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Espresso Machine Explosion
Why an espresso machine might explode and what you can do to prevent it.
Published December 20, 2021
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Erik Hedlund
Coffee experts@The Coffee Lab
In a world where we rely on technology for so much, machines are often our best friends and we need them to get a lot of different things done, including making our favorite cup of coffee in the morning. However, machines, including espresso machines, can be dangerous and even life-threatening if they are not functioning the way that they are meant to. In terms of espresso machines, there have been explosions of these machines that have led to injury. Maybe your espresso machine has exploded, and you want to find out more about what caused it, or perhaps you have just purchased a new espresso machine and want to make sure that you prevent this potentially dangerous problem from happening in the future. Read on to find out more about why espresso machines can be at risk of explosion, how to prevent it, and how espresso machines use pressure to make your coffee.
Why Do Espresso Machines Sometimes Explode?
Espresso machines are becoming a more and more popular appliance for the kitchen, but with horrific incidents in the past of these machines exploding and causing injury, it is important to be aware of the reasons behind why this happens so that you can prevent it happening to yours. An espresso machine is basically a pressure system. When this pressure system or any of the other individual parts fail, this can lead to the stored energy in the boiler of the machine being let out, which has the potential to cause a dangerous explosion. Some common things that could go wrong with your espresso machine and lead to an explosion include:
The Steam Boiler
Most espresso machines will be installed with a stainless-steel or copper steam boiler. This works by heating up the water to between 110-125 degrees to produce the necessary steam for making coffee. This steam is then held in the boiler under a high amount of pressure and is only released when you either open the tap on the machine to force the water through the coffee grounds to make espresso or use the steam wand for steaming milk.
The Pressure Relief Valve
An overpressure valve on espresso machines is another significant component of the machine. If the espresso machine overpressure valve is faulty, this can put the machine at a higher risk of exploding as it can lead to over-pressurization in the machine, with the heat continuously supplied to it. If the valve is not working correctly, it can cause serious malfunctions in the machine and eventually lead to an explosion if not fixed.
How to Prevent Espresso Machine Explosions
Since the espresso machine works as a pressure system, there are legal requirements in most countries to ensure that the machine is working correctly, particularly in commercial settings, where business owners are legally required to have the machine serviced on a regular basis and have the boiler evaluated for safety. It should be checked before the first use and then annually.
While it can be a scary thought to consider that an espresso machine might explode at any time, being well-informed about anything that could go wrong and how to respond to any issues will make it easier for you to prevent any dangerous incidents like this.
How Does the Pressure System Work?
An espresso machine is a pressure system because this is an important component in making your coffee. While you can get the perfect coffee beans, water temperature, and brewing time, the amount of pressure used to force the water through the coffee grounds and extract all the goodness from them will have a major impact on how your coffee ultimately tastes.
Atmospheric or barometric pressure is a measure of the pressure or force that is exerted by the atmosphere. When making espresso, nine bars of pressure is the typically amount to go for, which is roughly around nine times of the weight of the pressure of the air at sea level. To put this into perspective, consider when you are pumping up your car tires with air. Most tires function at 32PSI or pounds per square inch of air. In contrast, the nine bars of pressure used by an espresso machine is the equivalent of 130PSI, which is far more than you would put in your tires.
The Basics
Understanding the pressure in an espresso machine can be fairly straightforward. Pressure requires two things to exist; something that generates the movement of water and something that will try to stop it. In the case of an espresso machine, the pump generates the water movement, and the coffee puck offers the resistance. If there is no restriction and the water does not encounter any resistance, then there will be no pressure.
Espresso machines use a few different ways to manipulate pressure. In most cases, the pump will regulate the water pressure to a fixed value, usually nine bars of pressure. The pressure regulation from the pump uses a spring that is constantly under tension and adjusts to ensure that the pressure is maintained in a stable way no matter the flow. The group jet is another device that is required to control pressure in an espresso machine. This provides enough resistance for the pump to be able to easily maintain nine bars of pressure through the system on machines that have multiple groups.
How Pressure is Controlled in Espresso Machines
If you took a high-pressure hose and put nine bars of pressure through your coffee grounds, it would make a huge mess. This is why it’s important to consider the way that those nine bars of pressure are applied to the coffee when using an espresso machine. Forming a coffee puck and controlling the time that the coffee is extracted for are important parts of making espresso since they are in place to manage this pressure. Creating a puck helps to avoid a huge mess when the water is blasted through the coffee grounds at a high amount of pressure since it offers more resistance to the water being pushed through. This is why it is so important to make sure that the coffee is ground very finely, and then made into a puck by tamping it into a portafilter. Once this is done correctly, it should create a uniform, dense surface area that offers just enough resistance to the water.
Why is the Correct Pressure Important for Making Espresso?
The correct pressure is necessary for brewing espresso since it will guarantee quality and consistency each time you pull a shot. In general, eight or nine bars of pressure tends to be the minimum requirement when it comes to espresso machine pressure. If there is not enough pressure, the coffee will be under-concentrated and weak, while on the other hand, if the pressure is too high, the espresso will be bitter and over-extracted.
If you are considering buying an espresso machine for your home or business, you may notice that the bar pressure rating is one of the main features that is advertised. The number of bars indicates how much pressure will be used by the machine to push the water through the ground coffee in the portafilter. Nine bars is the industry recommended standard for brewing espresso. In general, with a pump-driven machine, seven to nine bars will be sufficient. While there’s a popular idea that bigger is better when it comes to how much pressure you use to brew coffee, it’s worth bearing in mind that anything over ten bars of pressure is unlikely to have much of an impact on the quality of the espresso and might not always be worth paying more for. While some machines with higher pressure levels might be able to help you brew a better espresso compared to a machine with nine bars, be aware that much of this will depend on other factors including the size of the portafilter, how finely the coffee is ground and the age and condition of the machine.
It is also worth considering that many machines that claim to have a higher bar pressure will actually produce a lower bar when the machine is in use. Along with this, it’s always better to go for a higher quality machine that uses the standard nine bars of pressure rather than a substandard machine with a higher-pressure bar since substandard machines will deteriorate more quickly and the bar pressure will decrease over time.
Along with this, the more pressure the espresso machine creates, the larger the risk of explosion will be if something were to go wrong with the machine. Because of this, it is always wiser and safer to own a nine-bar espresso machine that you know what you are doing with, rather than owning a high-pressure machine that you could be putting yourself in danger with by not using it correctly.
Since espresso machines are pressure systems that use high amounts of pressure to push the water through the coffee, it’s important to understand how this works and the risks of explosion involved to keep yourself safe.
About the author
Erik Hedlund
With Era of We and The Coffee Lab, I hope to share knowledge, increase the value of coffee – and secure the future of coffee.
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