how to replace safety valve in pressure cooker quotation

Pressure cookers are not an innovative cooking technology, but seemingly slightly forgotten. They are known for a long time, even before ceramic hobs, modern ovens, bakeries and various facilitating small appliances that save a lot of manual work. The fact is, however, that their application is back - regardless of whether old antiques will be removed or a new purchase will be made.

The new kitchen stoves are almost identical in appearance to those of the past. The difference is that nowadays, fear of exploitation is eliminated little by little, because there is enough information available for proper operating instructions, possible malfunctions, implementation of advanced safety mechanisms and more. Experts recommend a new investment for a new type of dimension in cooking.

The sealis one of the most wear-resistant elements, so the problem arising from it must also be noted. It may simply be contaminated by frequent cooking, food spraying and more. Clean it after removing the cover, then reposition it as directed in the manual

Closing mechanism - this is about the auto-lock function. For those models that do not have one, the problem may be with the locking mechanism or incorrect locking. This results in the inability to reach the correct pressure

Valve - The pressure valve may not be correctly installed. This is a common cause of under-pressure. Remember to clean the pan frequently, especially the valve. For this purpose, there is a certain technique that must be followed

Old Seals and Valve - Depreciation is a normal process that requires replacement. For these and other silicone and rubber components, it is recommended to replace it at about 18 months

Thick liquids and other thickeners - delicious dishes become cooked in a pressure cooker - fast and easy, but some products impede the process of reaching the required pressure. These are thick liquids and flour, which usually plays the role of thickener. It is recommended that they be eliminated or added thereafter

Handle - Used frequently and can loosen over time. May be the cause of shortage of high pressure. Check the goodness of the handle before setting the pan to cook your meal

Liquids - they are allowed, but must be maintained within certain limits. Otherwise, it will take a long time to reach the required pressure. Follow the instructions for the maximum that can be set so you have no problems

Food - The maximum capacity according to different recipes must be respected here. Usually, food is placed in the space, and for others up to half. Consider the instructions carefully to allow the permitted amount of ingredients, spices and liquids

Frozen foods - Cooking frozen foods in a pan is allowed, but the process is prolonged. In them, the pressure builds up more slowly. Keep in mind that any frozen food extends its preparation by about 30 minutes

Valve Problems - The valve is a basic element that serves to maintain the desired pressure. It must be properly secured and replaced for at least a year and a half, as wear may be a major problem in this regard.

Depreciated seals- Worn pot seals need to be replaced again as they wear out over time. The cookware may also contain other rubber or silicone parts that may need more frequent replacement

Outside temperature - this problem is actually related to improper operation - the heat can be very reduced. Look for the manual of your pot model to find out the right time for this action

Food that is cooked - If you put flour or some thick liquid in the pressure cooker, it can cause food to be thrown out. The spraying process occurs when the pressure is released

An excessive amount of food has been placed - the limit principle applies here. Each vessel has a maximum capacity that should not be exceeded. In this case, the problem will be in the form of spraying food out. It is usually recommended that зна an empty saucepan, except for fruits, cereals, legumes and some other

The valve is not well adjusted - steam is released through the valve, and it may not be properly adjusted. This is normal at first, but keep in mind that at this point you need to adjust yourself to eliminate excessive steam

The pan is too hot - the heat used must be adapted to the cooker. You may find it harder at first, but you will get used to it later. This may be a clear indication of the subsequent evaporation of steam, so take care of less pressure to reduce heat

Food is not prepared properlyThis is a common occurrence for anyone who starts using the appliance. Do not try the pressure cooker for the first time when you have guests. Foods that are slightly raw or overcooked may be due to an incorrect recipe or to:

Heat during pressure cooking - do not leave heat to a maximum so as not to remove dried, boiled or charcoal food. Adjust the heat level according to the needs of the different foods

Pressure cooking is the process of cooking food under high pressure steam and water or a water-based cooking liquid, in a sealed vessel known as a pressure cooker. High pressure limits boiling, and creates higher cooking temperatures which cook food far more quickly.

The pressure cooker was invented in the seventeenth century by the physicist Denis Papin, and works by expelling air from the vessel, and trapping steam produced from the boiling liquid. This is used to raise the internal pressure up to one atmosphere above ambient and gives higher cooking temperatures between 100–121 °C (212–250 °F). Together with high thermal heat transfer from steam it permits cooking in between a half and a quarter the time of conventional boiling.

According to New York Times Magazine, 37% of U.S. households owned at least one pressure cooker in 1950. By 2011, that rate dropped to only 20%. Part of the decline has been attributed to fear of explosion, although this is extremely rare with modern pressure cookers, along with competition from other fast cooking devices, such as the microwave oven.

In 1679, French physicist Denis Papin, better known for his studies on steam, invented the airtight cooker used steam pressure to raise the water"s boiling point, thus cooking food more quickly. In 1681 Papin presented his invention to the Royal Society of London as a scientific study; he was later elected as a member.

In 1918, Spain granted a patent for the pressure cooker to José Alix Martínez from Zaragoza. Martínez named it the olla exprés, literally "express cooking pot", under patent number 71143 in the Boletín Oficial de la Propiedad Industrial.360 recipes for cooking with a pressure cooker.

In 1935, the Automa pressure cooker was introduced. Mountaineers attempting to climb Mount Everest took it along with them to cook in higher altitudes.

In 1938, Alfred Vischer presented his invention, the Flex-Seal Speed Cooker, in New York City. Vischer"s pressure cooker was the first designed for home use, and its success led to competition among American and European manufacturers.1939 New York World"s Fair, the National Pressure Cooker Company, later renamed National Presto Industries, introduced its own pressure cooker.

Super cocotte décor SEB, 1973. Aluminium body, polyamide lacquered with an embossed aluminium lid and a stainless steel stirrup. On display at the Musée gallo-romain de Fourvière, Lyon. 18/10.

Today, most pressure cookers are variations on the first-generation cookers, with the addition of new safety features such as a mechanism that prevents the cooker from being opened until it is entirely depressurized.

These include an electric heat source that is automatically regulated to maintain the operating temperature and pressure. They also include a spring-loaded valve (as described above) and are typically non venting during cooking.

