how pressure cooker safety valve works quotation

2023-05-21 21:22:12

Pressure cooking is a wonderful way to prepare food that cooks thoroughly and quickly at a high temperature. Some are worried about the dangers of using a pressure cooker, so it is helpful to find out how to check your pressure cooker safety valve for safe operation.

For those worried that a pressure cooker might explode, the safety valve is the design feature that prevents this from happening. If the cooker has a safety valve, you can see it installed on the cooker’s lid.

A pressure cooker is designed to trap the steam inside to increase the pressure. However, too much pressure is not safe. The valve must release pressure if it gets too high.

The blog of pressure cooking today has many recipes that are delicious. There are 25 recipes for pasta so you can try a new one every day for nearly a month.

There is a weight inside many of the safety valves that is lifted by the internal steam pressure when it reaches a certain amount. When the pressure lifts the weight inside the valve, this allows some steam to escape.

Jeffrey Eisner who says “he is a nice Jewish boy from Long Island.” He started with pressure cooking by making a simple mac and cheese dish with a recipe that he shared on YouTube. The video was an immediate success and led to his making new recipes for pressure cooking.

In a sealed cooker, as the pressure builds up, the boiling point of water rises. This phenomenon is the cause of the increased heat that cooks the food more thoroughly and faster.

The science that explains this is fascinating. The normal boiling point of water under standard atmospheric pressure of 15 pounds per square inch (psi) is 212°F (100°C). In a pressure cooker, the atmospheric pressure doubles from 15 psi to 30 psi. This added pressure raises the boiling point of water from 212°F (100°C) to 250°F (121°C).

If you see steam escaping from the safely valve do not worry. The steam escaping from the safety valve is its normal function, which means the valve is working properly.

If the internal pressure within the cooker gets high enough, this lifts a weight in the safety valve that allows steam to escape. The escaping vapor lowers the pressure. You can hear the steam escaping, making a whistling sound, or rattling the valve.

The first pressure cooking devices were used in the 17th century. They were useful to remove fat and collagen from bones so that the bones could then be ground down to make a pure bone meal.

The inventor of the device, Denis Papin, called it a “steam digester” or “bone digester.” His invention was the precursor to both pressure cookers and the steam engine. Surprisingly, the early designs did not have any safety features, and this caused some of the first ones to explode while being used.

The legacy of those early pressure-cooking devices may be why some still fear this problem even today. Papin, to his credit, came up with a design improvement that is what we call a safety valve to avoid the dangers of these explosions.

By the 1930s, the modern pressure cooker design became useful in a home kitchen. The Flex-Seal Speed Cooker, invented by Alfred Vischer, came out in 1938.

These home cookers became even more popular in 1939 with the release of the design by the National Pressure Cooker Company (now called National Presto Industries), which is still manufacturing these cookers today.

The first-generation cookers had a safety valve that worked with a weight. When the internal pressure rises high enough to lift the weight, some steam escapes, and the valve makes a distinctive rattling sound.

Second-generation cookers use a spring-loaded valve that makes less noise and is adjustable for pressure sensitivity by using a dial, which is on the cooker.

Third-generation models are the most recent versions. They use an electric heating source that is regulated by the internal pressure. These devices do not need a safety valve because the heat source automatically shuts off before the pressure gets too high.

Suppose you are thinking about getting a new cooker. In that case, there is another device that you might consider called a food dehydrator, which I describe in the article entitled, “How Much Electricity Does a Dehydrator Use?” here.

For the styles of cookers with a safety valve, it may not be obvious when the valve is not working if it is blocked. You may notice the lack of steam while the cooker is heated. The valve could rarely be blocked, but if not cleaned properly, it is possible.

Alternatively, the valve may be broken, missing, or the pot may not seal properly. These problems might allow too much steam to escape. This leakage may cause the cooker not to heat up properly and not allow the internal pressure to build up to the proper level.

One of the signs of a problem with a lack of pressure is that the food takes much longer to cook than you normally expect when using a cooker of this type.

One tip in the video is not to open the cooker after finishing cooking and take the lid to run it under cold water. This sudden temperature change can make the safety valve work less well and may cause the need to change the valve more frequently.

If you use a cooker that needs a valve to work properly and the valve is broken or missing, you can replace it with a new valve. Be sure to get the manufacturer’s specifications to ensure you use the correct replacement part.

