RFHHA FREE FACEBOOK CME OF JANUARY 2015 THEME: Laboratory Science planning & Designing Session 6 : General mechanical engineering services HEATING SYSTEMS Spaces heated by low-pressure hot water systems should use low surface temperature radiators or overhead radiant ceiling panels. The surface temperature of wall-mounted radiators should not exceed 43ºC. Ceiling-mounted radiant panels can exceed this surface temperature and allow space savings. Radiators should be located under windows or against exposed walls. There should be space between the top of the radiator and the windowsill to prevent curtains reducing the output. There should be adequate space underneath (at least several inches) to allow cleaning machinery to be used. Where a radiator is located on an external wall, back insulation should be provided to reduce the rate of heat transmission through the building fabric. All radiators should be fitted with thermostatic control valves. These should be of robust construction and selected to match the temperature and pressure characteristics of the system. The thermostatic head should incorporate a tamper-proof facility for pre-setting the maximum room temperature. It should be controlled via a sensor located integrally or remotely. To provide frost protection, the valve should not remain closed below a fixed temperature. Radiators should be used to offset only building fabric heat loss in mechanically ventilated rooms. All rooms should have local heating controls; the facility should be controlled throughout by the building management system (BMS) (see paragraphs 6.63–6.65 for details). VENTILATION AND AIR-CONDITIONING SYSTEMS Where possible, natural ventilation should be used. Mechanical ventilation should be provided to general areas such as plantrooms, toilets and storage areas. Mechanical ventilation to internal rooms other than laboratories should provide minimum air change. In some cases, cooling will be necessary to maintain comfortable conditions. A low-velocity mechanical ventilation system should be used. Diffusers and grilles should be located to encourage uniform air movement without causing discomfort to staff. The design should allow for airflow from naturally ventilated spaces or spaces with a mechanical air supply, into spaces that have only mechanical extract ventilation, via transfer grilles in doors or walls. The design should avoid the introduction of untempered air and should not prejudice the requirements of fire safety, privacy, security or comfort. There may be limited scope for using recirculated air ventilation systems in pathology facilities. However, the viability of this energy-saving option should be considered. The supply air distribution system should not distort the unidirectional and stable airflow pattern required for fume cupboards and microbiological safety cabinets. Supply air ceiling diffusers or grilles should not discharge directly towards fume cupboards or safety cabinets, unless the terminal velocity is such that the airflow pattern is unaffected. Grilles and diffusers should be positioned some distance from the front face of fume cupboards and safety cabinets. The design should ensure that high air change rates and/or opening and closing doors do not have an adverse effect on the performance of safety cabinets or fume cabinets. A damped door closure mechanism may help. The airflow rate for laboratory spaces will be determined by the following criteria: • minimum requirement for air changes per hour (when occupied); • heat gain from laboratory equipment; • solar heat gain; • use of fan coil or split local air-conditioning units to offset heat gains; • extraction air volumes from fume cupboards, safety cabinets and other items of extract equipment. Laboratories containment rooms and rooms using solvents or hazardous materials should be designed with supply and extract systems balanced to maintain negative pressure. Negative pressure will range from –30 Pa to –50 Pa. Ventilation systems for clean laboratories should maintain positive pressures at all times. They should normally use 100% fresh air. In some circumstances, however, it may be possible to re-circulate the ventilated air. Temperature control should be achieved by means of reheat coils in supply air systems. HOT AND COLD WATER SYSTEMS Hot and cold water supplies to laboratories should be served by separate storage vessels and pipework distribution systems. There should be signs stating that the water is non-drinkable. Hot and cold water for general areas of the facility should be taken from the general water supply. The hot water supply should be 60ºC ± 2.5ºC at the storage vessel outflow. The return temperature at the calorifier should be at least 50ºC. Outlet temperatures and fittings for washbasins, sinks and showers are shown on Activity Data Sheets relating to pathology facilities. The cold water supply should be kept below 20ºC to restrict microbiological growth. All pipework, valves and flanges for water supply systems should be insulated and vapour-sealed. An emergency drenching shower should be provided for staff. The floor below the shower should be graded and drain into a suitable gully. Hot and cold water systems should be designed in accordance with a number of regulations and guidance applicable to country. COOLING SYSTEMS Chilled water cooling systems should be used rather than the direct expansion type. If the location permits, the pathology facility could be connected to the main hospital chilled water plant. Evaporative-type heat rejection plant should not be used. If cooling cannot be provided from a central chilling plant, a separate air-cooled chiller plant using nvironmentally friendly refrigerant should be used. There may be a need to maintain temperatures within specified limits to prevent equipment failure. Temperature limits should be obtained from equipment manufacturers. Consideration should also be given to the selection of a chilling plant that offers low ambient free cooling to applications requiring year-round cooling (for example chilled water circuits serving fan coil units in equipment rooms). DRAINAGE AND WASTE SYSTEMS The internal drainage system should use the minimum of pipework and remain water/airtight at all joints and connections. The system should be sufficiently ventilated to retain the integrity of water seals. Laboratory waste systems should be made of heat-sealed polypropylene. High silicone iron alloy (14.5%) should be used below ground. Laboratories should be provided with an acidresistant waste and vent system connected, after dilution, to the foul sewer outside the building perimeter. Space should be available for a neutralisation tank since this is likely to be required in the future. Sink traps and piping to floor drops should be made of acid-resistant materials. Below ground, acidresistant pipes will not be damaged by minor quantities of acids and solvents. Vents should be routed through the roof and not connected to sanitary vent piping. Drainage systems from pathology laboratories may contain pathogens. To prevent any risk of crossinfection, the system should be routed to avoid other hospital accommodation such as critical care areas, operating theatres and catering departments. Drainage