Probe for Impeller of Portable Appliances of UL 507 Figure 9.1

Portable fans and window fans
Other than as described in 9.2.2, a moving part that causes a risk of injury to persons shall be guarded or enclosed.

A moving part such as a rotating grille, rotating air deflector driven by an airstream, or an impeller is not required to be guarded when the moving part complies with all of the following applicable requirements:

a) When motor driven, the impeller:
1) Does not weigh more than45g (0.1 pound);
2) ls not more than 203.20 mm (8 inches) in diameter; and
3) Is not more than 3.2 mm (1/8 inch) thick and has no reinforcement beyond the nose cone.

b) When driven by an airstream, the moving part:
1) Does not weigh more than 454 g (1 pound);
2) Does not have a diameter that exceeds 508 mm (20 inches); and
3) Complies with Section70, Drop Test, without breakage of the blades.

c) The moving part:
1) Does not rotate faster than 2000 revolutions per minute; and
2)Complies with the requirements specified in Section 56, Unguarded Impeller Tests, Section 61, Impact Test on Guards, and Section 70, Drop Test, without breakage of the blades.

d) The output power of the motor driving the part is not more than 35 watts (0.047 horsepower).

e) The “K” factor of the moving part determined as specified in 9.2.5 is less than 732.

f) A blade:
1) Employs a rounded leading edge with a diameter of at least 3.2 mm (1/8 inch); and
2) Is composed of material having:
i) A tensile strength of at least 6.895 MPa (1000 psi), in accordance with ASTM D638; and
ii) Elongation of not more than 206.85 MPa (30,000 psi), in accordance with ASTM D790.

g) An air deflector driven by the airstream has no leading edge and all exposed surfaces are smooth and well rounded.

An unguarded impeller that complies with Exception No. 1 to 9.2.2 shall produce an impact force of 175 N(39.34 pounds) or less.
Factors to be considered when judging whether a moving part or a portion of a part is likely to cause a risk of injury to persons shall include, but are not limited to:
a) The portion of the blade being contacted – trailing edge, leading edge, or periphery;
b) The blade material and angle, and type and sharpness of exposed edge; and
c) The energy available.

Conventional designs of impellers meet the requirement of being guarded when:
a) The relationship between mass (W) in kg, radius (r) in mm, and speed (N) in revolutions per minute is such that K in the following equation is less than 29264: K = 6 x10′(wr’N)
b) The guarding is such that the probe illustrated in Figure 9.1cannot touch the leading edge of the blade and hub when inserted as described in 9.2.6. For a reversible fan, both edges of the blade are considered leading edges. When K is greater than 29264, the probe shall not touch any part of the impeller.

The portion of an impeller that entails a risk of injury to persons shall be guarded so that the probe illustraled in Figure 9.1 does not louch the part when inserled with a force of 4.45 N (1 pound) for a maximum of 5 seconds through any opening in the guard.

During an examination to determine whether an appliance complies with the requirements specified in 9.2.6, the guards and impellers of desk and stand fans are not to be removed before examination.

When a part used to comply with the requirement in 9.2.6 is made of a polymeric material, a sample is to be exposed for 7 hours to air at 70°C (158°F). While in the oven, the part is to be assembled to the fan and the fan is to be in its intended operating position. After the sample has cooled to room temperature, the probe illustrated in Figure 9.1 is to be inserted through each opening in the guard. The probe shall not be able to touch any portion of an impeller that can cause a risk of injury to persons.

A guard employed to comply with the requirement in 9.2.6 shall be attached to the fan in any of the following ways:
a) Permanently;
b) By means requiring the use of a tool or tools for removal; or
c) By means not requiring the use of a tool or tools for removal provided that the securing means remain attached to the front or rear guard; and
1) Two separate motions, for example push and turn, are required to disengage the
securing means; or
2)A force of 22.24 N (5 pounds) is required to disengage the securing means.

The removal force specified in 9.2.9(c)(2) is to be measured after conditioning the holding means by removing and replacing the guard ten times in the intended manner.

An enclosure, a frame, a guard, a handle, or other part of the fan that is exposed to contact during intended operation shall not be sufficiently sharp to constitute a risk of injury to persons.

Non-metallic impellers on portable fans and window fans shall comply with Section63, Impeller Test for Portable Fans.