Some of these problems include the ventilation knob being open or not enough liquid is in the cooker (requires at least one cup). Another cause is the sealing ring is missing, damaged, covered with food particles, or not in the proper position.

The video narrator shows how she cleans her float valve for her instant pot that she uses as a cooker. If you use too little liquid or too much, the cooker may not pressurize.

For the type with screws, hold the valve from the bottom of the lid with the pliers and use the screwdriver to remove the screws from the top to remove the broken part. Replace it with the new one and tighten the screws that hold it in place by holding it with the pliers from the bottom of the lid again and tightening the screws from the top.

For the type with a nut, use the wrench to loosen it for removal and perhaps a socket when you put on the new valve to tighten it with enough torque to hold it securely in the proper position.

Modern pressure cookers that are in good repair are quite safe. The one caution to remember is not to overfill the cooker so that the food might block the safety valve. This overfilling with food would be very difficult to do and not something to worry about for normal use.

Be careful where you keep your cooker on the countertop because it is important to know how hot a stovetop can get. Even when turned off, a stovetop may still be very hot, which I discuss in this article.

Now you know everything you need to know about a pressure cooker safety valve. You know what they do, how they work, and how to replace one if it needs repair. Enjoy your pressure-cooking recipes without worrying about the safety valve.

If having a safety valve on your cooker still bothers you, consider buying an electric cooker without a valve that instead has a built-in safety feature that automatically shuts off power if the pressure gets too high.

how pressure cooker safety valve works quotation

Pressure cookers have become an essential part of everyday cooking. As they don’t have any complicated functionalities, they are quite easy to prepare.

However, in technological aspects, a pressure cooker is a bit complicated. In order ensure user-safety, they have been equipped with different safety features – among them safety valve is a crucial one.

Pressure cookers have to deal with a lot of steam pressure in the cooking process. At some point, it has to release the excess steam to prevent the cooker from blowing up or exploding.

This release happens through the safety valve that holds weight. When the pressure is too high, it lifts the weight and steam escapes through making a buzz sound.

One of them is a classic whistle with pressure regulating valve and another is pressure regular valve present a little away from the first one. It is fixed onto the cooker lid and made from synthetic rubber like hardened viton or neoprene which helps in maintaining the pressure and good seal.

When the pressure inside the cooker increases, the inner part of safety valve will sense the elevation. And when it exceeds the normal levels, the rubber will start to melt and disc will lift.

Once the excess pressure is released, the disk goes back into its position. And the safety valve will open only when other means of steam release have failed as a last resort to prevent any explosion.

Pressure or steam release doesn’t always mean danger. It mostly indicates some dysfunctions that need attention. We have mentioned some of the possibilities below for your reference.

Damaged gasket – Usually, a rubber ring is present to seal the cooker. When there is a damage to it or if placed unevenly, it can compromise the cooker seal and let the pressure escape through the safety valve.

Overfilled pressure cooker – If the appliance is filled up with food ingredients without any space left for the steam, then this can block the regulating valve due to food expansion or foaming.

If the pressure cooker is made from cheap quality and from on an unknown brand, then they are a safety hazard as they compromise on the protection and health of a consumer. They often have low-quality safety valve which malfunctions easily and lead the steam to escape.

When the food and water quantity is little and water boils away, this can result in burnt and empty cooker. And the temperature gets too hot very quickly, leading to break down of the safety valve.

If the pressure cooker is placed over a larger burner and on a high flame, then the flame starts licking the sides of the appliances, leading to high temperature build up and damaging the safety valve.

Not cleaning the pressure cooker regularly can lead to clogs in the pressure regulating valve and this lets the safety valve to emit the steam from the cooker.

Some of the models come with a manual setting sealing feature. In such case, never forget to turn them on or else the steam takes safety valve for escape.

If you suspect the pressure cooker is not because of the safety valve, then the first thing is to take the appliance to the nearest service centre. You can use the cooker without the lid on but it is better to avoid using it with the lid until you get it repaired.

Yes, it is possible to replace safety valve of a pressure cooker. And moreover, it is recommended to replace it if the valve is out of friction or damaged.

Replacing the safety valve can be done in two methods – one includes changing it from inside and another from the outside. Below are the clear instructions for the same.

Make sure the pressure cooker is filled up to only 2/3 full and the rest of 1/3 part has to be empty so that the foods have enough space to swell and foam.

