Table 3.

Potential causes of failure and related countermeasures/safeguards

Issue	Technical details and safeguard	Comments
Failure of control and management system and/or electromechanical system	The process is coordinated by a programmable logic controller (PLC) using a digital computer for automation of electromechanical processes. In LAPS, sensors, pumps, valves, doors and conveyors are controlled in this way. PLCs are designed for multiple arrangements of digital and analogue inputs and outputs, extended temperature ranges, immunity to electrical noise, and resistance to vibration and impact. Programs to control the machine operation are stored in battery‐backed‐up or non‐volatile memory. A human–machine interface (HMI) is employed to allow interaction with people for the purpose of routine monitoring of pressure curves and bird behaviour. The HMI screen (built using LookoutDirect software) displays a graphical animation of process flow, event driven controls, and lights to give warnings. Real time changes are shown on the display screen thereby the status of safety features, position of transport modules on conveyors and in chamber, chamber door status and the pressure within of chamber, status of electromechanical devices, valves and pumps and hydraulic and air services chamber are all available	The HMI provides clear information of each process involved with handling and stunning the birds. The user manual provides information on interpretation and actions required in case of alerts. The user manual describes the maintenance procedures for all the equipment and also the calibration of the pressure gauge
Electrical failure	Many poultry processing plants are fitted with back‐up generators but in addition the LAPS system is fitted with its own battery back system, which ensures sufficient power for all systems needed to complete the LAPS cycle and move modules	The user manual required regular checks and tests of electrical back facilities
Failure of Chamber integrity and operation	Specialist certified manufactures to international standards for low‐pressure vacuum chambers construct the chamber walls and doors and portals using high‐quality steel. The machine withstand pressures greater than those incurred during LAPS. The metal parts of the chamber and doors and portals have a low risk of damage or wear during operation. The door seals are made of high quality rubber and over several months are liable to wear. To detect such wear, the operational procedures require a leak test of each chamber each day of operation. The LAPS system cannot be used if a leak test has not been made in the previous 24 h	High‐quality materials are used in construction and production techniques are used in manufacture that ensure high reliability in operation similar to those used for submarine construction. The door seals have potential for wear and their efficiency is checked daily and replaced when necessary. The user manual describes the maintenance procedures for all the equipment and also the calibration of the pressure gauge. To minimise risk of failure of monitoring equipment, the HMI has alarms to alert the operators of any equipment failure from movement of transport modules to door closure etc. Various pumps, valves, doors and conveyors use electrical motors or compressed air or hydraulic systems and these are monitored for operational state and effectiveness and maintained as described in the owner's manual