How do BE decide when to use frangible pins?

[Olliepop]

I was fence judging at Eland yesterday for the 100 and Novice and our fence was one which had a frangible pin device on it. It was an oxer made from telegraph poles which had frangible pins fitted to the front rail and the back rail.
Someone in the 100 gave it a hard enough clonk to displace the pin on the back rail.
I was just musing really as to what makes BE/ FEI decide when a frangible pin is needed/ no needed. Obviously some fences you can't do it due to them being a box type fence. Is anything with rails fitted with pins? Are other types? I think the upright Novice gate was also pinned yesterday.

 

[Birker2020]

I was fence judging at Eland yesterday for the 100 and Novice and our fence was one which had a frangible pin device on it. It was an oxer made from telegraph poles which had frangible pins fitted to the front rail and the back rail.
Someone in the 100 gave it a hard enough clonk to displace the pin on the back rail.
I was just musing really as to what makes BE/ FEI decide when a frangible pin is needed/ no needed. Obviously some fences you can't do it due to them being a box type fence. Is anything with rails fitted with pins? Are other types? I think the upright Novice gate was also pinned yesterday.

Not sure of the answer to this but many years ago we were at Badminton walking around the stands. OH is Head Groundsman at riding club and was looking at costs of pins, they were £500 per jump. Totally out of the question for most riding clubs, so I am not sure what guidelines BE/FEI use to determine the use of them. I thought they were mainly for use with the telegraph pole/trakenher type of fences.

They said at the time (going back many years now) that if a horse hits a fence above the knee it most usually will have a slow rotational fall but those that hit a solid fence below the knee tend to scrabble over. So I am wondering if it is the height of the fence that determines whether frangible pins are required also.

This from a website in 2002 : A frangible pin fence, at this point in development, is always a post and rail jump of some type--an oxer (two verticals jumped as one unit), a vertical, a triple bar, or even a corner. A steel sleeve is insert into the upright post. A special aluminum pin is inserted in the sleeve to support the top crosspole. The pin is designed with a narrow 20mm neck that shears under sufficient pressure. Each upright is built to allow the top pole to drop 40 cm, creating the required 20 cm in the center.

During the initial trial period in 2002, 29 fences were jumped by 2,344 horses in nine events of various levels and geographies in the UK. The pins broke once. Further testing was done at 12 events and complete load testing and monitoring at two events. To date the pins have broken four times.

The pins have been used twice in the United States, in the fall 2002 Fair Hill CCI three star and 2003 spring Rolex Kentucky CCI four star events. No pins were activated