In order to comply with the necessary safety conditions, it is important that the operating parameters of technological installations do not exceed emergency values. If such situations arise, then the automatic control system should immediately stop the operation of the equipment and prevent it from starting until the troubleshooting or until the required values of the technological parameters of the controlled environment are reached.
There are a huge number of process control devices on the market today. So, for example, one of the sensors for measuring and controlling pressure is an electrocontact pressure gauge.
Content
What is this sensor and when is it used
Electrocontact pressure gauge is a sensor that is used to measure gauge and vacuum pressures in various media (liquid, gas, steam), is used as a signaling device of direct action and allows you to control production processes, while a special condition for the medium is the exclusion of its crystallization.
EKM is used to issue control signals to actuators that maintain pressure values in the pipeline, as well as compressor units, hydraulic systems, pneumatic equipment or household autoclaves at a certain value.
The electrocontact pressure gauge is popular in many industries and infrastructure systems:
- Energy;
- Metallurgy;
- Oil and gas and petrochemical industry;
- Water supply systems;
- Machine-building installations;
- Heat generation and distribution.
Also, EKM is in demand in the safety automation systems of thermal power plants, central heating stations and boiler houses.
Varieties of sensor models
A lot of manufacturers are engaged in the production of electrocontact pressure gauges, some offer a fairly wide range of models, the list below is divided according to various manufacturers:
- TM (TV, TMV), 10th series;
- PGS23.100, PGS23.160;
- EKM100Vm, EKM160Vm;
- TM-510R.05, TM-510R.06, DM2005Sg and its analogue TM-610.05 ROSMA.
All listed models are divided into pressure gauges with microswitches and with magnetomechanical contacts. Manufacturers also produce explosion-proof and vibration-resistant or liquid-filled devices (internally filled with dielectric oil, most often glycerin) so that the readings of the pressure gauge needle do not “jump” with increased pulsation of the medium being measured.The glycerin inside the EKM will keep the needle from moving too fast.
The principle of operation of electrocontact pressure gauges
The principle of operation of the EKM is to close or open a certain set value with a moving contact. The movable contact of the electrocontact manometer is the pointer showing the pressure, which turns when the pressure in the measured medium changes. Setpoint (adjustable) the value is set manually using two arrows (minimum and maximum value). These pressure gauge needles are stationary after the values have been set.
The value of the movable arrow in the working process, as a rule, is between two setting values, but when it crosses the limit value, the contacts of the internal electrical circuit close or open (depends on the type of model execution). These contacts can be used in various relay circuits to control, for example, pneumatic or electromagnetic valves, as well as magnetic starters of various motors.
Note! The switching capacity of the contacts of the electrocontact pressure gauge does not allow switching high load currents.
Each electrocontact pressure gauge has a marking that describes all its characteristics and variety.
EKM device
The EKM is a device shaped like a cylinder and very similar to a conventional pressure gauge. But in contrast to it, the EKM includes two arrows that set the values of the settings: РMax and Rmin (their movement is carried out manually on the scale of the dial).The movable arrow, showing the real value of the measured pressure, switches the contact groups, which close or open when it reaches the set value. All arrows are located on the same axis, but the places where they are fixed are isolated and do not touch each other.
The axis of the indicator arrow is isolated from the parts of the device, its body and scale. It rotates independently of the others.
Special current-carrying plates (lamellas) connected to the corresponding arrow are connected to the bearings with which the arrows are attached, and on the other hand, these plates are brought into the contact group.
In addition to the above components, EKM, like any pressure gauge, also has a sensitive element. In almost all models, this element is a Bourdon tube, which moves along with an arrow rigidly fixed on it, and a multi-turn spring is also used as this element for sensors measuring pressure of a medium above 6 MPa.
Wiring diagrams for electrocontact pressure gauges
The figure shows typical possible EKM connection schemes.
- 1 - the main showing arrow;
- 2 and 3 - limit value settings;
- 4 and 5 - areas of closed and open contacts;
- 6 and 7 - external circuits, in which there is an electrocontact pressure gauge.
Consider the operation of the EKM contacts using the example of a sensor with version 1. When the pressure reaches the set value (2), the working arrow (1), i.e. when the working pointer (1) enters zone 4, the EKM contact closes. When the pressure value drops below the set arrow (2), the contact will open.
Which contact groups can be used depends on the type of device, and they exist according to GOST 13717-84 Appendix 1 of the following types:
- VERSION 1 - Normally open (BUT), with one contact;
- VERSION 2 - Normally closed (NZ), with one contact;
- VERSION 3 - With two contacts, both normally closed (NZ);
- VERSION 4 - With two contacts that are normally open (BUT);
- VERSION 5 - With two contacts, when one of them is normally closed (NZ), and the second is normally open (BUT);
- VERSION 6 - With two contacts, when one of them is normally open (BUT), and the second one is closed (NZ).
Advantages and disadvantages
Like any technical device, EKM has its advantages and disadvantages.
Flaws:
- Load power limitation due to too low switching current limit value, which has a range of 0.3 to 0.5 A (EKM with sliding contacts) up to 1 A (contacts with magnetic preload);
- High cost, compared with a pressure switch, the price can be two or three times more.
Advantages:
- Visualization of settings is clear and understandable;
- Setting the operation limits is quite simple and does not require special keys, special knowledge and a lot of time;
- Assembly in a single housing, which allows you not to use additional tees when connecting.
EKM manufacturing companies
The main and best known manufacturers of EKM sensors are:
- Heat control;
- Warm climate;
- WIKA;
- Teplopribor;
- Analytpribor;
- Expert;
- Pressure gauge.
A brief overview of some sensor models and their features
TM-510R.05, TM-510R.06
TM-510R.05, TM-510R.06 from the manufacturer CJSC "Rosma" are assembled on the basis of pressure gauges TM-510, and after installing the electrocontact prefix they become full-fledged EKM.
In these models of EKM, contacts with magnetic preload are used, which allow switching high currents with high breaking power of contacts, compared to devices with sliding contacts.
EKM TM-510R.05, TM-510R.06 are characterized by reliable electrical connection under dynamic loads.
Main characteristics:
- Two-pin electrical circuit;
- Maximum possible voltage ~380 V;
- Maximum possible current — 1 A;
- Maximum possible breaking capacity of contacts — 30 W;
EKM100Wm
EKM100Wm - is an electrocontact pressure gauge on microswitches, designed to close or open an electrical circuit when a predetermined pressure limit is reached. Provides visual indication of controlled pressure.
If necessary, it can be equipped with additional options:
- Bosses, elbows or impulse pipes;
- Taps and valves;
- Gaskets, adapters, dampers, etc.
Model EKM100Wm has the following characteristics:
- Range of possible measurements up to 4 MPa;
- Accuracy class 2.5;
- Case diameter 100 mm;
- electrocontact group V version according to GOST 2405-88.
Technologies do not stand still, everything is being improved, including the design of the measured instruments.
So, for example, modern digital sensors EKM-1005, EKM-2005 from Teploklimat, Teplokontrol and Elemer manufacturers will soon replace obsolete pointer devices. These are electronic indicating modern intelligent contact pressure gauges with both discrete and analog output (4-20mA).
They are already in high demand on the market. Therefore, no matter what characteristics the device has, sooner or later a new one will appear, more convenient and useful in work.
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