Second-generation electric, with digital controller. Delayed cooking becomes possible and the controller shows a countdown timer when working pressure is reached.

Third-generation electric, with smart programming, which includes pre-set cooking times and settings based on heating intensity, temperature, pressure and duration.

Some pressure cookers are multifunctional (multicookers): pressure cooker, saute/browning, slow cooker, rice cooker, egg cooker, yogurt maker, steamer, sous vide, canner, and stockpot warmer that can also be used to keep cooked food warm.Ninja Foodi pressure cooker, which was the first pressure cooker that could also air fry, several other pressure cooker manufacturers, including Instant Pot, have come out with their own pressure cookers that can air fry, which are now known as pressure air fryers. Pressure air fryers have two separate lids, one for pressure cooking, and one for air frying.

At standard pressure the boiling point of water is 100 °C (212 °F). With any food containing or cooked with water, once the temperature reaches the boiling point, any excess heat causes some of the water to vaporize into steam efficiently carrying away heat keeping the food temperature at 100 °C.

In a sealed pressure cooker, as the water boils, the steam is trapped in the cooker which raises the pressure. However, the boiling point of water increases with pressure resulting in superheated water.

In a sealed pressure cooker the volume and amount of steam is fixed, so the temperature can be controlled either directly or by setting the pressure (such as with a pressure release valve).

For example, if the pressure reaches 1 bar or 100 kPa (15 psi) above the existing atmospheric pressure, the water will have reached a temperature of approximately 120 °C (248 °F) which cooks the food much faster.

Pressure cookers also use steam and water to rapidly transfer the heat to the food and all parts of the vessel. While, compared to an oven, a pressure cooker"s 120 °C is not particularly high, ovens contain air which is subject to thermal boundary layer effects which greatly slows heating, whereas pressure cookers flush air from the cooking vessel during warm up and replace it with hot steam. For items not placed within the liquid, as this steam condenses on the food it transfers water"s latent heat of vaporization, which is extremely large (2.275 kJ/g), to the surface, rapidly bringing the surface of the food up to cooking temperature. Because the steam condenses and drips away, no significant boundary layer forms and heat transfer is exceptionally efficient, and food heats much faster and more evenly.

However some recipes require browning to develop flavors as during roasting or frying. Higher temperatures are attainable with conventional cooking where the surface of the food can dry out. Such browning occurs via the Maillard reaction, at temperatures higher than the roughly 120 °C (248 °F) achieved in pressure cooking. Because those temperatures are not reached in pressure cooking, foods are generally browned by searing them, either in the open pressure cooker or another pan beforehand.

A pressure cooker can be used to compensate for lower atmospheric pressure at high elevations. The boiling point of water drops by approximately 1°C per every 294 metres of altitude (see: High-altitude cooking), causing the boiling point of water to be significantly below the 100 °C (212 °F) at standard pressure. This is problematic because temperatures above roughly 90°C are necessary to cook many common vegetables in a reasonable time. For example, on the summit of Everest (8,848 m (29,029 ft)), the boiling point of water would be only 70 °C (158 °F). Without the use of a pressure cooker, many boiled foods may remain undercooked, as described in Charles Darwin"s

Having crossed the Peuquenes [Piuquenes], we descended into a mountainous country, intermediate between the two main ranges, and then took up our quarters for the night. We were now in the republic of Mendoza. The elevation was probably not under 11,000 feet (3,400 m) [...]. At the place where we slept water necessarily boiled, from the diminished pressure of the atmosphere, at a lower temperature than it does in a less lofty country; the case being the converse of that of a Papin"s digester. Hence the potatoes, after remaining for some hours in the boiling water, were nearly as hard as ever. The pot was left on the fire all night, and next morning it was boiled again, but yet the potatoes were not cooked.

When pressure cooking at high altitudes, cooking times need to be increased by approximately 5% for every 300 m (980 ft) above 610 m (2,000 ft) elevation. Since the regulators work off the pressure differential between interior and ambient pressure, the absolute pressure in the interior of a pressure cooker will always be lower at higher altitudes.

Weight is a concern with backpackers, so mountaineering pressure cookers are designed to operate at a lower differential pressure than stove-top units. This enables them to use thinner, and therefore lighter materials. Generally, the goal is to raise the cooking temperature enough to make cooking possible and to conserve fuel by reducing heat lost through boiling.Sherpas often use pressure cookers in base camp.

Pressure cookers employ one or more regulators to control the pressure/temperature. All types have a calibrated pressure relief valve, as well as one or more emergency valves.

With the simplest types, once the desired pressure is reached, the valve opens, and steam escapes cooling the vessel and limiting the temperature. More advanced stovetop models have pressure indicators that permit the user to adjust the heat to prevent the steam from escaping. Third generation types automatically measure the state of the vessel and control the power so as to not release steam in operation.

Pressure cookers are available in different capacities for cooking larger or smaller amounts, with 6 litres" capacity being common. The maximum capacity of food is less than the advertised capacity because pressure cookers can only be filled up to 2/3 full, depending on ingredients and liquid (see Safety features section).

Because of the forces that pressure cookers must withstand, they are usually heavier than conventional pots of similar size. The increased weight of conventional pressure cookers makes them unsuitable for applications in which saving weight is a priority, such as camping. Nonetheless, small, lightweight pressure cookers are available for mountain climbers

A gasket or sealing ring, made from either rubber or silicone, forms a gas-tight seal that does not allow air or steam to escape between the lid and pan. Normally, the only way steam can escape is through a regulator on the lid while the cooker is pressurized. If the regulator becomes blocked, a safety valve provides a backup escape route for steam.

The twist-on design has slots on the lid engaging with flanges on the body, similar to a lid on a glass jar, that works by placing the lid on the pot and twisting it about 30° to lock it in place. A common modern design, it has easily implemented locking features that prevent the removal of the lid while under pressure.

The center screw design has a bar that is slotted in place over the lid and a screw tightened downward to hold the lid on. Though an older design, it is still produced due to its ease of construction and simplicity.

The bolt-down design has flanges on both its lid and its body for bolts to be passed through, and usually uses wingnuts that hinge on the body and so are never fully removed from the cooker; this sealing design is typically used for larger units such as canning retorts and autoclaves. It is very simple to produce, and it can seal with simple and inexpensive gaskets.

