SJH Projects has an established and expanding range of its own blast protection products. Many of these developments are initiated by partners and customers highlighting issues they have come across.
The products are subject to constant improvement and updates. We can provide bespoke developments for both blast and ballistic protection and have undertaken many such projects which do not appear on this website for reasons of customer confidentiality.
The SJH Projects XPT explosion protection technology, cast material has found its way into customer systems, most notably for vehicle underside protection for both civil and military programmes.
Our blast containment products include our wide selling Mailsafes, our Detsafes for the transportation and storage of detonators, cladding for X-Ray screening equipment and specialist items for testing detonators and for isolating live detonators and other energetic items.
As well as assessing the vulnerability of buildings and facilities to blast, we can also provide materials and engineered solutions to deal with specific issues at critical points and the facility as a whole. This includes advice on glazing, testing and HVM.
Our XPT material is used in combination with ballistic materials to provide underside blast protection to both military and civilian vehicles. We can also advise on the wider issues of survivability technologies to withstand blast and fragmentation. Our Minesafe system has been successfully deployed on operations.
Our XPT (eXplosion Protection Technology) material is a proven blast mitigator that offers flexibility in application across a wide range of sectors. Its excellent energy absorption and thermal insulation are key to performance in a demanding environment.
SJH Projects Ltd has become the key distributor for the range of surrogate human parts produced by Adelaide Test & Evaluation Systems of Australia.
Protection from blast is not merely best practice, but a moral and ethical imperative. For public venues that come under the scope of Martyn’s Law, it will become a legal requirement. Employers, governments and security professionals have a responsibility to:
By understanding the science behind explosions and prioritizing protective measures, we can mitigate the devastating consequences of these events and fulfil our duty to safeguard lives and property.
To provide effective explosive blast protection, it helps to better understand the threat, how it is a combination of definable factors and how they can each be managed and defeated.
The key factors that make up an explosive threat are the shockwave, impulse, fragmentation and heat. For any given explosive event, the relative importance of these factors will alter and your protective system or products should reflect this. A detailed explanation on the anatomy of an explosive event can be found in our long form article Blast Mitigation in Public Spaces.
The explosive shockwave sits on the surface of the expanding sphere of air that is pushed outwards from the centre of the blast at up to 7000 metres per second. This very high pressure, short duration pulse has a cutting effect that can most often be seen on damage to equipment, or injuries that result from being close to the blast. The blast shockwave dissipates quickly with distance and so is not often the primary issue when the target is set further back – known as the stand-off distance.
To protect against the shockwave there are two main options:
The issue of the shockwave becomes exacerbated in a confined space or in a containment role. Like any wave, the blast shockwave can reflect and create localised wave reinforcements with much higher localised pressures. A material such as XPT captures the shockwave, greatly reducing the reflection effects. This makes it suitable for confined spaces such as vehicle wheel arches and an array of containment applications as seen in our Mailsafe and Detsafe blast protection systems.
Behind the invisible shockwave is the gaseous products that result from the chemical reaction of the explosion. This impulse does not have the same cutting effect as the shockwave, but is the mechanism that lifts a vehicle, knocks down a building or throws street furniture and other items away from the centre of the explosion.
If your target has survived the cutting effect of the shockwave (with or without the assistance of additional protective materials) it now has to withstand the bulldozer effect of the impulse. For a vehicle this might mean that the hull has not been breached but it could then be lifted and thrown, which is still very dangerous for the occupants. For glazing it requires the use of laminated glass or anti-shatter, anchored blast film to stay in place during the impulse phase and prevent broken glass being thrown into the building. Impulse and management of product gases is a particular issue in containment applications.
Weapons such as artillery rounds, mortars and grenades are engineered to create specific fragmentation. IEDs such those used in the London 7/7 bombers clad their devices with nails. This is known as primary fragmentation. Secondary fragmentation is that which is lifted and thrown by the outgoing blast pressure waves and can be just an injurious and should be treated in the same way. This ballistic protection layer should be capable of stopping the fragments and is usually also the layer that resists the blast impulse. High hardness steel is a longstanding method of ballistic protection, but for mobile applications for vehicles, and personal armour, there is an increasing use of lighter fibre reinforced composites such as Kevlar and Dyneema.
The captured fragments from a World War 2 Japanese model mortar round. Primary fragmentation designed for effect.
A common misconception, as a result of TV and Hollywood action films, is that explosions always come with a large and impressive fireball. This is not actually the case, and a high-speed camera is usually required to see any significant flame. Examination of the majority of post-blast scenes will show very little evidence of overt heat damage – the pulse tends to be of too short a duration to be an issue.
It can be seen that effective blast protection is a carefully engineered balance between the key elements of the threat and the practical limitation on choice for protection, posed by the target.
A discussion at the DSEI defence show in London posed the question on the possibility of adapting our Detsafe technology to safely contain an array
We have recently completed the design phase for a novel blast/pressure containment vessel. This will allow the customer to perform research and proofing of their
Steve Holland of SJH Projects participated in PASS 2025 ( The Personal Armour Systems Symposium) in Bruges in September. PASS is the premier technical event
