essential for bringing a newly installed plant into routine
production. It includes mechanical completion and provisional acceptance, pre-commissioning,
first start-up and post-commissioning.
Special efforts are needed to ensure safety at this stage of the development. Since start-up and
shutdown procedures are responsible for many accidents, these procedures merit special attention.
Operation
Operation includes normal start-up, normal and emergency shutdown, and most activities performed
by the production team. Whilst inherently safe plant design limits inventories of hazardous substances,
inherently safe operation ensures the number of individuals at risk are minimized. Access to the
plant for non-essential operational people such as maintenance engineers, post staff, administrators,
quality control samplers, warehouse staff delivering raw material or plant items or collecting
finished product, members of security, visitors etc., must be controlled.
Safe handling of chemicals demands a combination of ‘hardware’ and ‘software’ such as
operating procedures, staff selection and training. Within the UK there is a duty under the Management
of Health and Safety at Work Regulations 1992 for an employer to make appropriate arrangements
for the effective planning, organization, control, monitoring and review of the preventive and
protective measures. Systems of work will generally include:
• The selection and supervision of personnel with clearly-defined job descriptions.
• Planning and coordination of all activities – in particular those involving different sections,
departments or tradesmen.
• Training and instruction of the workforce. Retraining. This should cover both normal and
emergency situations.
• Provision of operating instructions and procedures. These should eliminate confusion and
provide continuity on, e.g., shift changeover. Errors in identification of valves, pumps, pipes,
storage tanks, and the sequence in which they are to be operated is a common cause of
accidents, e.g. on staff changeovers.
• Provision of adequate supervision.
• Inspection, testing, maintenance and replacement of equipment as necessary.
• General conditions of work, e.g. maintenance of adequate general ventilation, local exhaust
ventilation, access, lighting, fire precautions, occupational health measures, housekeeping.
• Auditing of health, safety and environmental matters.
A checklist is given in Table 13.1.
Maintenance
Maintenance embraces regular inspection, periodic examination by ‘competent persons’, and
repairs. Accidents may arise as a result of the lack of maintenance, during maintenance, and as a
consequence of faulty maintenance. Preventive maintenance can be a legal requirement for, e.g.,
pressure vessels/boilers, lifting gear, power presses. A system is required for monitoring compliance
with scheduled preventive maintenance programmes, backed up by in-service inspection. Breakdown
MAINTENANCE 413
414 OPERATING PROCEDURES
Table 13.1 Safety systems in operation
Access
System for
Control of access to site; maintenance of security
Designation of restricted areas, e.g. containing flammable materials, ‘eye protection’
zones, ‘hearing protection’ zones, radiological hazards, microbiological hazards
Ensuring freedom from obstruction of roads, stairs, gangways, escape routes Control
of vehicles
Communication systems
Maintenance of adequate
Written instructions, maintenance procedures etc.
Log books, recipe sheets, batch sheets
Identification of vessels, lines, valves etc.
Intershift communication and records
System for reporting and follow-up of
Plant defects
Process deviations
Hazardous occurrences (‘near misses’)
Accidents: minor/major injury and/or material loss
Warnings, notices
Notices relating to specific hazards
Notices relating to temporary hazards (and their subsequent removal)
(See also permit-to-work systems and operating procedures)
Alarms; emergency communications
Control of contractors Familiarization with plant hazards, rules and safety practices, security
Clear delineation of work, responsibilities and handover
(
See also
maintenance, permit-to-work systems, personal protection, site restrictions,
access, modifications, personal hygiene etc.)
First aid provisions
Maintenance of adequate provision for
Emergency showering
Eye-washing
Decontamination from chemicals (and antidotes if relevant)
First aid (equipment, materials, trained personnel) and resuscitation
Housekeeping Regular cleaning of floors, ledges, windows, by appropriate procedures (e.g.
‘dustfree’ methods)
Removal of empty containers, scrap, waste
Prompt treatment of spillages
Redecoration
Inspection and testing
Implementation of a system for routine, regular inspection of
(including cleaning/ General ventilation provisions
maintenance where necessary) Local exhaust ventilation provisions (test and report at regular intervals)
Fire protection
Alarm systems (HTA, HPA, fire, evacuation etc.)
Plant and equipment generally; portable tools; flexible hoses; lifting equipment;
pressure systems
Safety devices, e.g. PSVs, explosion reliefs, trips
Monitoring and control instruments
Protective clothing/equipment and emergency equipment
Drains and floor drainage; bund walls
Electrical equipment; earthing and bonding
Maintenance
Systems include arrangements for
Issue, control, testing and repair of lifting gear, ladders, scaffolding etc.
