In the Fire Service, the knowledge of how to tie and use knots is essential. While there are many knots available, the following knots described in this section should be adequate to meet the needs of Seattle fire fighters in most situations.
Keep in mind that it is more important to be able to tie these standard knots automatically, while under the stress of an emergency, than to know a greater number of knots and yet have failed to acquire skill in their use. The ropes used on operation companies range in size from 1/4″ woven cotton tie ropes to 1/2″ Kern mantle nylon life safety rescue ropes. They can vary in length from just a few feet to 300 foot lengths. Ropes and knots are used daily in securing equipment, fire suppression, rescue work, and emergency medical applications. Whether working with rope or knots in an emergency or training, SAFETY should be on the mind of all involved.
The Seattle Fire Department separates the use of ropes into two categories:
- Life Safety.
A utility rope is a rope that is used for any function other than that of life safety. Tie ropes, practice ropes, RIG ropes, roof ropes and other ropes that are marked as such all fall under the umbrella of utility rope.
Life Safety rope is defined as any rope used to support the weight of members or other persons during rescue, fire fighting, other emergency operations, or during training evolutions. Operations companies use 2″ static kern mantle life safety rope for all operations level rescues. In addition, some accessory cord such as 8mm guide sling for the Load Releasing Hitch and prussic loops are used in life safety applications.
Common Breaking Strengths of Rescue Rope:
8mm – 3, 100 lbf (Accessory Cord)
1/2″ – 9, 000 lbf
A point to remember is that the words “static” and “dynamic” are misleading. Static means non-moving. There is no such thing as a statie rope system, for example, even steel is ME Considered to be static. Low- stretch and high-stretch more accurately describe and identify real world conditions.
Low Stretch (Static):
Operations life safety ropes have a relatively low stretch ratio, (usually between 10 and 20 percent till failure) due to a non-spiral constructed core bundle. Two to five percent elongation will occur with a working toad (200 Ibs.). Low stretch ropes are called “static”.
High Stretch (Dynamic):
High stretch or “dynamic” ropes shave relatively high stretch ratio, (usually between 20 and 50 percent till failure) due to a spiral constructed core bundle. Operations utility ropes are “dynamic” high stretch.
- Avoid walking or standing on the rope.
- Do not drag the rope. Added abrasion leads to less sheath life.
- Do not leave a rope under tension for any extended period of time unless necessary.
- Remove all knots as soon as possible.
- If rope cleaning is needed, clean by rinsing with clean fresh water, Rope safety.
- Dry wet rope (hang dry) before bagging.
- Exposure to the sun’s ultraviolet radiation will damage the rope, keep exposure to a minimum.
- Nylon moving across nylon can melt through the stationary piece.
- Be careful when running nylon over nylon, for example moving rope over stationary webbing
- Be sure to pad sharp edges Avoid adding twists and kinks when bagging/coiling the ropes
TYPES OF ROPE
1/2″ (Low-Stretch) Static Kern mantle Rescue Rope.
All operations ladder companies carry 3 bags of life safety ropes. These ropes may vary in color as well as length. Typically, most ladder companies will carry (1) 150′ and (2) 300′ life safety ropes. This is a life safety rescue rope that is rated at 9000 lbs. breaking strength, in slow pull tests. A rescue load is considered to be 600 lbs. In order to meet NFPA certifications, the rope has a 15: 1 safety factor (600 lbs. x 15 = 9, 000 lbs.)
One of the primary uses for 8mm Accessory Cord is the prusik loop and the 25-30 foot guide-sling. The guides ling is used primarily for tying a load releasing hitch, however, the guide sling can also be used for any accessory rigging need (anchors, fall restraints, etc. ).
System Prussic Loops –
The short prussic loop is 57″ and the long prussic loop is 71 They are tied (created) with a double overhand bend and are tightened down using a compound 9: 1 pulley system until 2 inches of tail remains protruding from the bend. The strength of 8mm material is (3630 lbf) according to the manufacturer.
Any rope that is not classified as “life safety” ropes will fall under the category of “utility” Utility ropes shave multiple us such hoisting equipment, stabilizing vehicles, medical calls, salvage, etc. They are usually made of Manila, nylon or other synthetic materials.
To achieve a functional breaking strength, the ropes or other material is placed in the position of function and slow pulled to failure. A rope can stand more force in a shock load situation than in a slow pull test. The reason, according tone theory, is low pull testing lows fibers to change alignment and move in relation to each other. In testing that involves shock loading, the shock occurs in less than. 5 seconds and the fibers do not have time to realign.
Dynamic energy may be explained as the energy generated by movement (for example, a falling object). If a rope was attached to this falling object and used to arrest its fall, then the energy of the object would be transferred to the ropes. In effect, this transference would be dynamic tensioning of the rope.
Residual strength is the remaining strength in a rope that has been used for a period of time. As a rope is used; high load forces, abrasion and other factors combine to reduce the strength of the ropes. Factors that affect the residual strength are: arresting falls, corrosive chemicals, sunlight, abrasion, etc.
Resistance to Cutting (Life Safety):
Demonstrations have shown modern rescue ropes are capable of sustaining considerable damage, without failure. One experiment showed a 13mm low-stretch ropes sawed 88% through, was able to statically hold a 600 lb. rescue load. This was repeated over a 90 degree edge and the same 12% remaining material was able to hold the same 600 lb. rescue load without failure. Failure did not occur until the utility knife was used to saw through the balance of the material. But still, care should be taken to protect ropes from sharp objects.