Part-14 Air Blowers and Compressors

14 AIR BLOWERS AND COMPRESSORS ........................................................ 2
14.1 GENERAL ...................................................................................................... 2
14.1.1 Scope 2
14.1.2 References 2
14.1.3 Submittals 2
14.2 PRODUCTS ................................................................................................... 2
14.3 AIR BLOWERS .............................................................................................. 3
14.3.1 Centrifugal Blowers 3
14.3.2 Positive Displacement Blowers 4
14.4 AIR COMPRESSORS .................................................................................... 5
14.4.1 General 5
14.4.2 Reciprocating Compressors 5
14.4.3 Rotary Compressors 5
14.4.4 After Cooler 6
14.4.5 Air Receivers 6
14.4.6 Fabrication Requirements 7
14.4.7 Booster Compressor 7
14.5 INSTALLATION AND COMMISSIONING ...................................................... 8
14.5.1 Installation and Commissioning 8
14.5.2 Testing 8

14 AIR BLOWERS AND COMPRESSORS
14.1 GENERAL

14.1.1 Scope
1 This part specifies the requirement for the design, manufacture, construction, installation, testing and commissioning of air blowers and compressors.

2 Related Sections and Parts are as follows:

Section 1 General
Section 8 Drainage Works
Section 10 Instrumentation, Control and Automation
Section 13 Building Electrical Works
Section 21 Electrical Works
14.1.2 References
1 The following standards or revised/updated versions are referred to in this part:

BS ISO 10816 ........... Part 1 and Part 3, Mechanical vibration in rotating and reciprocating machinery
BS 970 (ISO 683) ....... Wrought steels for mechanical and allied engineering purposes
BS 1123 .................... Safety valves, gauges and fusible plugs for compressed air or inert gas installation
BS 5169 .................... Specification for fusion welded steel air receivers
BS 5493 ..................... Code of Practice for protective coating of iron and steel structures against corrosion
BS EN ISO ................. Paints and varnishes. Corrosion protection of steel structures by protective paint systems
BS ISO 1217 .............. Displacement compressors. Acceptance tests
BS1042 ...................... Measurement of fluid in closed conduits
ISO 10474 ................. Steel & Steel Products Inspection Documents
PD 5500 ..................... Specification for unfired fusion welded pressure vessels

British Compressed Air Society's Code of Practice and the Pressure Systems and Transportable Gas Containers Regulations 1989

List of ‘Approved Suppliers’ prepared by the Public Works Authority
14.1.3 Submittals
1 In addition to the requirements of Part 1 of this Section, the Contractor shall reconfirm the information provided in the Technical Submission Schedules submitted with his Tender.

14.2 PRODUCTS

1 The Contractor shall assess which type and configuration of blowers or compressors that will offer the best whole life cost benefit for use on the plant to supply the process air requirements.

2 The number of blower/compressor sets provided shall be sufficient to ensure the full range of process air requirements can be met and that a minimum of one standby unit for each application is available at maximum process airflow. Blower/compressor sets shall be the same model with the same rated capacity for each separate application.

3 The motor rating shall be rated at least 10% greater than the maximum power required under all climatic and operating conditions.

4 Each blower/compressor set shall be provided with an acoustic enclosure and a surge protection system. The acoustic enclosure shall limit the noise level to not more than 75Db(A) when measured at 1 metre distance from any point at the enclosure surface at any time. The enclosure ventilation shall be designed to ensure that adequate cooling of the blower set is maintained. Consideration should be given to ducting the enclosure exhaust direct to atmosphere to limit the temperature rise within the blower house to a maximum of 5°C above ambient. The enclosure shall be designed to allow for ease of access to the blower set, without the necessity to lift the complete enclosure, to allow for routine inspection and maintenance procedures.

5 The level of vibration in each blower / compressor shall be within the limits and comply with BS ISO 10816, Part 1 and Part 3.

6 The blower/compressor sets shall be of a proven design with at least five years operational experience in similar applications. Where multiple units are required to meet the duty in addition to single duty applications, the design shall be proven in applications where two or more units are automatically controlled to meet the varying air demand.

14.3 AIR BLOWERS

14.3.1 Centrifugal Blowers
1 Blower sets shall comprise of single stage centrifugal air blowers with modulating powered inlet and outlet guide vanes, gearbox, lubrication system, electric drive motor, and suction and discharge flexible stainless steel connection compensators, all mounted on a common baseplate. The sets shall be installed on flexible machine mounts.

2 The volume flow rate from the blowers shall be modulated control on the inlet and outlet guide vanes which shall be capable of varying the delivery rate down to 45% of the rated output without causing the blower to go into surge when operating either singly or in parallel. A high operating efficiency shall be maintained throughout the flow range.

3 Materials and equipments of construction shall give a design running life of at least 100,000 hours before major maintenance is necessary.