The internally fitted lid design employs an oval lid that is placed inside and presses outward; the user inserts the lid at an angle, then turns the lid to align it with the pot opening on top because the lid is larger than the opening. A spring arrangement holds the lid in place until the pressure forms and holds the lid tightly against the body, preventing removal until the pressure is released.

Gaskets (sealing rings) require special care when cleaning (e.g., not washed with kitchen knives), unlike a standard lid for a saucepan. Food debris, fats, and oils must be cleaned from the gasket after every use. Gasket/sealing rings need replacing with a new one about once a year (or sooner if it is damaged e.g. a small split). A very dry gasket can make it difficult or impossible to close the lid. Smearing the gasket sparingly with vegetable oil alleviates this problem (using too much vegetable oil can make the gasket swell and prevent it sealing properly). A gasket that has lost its flexibility makes bringing the cooker up to pressure difficult as steam can escape before sufficient pressure is generated to provide an adequate seal; this is usually a sign that the gasket needs replacing with a new one. Oiling the gasket with vegetable oil may alleviate the problem temporarily, but a new gasket is often required.

Early pressure cookers equipped with only a primary safety valve risked explosion from food blocking the release valve. On modern pressure cookers, food residues blocking the steam vent or the liquid boiling dry will trigger additional safety devices. Modern pressure cookers sold from reputable manufacturers have sufficient safety features to prevent the pressure cooker itself from exploding. When excess pressure is released by a safety mechanism, debris of food being cooked may also be ejected with the steam, which is loud and forceful. This can be avoided if the pressure cooker is regularly cleaned and maintained in accordance with the manufacturer"s instructions and never overfilled with food and/or liquid.

Modern pressure cookers typically have two or three redundant safety valves and additional safety features, such as an interlock lid that prevents the user from opening the lid when the internal pressure exceeds atmospheric pressure, preventing accidents from a sudden release of hot liquid, steam and food. If safety mechanisms are not correctly in place, the cooker will not pressurize the contents. Pressure cookers should be operated only after reading the instruction manual, to ensure correct usage. Pressure cooker failure is dangerous: a large quantity of scalding steam and water will be forcefully ejected and if the lid separates it may be propelled with considerable force. Some cookers with an internally fitted lid may be particularly dangerous upon failure as the lid fits tighter with increasing pressure, preventing the lid from deforming and venting around the edges. Due to these dangers pressure cookers are generally over-engineered in a safety regard and some countries even have regulations to prevent the sale of non-compliant cookers.

For first generation pressure cookers with a weighted valve or "jiggler", the primary safety valve or regulator is usually a weighted stopper, commonly called "the rocker" or "vent weight". This weighted stopper is lifted by the steam pressure, allowing excess pressure to be released. There is a backup pressure release mechanism that releases pressure quickly if the primary pressure release mechanism fails (e.g., food jams the steam discharge path). One such method is a hole in the lid that is blocked by a low melting point alloy plug and another is a rubber grommet with a metal insert at the center. At a sufficiently high pressure, the grommet will distort and the insert will blow out of its mounting hole to release pressure. If the pressure continues to increase, the grommet itself will blow out to release pressure. These safety devices usually require replacement when activated by excess pressure. Newer pressure cookers may have a self-resettable spring device, fixed onto the lid, that releases excess pressure.

On second generation pressure cookers, a common safety feature is the gasket, which expands to release excess pressure downward between the lid and the pot. This release of excess pressure is forceful and sufficient to extinguish the flame of a gas stove.

The recommended maximum fill levels of food/liquid avoids blockage of the steam valve or developing excess pressure: two-thirds full with solid food, half full for liquids and foods that foam and froth (e.g., rice, pasta; adding a tablespoon of cooking oil minimizes foaming),pulses (e.g., lentils).

Pressure cookers are typically made of aluminum (aluminium) or stainless steel. Aluminum pressure cookers may be stamped, polished, or anodized, but all are unsuitable for the dishwasher. They are cheaper, but the aluminum is reactive to acidic foods, whose flavors are changed in the reactions, and less durable than stainless steel pressure cookers.

Higher-quality stainless steel pressure cookers are made with heavy, three-layer, or copper-clad bottoms (heat spreader) for uniform heating because stainless steel has lower thermal conductivity. Most modern stainless steel cookers are dishwasher safe, although some manufacturers may recommend washing by hand. Some pressure cookers have a non-stick interior.

Pressure cooking always requires a water-based liquid to generate the steam to raise the pressure within the cooker. Pressure cooking cannot be used for cooking methods that produce little steam such as roasting, pan frying, or deep frying. A minimum quantity of liquid is required to create and maintain pressure, as indicated in the manufacturer"s instruction manual. For venting cookers more liquid is required for longer cooking times. This is not desirable for food requiring much less liquid, but recipes and books for pressure cookers take this into account.

Food is placed inside the pressure cooker with a small amount of water or other liquid such as stock. Food is either cooked in the liquid or above the liquid for steaming; the latter method prevents the transfer of flavors from the liquid.

Sauces which contain starch thickeners can tend to burn onto the interior base of the pressure cooker which may prevent the cooker from reaching operating pressure. Because of this issue, sauces may require thickening or reduction after pressure cooking.

With pot in pot pressure cooking, some or all of the food is placed in an elevated pot on a trivet above water or another food item which generates the steam. This permits the cooking of multiple foods separately, and allows the use of minimal water mixed with the food in the pot which permits thick sauces which would otherwise scorch onto the bottom of the pan to be cooked.

The lid is closed, the pressure setting is chosen and the pressure cooker is heated to boil the liquid. The cooker fills with steam and vents air. As the internal temperature rises, the pressure rises until it reaches the desired gauge pressure.

It usually takes several minutes for the pressure cooker to reach the selected pressure level. It can take around 10 minutes or longer depending on: the quantity of food, the temperature of the food (cold or frozen food delays pressurization), the amount of liquid, the power of the heat source and the size of the pressure cooker. There is typically a pop-up indicator that shows that the cooker has pressure inside, but it does not reliably signal that the cooker has reached the selected pressure. The pop-up indicator shows the state of the interlock which prevents the lid from being opened while there is any internal pressure. Manufacturers may use their own terminology for it, such as calling it a "locking indicator."

