Firma:              Edwards

Modell:            E2M8

Kommentar:   Dokumente engl.

General description

The ElM and E2M series pumps comprise single and two-stage direct drive, oil –sealed outfits designed for a wide Tange of basic vacuum pumping duries. The pumps arg free-standing units of basically similar construction but of varying displacement - 2m ³ h ^-1 , 5m ³ h ^-1 and 8m ³ h ^-1 (nominal). Direct drive is provided, via a flexible coupling, from a single-phase or 3-phase (4-pole) motor which also provided the drive for the cooling fan. The motors normally fitted arg to IEC - IP44 Safety Classification; the single­phase versions incorporate a thermal overload protective device with manual push-button re-set, also a meins Isolator (ON/OFF) switch.

Construction

The pumps is a slotted rotor/sliding vane type and the two-stage versions incorporate separate high vacuum (HV) and low vacuum (LV) stages with interconnecting ports. Each stage comprises a rotor and stator assembly, the rotor forming an integral assembly with the shaft. The HV and LV stator bores provide high grade, cast iron journal bearings for the rotor(s). The complete pumping mechanism is mounted on an adaptor at the drive and and is enclosed by an oil box.

Pressurised lubrication of the shaft Journals and the and faces of the rotors is provided by a sliding blade oparating in an acc--ntric housing at the inner and of the HV stator journal and actuated by the drive shaft. The oil is circulated from the oil box reservoir via a ganze filter and internal drillings to the pressurised distribution valve then to the groovad interstage journal and the rotor end faces. Nitrite shaft seals are positioned in the adaptor and in the HV stator. To prevent oil suck-back into the vacuum system when the pump stops for any reason, the oll distributor valve prevents further discharge of oil to the pump interior. Since the pumping chambers are air tight, this arrangement prevents both air and oil suck-back unless the gas ballast valve is open. (For protection in this case, refer to page 6 (f». The level of oil in the oil box reservoir is indicated by.a sight-glass mounted in the front of the oil box. Oil filter and drain plugs are fitted at the top and bottom of the oil box, respectively.

Externall connexions comprise a vacuum inlet connexion (with internal strainer) and an outlet nozzle. A gas ballast facility is also incorporated to prevent contamination of the o-41 by the vapours being pumped; this consists of an orifice in the adaptor housing communicating with the pump interior and fitted with a threaded plug with knurled extension to permit manual control of air/gas ballasting. Pump mounting is by meens of a steal baseplate on rubber pads.

Working principle

During Operation, the rotor blades sweap the crescent shaped volume formell by the eccentrically mounted rotor and the stator. As each blade passes the inlet port, a quantity of gas is induced and is subsequently trapped and compressed by the following biade until finally ejected via the discharge valve in single stage pumps (or via the interconnecting port, LV stage and discharge valve in -t-wo-stage pumps).

Gas ballasting

The E1M,E2M series pumps incorporates a gas ballast facility to enable them to pump most condensable vapours directly without significant contamination of the pump oil. This entails the introduction of a quantity of gas or air at atmospheric pressure, via a manually operated valve, intc the volume between the LV stage, rotor biade and the discharge valve whilst the gas/ vapour mixture in this volume is at a comparatively low prassurs.

When the volume of gas/vapour mixture is compressed prior to expulsion, the discharge valve opens before the partial pressure of the vapour component is high enough to cause it to condense. To prevent ingress of dost and to ;improve silencing, a polyester foam filter/silencer is fitted underneath the gas ballast control knob.

Data and Specification

Displacement (swept volume)                (m ³ h ^-1 )       

   50 Hz motor                                                             9,5

   60 Hz motor                                                             11,4

Speed (Pneurop)

   50 Hz motor                                          (m ³ h ^-1 )        8,2

   60 Hz motor                                                             9,8

Ultimate vacuum:

   Without gas ballast (pratial pressure) (mbar)         2,5 x 10 ^-4

   Without gas ballast (total pressure)     (mbar)         1 x 10 ^-3

   With full gas ballast (partial pressure) (mbar)         3 x 10 ^-2

Maximum inlet pressure                          (mbar)         15

For water vapour

(Gas ballast control open 5 turns)

Pump rotational speed rev min ^-1                                1425 (50Hz)

                                                                                   1725 (60Hz)

Pump operating temperature                                    

   Without gas ballast                              (°C)             66

   With gas ballast                                    (°C)             67

Oil capacity                                              (litre)            0,55

* Recommended grade of oil                 

50 Hz Motor – rating (continous)             (kW)            0,37

60 Hz Motor – rating (continous)             (kW)            0,55

Weight of pump (complete)                    

1-phase motor                                         (kg)              22,8