It is important to add adequate amount of liquid into the pressure pot. If not, the water runs out quickly, cause rapid heat increase and lead to explosion. Not to say that burns caused food burns as well.

To maintain the pressure cooker longevity and prevent any disasters, it is important to check the safety valve and gasket on a regular basis. If there is any damage, getting it repaired or replacing is very important. Safety valve in a pressure cooker plays a very significant role.

We believe any questions and doubts about the safety valve has been clarified by the information present in this article. If it hasn’t then, write them to us in the comment section below.

how pressure cooker safety valve works quotation

You may have heard or read a quote that “With great powers comes great responsibilities”. You must be confused about why I am quoting this statement right now but that quote fits well with the working of a pressure cooker. Yes! You heard it right. I am going to tell why this statement was related to the most useful kitchen equipment- Pressure cooker.

The pressure cooker was invented in 1902 by Denis Papin. That means we are using this equipment for more than 100 years. Isn"t that amazing? Yes, it is. These 100 years prove how much we trust this kitchen utensil. And the most amazing thing about the cooker is that it never stops evolving itself from all these years. Now we have its many varieties such as stainless steel pressure cooker, aluminum, electrical, non-sticky and many more. And don’t forget the fact in this world of window shopping you can even buy a cooker online.

Now when you buy a new pressure cooker that might be your 2nd, 3rd or 4th but if you are using it for the first time then there comes the tough part because it is usual that human needs to learn about the new things before using it. Traditional pressure cookers had fewer safety features than the new and modern pressure cookers. Let see these qualities in a more understandable way below:

A few years ago when the cookers were not that modern, there was a fear of explosion due to the food blocking the release valve because those cookers were only equipped with a primary safety valve. As the technology is evolving its cooking process has also changed, now the food blocking steam will give a signal to the safety device of the cooker. Many reputable manufacturers like United Pressure Cooker also provide modern pressure cookers that have sufficient safety features which prevent them from exploding. The mechanism is simple- when the safety valve releases too much pressure, some remains of food being cooked may also be discharged with the steam, which is loud and forceful. Regular cleaning and good maintenance of the pressure cooker can prevent this from happening.

Many advanced pressure cookers have more than one safety valve with extra safety features like an interlock lid that protects sudden opening the lid by the user which prevents accidents from a sudden release of hot liquid, steam, and food.

For better and safe use of the pressure cooker, one must read all the instructions and should understand how the pressure cooker works. Negligence of such rules can cause a high build of steam inside the cooker which will result in forcefully ejections of the water.

So, after going through all these points you must have understood why the quote “With great powers comes great responsibilities” relates to the pressure cooker. Well, you should work safely not with just the cooker but with every utensil in the kitchen. In the meantime, you can also shop high safety-enabled pressure cookers with United Pressure Cooker.

how pressure cooker safety valve works quotation

A safety valve is a valve that acts as a fail-safe. An example of safety valve is a pressure relief valve (PRV), which automatically releases a substance from a boiler, pressure vessel, or other system, when the pressure or temperature exceeds preset limits. Pilot-operated relief valves are a specialized type of pressure safety valve. A leak tight, lower cost, single emergency use option would be a rupture disk.

Safety valves were first developed for use on steam boilers during the Industrial Revolution. Early boilers operating without them were prone to explosion unless carefully operated.

Vacuum safety valves (or combined pressure/vacuum safety valves) are used to prevent a tank from collapsing while it is being emptied, or when cold rinse water is used after hot CIP (clean-in-place) or SIP (sterilization-in-place) procedures. When sizing a vacuum safety valve, the calculation method is not defined in any norm, particularly in the hot CIP / cold water scenario, but some manufacturers

The earliest and simplest safety valve was used on a 1679 steam digester and utilized a weight to retain the steam pressure (this design is still commonly used on pressure cookers); however, these were easily tampered with or accidentally released. On the Stockton and Darlington Railway, the safety valve tended to go off when the engine hit a bump in the track. A valve less sensitive to sudden accelerations used a spring to contain the steam pressure, but these (based on a Salter spring balance) could still be screwed down to increase the pressure beyond design limits. This dangerous practice was sometimes used to marginally increase the performance of a steam engine. In 1856, John Ramsbottom invented a tamper-proof spring safety valve that became universal on railways. The Ramsbottom valve consisted of two plug-type valves connected to each other by a spring-laden pivoting arm, with one valve element on either side of the pivot. Any adjustment made to one of valves in an attempt to increase its operating pressure would cause the other valve to be lifted off its seat, regardless of how the adjustment was attempted. The pivot point on the arm was not symmetrically between the valves, so any tightening of the spring would cause one of the valves to lift. Only by removing and disassembling the entire valve assembly could its operating pressure be adjusted, making impromptu "tying down" of the valve by locomotive crews in search of more power impossible. The pivoting arm was commonly extended into a handle shape and fed back into the locomotive cab, allowing crews to "rock" both valves off their seats to confirm they were set and operating correctly.