Timing the recipe begins when the selected pressure/pressure is reached. Once the cooker reaches full pressure, the heat is lowered to maintain the pressure. With pressure cookers accurate timing is essential using an audible timer.

With first generation designs, the pressure regulator weight begins levitating above its nozzle, allowing excess steam to escape. In second generation pressure cookers, either a relief valve subsequently opens, releasing steam to prevent the pressure from rising any further or a rod rises with markers to indicate the pressure level, without constantly venting steam. At this stage, the heat source is reduced to the lowest possible heat that still maintains pressure, as extra heat wastes energy and increases liquid loss. In third generation pressure cookers, the device will detect the vessel has reached the required cooking temperature/pressure and will maintain it for the programmed time, generally without further loss of steam.

Recipes for foods using raising agents such as steamed puddings call for gentle pre-steaming, without pressure, in order to activate the raising agents prior to cooking and achieve a light, fluffy texture.

Small containers such as plastic pudding containers can be used in a pressure cooker, if the containers (and any covering used) can withstand temperatures of 130 °C (266 °F) and are not placed directly on the interior base. The containers can be used for cooking foods that are prone to burning on the base of the pressure cooker. A lid for the container may be used if the lid allows some steam to come into contact with the food and the lid is securely fitted; an example is foil or greaseproof paper, pleated in the center and tied securely with string. Containers that are cracked or have otherwise sustained damage are not suitable. Cooking time is longer when using covered containers because the food is not in direct contact with the steam. Since non-metal containers are poorer heat conductors, the type of container material stated in the recipe cannot be substituted without affecting the outcome. For example, if the recipe time is calculated using a stainless steel container and a plastic container is used instead, the recipe will be undercooked, unless the cooking time is increased. Containers with thicker sides, e.g., oven-proof glass or ceramic containers, which are slower to conduct heat, will add about 10 minutes to the cooking time. Liquid can be added inside the container when pressure cooking foods such as rice, which need to absorb liquid in order to cook properly.

The flavor of some foods, such as meat and onions, can be improved by gently cooking with a little pre-heated cooking oil, butter or other fat in the open pressure cooker over medium heat for stove-top models (unless the manufacturer advises against this) before pressure cooking, while avoiding overheating the empty pressure cooker not heating the empty cooker with the lid and gasket in place to avoid damage. Electric pressure cookers usually have a "saute" or "brown" option for frying ingredients. The pressure cooker needs to cool briefly before adding liquid; otherwise some of the liquid will evaporate instantly, possibly leaving insufficient liquid for the entire pressure cooking time; if deglazing the pan, more liquid may need to be added.

After cooking, there are three ways of releasing the pressure, either quickly or slowly, before the lid can be opened. Recipes for pressure cookers state which release method is required at the end of the cooking time for proper results. Failure to follow the recommendation may result in food that is under-cooked or over-cooked.

To avoid opening the pressure cooker too often while cooking different vegetables with varying cooking times, the vegetables that take longer to cook can be cut into smaller pieces and vegetables that cook faster can be cut into larger pieces.

To inspect the food, the pressure cooker needs to be opened, which halts the cooking process. With a conventional saucepan, this can be done in a matter of seconds by visually inspecting the food.

This method is sometimes called a quick release, not to be confused with the cold water release (mentioned below). It involves the quick release of vapor by gradually lifting (or removing) the valve, pushing a button, or turning a dial. It is most suitable to interrupt cooking to add food that cooks faster than what is already in the cooker. For example, since meat takes longer to cook than vegetables, it is necessary to add vegetables to stew later so that it will cook only for the last few minutes. Unlike the cold water release method, this release method does not cool down the pressure cooker. Releasing the steam with care avoids the risk of being scalded by the rapid release of hot steam. This release method is not suitable for foods that foam and froth while cooking; the hot contents might spray outwards due to the pressure released from the steam vent. Pressure cookers should be operated with caution when releasing vapour through the valve, especially while cooking foamy foods and liquids (lentils, beans, grains, milk, gravy, etc.)

The natural release method allows the pressure to drop slowly. This is achieved by removing the pressure cooker from the heat source and allowing the pressure to lower without action. It takes approximately 10 to 15 minutes (possibly longer) for the pressure to disappear before the lid can be opened. On many pressure cookers, a coloured indicator pin will drop when the pressure has gone. This natural release method is recommended for foods that foam and froth during cooking, such as rice, legumes, or recipes with raising agents such as steamed puddings. The texture and tenderness of meat cooked in a pressure cooker can be improved by using the natural release method. The natural release method finishes cooking foods or recipes that have longer cooking times because the inside of the pressure cooker stays hot. This method is not recommended for foods that require very short cooking times, otherwise the food overcooks.

This method is the fastest way of releasing pressure with portable pressure cookers, but can be dangerous if performed incorrectly. Hence it is safer to release pressure by using the other methods. The manufacturer"s instruction book may advise against the cold water release or require it to be performed differently.

The cold water release method involves using slow running cold tap water, over the edge of the pressure cooker lid, being careful to avoid the steam vent or any other valves or outlets, and never immersing the pressure cooker under water, otherwise steam can be ejected from under the lid, which could cause scalding injury to the user; also the pressure cooker lid can be permanently damaged by an internal vacuum if water gets sucked into the pressure cooker, since the incoming water blocks the inrush of air.

The cold water release is most suitable for foods with short cooking times. It takes about 20 seconds for the cooker to cool down enough to lower the pressure so that it can be safely opened. This method is not suitable for electric pressure cookers, as they are not immersible. This type of pressure cooker cannot be opened with a cold water quick-release method.

The cold water release method is not recommended when cooking pulses e.g. red kidney beans, as the sudden release of pressure can cause the bean to burst its skin.

Most pressure cookers have a cooking (operating) pressure setting between 0.8–1 bar (11.6–15 psi) (gauge) so the pressure cooker operates at 1.8 to 2.0 bar (absolute). The standard cooking pressure of 15 psi gauge was determined by the United States Department of Agriculture in 1917. At this pressure, water boils at 121 °C (250 °F) (described in vapour pressure of water article).

