A reliable manometer is a guarantee of trouble-free operation of the system, regardless, plumbing is, gas pipeline, heating system or closed cycle of any production. There are different types of such devices and in this article we will dwell on them in detail.
pressure gauges
There are three main types of pressure:
- Atmospheric. This is when the atmosphere affects the earth's surface, as well as everything on it. A healthy person does not feel it, as it is usually compensated by the internal pressure of the body.
- Tap water may be overpressure. Hence the rule - it occurs in an enclosed space in different environments.
- Absolute occurs when the interaction of the first and second types of pressure, that is, it is the sum of atmospheric and excess.
A manometer is a device, which measures the second type of pressure (redundant) in different systems.
device selection
Today's industry uses different types of manometers. To make the right purchase of a measuring instrument, which will be suitable for all parameters to solve production processes, you need to know:
- Manometer type.
- Working range of pressure measurement.
- Its accuracy class.
- The environment of its installation.
- Housing dimensions.
- Functional load of the device.
- Where it will be installed, as well as the size of the thread of the fitting.
- Operating conditions.
If you follow the above list, then you can choose the optimal device, as all manufacturers of manometers adhere to the established standards. Therefore, the devices of different companies are essentially interchangeable.
types of manometers
Modern instrumentation offers several types of devices, which are pressure gauges in different ranges:
- Manometers, working from 0 to any values with a plus sign.
- Manovacuummeters are designed to measure excess values from - to +.
- Vacuum gauges work with indicators below atmospheric in the range from -1 to 0. That is, measure the liquefied gases.
- Manometers, which work with extremely low values up to +40 kPa.
- Types of vacuum gauges are traction meters and traction meters.
- Pressure gauges measure low excess pressure at low values.
To make the right choice of the device on an admissible interval of pressure it is necessary to know working values of pressure of technological process., for which the projector of the measuring device was bought. Make no mistake in operations with plus and minus signs and add 30% to the working indicator.
The measuring instrument is selected taking into account the conditions and operating environment. This will be a special manometer for working with air, with water, a couple, oxygen, ammonia, acetone or gas. The environment may be different, including aggressive, therefore, the materials of the devices are designed for such operating conditions. Indicators of the case, in particular, strength, diameter, when choosing are taken into account, if it should be operated in conditions of vibration or high humidity, to prevent damage to the housing from corrosion or mechanical impact.
functional load
The device for measuring pressure is selected depending on the needs of the production process, it must correspond to the functions and operating conditions. Manometers are divided into the following types of functional load:
- What they show. Technical direction. Designed to measure pressure.
- Signal. Needed to control the external electrical circuit.
- For accurate measurement. Accuracy class from 0,6 / 1,0 from.
- Exemplary. Used to check the accuracy of technical manometers.
- Recorded. The measured pressure is recorded in the form of a diagram on paper.
The type of the case of the device informs about appointment, he can be:
- Vibration resistant.
- explosion-proof.
- Corrosion resistant.
Manometers are used in boiler systems, ship and railway equipment. There is a group of devices, able to operate in the food industry. The material of the measuring instrument body allows to meet the conditions of service.
installation of a pressure gauge
Be sure to know the cases before installation, when measuring instruments should not be used:
- When the manometer calibration period has expired, there is no seal or mark of verification.
- If the appliance is damaged, example, broken glass.
- When the arrow does not return to zero when the appliance is switched off.
- Installation at a height above cannot be allowed 3 meters from the site.
The device is installed in a prominent place, so that any employee can see his testimony. The manometer is mounted on the pipeline between the shut-off valve and the vessel.
The case must have a diameter of at least 10 centimeters, no less 16 centimeters in height 2-3 meters. Manometers, which are used to measure gas pressure, have different body colors. Example, if the housing of the device is blue, then it means in front of you a device for measuring oxygen pressure, yellow indicates the purpose of working with ammonia, red is used for flammable gases, black - non-flammable, white is intended for acetylene.
Installation of the mechanism before the manometer is extremely important, which will turn off and purge it, example, it can be a three-way valve. It is also necessary to install a siphon tube, its diameter must be at least one centimeter. Once the device is installed, you need to put a red line on the scale of the manometer, it will indicate the working pressure.
so, precision, with which the device measures pressure, depends on its correct choice and installation, as well as operating conditions. When making a choice take into account the physico-chemical properties of the measured medium and the required measurement accuracy. It is rational to measure viscous liquids with membranes, since tubular complicate the transfer of pressure through thin tubes. To measure gaseous media, containing aggressive gases, example, sulfur dioxide, use protected devices. They are equipped with a special housing with a color characteristic of each gas, also have markings on the scale of the device.