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Investigations of the effectiveness of powder-actuated captive-bolt pistols under the aspects of animal welfare and safety at work


In Germany, the Physikalisch-Technische Bundesanstalt (PTB), as a Notified Body, is in charge of the serial testing of powder-actuated captive-bolt pistols in accordance with Machinery Directive 2006/42/EC exclusively under the aspect of safety at work. Each year, initial or repeated testing is carried out for up to ten designs for the European market alone. Due to the high failure rates of such captive-bolt pistols (between 4 % and 9 %, according to literature) which have been picked up by the media, the Federal Centre for Meat Research (Max-Rubner-Institut, MRI) in Kulmbach and the manufacturer Schermer in Ettlingen considered it necessary to also investigate the effectiveness of different types of devices under the aspect of animal welfare. Since 1 January 2013, with the new ordinance 1099/2009, attempts have been made to improve animal protection at the time of slaughtering. PTB supports these efforts within the scope of a scientific research project.

Hereby, PTB undertook the task of determining the kinetic impact energy of the bolt (Fig. 1) of certain captive-bolt pistols by Schermer, in combination with three different cartridge charges, whereas the physically (and animal-welfare-) relevant effectiveness was checked by MRI. The kinetic energy dissipation of the tested captive-bolt pistols of the types KR, KL and KS is generally influenced by the length and the weight of the bolt as well as by the propelling charge used. The results show that in the case of theKS captive-bolt pistol, the existing bolt retrieval system, which is supposed to facilitate the operator's work when retrieving the bolt from the animal's skull, may reduce the impact energy, as opposed to the unbuffered models. Bolt retrieval systems not only help retrieve the devices, but also damp the kinetic energy of the backstroke of the devices after triggering in order to minimize potential long-term injuries of the operator.

Figure 1: Test set-up for the captive-bolt pistol with prepared bolt head for the acquisition of the impact velocity using an IR light barrier.

This buffering serves safety at work for the slaughterers and makes sense in this context; however, they contribute to cattle being insufficiently stunned (failure rate: approx. 6 %). The results were collected at two different slaughterhouses by MRI within the scope of the project; they were obtained by observing the stunning effectiveness of these devices on bulls, cows and heifers.The project has clearly shown how important it is to determine the required key parameters with great accuracy (contact point, impact direction and velocity, exit length and diameter of the bolt depending on the type and size of animal observed) for stunning by means of captive-bolt pistols with regard to both animal welfare and safety at work.

Figure 2: Impact energy of the KS stunner compared to the KR and the KL.

By measuring the impact energy of the captive bolt at the contact point, its energy dissipation to the animal's skull was deducted, since its mass was known. Figure 2 shows the differences in the effectiveness as a function of the stunner and the cartridge charge used. The KS stunner releases, at highest charge, a maximum of 360 joules. The KL device has, at maximum charge, a maximum energy dissipation of more than 380 joules. This may be the best energy dissipation value, the variability range at medium cartridge charge is, however, high in comparison. The effectiveness and the efficiency of the devices as well as of the cartridges have to be investigated in more depth.

Pursuant to the new ordinance VO (EC) No. 1099/2009 (which has been in force since 1 January 2013) for the protection of animals at the time of killing, the manufacturers of these devices are, according to Article 8, required to indicate for each type of animal the exact minimum impact energy as a function of the cartridge charge used.

The conclusion of these investigations is that it is a tightrope walk to comply simultaneously with the requirements of safety at work for personnel and with animal welfare requirements and that this can only be achieved if the minimum impact energies are perfectly defined as a function of all relevant influence parameters, especially also depending on the type of animal, and are complied with in daily practice. The above-mentioned new ordinance is, thus, a step in the right direction at any rate.




Holger Schönekeß, Dept. 1.3, WG 1.33, e-mail: Opens window for sending emailholger.schoenekess(at)ptb.de