The higher temperature causes food to cook faster; cooking times can typically be reduced to one-third of the time for conventional cooking methods. The actual cooking time also depends on the pressure release method used after timing Christmas puddings are typically timed according to their weight. Frozen foods need extra cooking time to allow for thawing.

When pressure cooking at 1 bar/15 psi (gauge), approximate cooking times are one minute for shredded cabbage, seven minutes for boiled potatoes (if cut small, not diced) and three minutes for fresh green beans. If the pressure is released naturally after timing

Some recipes may require cooking at lower than 1 bar/15 psi (gauge) e.g. fresh vegetables, as these can easily overcook. Many pressure cookers have 2 or more selectable pressure settings or weights.

Some pressure cookers have a lower or higher maximum pressure than 1 bar/15 psi (gauge) or can be adjusted to different pressures for some recipes; cooking times will increase or decrease accordingly. This is typically done by having different regulator weights or different pressure or temperature settings. Some pressure cookers operate at lower pressures than others. If the recipe is devised for a higher pressure and the pressure cooker does not reach that pressure, the cooking time can be increased to compensate.

Less energy is required than that of boiling, steaming, or oven cooking. Since less water or liquid has to be heated, the food reaches its cooking temperature faster. Using more liquid than necessary wastes energy because it takes longer to heat up; the liquid quantity is stated in the recipe. Pressure cookers can use much less liquid than the amount required for boiling or steaming in an ordinary saucepan. It is not necessary to immerse food in water. The minimum quantity of water or liquid used in the recipe to keep the pressure cooker filled with steam is sufficient. With non venting pressure cookers, steam isn"t continually escaping, thus evaporation losses are non existent once it has reached pressure. Overall, energy used by pressure cookers can be as much as 70% lower than used by cooking in a pan.

Because of this, vitamins and minerals are not leached (dissolved) away by water, as they would be if food were boiled in large amounts of water. Due to the shorter cooking time, vitamins are preserved relatively well during pressure cooking.

Several foods can be cooked together in the pressure cooker, either for the same amount of time or added later for different times. Manufacturers provide steamer baskets to allow more foods to be cooked together inside the pressure cooker.

Not only is this steam energy transmitted quickly to food, it is also transmitted rapidly to any micro-organisms that are present, easily killing even the deadliest types that are able to survive at the boiling point. Because of this enhanced germ killing ability, a pressure cooker can be used as an effective sanitizer for jam pots, glass baby bottles, or for water while camping.

Some foods are not recommended for pressure cooking. Foods such as noodles, pasta, cranberries, cereals and oatmeal can expand too much, froth and sputter, potentially blocking the steam vent and creating an unsafe condition.

An ≥ 121 °C) is a type of pressure cooker used by laboratories and hospitals to sterilize equipment. A stovetop autoclave is essentially a higher-pressure cooker with a gauge, used as an autoclave in poorer areas.

Pressure canners are large pressure cookers which have the capacity to hold jars used in canning. Pressure canners are specifically designed for home canning, whereas ordinary pressure cookers are not recommended for canning due to the risk of botulism poisoning, because pressure canners hold heat (≥ 115 °C) and pressure for much longer than ordinary pressure cookers; these factors are a critical part of the total processing time required to destroy harmful microbes such as bacterial spores.

A pressure air fryer (not to be confused with a pressure fryer) is a recent combination of a pressure cooker and an air fryer, with two separate lids, one for pressure cooking and one for air frying. The air frying lid has a convection fan in it that allows it to air fry foods, similar to an air fryer oven. This innovation was popularized by the Ninja Foodi Pressure Cooker, marketed as the first pressure cooker that can crisp and air fry.

A pressure oven is a recent combination of an oven and pressure cooker, usually as a countertop convection oven. They operate at low pressures, 10 kilopascals (1.5 psi), compared to other pressure cookers.rotisserie. Although having insufficient pressure for most conventional pressure cooking functions, they do also have non-pressure oven modes.

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Rick Rodgers; Arlene Ward & Kathryn Russell (2000). Pressure Cooking for Everyone. Chronicle Books. p. 12. ISBN 9780811825252. Retrieved 30 June 2016.

The Lancet (May 2003). "A more challenging summit than Everest". The Lancet. 361 (9372): 1837. doi:10.1016/s0140-6736(03)13535-0. ISSN 0140-6736. S2CID 30840142.

Park, Je Won; Kim, Young-Bae (March 2006). "Effect of Pressure Cooking on Aflatoxin B in Rice". Journal of Agricultural and Food Chemistry. 54 (6): 2431–2435. doi:10.1021/jf053007e. PMID 16536630.

Wise, Victoria (2005). The Pressure Cooker Gourmet: 225 Recipes for Great-Tasting, Long-Simmered Flavors in Just Minutes. Harvard, Mass: Harvard Common Press. p. 262. ISBN 1-55832-201-9.

Yadav SK, Sehgal S (February 1995). "Effect of home processing on ascorbic acid and beta-carotene content of spinach (Spinacia oleracia) and amaranth (Amaranthus tricolor) leaves". Plant Foods Hum Nutr. 47 (2): 125–31. doi:10.1007/bf01089261. PMID 7792260. S2CID 19736809.

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"Burning Issue: Canning in Pressure Cookers". National Center for Home Food Preservation. September 2015. Archived from the original on 13 November 2018. Retrieved 13 November 2018.

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The two valves referred above, are the Primary Release Valve and the Secondary Release Valve. The Primary Release Valve is usually a dead weight type of valve, closing an orifice by means of a conical pin, engaging the orifice. The dead weight determines the normal cooking pressure which is usually 15 lbs per sq. in. When heat is applied to the pressure cooker, steam pressure builds up to the cooking pressure, and thereafter with further application of heat, steam is let out into the atmosphere, by the lifting of the dead weight of the Primary Release Valve.

Thus, at no time the pressure cooker is expected to function beyond the normal cooking pressure. The dead weight of the Primary Release Valve is also referred to as Vent Weight, because it vents the excess steam.