may also contain chemicals and should be designed for maximum dilution. Frequently-used large-volume appliances such as glassware washing machines should be located upstream. Large-capacity catch-pot receivers should be provided where appropriate. The internal drainage system should be connected to the main drainage system as far downstream as possible to ensure maximum dilution. The designer should liaise with the statutory authority to agree maximum discharge volumes and the method of connection to main services. The drainage system should allow easy access for inspection and maintenance. Access should be above the appliance flood/rim level so that spillage of contaminated effluent can be minimised. Access for cleaning should cause minimal disturbance to laboratory staff. The designer should be familiar with the types of discharge produced by specialist equipment and the effect that the mixing of various chemical discharges may have upon the drainage system. If radioactive effluent is to be discharged into the drainage system, the requirements for catch-pot recovery, dilution and maintenance should be discussed and agreed with the radiological protection advisor. Autoclaves (except those used for decontamination of infected material), glassware washing machines and refrigerators should not be connected directly to the drainage system. They should have an air gap to prevent the ingress of bacteria. The sterilizer for discarded material should be connected to the drain via a vented break tank and trap. The break tank should be vented outside the building. The vent termination should be above roof level and clear of any ventilation inlet or window. The trap should be positioned between the break tank and the connection to the drainage system. Floor gullies can become contaminated, and should be avoided or minimised. Metal pipework is not suitable for use in pathology laboratories. Copper and lead are not suitable for use with effluents containing azide and mercury compounds. Glass, polypropylene, and other plastics are suitable, but consideration should be given to the chemical characteristics, temperature of the fluids discharged, and arrangements for fixing and supporting the drain. EXTRACT SYSTEMS Extract fans should be located close to the point of discharge to ensure that the extract system is maintained at negative pressure. Extract ducts from general extract, chemical fume cupboards and other special extract systems within the same laboratory unit may be combined into extract manifolds on each floor. A manifold system offers the following advantages: • greatest dilution at stack discharge; • increased flexibility for future additions; • capital cost saving because of fewer fans and controls; • optimum use of roof space; • higher efficiency of energy use; • reduced maintenance cost; • energy recovery capability. Staining areas should have bench extract systems that ensure air flows away from operators’ faces. Low level extract should be provided adjacent to equipment for use when solvents are changed or when specimens in formaldehyde are opened. External discharge arrangements for extract systems should be protected against back pressure from adverse wind effects. They should be located to avoid reintroduction of exhausted air into the building through air intakes and windows. CONTROL SYSTEMS All supply and extract systems should have local control systems. These should be integrated with the overall BMS . Controls should include temperature, pressure and time-switching functions. Their selection should take account of the extent to which they can be linked to the BMS serving the whole hospital. Supply and extract fans should be interlocked. This will ensure that the supply fan will not operate unless airflow is established with the extract system. All heater battery coils and filters should be provided with frost protection control. Control systems should incorporate energy-efficient equipment including: • high-efficiency motors; • variable air volume systems (in laboratories); • suitable air-to-air heat recovery systems. Laboratory air-conditioning systems should be controlled to ensure comfort, operational safety and regulatory compliance, and to satisfy process constraints. A well-controlled system should provide flexibility and minimise the operational costs of the system. A control system should provide the following minimal safety responses: • detection of equipment failure by the BMS and automatic initiation of standby equipment; • maintenance of relative negative and positive pressures in the laboratories; • cessation of the air supply to laboratories to increase negative pressure levels in response to fire or smoke detection. Opening exit doors should not be affected by this provision. The control of supply air volumes using a variable air volume (VAV) type system is recommended for large laboratories. Supply and extract air volumes should be balanced to achieve desired pressurisation levels. Each fume cupboard should be controlled to maintain a constant face velocity. The VAV supply system should provide temperature control and maintain the minimum room ventilation rate. Laboratory spaces should be comfort cooled without local humidity control. Large laboratory spaces should be zoned, with each zone equipped with a thermostat for individual control. Local control of ventilation plant It may be necessary to have more than one microbiological safety cabinet and fume cabinet. Therefore, local controls for operating any associated ventilation plant will be necessary. Work in the containment level 3 rooms should only be undertaken when ventilation systems serving associated rooms are operating. Where “make up” air is provided by mechanical ventilation, a supply air failure warning system should be provided. If any safety enclosure or room extract system fails, the associated supply system should be capable of being shut down automatically or reduced to prevent pressurisation of the room and possible contamination of adjacent areas. The ventilation control system for safety cabinets should incorporate a five-minute delay timer. This will ensure that the system will continue to run after work has finished and purge any remaining contaminants. PNEUMATIC TUBE SYSTEMS A pneumatic tube system will be required for the transfer of specimens to and from other departments to stations within the pathology facility. The system should be designed in accordance with HTM 2009. BUILDING MANAGEMENT SYSTEM Engineering plant and equipment should be monitored and regulated by the BMS, in accordance with HTM 2005 – ‘Building management systems’. Plant and system operational data should be recorded and reported. The BMS should also monitor, measure and record energy consumption for the facility. If the main site has a BMS, the pathology facility should be set up as an outstation so that systems serving the facility can be monitored and controlled at a central station. The engineering systems within the facility should be capable of management from both the central station and the outstation itself. Ref: HBN NOTES, RFHHA DIGITAL LIBRARY Dr Madhav Madhusudan Singh
Posted on: Mon, 05 Jan 2015 17:03:59 +0000
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