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Cable glands are an essential component of any electrical installation, and understanding the different types of thread used in cable glands is important. The three most common types of threads used in cable glands are NPT, Metric, and PG. Understanding the differences between these thread types will help you choose the right cable gland for your needs.
Considerations for Selecting the Right Thread Type
When selecting an&#;industrial cable gland thread type, several crucial considerations come into play. First, assess the cable type, diameter, and material properties. Next, consider the installation environment, including corrosion protection needs, enclosure materials, and ingress protection ratings. Ensure compatibility with accessories like locknuts and sealing washers. Lastly, choose a suitable cable gland type based on safety requirements and standards. Proper selection ensures reliable connections and compliance with regulations.
CABLE GLAND THREAD TYPES
1) NPT (National Pipe Thread)
Definition
:
NPT is a widely used thread standard in North America, commonly found in electrical and plumbing applications.
Thread Characteristics
:
Tapered Threads
: NPT threads have a&#;
1/16 taper
, meaning they gradually narrow towards the end. This taper allows the flanks of the threads to seal together effectively when torqued.
The Flank Angle is 60˚
Sealing Properties
: NPT threads create a reliable seal, making them suitable for applications where moisture or dust ingress must be minimized.
Example
: An NPT size might be labeled as &#;1/2&#; NPT,&#; indicating a half-inch diameter with tapered threads.
2) Metric Threads
Definition
:
Metric threads follow the ISO metric system and are prevalent in most IEC (International Electrotechnical Commission) countries.
Thread Characteristics
:
Straight Threads
: Unlike NPT, metric threads are straight without taper.
Designation Format
: Metric threads are denoted as &#;M&#; followed by the diameter in millimeters (e.g., M12) and the pitch (e.g., M12 x 1.5).
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The Flank Angle is 60˚
Pitch
: The pitch represents the distance between adjacent threads.
Example
: An M20 x 1.5 metric thread specifies a 20 mm diameter with a pitch of 1.5 mm.
3) PG (Panzer-Gewinde)
Definition
:
PG threads originate from Germany and are commonly used in European electrical installations.
Thread Characteristics
:
Unique Flank Angle
: PG threads have a smaller depth but a larger flank angle compared to NPT and metric threads. This results in a wider pitch along with a straight thread.
The Flank Angle is 80˚
Applications
: PG threads are ideal for cable glands in harsh environments, offering robust sealing capabilities.
Example: PG sizes include PG 9, PG 11, PG 13.5, PG 16, PG 21, PG 29, PG 36, and PG 42.
Remember, selecting the appropriate thread type ensures reliable cable management and protection. At Amphenol TPC Wire & Cable we offer cable glands with options for metric, PG, or NPT threads. Feel free to contact us for more information or to discuss your specific needs!&#;
Selecting the Correct Cable Gland & Accessories
When the cable is armored, check the following in addition:
The following steps, together with the information throughout our cable gland catalog, will ensure that the CMP Cable Gland selected will be fit for purpose and perform to relevant specifications.
For installations in explosive atmospheres, special considerations should be taken into account to ensure compliance with national or international standard codes of practice.
Accessory Selection
In addition to entry thread sealing washers, CMP also provides standard locknuts, grounding locknuts, earth tags, serrated washers and shrouds as required, which should be used as appropriate to the installation standard or equipment configuration.
These CMP accessories may be critical to the safety of the installation and overall performance, it is vital that the CMP accessories are correctly specified and installed. Accessories are not typically included with the cable glands as standard, unless a cable gland pack/kit is ordered.
In order to maintain product warranty it is vital that genuine CMP accessories are used for installation of CMP cable glands. Compatibility of material selection, short circuit rating (in the case of earth tags and grounding locknuts) and sealing performance (in the case of sealing washers) cannot be guaranteed if accessories from other sources are used.
*If the cable armor is of a non-standard material, e.g. Aluminium Wire Armor, it may be necessary to consider an alternative Cable Gland material, e.g. Aluminium.
**For certain medium voltage and high voltage cables, with higher fault rate levels, CIEL Cable Glands, which have been tested for higher SCC faults may be required.
See our accessories range here >
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