General information about solenoid valves. General information about solenoid valves Non-use of positioners in fast circuit valves
Our company uses quite a large number of pneumatic valves. Both conventional shut-off and regulating ones with positioners. Now we will talk about steam pipelines and pneumatic valves on them.
Before me, apparently, my predecessors installed “cheaper” valves, but at the moment I already want to switch to the “optimal” tariff. There were Chinese and Turkish valves installed during reconstruction by contractors. They have served their purpose, look bad, and constantly require replacement of seals, springs, etc.
In places where regulation was needed, positioning pneumatic valves from ASCO were installed everywhere. There will be a separate conversation about this company. In a nutshell, they did a cool thing by releasing a new line of positioners that are not compatible with old valves. The new valve was modified quite a bit to accommodate the new positioners, and as the old positioners failed, we simply had to change the entire valve. A very effective solution from a sales point of view, well done ASCO. But in my opinion, extracting money for new valves from an uncomprehending management is not a very entertaining activity, so ASCO has a big minus in mind.
Yesterday I stayed at work until one in the morning. This is Kip’s reality... This happened before and will happen later.
A call to the solenoid valves, although it was immediately clear that the cause of the installation’s inoperability was unlikely to be due to good Dutch solenoid valves with an Asco coil. We took it apart and looked - a suspicion crept in that the installation was not letting water in, not because of the valves, but because of banal scale.
And today I connected the frequency switch to the engine on a packaging machine. Otherwise, when they change products, everything sometimes flies very quickly. We screwed a box with a frequency converter - Mitsubishi, variable resistor and automatic machine - directly into the case. That's all happiness is. So we are slowly modernizing...
In the penultimate emergency situation, it seemed to me that one electromagnetic gas valve was acting up. Gas is a serious thing, so I immediately found and ordered a new one.
In an automated system, I actively use EM valves and gas pressure regulators (well, dampers with a drive) from the Belarusian company TermoBrest. Everything for them has already been welded and approved by the project... so there’s nothing to think about here - you need to take the same one. The only thing is that I took it to a lower operating pressure. Valves of the same type for different pressures differ quite significantly in price. Therefore, the supply here will cost a pretty penny, especially if more than one valve is needed.
Today I tried something like a non-working valve - but it seems to be working fine... So now I’m thinking - change it (which seems quite difficult - turn off the gas, stop production) or let a new one be in reserve...
216. To control work and ensure safe operating conditions, vessels, depending on their purpose, are equipped with:
1) shut-off or shut-off and control valves;
2) instruments for measuring pressure;
3) instruments for measuring temperature;
4) safety devices;
5) liquid level indicators.
217. Vessels equipped with quick-release lids have safety devices that prevent the vessel from being turned on under pressure if the lid is not completely closed and opening it when there is pressure in the vessel. Such vessels are also equipped with locks with a key mark.
218. Shut-off and shut-off and control valves are installed on fittings directly connected to the vessel, or on pipelines supplying the vessel and discharging the working medium from it. In the case of a series connection of several vessels, the installation of such fittings between them is determined by the project developer.
219. The fittings are marked as follows:
1) name or trademark of the manufacturer;
2) nominal bore, mm;
3) conditional pressure, MPa (working pressure and permissible temperature may be indicated);
5) brand of body material.
220. The quantity, type of fittings and installation locations are selected by the developer of the vessel project, based on specific operating conditions and these Requirements.
221. The direction of its rotation when opening or closing the valve is indicated on the flywheel of the shut-off valve.
222. Vessels for explosive, fire hazardous substances, substances of hazard classes 1 and 2 according to GOST 12.1.007, evaporators with fire or gas heating are equipped on the supply line from the pump or compressor with a check valve that is automatically closed by pressure from the vessel. A check valve is installed between the pump (compressor) and the shut-off valves of the vessel.
223. Fittings with a nominal bore of more than 20 mm, made of alloy steel or non-ferrous metals, have a passport of the established form, which contains data on the chemical composition, mechanical properties, heat treatment modes and the results of quality control of manufacturing using non-destructive methods.
Reinforcement that is marked, but does not have a passport, is used after an inspection of the reinforcement, testing and verification of the grade of material. In this case, the owner of the valve draws up a passport.
224. Each vessel and independent cavities with different pressures are equipped with direct-acting pressure gauges.
The pressure gauge is installed on the vessel fitting or pipeline between the vessel and the shut-off valve.
225. Pressure gauges have an accuracy class of at least: 2.5 - for a working pressure of a vessel up to 2.5 MPa (25 kgf/cm2), 1.5 - for a working pressure of a vessel above 2.5 MPa (25 kgf/cm2) .
226. The pressure gauge is selected with such a scale that the limit for measuring working pressure is in the second third of the scale.
227. On the pressure gauge scale, the owner of the vessel puts a red line indicating the operating pressure in the vessel. Instead of the red line, a metal plate painted red and tightly adjacent to the glass of the pressure gauge is attached to the pressure gauge body.
