SMOKE SPILL INDUCTION MOTORS

STANDARDS

AS 1668, AS 1359, BS 7349, BS 4999, BS 5000, IEC 34, IEC 72.

GENERAL

Western Electric Smoke Spill motors are designed to meet the requirements of Bitish and Australian Standards.

AS 1668. 1 states that the objectives of Smoke Control are:

        a) to vent smoke from the fir-affected compartment: and

        b) to reduce the spread of smoke to fire isolated exits and other compartments.

 

In general Smoke Spimm motors are required to continue to operate driving extraction fans in a building, in the case of a fire. Usually these motors operate air circulation fans as part of the normal operation of the building, however if a fire occurs they must continue to operate for a period of time to extract smoke and\or dangerous fumes from the building and allow rescue services some assistance in rescuing any occupants still in the building. it is expected that hte fumes being extracted will be at high temperatures, well above normal ambients. These motors must be able to operate for a short period in high ambient temperatures - usually 250deg C. for 2 hours.

 

AS 1668.1 defines a Smoke-Spill fan as follows:

Each Smoke-Spill fan, complete with its drive, flexible connections and control gear, shall be constructed and installed so that it is capable of continous operation at it’s rates capacity as required as follows:

        a) Except as required be b), the fan shall operate for a period of not less that 2 hours with a smoke-spill air temperatures of 200 deg C.

         b) Where the smoke-spill fan serves as a single compartment and is located at the same level as the compartment. it shall operate for a period of not less that 30 minutes with a smoke spill air temperature of 300 deg C.

If the building has an approved aprinkler system installed throughout and fire isolated exits are pressurized, the need only comply with a), as above.

Motors driving such fans may be mounted in the air stream provided -

        i) They are capable of operating at the appropriate temperatures and for the specified period : and

        ii) any intergral high temperature cut-outs fitted are electrically isolated during a smoke control operations

 

STANDARD ELECTRIC MOTOR SPECIFICATIONS

Voltages 380v, 400v, plus other options.

Frequency 50Hz, (60Hz)

Speeds - single speed or 2 speed

Connections - 2.2 Kw and below- 240v Delta/ 415v Star.

3Kw and above - 415v Dleta with 6 leads for Star and Delta startings.

2 speed motors are supplied for DOL starting only. If star/ delta starting is required it must be specified with the inquiry and the order.

Protection - TP55, (IP56, IP65, IP66).

Shaft Hole - all motors are supplied with a drilled and tapped hole to DIN standards, in the end of the shaft.

Cooling - TEFC, (Totally Enclosed Fan Cooled), TEAO, (Totally Enclosed Air Over). TEAO motors are supplied without a cooling fan and rely on the air flow from the ‘load’ fan they are driving for their cooling.

Terminations/Connections - Standard Terminal box and terminal block oe extended leads and a blanking plate.

Special Requirements for Smoke Spill motors.

Bearings with C3 or C4 radial clearances.

High Temperature Grease.

Stainless Steel Nameplates.

Special Stator Windings - Class H or Class F, depending on the time and termperature rating specified by the customer. Class H windings with special materials are also available.

 

The following information is Required when ordering a Smoke Spill motor.

Kw ratings (or rating for 2 speed)

Speed or Speeds.
Voltage

Frequency

Temperature Rating in deg. C.

Time Requirement

Mounting - foot or flange

TEFC or TEAO.

Standard Terminal Box or Blanking Plate and Extended leads

With or without fan.

With or without fan cowl.

With or without anticondensation heaters.

(Only to be operated when the motor is off)

With or without thermistors. (Thermistor circuit will need to be disabled in the case of a fire)

Type of motor starter or if using a variable frequency drive.

 

Motor Testing

Sample motors, prepared to Western Electric Smoke Spill Specifications, have been tested, and independently witnessed, to ensure compliance with the following requirements:

200 deg C. for 2 hours

250 deg C. for 3 hours

300 deg C. for 30 minutes.

 

The motors were run in a normal ambient temperature at full load driving a fan until the temperature stabilized at normal operating temperature. The motor/fan units were then placed into a large oven at the required temperature and continued to operate for the required time. The motors were closely monitored during these tests, and all data was recorded. Copies of the test reports on these motors are available on request.

 

The Future

Australian Standards have produced a new Draft Standard called "Methods of Test and Rating Requirements for Smoke Spill Fans". This standard is based on the requirements of the European Standard EN BKXF-3 "Specifications for powered smoke and heat exhaust ventilators"

The following sections are all taken from the new draft standard.