It may be added here, that, after the attainment of cooking pressure, the heat application is reduced, so that, while the steam pressure is maintained, very little of steam is let out to the atmosphere. This is done to minimise the heat required for cooking. Application of more heat than required, merely results in generation of steam which is let out to the atmosphere and is not useful in the cooking process.

The Secondary Release Valve, is expected to work only in an emergency, when the Primary Release Valve has failed to function for some reason, for example, the food particles can clog the steam-release hole of the Primary Release Valve.

The Secondary Release Valves are usually of three types. In one type of Secondary Release Valve which is of the non-fusible repeat functioning type, the pressure exerted by a spring on the valve stem, controls the pressure of steam under conditions of emergency release.

In a second type of the Secondary Release Valve, it has a fusible low melting alloy, encased in a non-fusible metal retainer of good heat conducting material like aluminium. When the Primary Release Valve has failed to function, the steam pressure builds up to increasing value and the temperature of the steam also increases correspondingly; and, at a particular stage of steam pressure, the temperature is sufficiently high, so as to cause the melting of fusible metal alloy. The alloy melts, creates an opening in the lid, and through the opening, steam under excess pressure is safely let out. The fusible metal alloy safety valve has to be replaced by a new fusible Secondary Release Valve.

In the said known art of the second type, the Safety Release Valve is made up of two parts, viz. the safety fuse retainer and a holding nut. The safety fuse retainer is fastened to the lid of the pressure cooker by means of holding nut. The safety fuse retainer has at its centre, the low melting fusible alloy (FIG. 1). The retainer and the nut are usually made of aluminium, to pick up the temperature of the steam rapidly and transmit it to the fusible alloy faster. The safety fuse retainer and the nut are clamped tight to the lid so that steam cannot escape in any manner at the joint.

In the said third type of Secondary Release Valve, there are two parts made of two dissimilar materials, one metallic, another non-metallic. The metallic part is a "pintle" made of fusible low melting alloy. It is suspended from a hole in a thick rubber housing (the non-metallic material). The rubber housing is s lipped into a hole, (and held in position) on the lid of the pressure cooker. When excessive steam pressure builds up, the rubber housing ejects out of the lid, exposing an orifice in the lid and steam is allowed to escape. The fusible metal "pintle" has a head and conical bulbous portion connected by a narrow neck. The head prevents the "pintle" from falling into the cooker. When excess pressure builds up and the rubber has not ejected, the bulbous portion of the "pintle", ejects out of the hole in the rubber and steam releases. If the ejection of "pintle" also fails with further build up of pressure, the "neck" melts and steam releases.

The Thermally Fusible Safety Type Secondary Release Valve is one of the most popular and widely used Valves and has proved itself over the years. Nevertheless, this type of Secondary Release Valve still offers scope for further improvement, as explained below:

At the commencement of cooking, the lid of the pressure cooker is closed, and heat is applied. The manufacturers of all pressure cookers advise the users to let out steam and air, through the orifice meant for the dead weight of the Primary Release Valve, for a while and then place the dead weight. The reasons for this instruction are two: By following the instruction, the user first ensures that the Primary Release orifice is clear and there is no danger of prior choking by food particles.

Secondly, when steam and air are released through the orifice prior to the placement of the dead weight, it carries with it most of the air which was present inside the pressure cooker when the lid was closed. If the manufacturers" instructions were not followed and the Vent Weight (the Dead Weight of the Primary Release Valve) had been placed from the time of turning on the heat, the following conditions would result.

With the application of heat, the temperature of water inside the pressure cooker gradually rises to 100° C. and beyond. The steam pressure, in the empty space inside the pressure cooker continues to build up. At the same time the pressure of the air inside the empty space also increases; thus at any point of time, for a given temperature inside the pressure cooker, the pressure would be the sum total of the steam pressure and the air pressure taken separately. If for any reason, the Primary Release Valve fails to function, the pressure and temperature of the steam would increase until the temperature sensitive fusible metal alloy of the Secondary Release Valve melts, and releases excess pressure. Since the fusible metal alloy is sensitive to steam temperature and not to its pressure, there is the liklihood of the cooker being subjected to higher pressures than expected, the excess pressure over the steam pressure being contributed by the individual pressure of air. Thus, the performance of the thermally fusible safety valve gets vitiated by the presence of air and the error can be as much as 10 psi, decreasing the factor of safety in mechanical strength, provided in the Design of the pressure cooker.

It is also known to have an independent air ventile fitted to the lid of a pressure cooker. This is in addition to the existing safety release valve. Thus the known art suggests two independent units each functioning independantly and achieving individual purposes. The air ventile is a simple pintle made of nonfusible material which lifts at and closes the air escape opening when some air and some steam has escaped. Thereafter, the safety release valve of any of the known three types discussed above comes into function with all the drawbacks attached to it. We have noticed that this independant air ventile is not effective to let out substantially all the air and only a part of the air is vented out. This is because the object in the prior art was to retain the flavour of the cooked food by exitting some air in the beginning before the actual cooking took place. The probable explanation can be that if air is not exitted in the beginning, then after the cooker has cooled and is opened, the trapped air escapes with the aromatics from the food items. If the air is even partly exitted, then the loss of aroma is limited and the prior art claims that the aroma is maintained.

We have investigated and found, that unless substantially all the air is first exitted (with accompanying steam) there will be unnecessary build up of pressure due to the partial pressure of the trapped air which will affect the functioning of the safety release valve.

Because the objective was very limited in the known art, no consideration was given to any other aspects of the air ventile nor was there any consideration of the air ventile co-related with the pressure at which the safety release valve would operate.

In our investigations, it has been found that it is necessary to co-relate the function and construction of the air ventile and the safety release valve to exit almost all the air and then to immediately seal the vent and thereafter build up substantial steam pressure. For this, we had to dispense with independant units of air ventile and the safety release valve and device a single unit having both constructions and functions and give better advantages to us. We had to design a novel and new system itself co-relating the time to exit air, the clearance between the opening and the valve stem, the sealing pressure for air ventile, the lift of the air ventile as well as optimum weight of the integrated valve system.

Our approach gives an economical construction, as we have combined the functions of two independant units by designing a new unit unique in construction and function.

We have further found that our new system can be easily retrofitted in old pressure cookers in use, but having only Safety Release Valves and Primary Release Valves and thus giving even old pressure cookers the advantage of air vent and safety release.