4 The impeller shall be statically balanced and the whole rotor shall be dynamically balanced. The first responsive critical speed of the rotating assembly shall be at least 10% above the maximum operating speed.

5 The gearboxes shall be of the parallel shaft high speed helical type. The gears shall have a minimum AGMA service factor of 1.5. A labyrinth oil seal shall be fitted to each shaft to prevent oil seepage from the casing under operating and static conditions. The seals shall be designed to ensure there is no contamination of the process air.

6 Each gearbox shall be fitted with an oil level sight glass and a drain plug which shall be readily accessible in operation.

7 The baseplate shall be provided with lifting points to allow the complete set to be handled using chain slings.

8 Instrumentation for the safety monitoring of air blowers shall include oil temperature, oil level, air temperature at inlet and outlet from the blower, outlet air pressure, surge conditions, bearing temperature and vibration and motor running current. The instruments shall provide signals for the shutting down of air blowers if unsafe conditions arise and for visual indication of the fault. Additionally, the contractor shall provide all necessary instrumentation for measuring the airflow from each blower.

9 Each blower shall be equipped with an inlet air filter, automatic unloading device, pressure relief valve, pressure switch and under load (no flow) detection device to trip the blower in case of drive/flow failure.

10 Each blower shall be performance tested at the manufacturer’s works, using the control motors, to BS ISO 1217:1996. Air flow measurement for these tests shall be carried out in accordance with BS 1042. Blower casings shall be works hydro-statically tested to 1.5 times the maximum working pressure.

14.3.2 Positive Displacement Blowers
1 The blowers shall be complete with all ancillary equipment which may be required to enable the units to operate correctly.

2 Blowers shall be air-cooled and of the double rotor positive displacement rotary type with cast iron casings delivering oil-free air.

3 Each blower shall be complete with an automatic unloading device, dead-weight pressure relief valve, spring type pressure relief valve, pressure gauge, pressure switch and non return valve of the wafer or nozzle ring check pattern.

4 The blower speed shall not exceed 70% of the maximum designed speed or 2300 rpm whichever is the lower.

5 Each blower shall have an under load detection relay or other similar device to trip the blower in the event of a drive or flow failure.

6 The blower casing shall be high-grade cast iron adequately ribbed to assist cooling and avoid distortion. The rotors shall be spheroidal graphite iron with integral shafting. Timing gears shall be of nickel cast iron positively keyed to the rotor shafts, they shall be accurately ground with close clearances to prevent interference between rotors.

7 The blower shall be fitted with an oil lubrication system for the bearings and timing gears. The blower shall be fitted with mechanical seals to prevent the ingress of oil into the rotor chamber.

8 The lubrication system shall include filling and drain plugs and oil level indicators visible from outside the acoustic cover.

9 The drive between the blower and motor shall be of the vee belt or flat toothed belt type and of approved design.

10 The complete blower assembly shall be mounted on steel section frame which shall incorporate a blower mounting plate, motor adjustment slides and guard support brackets, the frame is to be supported on anti vibration mounts.

11 An inlet silencer complete with replaceable filter element shall be fitted to each blower, the silencer shall be fitted with a visual indicator to warn of filter blockage.

12 Outlet silencer shall be fitted to maintain noise levels as low as possible. A flexible coupling shall be fitted to prevent vibration transmission to the air supply system.

13 Silencers are to be of the reactive type, absorptive type silencers will not be permitted.

14 Components likely to wear in the course of normal operation shall be capable of replacement with readily available replacement components.

14.4 AIR COMPRESSORS

14.4.1 General
1 The design and installation of the compressed air system shall be in accordance with the requirements of the British Compressed Air Society's Code of Practice and the Pressure Systems and Transportable Gas Containers Regulations 1989.

2 Compressors shall be rated to achieve the duty at optimum efficiency and may be selected from one of the following types unless otherwise specified in the particular specifications:-

(a) (a) Reciprocating Single Stage

(b) (b) Reciprocating Multi Stage

14.4.2 Reciprocating Compressors
1 Reciprocating Single Stage Compressors shall be of inherently oil free design. The compressor shall be of cast iron construction with aluminium cylinder heads and shall be air cooled. The unit, complete with electric motor, shall be mounted on a rigid bedplate incorporating anti vibration mountings. The drive arrangement shall be belt or shaft driven and shall be fully guarded. A suitable means of achieving alignment shall be provided and where appropriate flexible couplings shall be used.

2 Reciprocating Multi-Stage Compressors shall be as above but incorporate interstage cooling and be of the short stroke design for low piston speeds.

3 Both single and multistage units shall be provided with the following:-

(a) Low oil level cut out switch.

(b) Crank case oil sight glass.

(d) Silencer complete with pressure gauge and low pressure cut out (filter blockage protection).

(e) Pressure gauge tappings after each stage for compressors up to 15kW, and gauges and safety valves on compressors over 15kW.

(f) Oil pressure indicator on compressors over 100kW.

