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Steam valves are used to release pressure to make sure the safety of the home appliance. Since there are a varoety pf steam valves in our daily life, here will introduce you some famous steam valve for you to have a basic knowledge. Of course, the type of steam valves is not limited in the following ones and these are just for your reference. 
Safety Valves
You can find a few steam valves on the engine of a locomotive. Steam locomotives work on the pressure created when water evaporates and expands into steam. Sometimes, the engines get too hot and too much steam is created, which will force the machinery of the train to run too fast. When this situation happens, the safety steam valve will help to  release a bit of steam to make the pressure regulated for safety.
Pressure Valves
Steam engines also have pressure valves. The pressure valves release steam from a boiler, where the steam is first created by heating water, into another chamber where the steam is converted into energy.

 
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Before you go to buy a new steam valve, you should figure out what size of steam valve you need first. A steam valve is a tool that makes steam to escape from a source so as to decrease the build up of pressure. In most cases, steam valves are attached to water heaters, but are also applied in industrial settings. It's necessary for you to get the basic knowledge about the size of the valve before you want to repalce a faulty steam valve or install a new one, for valves come in a variety of sizes.
More Instructions
1), Mark the pipe that you plan to attach the steam valve to.
2), Hold the ruler up to the opening of the pipe, being sure that its beginning edge is matched with the outer surface of the pipe. Also, be sure that you are holding the ruler at the center of the pipe's diameter.
3), Mark where on the ruler the other other end of the pipe's outer edge is located. Read how many inches wide the pipe is. This is the size of steam valve you will need to purchase to install on this pipe.
Tips
In the U.S.the steam valves for most water heaters measure either 3/4 inch or 1 inch.



 
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Steam radiators can provide latent heat to our home especially in the cold weather. The operating principle of steam radiator is to heat water to the point then it will convert into steam, which is distributed through the house via radiators. But after a long time use, the packing around the steam radiator will wear off, causing leaks of the valve. However, this problem can be easily solved by ourselves if you will follow the instructions below.
 More Instructions
1), Turn off the thermostat and allow the system to cool. Close the intake valve on the leaking radiator by turning the handle in a counterclockwise direction.
2), Remove the screw on top of the valve handle with a screwdriver; lift the handle off the valve assembly. Locate the packing nut at the bottom of the valve stem. Loosen the nut with a crescent wrench, turning counterclockwise. Remove the packing nut from the stem. Remove the old gasket and any other debris from inside the nut with the needle-nose pliers.
3), Wrap 3 to 4 inches of graphite valve packing loosely around the valve stem in a clockwise direction. Do not stretch or break it.
4), Replace the packing nut and tighten it  by using the crescent wrench in a clockwise direction. When the nut is tight, it will compress the graphite packing into a new gasket. Replace the handle and the screw. Turn the handle in a clockwise direction to open the valve.
5), Turn on the thermostat to check if there is leaks.

 
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You can remove drain valves on radiators by using pliers. The flow of heated liquid can be offered to a room through steam and hot water radiators. The radiators work through a single pipe flowing into a valve that links to the radiator. The valve, connecting on both steam and hot water models, is used for controlling the flow of liquid in and out of the radiator. The valve makes the liquid to be forced into the radiator when it is on, and bypasses the radiator when it is off. It's simple to replace a valve on the radiator.
 More Instructions
1), Switch the compression fittings or unions off. The connection, called a union or compression joint, is a nut on the pipe. Loose it then you can disconnect the two sections with no need to twist the pipe. Before you remove any of the pipes, you have to separate the union. The connection is linked to the radiator or to the valve coming form inlet pipe.
2), Separate the other connections to the valve. There are three pipes joined together in most valves. Two will be linked with unions or compression fittings, which you need to remove in Step one. Screw other pipes directly into the valve. Use pipe wrench to grip the pipe to make it stable when you are spinning the valve. Rotate the valve connection, which is like a hexagonal nut, conterclockwise by using pipe wrench.
3), Apply thread sealant to the threads of each pipe and fitting involved.
4), Attach the replacement valve in the opposite direction.

Tips
Apply some spray lubricant to the connections with rust and allow it to soak in to aid with the removal of the valve.



 
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It's essential for steam boilers to equip with safety relief valves, which can prevent the interior pressure of a boiler from rising to unsafe levels. Typically,  steam safety relief valves will own a large spring that will add a downward force on a metal piston. When the pressure in a steam boiler rises high enough, it will apply the force of the spring and the piston will lift to relieve the interior pressure outside. So it's important for industrial process safety to consider the design and size of a safety relief valve. The size should accord with the required minimum standard. You can turn to the American Petroleum Institute (API), specifically the Recommended Practice 520 to find out some tips for sizing procedures and formulas of steam valves.
More Instructions
1), Decide all of the possible overpressure scenes for a steam boiler. This is the basic thing for the sizing of the valve. For instance, in a natural gas boiler, it's possible for the gas burner to be out of work, making excess heat for boiling the water.
2), Decide the maximum steam generation capacity and the maximum pressure rating of the boiler. For example, suppose the boiler has a maximum steam generation of 50,000 pounds per hour with a maximum pressure of 300 psi and a temperature of 422 degrees Fahrenheit.
3), Use the formula from API 520 to decide the minimum required orifice size of the valve.  The formula is A = W/(C x Kd x P x Kb x Kc) x √(T x Z)/M where A is the orifice area in square inches, W is the steam generation, C is a steam coefficient equal to 330, P is the pressure, Kd, Kb and Kc are all constants equal to 1.0 in this case. T is the temperature of the steam, Z is the steam compressibility factor (assume it is 1.0) and M is the molecular weight of the steam, which is 18.01. This calculates out to be 2.44 square inches.


 
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A steam relief valve is a tool used to release pressurized steam from appliances, such as a water heater. When water heaters are working well, they accumulate steam that must be released to avoid dangerous explosions. When building a new water heater, it is essential
to install a steam relief valve. Here are some tips for installation of a steam relief valve.
1), Turn off your hot water heater before installation.If your hot water heater is used in electricity, then you just unplug it from the wall. But if your hot water heater relies on gas, then you should bother to turn off the gas line which leads into it.
2), Turn off the main water source which connects to the hot water heater.
3), Allow the hot water heater to stay for an hour, so that the steam inside of it can cool entirely.
4), Remove the steam relief valve that is installed on your water heater with the wrench. Turn the wrench counterclockwise to detach the steam relief valve.
5), Place a layer of sealant tape on the pipe threads of your new steam relief valve.
6), Screw the new valve onto the water heater with your hands.
7), Tighten the steam relief valve into place by turning it clockwise with the wrench.
8), Turn the new steam relief valve to the closed position. You can now reinstall the water heater to its power supply and turn on the water line to check whether it can work or not.