Often during installation work with conductive power and power cables, it becomes necessary to use a special device when entering them into distribution cabinets and when using junction boxes with switching rails. The issue of using cable protection devices from breaking insulation of creases and bends is especially acute.
Stuffing box
At the entrance of small power supply cables to the distribution panels, as well as the duct, damage to the insulation or cable breaks is possible with the subsequent breakdown of one of the phases. In such cases, a special protective device is used - the stuffing box input. These are special elements necessary for connecting cable products to any type of electrical equipment. Thus, the cable can be easily inserted into any type of housing.
Kinds
The stuffing box input is primarily divided into two types - with and without a clamping mechanism.
In addition, they are divided by type of material from which they are made:
- Plastic inlets, namely polyamide, are the most common because of their low cost and increased tightness properties. However, one should not forget about some of the disadvantages, the most significant of which is the possible breakdown of the thread when tightening the lock and clamping nuts, as well as the occurrence of microcracks during operation in hazardous areas where an explosion is possible.
- Metal stuffing box inputs are not structurally different from plastic ones. But at the same time they are more reliable and resistant even when working in explosive rooms. They are made of nickel-plated brass, as well as stainless steel.
Design Features
Stuffing box is a construction of several elements, each of which carries a specific function. It has a clamping and locking nut, necessary for reliable fixation of both the cable itself and at the junction with the case of the electrical cabinet. There are also special seals necessary to protect against moisture and dust according to the requirements of safe operation of the equipment.
And one of the main elements is a gear coupling, which gives the connection additional strength during the installation and operation of electrical equipment.
Application
Cable glands are used not only to protect the cable from direct damage, but also to protect the electrical cabinet itself of any type of equipment from direct dust and moisture. This can protect the installation from short circuiting due to breakdown between the discharge contacts through dust or moisture.
Another important positive feature is the possibility of rigidly securing the supply cables at the cable entry points into the electrical cabinets using the cable gland. During operation, even a well-fixed cable can be damaged. This can be done both by staff and those working on this equipment. In this case, the contact at the junction of the supply wires of the cable may be damaged, as well as a short circuit due to the contact of dangling wires to adjacent contacts. In some cases, there is a short circuit to the housing, and even a grounded installation can be dangerous if it is touched. These and other types of unpleasant breaks and short circuits incapacitate a working installation, lead to disruption of the technological process and expose working personnel to the risk of electric shock.
Do not forget that even the use of a gland entry does not exempt from the mandatory use of grounding in electrical installations. This is strictly regulated in the rules for installation and operation of power supply cables.