Safety valves also evolved to protect equipment such as pressure vessels (fired or not) and heat exchangers. The term safety valve should be limited to compressible fluid applications (gas, vapour, or steam).

For liquid-packed vessels, thermal relief valves are generally characterized by the relatively small size of the valve necessary to provide protection from excess pressure caused by thermal expansion. In this case a small valve is adequate because most liquids are nearly incompressible, and so a relatively small amount of fluid discharged through the relief valve will produce a substantial reduction in pressure.

Flow protection is characterized by safety valves that are considerably larger than those mounted for thermal protection. They are generally sized for use in situations where significant quantities of gas or high volumes of liquid must be quickly discharged in order to protect the integrity of the vessel or pipeline. This protection can alternatively be achieved by installing a high integrity pressure protection system (HIPPS).

In the petroleum refining, petrochemical, chemical manufacturing, natural gas processing, power generation, food, drinks, cosmetics and pharmaceuticals industries, the term safety valve is associated with the terms pressure relief valve (PRV), pressure safety valve (PSV) and relief valve.

The generic term is Pressure relief valve (PRV) or pressure safety valve (PSV). PRVs and PSVs are not the same thing, despite what many people think; the difference is that PSVs have a manual lever to open the valve in case of emergency.

Relief valve (RV): an automatic system that is actuated by the static pressure in a liquid-filled vessel. It specifically opens proportionally with increasing pressure

Pilot-operated safety relief valve (POSRV): an automatic system that relieves on remote command from a pilot, to which the static pressure (from equipment to protect) is connected

Low pressure safety valve (LPSV): an automatic system that relieves static pressure on a gas. Used when the difference between the vessel pressure and the ambient atmospheric pressure is small.

Vacuum pressure safety valve (VPSV): an automatic system that relieves static pressure on a gas. Used when the pressure difference between the vessel pressure and the ambient pressure is small, negative and near to atmospheric pressure.

Low and vacuum pressure safety valve (LVPSV): an automatic system that relieves static pressure on a gas. Used when the pressure difference is small, negative or positive and near to atmospheric pressure.

In most countries, industries are legally required to protect pressure vessels and other equipment by using relief valves. Also, in most countries, equipment design codes such as those provided by the ASME, API and other organizations like ISO (ISO 4126) must be complied with. These codes include design standards for relief valves and schedules for periodic inspection and testing after valves have been removed by the company engineer.

Today, the food, drinks, cosmetics, pharmaceuticals and fine chemicals industries call for hygienic safety valves, fully drainable and Cleanable-In-Place. Most are made of stainless steel; the hygienic norms are mainly 3A in the USA and EHEDG in Europe.

The first safety valve was invented by Denis Papin for his steam digester, an early pressure cooker rather than an engine.steelyard" lever a smaller weight was required, also the pressure could easily be regulated by sliding the same weight back and forth along the lever arm. Papin retained the same design for his 1707 steam pump.Greenwich in 1803, one of Trevithick"s high-pressure stationary engines exploded when the boy trained to operate the engine left it to catch eels in the river, without first releasing the safety valve from its working load.

Although the lever safety valve was convenient, it was too sensitive to the motion of a steam locomotive. Early steam locomotives therefore used a simpler arrangement of weights stacked directly upon the valve. This required a smaller valve area, so as to keep the weight manageable, which sometimes proved inadequate to vent the pressure of an unattended boiler, leading to explosions. An even greater hazard was the ease with which such a valve could be tied down, so as to increase the pressure and thus power of the engine, at further risk of explosion.

Although deadweight safety valves had a short lifetime on steam locomotives, they remained in use on stationary boilers for as long as steam power remained.

Weighted valves were sensitive to bouncing from the rough riding of early locomotives. One solution was to use a lightweight spring rather than a weight. This was the invention of Timothy Hackworth on his leaf springs.