It is therefore, an object of this invention which will ensure removal of all the air automatically without the necessity of the user venting the air as instructed by the manufacturers.

It is another object of this invention to propose a novel thermally fusible, dual metal, dual function, Safety Release Valve, which will have the dual functions of venting the air from the pressure cooker first and then function as an improved thermally fusible alloy of the Safety Release Valve, being sensitive only to steam temperature and unvitiated by air. It is a further object of this invention to propose such a dual function, dual metal, thermally fusible type, Safety Release Valve which can be used in a conventional pressure cooker without any change or without using any additional accessories.

It is still a further object of this invention, to propose such a thermally fusible, dual metal, dual function, Safety Release Valve, due to which the pressure regulating vent weight can be used even at the very beginning of cooking, without the user having to necesssarily vent the air.

Thus, according to this invention there is provided a novel dual functioning, dual metal, Safety Release Valve, which comprises a fusible metallic material held within the bore of a metallic retainer member, the stem of the said metallic retainer being adapted to be loosely and angularly held by a holding member, to an opening in the lid of the pressure cocker, the said stem also having a thin washer made of non-metallic resilient material adapted to seal under steam pressure, the opening in the lid of the pressure cooker, automatically, after substantially all the air is vented.

The fusible metallic material is made of conventional low temperature fusible metal alloys. The fusible material is held in the form of a plug at the lower end of the vertical bore in the metallic retainer member.

The holding member is adapted to be engaged externally to the lid of the pressure cooker on the protruding portion of the stem of the metallic retainer.

The lower body of the metallic retainer is provided with an undercut--cut portion externally adapted to provide a seat for the non-metallic resilient washer. The non-metallic resilient washer is made of nitrile rubber or other similar heat resilient elastic material.

FIG. 2 shows a cross - sectional view of the novel, dual function, dual metal, thermally fusible Safety Release Valve loosely held in a suspended maner to the lid of a pressure cooker onto which a conventional primary release valve is provided.

In FIG. 1, the conventional Safety Release Valve 8 is illustrated. The Safety Fuse comprises a fusible material 2 provided in the bore of a safety fuse retainer 10. The retainer 10 has an extended lower flange 9 accommodating the fusible material 2 within the bore 10A. The Safety fuse retainer is introduced from underside of the lid 11 through the hole 5 and is secured tightly to the lid by means of holding nut 12 using washer 13.

In FIG. 2, a cross section of part of the lid is shown carrying the conventional Primary Release Valve and the novel Safety Release Valve made of dual metal. In FIG. 2, the novel Safety Release Valve is shown in a suspended manner while in FIG. 3, the same fuse is shown in the working condition of the cooker under pressure.

Referring to FIGS. 2, 3, 4, 4A and 5, the novel dual function, dual metal, thermally fusible Safety Release Valve will be seen to consist of a hollow metal retainer I with a central vertical bore 7. At the lower end of the vertical bore, there is provided a temperature sensitive thermally fusible safety fuse 2 which is made of a conventional low temperature melting metal alloy. The fuse is held in the form of a plug having extension 2A held within a socket like provision 1A of the retainer 1.

The top end of the safety fuse metal retainer 1, is externally threaded to a limited extent so as to engage an internally threaded nut 3, such that the lower portion of the safety fuse retainer is loosely held in a suspended manner on the lid 4 of the pressure cooker through the hole 5 provided in the lid. It is also possible, to suspend the Safety fuse retainer by other means, such as by a cross--pin, 3A, FIG. 4A, instead of the nut. The lower end of the safety fuse retainer is provided with an under--cut portion 6A into which is securely held a washer 6 made of resilient material, such as, nitrile rubber or other similar heat resistant elastic material.

As per modification shown in FIG. 6, the holding unit 1 is provided with a narrow taper 8 externally tapering towards the top leaving a clearance between the top of the taper and the hole in the lid in the free suspended condition. The seal is seated below the lower base of the taper in the under-cut 6A as before.

Due to this construction of tapered exterior surface, the stem will gradually close the opening during lift of the retainer and there will be uniform pressure balance. The clearance between the stem and the hole in the lid gets gradually decreased and the pressure build up is faster due to reduced gap for escape of stream as compared to a straight exterior stem.

According to a modification, the air ventile is held to the hole in the lid of the cooker in a freely suspended manner by means of a holding sleeve--3A. , which replaces the holding nut 3. The sleeve is made specially for this purpose from a suitable flat metallic member having a central bore 3D whose diameter is slightly larger than the outer diameter of the stem of the air--ventile such that it can be slipped on the outer surface of the stem 1. The inner wall of the holding sleeve is provided with cylindrical groove 3B so as to accomodate a resilient clip 3C or holding spring 3C which has cut open ends as shown in FIG. 8. The distance between the inner edges of the clip is marginally less than the outer diameter of the stem. In view of the straight leg portions 3C1 and 3C2 of the clip which are separated by a distance less than the diameter of the groove, and also slightly less than the outer diameter of the stem of the spindle, these legs tend to expand when the stem is introduced between these legs and the stem can be slipped through. However, the outer surface of the stem is provided with a circular groove 1A whose diameter is about the same as the separating distance between the legs such that these legs snap into the groove and are held therein thereby arresting further insertion of the stem between the legs of the clip. For removing the stem it is necessary to hold to one edge of the sleeve and pull it to release from the clip with a slight pull, the clip is free of the stem.

For assembling the novel dual function, thermally fusible safety Release Valve of FIGS. 2 to 6, the holding nut 3 (or cross--pin ) is first removed and the top end of the Safety fuse retainer is introduced through the hole 5 of the lid from the underside of the lid. The safety fuse retainer already holds the safety fuse 2 and the resilient washer 6 in position at its lower end in the internal bore 7 and on the outside under-cut 6A respectively.

The holding nut is then threaded on to the upper end of the safety fuse retainer or the cross--pin is put in position in suitable aligned holes in the top of the stem. In view of the threading to the limited extent on the top portion of the safety fuse retainer, the safety fuse retainer is held floatingly and in a suspended manner in the hole of the lid.