The foreword to the draft standard states:

 

Smoke and heat exhaust ventilation systems are used widely to create smoke free areas beneath a buoyant smoke layer and to create negative pressures in fire affected compartments. These actions assist in evacuating people from a building, reducing fire and smoke damage, facilitating firefighting and retarding the lateral spread of the fire.

 

When air and the products of combustion are exhausted from a building by mechanical means in the event of a fire, a powered fan (known as a smoke spill fan) is generally used. It is therefore essential that the smoke spill fan temperature conditions when called upon to do so.

 

Dual Purpose smoke-spill fan - a smoke spill fan that has provision to allow its use for day to day comfort ventilation.

 

Smoke spill fan motor range - a range comprising smoke spill fan motors from the same manufacturer, which are physically similar, using the same form of construction and material and manufacturing method for the carcass, the cooling impeller when fitted, and end covers; the same insulation specification which includes insulation used for coil separation and slot insulation, winding impregnation materials (varnish or resin, tec. lead insulation, terminal blocks and other materials that could affect the integrity of the insulation): same bearing type, internal radial clearance, class of fit, lubricant and arrangement. The motor windings shall also be based on the same maximum winding temperature and class of insulation, in accordance with IEC34.1

The following may vary across the range -

a) the frame size;

b) the rotational speed;

c) the electrical windings, including multispeed;

d) he form of mounting, e.g. foot, flange, pad, clamp

 

Motor Rating/Motor Selection. The motors shall be selected for continuous operation at the power level required or the sir density at normal ambient temperature, not just for operation at elevated temperatures and lower densities.

 

Motor Rating/Insulation Integrity. The integrity of the insulation in motors is very dependent on the operational temperature of the windings. Relatively small decreases in the temperature rise above ambient will significantly extend the life of the insulation. Motor ratings for smoke spill fans shall be limited by the temperature rise for one class lower that the insulation class of the motor, as defined in IEC34.1 and given in the table below:

Notes:

1. It is recommended that motor ratings for all smoke spill fans be limited by temperature rise for one class lower that the insulation class of the motor.

2. The mechanical integrity of smoke spill fan motors placed in the airstream or subject to thermal conduction effects in determined largely by the ability of the lubricated bearings, supporting the motor shaft, to function satisfactorily at elevated temperatures. This mechanical integrity is enhanced by selecting the appropriate class of fit, internal radial clearance and lubrication for the rated smoke spill operating time and temperature. As a guide, bearings used in smoke spill fans which are exposed to elevated temperatures should have a C3 radial clearance and the appropriate high temperature lubricant suitable for the time/temperature rating.

 

Alternative Insulation. As an alternative for motors with Class B or Class F insulation, the motor rated power output should be 15% above the absorbed power for an air density of 1.2kg/m3.

 

Time/Temperature Ratings

Test Time and Temperature According to Rating

Notes: Rating 3 & 4 are not called for in AS 1668. 1, but are included within this Standard to accommodate ratings which may be specified by overseas markets. The special ratings may include other ratings requested by the supplier. (Refer to table below)

 

Summary

In the past there has been some confusion about exactly what tests and test procedures should be conducted on motors and fans to ensure that they will meet the requirements of Smoke spill standards. When this new standard is adopted (probably in 1998) it will ensure uniformity and compliance with the requirements of the standard for all motors that have been tested to this standard.

 

Another area of concern is that although new motors and fans will pass the requirements of the standard there is some doubt that they would comply with the requirements after they have been operating for 5 years. It has been suggested in Australia that all smoke spill motors should be replaced with new motors after a period of time - maybe 5 or 10 years. The new draft standard tries to address this problem by keeping the temperature rise of the motor during normal operation well below the rating of the materials. The bearings and grease are still probably the weakest link and will probably fail first without good maintenance.

 

Western Electric Australia plan to set up a test rig as specified in the new draft standard for combined motor and fan testing in compliance with the proposed new standard, so that when the new standard is released we will be ready with a range of motors tested to the requirements and independently witnessed. We will also offer this test facility to the fan producers to test the compliance to their fans.

 

Western Electric have always tried to ensure that the motors we supply for smoke spill applications are of the highest quality and designed to give reliable performance over many years. Smoke spill motors need to be well made and reliable because people’s lives are at stake if these motors do not perform to Smoke Spill Standards when they are needed.