These direct-acting spring valves could be adjusted by tightening the nuts retaining the spring. To avoid tampering, they were often shrouded in tall brass casings which also vented the steam away from the locomotive crew.

The Salter coil spring spring balance for weighing, was first made in Britain by around 1770.spring steels to make a powerful but compact spring in one piece. Once again by using the lever mechanism, such a spring balance could be applied to the considerable force of a boiler safety valve.

The spring balance valve also acted as a pressure gauge. This was useful as previous pressure gauges were unwieldy mercury manometers and the Bourdon gauge had yet to be invented.

Paired valves were often adjusted to slightly different pressures too, a small valve as a control measure and the lockable valve made larger and permanently set to a higher pressure, as a safeguard.Sinclair for the Eastern Counties Railway in 1859, had the valve spring with pressure scale behind the dome, facing the cab, and the locked valve ahead of the dome, out of reach of interference.

In 1855, John Ramsbottom, later locomotive superintendent of the LNWR, described a new form of safety valve intended to improve reliability and especially to be tamper-resistant. A pair of plug valves were used, held down by a common spring-loaded lever between them with a single central spring. This lever was characteristically extended rearwards, often reaching into the cab on early locomotives. Rather than discouraging the use of the spring lever by the fireman, Ramsbottom"s valve encouraged this. Rocking the lever freed up the valves alternately and checked that neither was sticking in its seat.

A drawback to the Ramsbottom type was its complexity. Poor maintenance or mis-assembly of the linkage between the spring and the valves could lead to a valve that no longer opened correctly under pressure. The valves could be held against their seats and fail to open or, even worse, to allow the valve to open but insufficiently to vent steam at an adequate rate and so not being an obvious and noticeable fault.Rhymney Railway, even though the boiler was almost new, at only eight months old.

Naylor valves were introduced around 1866. A bellcrank arrangement reduced the strain (percentage extension) of the spring, thus maintaining a more constant force.L&Y & NER.

All of the preceding safety valve designs opened gradually and had a tendency to leak a "feather" of steam as they approached "blowing-off", even though this was below the pressure. When they opened they also did so partially at first and didn"t vent steam quickly until the boiler was well over pressure.

The quick-opening "pop" valve was a solution to this. Their construction was simple: the existing circular plug valve was changed to an inverted "top hat" shape, with an enlarged upper diameter. They fitted into a stepped seat of two matching diameters. When closed, the steam pressure acted only on the crown of the top hat, and was balanced by the spring force. Once the valve opened a little, steam could pass the lower seat and began to act on the larger brim. This greater area overwhelmed the spring force and the valve flew completely open with a "pop". Escaping steam on this larger diameter also held the valve open until pressure had dropped below that at which it originally opened, providing hysteresis.

These valves coincided with a change in firing behaviour. Rather than demonstrating their virility by always showing a feather at the valve, firemen now tried to avoid noisy blowing off, especially around stations or under the large roof of a major station. This was mostly at the behest of stationmasters, but firemen also realised that any blowing off through a pop valve wasted several pounds of boiler pressure; estimated at 20 psi lost and 16 lbs or more of shovelled coal.

Pop valves derived from Adams"s patent design of 1873, with an extended lip. R. L. Ross"s valves were patented in 1902 and 1904. They were more popular in America at first, but widespread from the 1920s on.

Although showy polished brass covers over safety valves had been a feature of steam locomotives since Stephenson"s day, the only railway to maintain this tradition into the era of pop valves was the GWR, with their distinctive tapered brass safety valve bonnets and copper-capped chimneys.

Developments in high-pressure water-tube boilers for marine use placed more demands on safety valves. Valves of greater capacity were required, to vent safely the high steam-generating capacity of these large boilers.Naylor valve) became more critical.distilled feedwater and also a scouring of the valve seats, leading to wear.

High-lift safety valves are direct-loaded spring types, although the spring does not bear directly on the valve, but on a guide-rod valve stem. The valve is beneath the base of the stem, the spring rests on a flange some height above this. The increased space between the valve itself and the spring seat allows the valve to lift higher, further clear of the seat. This gives a steam flow through the valve equivalent to a valve one and a half or twice as large (depending on detail design).

The Cockburn Improved High Lift design has similar features to the Ross pop type. The exhaust steam is partially trapped on its way out and acts on the base of the spring seat, increasing the lift force on the valve and holding the valve further open.