(g) Final air temperature indicator on compressors over 100kW.

(h) Unloader valve unit.

(i) Air dryer system (Dehumidifier) where dry air is required.

14.4.3 Rotary Compressors
1 Rotary Screw Compressors shall be of the inherently oil free design and shall be either the single stage or multi-stage type depending on the duty.

2 The separate stages shall be enclosed in individual housings, the male rotor being gearbox driven whilst the female rotor is driven via a timing gear.

3 The rotor shafts shall be supported by precision made ball and roller bearings

4 Lubrication to the driving gear, bearings and timing gear shall be via an oil pump driven by the main shaft. The lubrication system shall be complete with oil filter and cooler, pressure gauge and fail-safe pressure switch.

5 On multi stage units air cooling shall be undertaken by an intercooler.

6 The compressor shall be motor driven via a flexible coupling and gearbox common to both stages. A suitable means of alignment shall be provided.

7 The complete compressor set ie. compressor, motor, gearbox and associated cooling equipment shall be supplied on a rigid bed plate suitable for floor mounting via anti vibration mountings.

14.4.4 After Cooler
1 All types of compressor shall be fitted with an aftercooler. These shall be of the air cooled type comprising an air to air heat exchanger. The aftercooler shall cool the process air to a temperature of 10oC above ambient. The aftercooler shall be fitted with an automatic condensation drain which shall be provided with a manual bypass.

2 Delivery lines from the Compressor Sets shall be fitted with the following equipment:-

(a) Oil trap/filter prior to entry into the air receiver. The filter shall be fitted with an auto drain and manual by pass.

(b) Adjustable safety valve (lockable).

(c) A solenoid valve for unloading (dependant upon compressor size) for applications where the compressor is directly coupled to a surge vessel.

(d) A non return valve.

(e) A high efficiency coalescing oil filter (0.001 micron filtration).

14.4.5 Air Receivers
1 Unless otherwise stated, one air receiver shall be provided, normally being online, but with the capacity to be isolated from the system.

2 These shall be manufactured from fusion welded steel and shall comply with BS 5169 or equivalent for the appropriate pressure class.

3 Air receivers greater than 1000 litres capacity shall be designed and manufactured in accordance with PD 5500 or equivalent.

4 Each integral air receiver shall have sufficient capacity to damp out air pulses from the compressor and to prevent pressure drops on process valve actuations.

5 The air receivers shall be connected such that the duty compressor delivers into either or, if two air receivers are specified, both of the air receivers. Diaphragm isolation valves shall be provided for isolating either of the receivers from the system.

6 The air receivers shall be suitable for floor mounting and shall be supplied with two inspection ports. The inspection ports shall be of the elliptical type and pressure sealed.

14.4.6 Fabrication Requirements
1 The air compressors shall be air-cooled. The cooling air shall be drawn directly from the ambient air, routed through the enclosure and exhausted upward through the enclosure box. The cooling air for the motor shall be drawn directly from the ambient air.

2 The drive motors shall be directly coupled to the air end by flexible coupling.

3 The compressors shall be suitable for indoor installation.

4 Each air compressor shall have an efficient filter for cleaning intake air and micro filter after the discharge. Each compressor shall be fitted with a silencer, which shall be sized to prevent excessive pressure drop.

5 All instrument tappings shall be via suitable bosses welded to the tank structure. The vessel shall be supplied with:

(a) Pressure gauge.

(b) Pressure relief valve.

(d) Lifting lugs.

6 The vessel shall be corrosion protected to give maintenance free service for a period of 20 years minimum, as defined in BS 5493 (partially replaced by BS EN ISO 12944) or equivalent and as specified in Section 8 part 8

7 Full certification in triplicate shall be supplied with the air vessel. The vessel shall also feature a stainless steel nameplate containing the following details.

(a) The manufacturers’ name.

(b) The date of manufacture.

(d) The maximum design pressure.

(e) The minimum design pressure where it is other than atmospheric.

(f) The design temperature

(g) The test pressure

14.4.7 Booster Compressor
1 In case discharge pressure in excess of 15 bar is required, then booster compressors will be required. Alternatively multistage piston type air compressor can also be proposed. The booster compressor package shall comprise the following items:

(a) Booster compressor and motor mounted on common base plate.

(b) V-belt drive with guard.

(d) Solenoid valve to close the inlet at standstill.

(e) Safety valve on the oil/water separator or after cooler.

(f) Anti vibration floor mounts.

(g) Suitably sized air receiver.

14.5 INSTALLATION AND COMMISSIONING

14.5.1 Installation and Commissioning
1 1 The equipment delivered to Site shall be examined by the Engineer to determine that it is in good condition and in conformance with the approved working drawings and certification. All equipment shall be installed in strict accordance with Part 1 of this Section 9.

14.5.2 Testing
1 Test Procedures shall be in accordance with Part 1 of this Section 9 and the particulars of the Contract.

END OF PART