For assembling the novel dual function thermally fusible safety release valve of FIGS. 7, 8 and 9, the holding sleeve 3A is first removed by exerting a slight pulling pressure and the top end of the safety fuse retainer is introduced through the hole 5 of the lid from the underside of the lid. The safety fuse retainer already holds the safety fuse 2 and the resilient washer 6 in position at its lower end in the internal bore 7 and on the outside under-cut 6A respectively.

The holding sleeve is then placed on the top of the stem and gently pressed, preferably slightly slantingly. The top of the stem is located between the two legs. The holding sleeve gently slips through until the two legs 3C1, 3C2 of the clip engage the outer groove 7A on the stem. By suitably position the groove 7A, the air ventile will remain in a suspended state as the earlier one.

The external diameter of the safety fuse retainer is smaller to a predetermined degree than the diameter of the hole in the lid. This is to give an intended annular gap for the escape of steam and air.

The Safety Valve is called a dual metal, dual function valve for the following reasons. Firstly the holding unit is made of a non - fusible metal like aluminium and in the central bore there is provided a fusible plug made of known fusible metal alloy.

Secondly, the Valve is intended to first let out substantially all the trapped air and some steam as a mixture in the initial stages in the suspended stage and then in the sealed stage function as the normal safety valve due to the melting of the alloy in the instance of excess pressure of steam and steam temperature.

Initially, the holding nut sits square on the external surface of the lid, on the slightly depressed and flattened portion of the hole in the lid. Due to the curvature of the lid, the Safety Release Valve assumes a dangling position, somewhat slanted to the vertical position.

When the lid of the pressure cooker is closed, and the dead weight of the Primary Release Valve has already been placed and heat is turned on, the temperature of water inside the pressure cooker gradually rises, say to about 80° to 90° C. Some steam is produced inside the pressure cooker and as the steam collects, it tends to increase the pressure above the atmospheric pressure. Then the steam and air start escaping through the annular gap around the Safety Release Valve. This causes slight lifting and tilting of the retainer, over the seal of the holding nut on the lid. A mixture of steam and air is then released, through the said annular gap, as the retainer and the holding nut are in a floating condition. Due to the escape of some steam and air, the pressure inside the cooker now drops back to a lower pressure. The temperature of steam again rises and the mixture of steam and air is released. The cycle repeats.

After a temperature of 100° C. (Boiling point of water) is reached, the rate of generation of steam becomes faster and substantially all the air is displaced, by this time, through the annulus in the lid. But the annular gap between the hole and the stem of the retainer does not allow the steam to pass through at the same rate at which it is generated. Consequently, the steam pressure inside the cooker builds up. When this stage has been reached, within a short time, the steam pressure rises sufficiently to lift the retainer straight-up bodily, causing the gasket of the retainer to come into contact with the underside of the lid with pressure. The gasket seals the annular gap effectively and no more steam can now escape through the hole in the lid.

After this stage has been reached, steam pressure within the pressure cooker starts building up further, until the Primary Release Valve becomes operational. The proposed Safety Valve is now ready to function as a thermally fusible Safety Release Valve, in the event of an emergency.

In instances of emergency where the pressure inside the cooker exceeds the normal 15 psi due to any unexpected malfunction of the Primary Release Valve, the fusible material, i.e. the Safety fuse 2 (FIG. 5) gets overheated and melts in the normal manner, thereby opening the central bore 7 of the safety fuse retainer 1, thus enabling the safe exit of steam. Thus, in the initial stages, the Safety Release Valve, of this invention, functions as an air-venting valve and in the later stages of operation, it functions as a thermally fusible safety fuse. The dual functions are thus achieved by this dual metal valve. Thus, it will be seen that even if the Primary Release Valve is used, before all the air escapes from the cooker, the dual functioning, thermally fusible Safety Release Valve takes care of releasing the air automatically. It also enables the housewife to even set the cooker with the Primary Release Valve accommodated from the very begining, because of the automatic dual functions of the thermally fusible Safety Release Valve of the invention.

After continued research and experimental studies, it has been discovered by us, that for the satisfactory functioning of the thermally fusible Safety Release Valve of this invention, it is important to keep the annular clearance between the outer wall of the safety fuse retainer and the hole in the lid, within a pre-determined range of values. The ratio of diameter of hole to diameter of stem of the safety fuse retainer should be between 1.05 to 1.20. It has been further discovered by us that if the clearance is below the said pre-determined range, the hole is sealed prior to removal of all the air by venting and if the clearance is more than the pre-determined range, we run the risk of excess delay in sealing of the annular gap or the gap may never seal at all.

Another factor responsible for a satisfactory functioning of the thermally fusible Safety Release Valve of the invention is the dead weight of the Safety Release Valve and the extent of lift that is available before the hole in the lid could be sealed. Here also, we have found that a predetermined extent of lift in the range of 1 to 3 mm is essential. Otherwise, a lesser extent of lift will seal the hole prior to air being completely expelled. If the lift is more than the predetermined range, either it takes a longer duration for sealing the hole when the pressure cooker is in operation, or the hole does not get sealed at all.

Moreover, if the dead weight of the thermally fusible Safety Release Valve of the invention is too less the hole gets sealed earlier before all the air could be vented. If the dead weight is too much, either it takes a longer duration for sealing the hole or the hole does not get sealed at all. Dead weight which depends on "lift" and stem diameter, and annular clearance, etc. has to be adjusted in such a way that the rubber washer of the safety fuse retainer, seals the annular gap, in the approximate pressure range 0.1 to 0.8 psi.

It has been further observed that for a successful functioning of the Safety Release Valve of the invention, the central/longitudinal axis of the same should be inclined to the vertical axis of the cooker by an amount of angle α ranging from 3° to 18° because when such an angle is maintained, the resultant force of the issuing steam takes the right time to bodily lift the valve when substantially all the air has been removed. At angles less than 3° to the vertical axis, the bodily lift is premature and at angles beyond 18° the bodily lift comes too late. It must be noted that this requirement is consequent to the lids of pressure cookers necessarily curved.

All the factors governing the design parameters of the proposed invention discussed above depend upon the partial pressures exerted by air and steam from the time of steam formation till the air is substantially removed and the safety valve seals the hole.

The two valves referred above, are the