Scheduled maintenance of key plant items
Use of job cards/log book to identify tasks precisely
Permit-to-work systems
Flame cutting/welding (or soldering, brazing etc.)
Line-breaking
Electrical work – certain classifications
Equipment removal, e.g. to workshop
Work on roof/at heights
Table 13.1 Cont’d
Isolation of safety services
Excavations
Introduction of non-flameproof electrical equipment into restricted area
Mechanical isolation, e.g. conveyors, lifts
Confined space entry
Radioactive areas
Microbiological ventilation systems, fume cupboards etc.
Other unusual/non-routine situations
Provision for trained persons to be present/on call, e.g. rescue, first aid, fire-
fighting
Instruction and training of personnel
Maintenance of guards on machinery, open vessels, handrails, screens at sampling/
drumming-up points etc. and on glass equipment
Use of sparkproof tools where appropriate
Record-keeping
Inspections, e.g. pressure systems, trips, relief devices, guards, lighting (
see
inspection
and testing)
Materials
Maintenance of adequate procedures for
In bulk, e.g. checks on tanker contents, earthing and bonding, identification of
receiving vessel
In small containers, e.g. carboy handling, cylinder unloading
Despatch of materials
Inspection of tankers, carboys, cylinders etc. prior to filling
Identification and labelling of materials; driver instructions
Use of earthing clips on portable containers of flammable liquids
Modifications to plant or process
System for
Control of changes in raw materials
Formal approval for plant/process changes
Hazard and operability study prior to implementation (repeat when in use)
Updating of all operating instructions, notices, procedures
Removal/isolation of obsolete plant/lines
Control of changes in personnel (
see
training)
Monitoring and follow-up
Systems for monitoring
Working environments
Toxic contaminants
Temperature
Noise
Lighting
Vibration
Ionizing radiation
Occupational health
Pre-employment medical for selection and establishment of base levels
Working conditions in specific areas
Employees’ routine medicals, exposure profiles
Biological monitoring where appropriate
Operating procedures
Systems include
Provision of clearly written operating instructions, accessible to operators,
referring to numbered/identified plant items, covering
Start-up and shutdown
Normal operation, draining, purging, excursions etc.
Operation at high or low rates
Emergency shutdown, service failures etc.
Procedures for non-routine operations, e.g. clearance of blockages,
reprocessing of materials, temporary process alteration
Pressure testing, sampling, chemical and atmospheric testing
Established procedures for draining, purging, venting, isolating, testing and inspection
prior to opening/entering/maintaining plant (see permit-to-work systems,
maintenance)
MAINTENANCE 415
416 OPERATING PROCEDURES
Quality control on raw materials, materials in process, products and wastes
Materials control to enable losses, over-use, under-use or accumulations to be
detected; control of quantities in storage
Permit-to-work systems
See
under ‘Maintenance’
Entry into confined spaces (e.g. vat, vessel, flue, sewer, boiler or similar)
Use of non-flameproof electrical equipment where flammable liquids/vapours/
dusts may arise
Personal hygiene
Checks on
Adequacy of washing/showering facilities (location and provision)
Skin cleansing, barrier and conditioning cream provision
Double locker system
Personal protection
Systems to ensure provision of
Overalls: special requirements (flame retardant, antistatic), frequency of laundering
Protective clothing: suits, spats, armlets, helmets, gloves for specific applications,
footwear (industrial and/or antistatic)
Hearing protectors
Eye protection: specific provision for various duties
Respirators: specific types for different applications
Safety management
Systems include
Safety audit system: hazard analysis
Checks on the adequacy and location of fire-fighting, emergency rescue and
alarm equipment
Practice in emergency situations
Emergency procedures for
Fire/explosion
Toxic release
Serious accidents
Spillage
Pollution incidents
(particularly when manning levels are low, e.g. weekends)
Major emergency procedures
Internal procedures (evacuation, communications, shutdown, damage control)
External liaison (fire, police, hospitals, neighbours)
Site restrictions
Systems include
Control over chemicals, containers etc. removal from site (
see also
waste disposal)
Prohibition of eating/drinking except in designated areas
Prohibition of smoking, carrying matches/lighters, except in designated areas;
arrangements for enforcing this
Restriction on employees permitted to drive works transport
Control of lone working
Control over equipment removal from site
Storage
Procedures for ensuring
Identification of all materials
Segregation of incompatible materials
Good housekeeping
Compliance with limits set for stocks of potentially hazardous chemicals
Storage, segregation and handling of gas cylinders
Display of appropriate warnings/notices
Training: management
Provision for
Refresher course on fundamentals of safety, hazard recognition, procedures
Participation in hazard and operability studies on existing operations and procedures
Training: operating personnel
Provision for
Formal training programme; refresher courses
Instruction in hazards associated with the work and safe procedures
Introduction of new legislation
Instruction and practice in emergency procedures
Table 13.1 Cont’d
Encouragement/enforcement of use of personal protection
Special training needs, e.g. first aid, emergency rescue/fire-fighting
Waste disposal
Systems for
Collection of combustible waste in appropriate containers (e.g. oily rags/other
material subject to spontaneous combustion)
Identification of wastes; analytical control procedures; labelling of containers
Segregation of wastes; identification of hazards due to inadvertent mixing of
wastes
Selection of appropriate disposal routes for liquids/solids to comply with acceptable
discharge levels
Disposal of toxic waste
Table 13.1 Cont’d
maintenance is also required to correct faults and repair damage. All maintenance on equipment
used with chemicals should be properly planned following a risk assessment, and recorded.