228. The pressure gauge is installed so that its readings are clearly visible to operating personnel.
229. The nominal diameter of the body of pressure gauges installed at a height of up to 2 m from the level of the observation platform is not less than 100 mm, at a height of 2 to 3 m it is less than 160 mm.
Installation of pressure gauges at a height of more than 3 m from the site level is not allowed.
230. A three-way valve or a device replacing it is installed between the pressure gauge and the vessel, allowing periodic checking of the pressure gauge using a control valve.
If necessary, the pressure gauge, depending on the operating conditions and properties of the medium located in the vessel, is equipped with either a siphon tube, or an oil buffer, or other devices that protect it from direct exposure to the medium and temperature and ensure its reliable operation.
231. On vessels operating under pressure above 2.5 MPa (25 kgf/cm 2) or at an ambient temperature above 250°C, with an explosive atmosphere or harmful substances of the 1st and 2nd hazard classes according to GOST 12.1.007 instead of a three-way valve, a separate fitting with a shut-off valve is installed to connect a second pressure gauge.
On stationary vessels, to check the pressure gauge, within the time limits established by these Requirements, by removing it from the vessel, the installation of a three-way valve or a device replacing it is not necessary.
On mobile vessels, the need to install a three-way valve is determined by the vessel design developer.
232. Pressure gauges and pipelines connecting them to the vessel are protected from freezing.
233. The pressure gauge is not allowed for use in cases where:
1) there is no seal or stamp indicating verification;
2) the verification period has expired;
3) when it is turned off, the needle does not return to the zero scale reading by an amount exceeding half the permissible error for this device;
4) the glass is broken or there is damage that affects the accuracy of its readings.
234. Inspection of pressure gauges with their sealing or branding is carried out at least once every 12 months. In addition, at least once every 6 months, the owner of the vessel carries out an additional check of the working pressure gauges with a control pressure gauge and records the results in the control check log. In the absence of a control pressure gauge, it is allowed to carry out an additional check with a proven working pressure gauge that has the same scale and accuracy class as the pressure gauge being tested.
The procedure and timing for checking the serviceability of pressure gauges by maintenance personnel during the operation of vessels are determined by the instructions for the operating mode and safe maintenance of vessels, approved by the management of the organization that owns the vessel.
235. Vessels operating at varying wall temperatures are equipped with instruments to control the speed and uniformity of heating along the length and height of the vessel and benchmarks to control thermal movements.
The need to equip vessels with the specified instruments and benchmarks, the permissible rate of heating and cooling of vessels are determined by the project developer and are indicated by the manufacturer in the vessel passport or in the operating manual.
236. Each vessel (cavity of a combined vessel) is equipped with safety devices against pressure increases above the permissible value.
237. The following are used as safety devices:
1) spring safety valves;
2) lever-weight safety valves;
3) pulse safety devices (hereinafter referred to as IPU), consisting of a main safety valve (hereinafter referred to as GPV) and a direct-acting pulse control valve (hereinafter referred to as IPV);
4) safety devices with degradable membranes (membrane safety devices (hereinafter referred to as MPU);
5) other devices, the use of which is agreed with the authorized body.
Installation of lever-weight valves on mobile vessels is not permitted.
238. The design of the spring valve eliminates the possibility of tightening the spring beyond the set value, and the spring is protected from unacceptable heating (cooling) and direct exposure to the working environment if it has a harmful effect on the spring material.
239. The design of the spring valve provides a device for checking the proper operation of the valve in operating condition by forcing it to open during operation.
It is allowed to install safety valves without a device for forced opening, if the latter is undesirable due to the properties of the medium (explosive, flammable, hazard classes 1 and 2 according to GOST 12.1.007) or according to the conditions of the technological process. In this case, valve operation is checked on stands.
240. If the operating pressure of the vessel is equal to or greater than the pressure of the supply source and the possibility of an increase in pressure from a chemical reaction or heating in the vessel is excluded, then installing a safety valve and pressure gauge on it is not necessary.
241. A vessel designed for a pressure less than the pressure of the source supplying it has an automatic reducing device on the supply pipeline with a pressure gauge and a safety device installed on the side of lower pressure after the reducing device.
If a bypass line is installed, it is equipped with a reducing device.
242. For a group of vessels operating at the same pressure, it is allowed to install one reducing device with a pressure gauge and a safety valve on the common supply pipeline up to the first branch to one of the vessels.
In this case, the installation of safety devices on the vessels themselves is not necessary if the possibility of pressure increase in them is excluded.
243. In the case when the automatic reducing device, due to the physical properties of the working medium, does not exclude excess pressure, the installation of a flow regulator is allowed. This provides protection against increased pressure.
244. The number of safety valves, their sizes and capacity are selected according to calculations so that a pressure does not create in the vessel that exceeds the design pressure by more than 0.05 MPa (0.5 kgf/cm 2) for vessels with a pressure of up to 0.3 MPa (3 kgf/cm2), by 15% for vessels with pressure from 0.3 to 6.0 MPa (from 3 to 60 kgf/cm2) and by 10% for vessels with pressure over 6.0 MPa ( 60 kgf/cm 2).
