APPENDIX A: Design of Plant, Equipment and Workplaces

Design of Plant, Equipment and Workplaces (DSEAR)

Introduction

The following provides guidance on the key areas employers need to address in order to meet the requirements of DSEAR and covers the need to control risks and undertake assessments prior to using any plant, equipment or area which handles, produces or process dangerous substances. It includes measures for making redundant plant and equipment safe.

Duties of suppliers

Legislation places a duty on suppliers of equipment to ensure:

that equipment and protective systems and devices are safe for their intended use
that the supplied equipment has met the essential health and safety requirements of legislation before the equipment can be placed on the market and will carry the CE mark
equipment that is intended for use in explosive atmospheres that has been shown to meet the essential health and safety requirements will also carry the explosion protection symbol illustrated below. The equipment will also be marked with other safety information including the equipment group and category e.g. whether it is for use in gas or dust atmospheres and the temperature rating
documentation is provided to the user specifying details of the intended and safe use of the equipment. The documentation may also specify applications for which the equipment is not suitable.

Selection of workplace and work processes

The Regulations require employers to take account of the design and organise safe systems of work at the workplace and provide suitable work equipment.

The Regulations require employers to ensure that:

plant, equipment and workplaces are designed, constructed, installed, operated and maintained to reduce the risks arising from dangerous substances
the selected plant and equipment should be suitable for the location it is to be used and its intended usage by taking into account the following:
- where hazardous areas may arise
- the substances that may be used with or near to the equipment
- how different substances may react or add to a fire or explosion hazard
- whether fire or explosion hazards may develop from inter-connected plant and process areas
- documentation provided by the supplier

If an employer designs and builds its own equipment for use by their own employees, the equipment will still have to meet the relevant essential health and safety requirements in the same way as any equipment purchased from a supplier.

Control measures

The employer must implement the control measures identified by the risk assessment and also where relevant the measures detailed below.

Reducing the quantity of dangerous substances to a minimum having regard to the process and operation being undertaken.
Plant, equipment, ducts, trunks and casings be designed and installed to minimise the accumulation or build up of dangerous substances and flammable residues e.g. duct work used for flammable dusts have adequate velocity maintained through out its length and with smooth inner surfaces and large radius bends. Where dusts and other residues may accumulate, suitable access points for cleaning and inspection should be provided. The opening of any access point should be provided with interlocks, valves or system of work to prevent a release of the dangerous substance
Designing plant and equipment that in the event of an emergency or during normal operations a premature release of a dangerous substance is avoided or minimised. For example using pipe work, enclosed systems and closed vessels
Where the dangerous substance is liable to spill or leak within a process or operation gives rise to a hazardous situation, then where reasonably practicable the substance be contained or run-off to a container or to a safe place.

Controlling the release of a dangerous substance at source by:

providing local exhaust ventilation
providing an enclosed cabinet or other enclosure with mechanical ventilation
providing adequate isolation valves to mitigate loss

The employer should ensure, as far as reasonably practicable, that work equipment cannot unintentionally ignite hazardous concentrations of dangerous substances either in the workplace or the equipment. As a minimum, controls are needed to ensure that:

fuel present when an ignition source is applied will not cause danger
fuel is supplied at a controlled rate, and does not accumulate, unburnt within the equipment
corrective action is taken to prevent danger in case of flame or combustion failure when not intended
prevention of an explosive atmosphere inside when plant has been shut down

The employer should ensure that work process and workplaces are designed and operated to avoid any adverse conditions when using dangerous substances. Information should be obtained on any adverse conditions that should be avoided when using the dangerous substance. If a chemical reaction is part of the process then a chemical reaction hazard assessment should be undertaken as part of the overall risk assessment. The chemical reaction hazard assessment should include, as necessary, the following:

Materials of construction
Vessel design pressure
Agitator configuration and speed
Reactant feed controls
Safe operating temperatures and pressures
Heat transfer and cooling rates
Process instrumentation and interlocks.
Process venting
Both normal operation and the effects of foreseeable process faults.

Mitigation measures

Employers are required to apply measures to mitigate the effects of a fire or explosion arising from work activities involving a dangerous substance as part of the overall risk assessment. The measures that can be taken as necessary are:

Separate the workplace in which the quantity of dangerous substance is manufactured or used from other parts of the premises and site boundary
Separate workrooms from such workplaces by physical barriers that are fire resisting structures and separated from areas where dangerous substances are stored
Control rooms or other occupied buildings on site processing dangerous substances should be designed or positioned to provide protection from dangerous occurrences
Prevent fire and explosion from spreading to other vulnerable equipment or into the workroom by designing and installing processing equipment accordingly
Discharge vent pipes containing flammable, highly flammable or extremely flammable liquids to a safe place outside; vent pipes should be fitted with a flame arrestor
Provide fire protection e.g. water deluge systems or fire protection coatings

Other issues to consider on the control and mitigation of risks are:

Keeping plant, equipment and control systems in an efficient state, working order and in good repair
Safe handling, storage and transport of dangerous substances and of waste containing dangerous substances
Segregating incompatible dangerous substances

Redundant equipment

In order to meet the requirements of DSEAR the employer must consider the risks from dismantling and disposal of redundant equipment. Based on the findings of the risk assessment employers should decide on the control measures to ensure the safety of employees and others during the cleaning and decommissioning process.

The following general requirements should be implemented before plant and equipment are mothballed, dismantled, transferred to a holding area or removed off site:

Plant and equipment should be adequately isolated from sources of dangerous substances by, for example, permanent disconnection or blanking plates
Drained and cleaned of residual material and where necessary gas freed. (Additional cleaning or inerting may be required depending on the risk assessment and the proposed disposal method.)

Where plant or equipment containing residual material is to be removed from site without cleaning or gas freeing then it will be necessary for the employer to ensure it can be handled and transported safely and those receiving it are aware of the hazards and are competent to deal with them.