Sunday, July 12, 2009

Safety Policy

Workshop Safety Policy

Objective: To develop and maintain safe working conditions in all workshops where electric, pneumatic or hydraulic type of machinery are operated.

Field of application: All workshops located on McGill University owned or leased property, including carpentry, welding, plumbing, or any other type of shops where professional technicians, professors or students use machinery in their daily tasks or in their learning process.

Personnel concerned: All McGill University staff, professors and students who use machinery in any of the Workshops.

Roles and responsibilities:

  • Workshop supervisor: Each workshop supervisor is responsible to maintain their machinery in good working condition and must ensure that each machine is equipped with all required safety devices, including guards and emergency stop. The supervisor will make sure that each machine is inspected at least once per month and that any deficiency in terms of working condition and / or missing or damaged safety devices is corrected promptly and that the machine is locked out until necessary repairs are completed. The supervisor will ensure that each machine user is properly trained before permitting use of a machine and that the user wears the appropriate personnel protective equipment (PPE) when operating the machine.
  • Machine user: Each machine user, including workshop supervisors, professors and students, is responsible to acquire the knowledge on how to operate a machine before operating it, and to apply best operating practices including McGill University’s “10 Basic Safety Rules for Machine Guarding”. Each user is responsible to report any defect on a machine, and to clean the work station and the machine after completing the work. All users shall comply with the following “General Safety Rules”.


  • Training: The content of training for each specific type of machinery must be available in writing and / or in electronic version. Personnel training records in each Department must be available, up to date and accessible to workshop supervisors.
  • Reports: Machine Inspection reports and Machine Repair reports must be documented and kept on file for a minimum period of two years.

General Safety Rules:

  1. Each machine has its own characteristics and presents specific hazards that you must know before you can operate it. Therefore make sure you have received proper training on how to safely operate the machine prior to using it.
  2. When you use a machine for the first time, you must be accompanied by a experienced technician who will assist you and make sure that you know and apply the appropriate safety rules.
  3. Before the equipment is started, inspect the condition of the machine and proper setting of the guards, locate the emergency stop button, check the state of the electrical cord, make sure the danger zone is not accessible, verify that the machine is stable and it will not move or tilt over when in operation.
  4. Make sure the work station is clean and that the working environment will remain safe and free of dust or other emission after the machine is in operation.
  5. Put on the appropriate personnel protective equipment (PPE) before the equipment is started.
  6. Advise the workshop supervisor before starting the work if you are to use a machine in a work room where you are alone.
  7. Advise the workshop supervisor immediately if a machine is defective or if a safety device is missing or damaged; DO NOT operate the machine.
  8. Use the appropriate machine for the work to be done.
  9. Verify that adjustable guards are attached and positioned properly before starting the machine.
  10. Clean up the work station and the machine after the work is completed. When a machine or work station is to be cleaned with compressed air, the compressed air pressure must be set at a pressure that is lower than 200 kPa (29 psi).
  11. Locate the nearest first aid kit, eye wash station, safety shower, emergency exit route and be aware of the emergency phone number.

Saturday, July 11, 2009

Multi plane balancing

Multi plane balancing

Multi plane balancing also referred to as Dynamic balancing method this occur when there is no resulting turning moment along the axis.

This type of unbalance can only be measured on a rotating balancer since it includes couple unbalance. Since dynamic unbalance is a combination of static and couple unbalance and since static and couple unbalance have different units, there are no unique units for dynamic unbalance. It can be expressed as static and couple or in terms of the balance corrections required.

Two-plane balancing is an operation where balance corrections are made at two locations or planes on the coupling axis. These locations must be well separated to effectively produce a two-plane balance. This separation makes part length a prime factor in determining whether single-plane or two-plane balancing is required. Generally, the longer a coupling or component is relative to its diameter, the greater the possible need for two-plane balancing. In two-plane balancing, the unbalanced particles or masses do not lie within a narrow plane; instead they are spread along the length of the coupling. For example, a coupling consisting of two elements and a floating shaft could be represented as two disks spaced on a shaft with each disk rotating. If both disks are perfectly uniform, then each of their centers of gravity would be located on the center of rotation. They will therefore spin with no vibration and will be in balance.

