PERJES ELECTROMAGNETIC LOCKS FOR SAFETY VA RANGE

COMPLEMENTARY MEMO TO THE CATALOG

Because the electromagnetic principle is simple, because thirty years of experience with major manufacturers such as OTIS, KONE and SCHINDLER are a guarantee of reliability, you have opted for the VA range security lock from PERJES.

This memo is an accompanying guide in the choice and the implementation. It is also intended to help you to optimize installation and maintenance times and costs, for optimum safety and longevity of your installation.

WHY IMPLEMENT VA SAFETY ELECTROMAGNETIC LOCKS?

The mission of the VA safety electromagnetic locks is mainly to secure lifting installations. However, they can be used in various other applications. Their function is nevertheless always the same: to support a load in order to block it.

There are two ways to take advantage of their benefits:

- installation as a laying stop: in this case, the load will rest on the lock(s) at each cycle. The equipment is thus safe and in a controlled position;

- installation as an anti-drift cleat: in this case, the load is in normal situation never supported by the lock(s). However, the security locks prevent the equipment from drifting in the event of a mechanical failure.

The installation of VA electromagnetic security locks may be mandatory, as on some hydraulic machines according to the EN 81-20 standard, or strongly recommended due to the additional safety they provide.

VA ELECTROMAGNETIC SECURITY LOCKS: WHICH IS THE BEST CHOICE?

Five categories of VA electromagnetic locks for safety are presented in the PERJES catalog: VA1, VA3, VA6, VA12 and VA20. They respectively offer shear holding forces of 2 T, 3 T, 6 T, 12 T and 20 T. Concretely, this means that the VA lock will be able to support a load of respectively 2 T to 20 T in static on its bolt.

However, applications are rarely static. They are most often mobile. In addition, they are not always compatible with a homogeneous distribution of weights. The contact area between the bolt and the receiving part is also generally not equal to the entire available area of the bolt. Or, they sometimes require to integrate the reality of materials’ work and life over years.

These variables must be taken into consideration. In this regard, a safety factor must be applied between the maximum weight of the equipment and the selected lock(s). Whether it is 2, 3, 4, ..., a reasonable but sure value of this coefficient will be determined by the principal according to the characteristics of his installation. As the case may be, a damping facility may be proposed in addition.

Several options are mentioned respectively for each VA security lock in the PERJES catalog. For some of them, the principal will often decide on his own whether they make sense in his case. For some other options, a consultation with the PERJES team is recommended. For example, in the case of a high number of cycles, reinforced contacts may be recommended. Also, if the environment is subject to particular constraints (humidity, temperature, dust, etc.), this is to be noted so that the appropriate options be considered.

RECOMMENDATIONS FOR INSTALLATION AND MAINTENANCE

PERJES VA electromagnetic locks for safety are simple facilities regarding their implementation. However, paying attention to a few rules during installation and maintenance allows their optimal functioning and longevity.

Pay attention to lubrification: never add oil. The VA electromagnetic locks for safety do not require greasing or lubricating their parts. Rather, the translation of the bolt must be done dry and adding lubricant is harmful.

Pay attention to voltage: the voltage, from 12 to 220 V (or more), direct or alternating, is your choice.

When energized, the expected voltage value must be effective at the lock’s terminals. If, for example, you are using a long cable, a voltage drop is to be expected. It should be anticipated upstream.

When power is off, the voltage must be really zero and not residual. A residual voltage could hinder the return to the rest position of the bolt.

Pay attention to tightening: when installing on your chassis, the tightening of the fixing screws of your VA security lock(s) must be appropriate, neither too light of course, nor however excessive. It wouldn't help. It is even inadvisable. The optimal tightening has been evaluated by the PERJES team in consultation with our historical customers to 5 daN.

Pay attention to contacts: direct metal-to-metal contact of cleat and abutment should be avoided, especially when there is no damping system. This is why we recommend, when VA safety locks are used as laying cleats, to match the abutment on which the bolt rests with a composite or rubber coating, of a high shore.

Pay attention to constraints: VA electromagnetic locks for safety offer significant shear holding forces (see above). However, their purpose is not to counter a radial force. Friction during the exit and entry of the bolt should therefore be avoided.