To optimise the flow through a given diameter of valve, the full-bore design is used. This has a servo action, where steam through a narrow control passage is allowed through if it passes a small control valve. This steam is then not exhausted, but is passed to a piston that is used to open the main valve.

There are safety valves known as PSV"s and can be connected to pressure gauges (usually with a 1/2" BSP fitting). These allow a resistance of pressure to be applied to limit the pressure forced on the gauge tube, resulting in prevention of over pressurisation. the matter that has been injected into the gauge, if over pressurised, will be diverted through a pipe in the safety valve, and shall be driven away from the gauge.

There is a wide range of safety valves having many different applications and performance criteria in different areas. In addition, national standards are set for many kinds of safety valves.

Safety valves are required on water heaters, where they prevent disaster in certain configurations in the event that a thermostat should fail. Such a valve is sometimes referred to as a "T&P valve" (Temperature and Pressure valve). There are still occasional, spectacular failures of older water heaters that lack this equipment. Houses can be leveled by the force of the blast.

Pressure cookers are cooking pots with a pressure-proof lid. Cooking at pressure allows the temperature to rise above the normal boiling point of water (100 degrees Celsius at sea level), which speeds up the cooking and makes it more thorough.

Pressure cookers usually have two safety valves to prevent explosions. On older designs, one is a nozzle upon which a weight sits. The other is a sealed rubber grommet which is ejected in a controlled explosion if the first valve gets blocked. On newer generation pressure cookers, if the steam vent gets blocked, a safety spring will eject excess pressure and if that fails, the gasket will expand and release excess pressure downwards between the lid and the pan. Also, newer generation pressure cookers have a safety interlock which locks the lid when internal pressure exceeds atmospheric pressure, to prevent accidents from a sudden release of very hot steam, food and liquid, which would happen if the lid were to be removed when the pan is still slightly pressurised inside (however, the lid will be very hard or impossible to open when the pot is still pressurised).

"Trial of HMS Rattler and Alecto". April 1845. The very lowest pressure exhibited "when the screw was out of the water" (as the opponents of the principle term it) was 34 lb, ranging up to 60 lb., on Salter"s balance.

how pressure cooker safety valve works quotation

Q. My mother-in-law recently gave me her pressure cooker, but I"ve heard so many horror stories about them that I"m afraid to use it. Are pressure cookers safe?

A. Pressure cookers are special pots with airtight, locking lids that feature a valve system that regulates internal pressure. Steam that builds up inside the pot cooks the food at a very high temperature. This ability to cook at extremely high temperatures means foods that take hours -- such as dried beans -- can cook in a fraction of the time, and "regular" meals can be on the table in minutes.

Although we"ve all heard the urban legends about exploding pressure cookers, modern pressure cookers are equipped with safety features to prevent such mishaps. These include lids that must be locked into place before pressure will rise, an expanding rubber gasket that prevents you from removing the lid until the pressure has been released to safe levels, and a safety valve that automatically reduces the pressure should there be a malfunction or in the event that you forget to turn down the heat when high pressure is reached.

how pressure cooker safety valve works quotation

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.

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 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 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.

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 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.

how pressure cooker safety valve works quotation

We are engaged in offering wide range of Pressure Cooker Safety Valves. The offered valve is manufactured using world class raw material and advanced methodology by our professionals. It is used in the fitting of various utensils and is hugely demanded in the market. Our precious clients can buy this Pressure Cooker Safety Valve at nominal costs.read more...

Our company also makes available durable Pressure Cooker Safety Valves. Our products are widely preferred for safe and fast cooking. These are easy to fit and easily maintain the pressure of cookers. These are best in quality, long functional and provided at economical market prices.

how pressure cooker safety valve works quotation

Series 415 Steam Safety Relief Valves are used in commercial and industrial applications for low-pressure, steam heating boilers and process equipment. They have a brass body (size 1/4 in.) or a bronze body (sizes 1, 1 1/4, 1 1/2 in.) construction with NPT threaded male inlet and threaded female outlet (drain) connection, stainless steel spring, top-guided stem, and non-stick Teflon disc-to-metal seating. Model 415SC has satin chrome finish. Model 415L has low pressure setting at 8psi (55 kPa) for pressure cookers and steam cleaning equipment. ASME Section IV at 15psi (103 kPa) set point.

how pressure cooker safety valve works quotation