Maintenance operations, particularly those which are non-routine, require a sound system of
work with strict administrative procedures, e.g. permit-to-work, to avoid risks arising from
modifications to established safe practices. A permit-to-work should be used wherever the method
by which a job is done is likely to be critical to the safety of the workers involved, nearby workers,
or the public; it is required whenever the safeguards provided in normal operations are no longer
available. The system has written instructions to explain how it operates and to which jobs it is
applicable. A form is used to control the work. This must be issued by a responsible person and
the recipient must be trained in the system and how to perform the work. Different forms are
applied to different tasks. Examples include:
• Entry into confined spaces where there is likely to be a danger from toxic or flammable gases,
ingress or presence of liquids, free-flowing solids, or oxygen deficiency or enrichment, etc.
(Table 13.2). Such work requires well-rehearsed procedures regulated by a permit. Figure 13.1
identifies the procedures for entry into confined spaces and Table 13.3 lists associated safety
requirements with a specimen permit (Figure 13.2). Detailed requirements in the UK are
specified in the Confined Spaces Regulations 1997.
• Hot work on plant, or in areas where flammable materials are handled, e.g. arc or gas welding
(see also Figure 5.4), flame-cutting, use of blow torches, grinding chipping concrete, introduction
of non-sparkproof vehicles.
Table 13.2 Control of oxygen gas
Ease of ignition, combustion rate and combustion temperature all increase when the oxygen content of an atmosphere >21%
(Chapter 6).
Enrichment of a room atmosphere >25% creates a hazardous situation: enrichment in a confined space is particularly
dangerous.
Precautions include
Never use oxygen to ‘sweeten’ the atmosphere in a confined space
When flame-cutting metals:
Use proper ventilation (all the oxygen supply to the torch may not be consumed)
Do not nip/kink the hose to cut off the oxygen supply while changing torches – always use the isolation valve
Do not leave blowpipes or torches inside a confined space during breaks
Wherever possible locate the cylinder outside the confined space
Do not use oxygen gas as a source of pressure in place of compressed air
Keep regulators, valves and piping on compressed gas systems clean and free from oil and grease
Close the cylinder valve when not in use
MAINTENANCE 417
418 OPERATING PROCEDURES
Request for work to be
done in a confined space
Work can be done
without entry
Work cannot be done
without entry
Withdraw from
service
Authorize work
Prohibit entry
Refer to supervisor in
charge of permits-to-work
Work to be done without
breathing apparatus
Withdraw from service
Isolate plant or section
concerned
Check no source of
ingress of gas/fumes etc.
Remove sludge and/or
deposits if present
Clean inside surfaces by
appropriate method
Ventilate thoroughly
Test atmosphere inside
Safe for entry without
breathing apparatus
Approve entry without
breathing apparatus
Specify: Protective clothing if needed
Second man outside
Rescue equipment
Reviving apparatus
Emergency back-up
Issue permit-to-work certificate
Specify time limit, cancellation in emergency
Work not finished inside time limit
Refer back to supervisor for renewal
or new permit
Re-check plant status, e.g. isolation,
cleanliness, work required
Work to be done with
breathing apparatus
Check that the wearing
of breathing apparatus
is practicable inside the
plant and during access
and egress
Withdraw from service
Isolate plant or section
concerned
Check no source of ingress
of dangerous material (e.g.
steam)
Not safe for entry without
breathing apparatus
Refer back for further cleaning/
purging as necessary
Approve entry with specified
breathing apparatus, life line etc.
Work finished inside time limit
Warn personnel
Return permit for cancellation
Return to service
Figure 13.1
Procedure for entry into a confined space