Plane Dynamic balancers are not as common as single plane static machines due to the nature of vertical balancing, but if the application suits 2 plane dynamic balancing on a vertical balancer then the advantages can be made over horizontal dynamic balancing such as rapid component loading / unloading and correction can be easier actually on the machine when a drill, mill or weld head is integrated.

Single plane balancing

Single plane balancing

Single plane balancing also called Static balancing method. This occurs when there is no resulting centrifugal force and the center of gravity is on the axis of rotation. A condition of static unbalance exists when the mass center does not lie on the axis of rotation. Static unbalance is also known as Force Unbalance. As defined, static unbalance is an ideal condition, it has the additional condition that the axis of rotation be parallel to the central principal axis. Static unbalance can be corrected with a single weight. Ideally the correction is made in the plane of the mass center and is sufficient to shift the mass center onto the axis of rotation. It is important to align the correction with the initial unbalance to move the mass center directly towards the axis of rotation. Static unbalance can be detected on rotating or non-rotating balancers.

Single-Plane Balancing is best represented by thinking of a disk which is placed on a machine and rotated to a specific speed. If the disk were to have a hole located off the geometric center, it would be out of balance because the hole would shift the center of gravity off the center of rotation. This unbalance can be thought of as a weightless rod connected at one end to a shaft and having a large iron ball equal in weight to the amount of unbalance, at the other end. The unbalanced weight (mass) rotates in a single plane of rotation.

Single plane machines are ideal choice for balancing components with large diameters to thickness ratios i.e. disc type components, such as flywheels, clutch parts, brake discs, pulleys, fans or gears.



There are more than one hundred years of history of balancing machine development. Germany’s Siemens invented motor in 1866. Four years later, Canadian Henry Martinson applied balance technology patent begins balancing adjustment industry. Dr. Franz Lawaczek brought modified balancing technology in Germany in 1907. All balancing procedures are conducted in pure mechanical balancing equipment. Adopt resonance speed of vibration system in rotor’s balancing rotate speed usually to reach the maximum amplitude. It’s insecure and has large measuring error in such method for measuring rotor balance.

Accompany with the popularity of electronic technology development and rigidity rotor balancing theory, we adopt electronic measuring technology in most balancing equipments after 1950s. Balancing machine with plane separation circuit technology effectively eliminates interactive infection between left and right sides of balancing work piece. The appearance of hard bearing balancing machine can be recognized as a leap in balancing machine development history until 1970s. It eliminates inconvenience for the frequent dynamic adjustments of traditional soft bearing balancing machine, forms permanent bench mark balancing machine by adopting enactment of balancing dimension in static. In 1980s, piezoelectricity transducer brought another revolution to balancing machine. Balancing machine adopted such technology basically replaces soft bearing balancing machine in balancing field which is unnecessary to work in high speed. After 1990s, soft bearing balancing machine widely applied in some special fields accompany with rapid advancement of integrated circuit and computer technology.

One common definition of balancing is when the mass centerline and the rotational centerline of a rotating part are equal. Another definition is when zero vibratory force or motion is imparted from the rotating part to the bearing .

Balancing is the process of attempting to improve the mass distribution of a rotor, so that it rotates in its bearings without uncompensated centrifugal force. This usually done by adding compensating masses to the rotor at prescribe locations. It can also be done by removing fixed quantities of material, for example by drilling .

The balancing of rotating bodies is importance to avoid vibrations. In heavy industrial machine such as steam turbines and electric generators, vibration could cause catastrophic failure. Vibrations are noisy and uncomfortable and when a car wheel is out of balance, the ride is quite unpleasant. In this case of a simple wheel, balancing simply involves moving the centre of gravity to the center of rotation but as we shall see, for longer and more complex bodies, there is more to it.

A balancing machine is a measuring tool used for balancing rotating machine parts such as rotors for electric motors, fans, turbines, propellers and pumps. The machine usually consists of two rigid pedestals, with suspension and bearings on top. The unit under test is placed on the bearings and is rotated either with a belt or end-drive. As the part is rotated, the vibration in the suspension is detected with sensors and that information is used to determine the amount of unbalance in the part. Along with phase information, the machine can determine how much and where to add weights to balance the part.