When safety valves are operating, the pressure in the vessel may be exceeded by no more than 25% of the operating pressure, provided that this excess is provided for by the design and is reflected in the vessel passport.
245. The capacity of the safety valve is determined in accordance with the ND.
246. The safety device is supplied by the manufacturer with a passport and instruction manual.
The passport, along with other information, indicates the valve flow coefficient for compressible and incompressible media and the area to which it is assigned.
247. Safety devices are installed on branch pipes or pipelines directly connected to the vessel.
The connecting pipelines of safety devices (supply, discharge and drainage) are protected from freezing of the working environment in them.
When installing several safety devices on one branch pipe (pipeline), the cross-sectional area of the branch pipe (pipeline) is at least 1.25 of the total cross-sectional area of the valves installed on it.
When determining the cross-section of connecting pipelines with a length of more than 1000 mm, the value of their resistance is taken into account.
Sampling of the working medium from the pipes (and in sections of connecting pipelines from the vessel to the valves) on which safety devices are installed is not allowed.
248. Safety devices are placed in places accessible for their maintenance.
249. Installation of shut-off valves between the vessel and the safety device, behind the safety device is not allowed.
250. The fittings in front of (behind) the safety device are installed subject to the installation of two safety devices and a lock that prevents them from being turned off simultaneously. In this case, each of them has the capacity provided for in paragraph 245 of these Requirements.
When installing a group of safety devices and fittings in front of (behind) them, the blocking is performed in such a way that in case of any valve shutdown option provided for in the design, the remaining switched on safety devices have a total capacity.
251. Discharge pipelines of safety devices and impulse lines of the IPU in places where condensate may accumulate are equipped with drainage devices to remove condensate.
The installation of shut-off devices or other fittings on drainage pipelines is not permitted. The media coming out of safety devices and drains is diverted to a safe place.
Discharged toxic, explosive and fire-hazardous process media are sent to closed systems for further disposal or to organized combustion systems.
252. Membrane safety devices are installed:
1) instead of lever-load and spring safety valves, when these valves are not advisable to use in the operating conditions of a particular environment due to their inertia or other reasons;
2) in front of safety valves in cases where safety valves do not operate reliably due to the harmful effects of the working environment (corrosion, erosion, polymerization, crystallization, sticking, freezing) or possible leaks through a closed valve of explosive and fire hazardous, toxic, environmentally harmful and the like substances. In this case, a device is provided to monitor the serviceability of the membrane;
3) in parallel with safety valves to increase the capacity of pressure relief systems;
4) on the outlet side of the safety valves to prevent harmful effects of working media from the discharge system and to eliminate the influence of back pressure fluctuations from this system on the accuracy of the safety valves.
The necessity and location of installation of membrane safety devices and their design are determined by the design organization.
253. Safety membranes are marked, and the marking does not affect the accuracy of operation of the membranes.
1) name (designation) or trademark of the manufacturer;
2) membrane batch number;
3) membrane type;
4) nominal diameter;
5) working diameter;
6) material;
7) minimum and maximum response pressure of membranes in a batch at a given temperature and at a temperature of 20°C.
Marking is applied along the edge annular section of the membranes, or the membranes are equipped with marking shanks (labels) attached to them.
254. The manufacturer issues a passport for each batch of membranes.
1) name and address of the manufacturer;
2) membrane batch number;
3) membrane type;
4) nominal diameter;
5) working diameter;
6) material;
7) minimum and maximum response pressure of membranes in a batch at a given temperature and at a temperature of 20°C;
8) the number of membranes in the batch;
9) name of the RD in accordance with which the membranes are manufactured;
10) name of the organization, according to the technical specifications (order) of which the membranes were manufactured;
11) warranty obligations of the manufacturer;
12) procedure for admitting membranes to operation;
13) sample membrane operation log.
The passport is signed by the head of the manufacturing organization and sealed.
The passport is accompanied by technical documentation for anti-vacuum supports, clamping and other elements, assembled with which the membranes of this batch are allowed for operation. Technical documentation is not attached in cases where the membranes are manufactured in relation to fastening units that the consumer already has.
255. Safety membranes are installed in the mounting units intended for them.
Work on assembly, installation and operation of membranes is carried out by specially trained personnel.
256. Foreign-made safety membranes manufactured by organizations not controlled by the territorial bodies of the authorized body are allowed for use only if there are special permits for the use of such membranes issued by the authorized body.
257. Membrane safety devices are placed in places that are open and accessible for inspection and installation (dismantling); connecting pipelines are protected from freezing of the working medium in them, and the devices are installed on branch pipes or pipelines directly connected to the vessel.
258. When installing a membrane safety device in series with a safety valve (in front of or behind the valve), the cavity between the membrane and the valve is connected by an outlet tube with a signal pressure gauge (to monitor the serviceability of the membranes).
259. It is allowed to install a switching device in front of membrane safety devices if there is a double number of membrane devices, while ensuring protection of the vessel from excess pressure in any position of the switching device.
260. The procedure and timing for checking the serviceability of safety devices, depending on the conditions of the technological process, are indicated in the operating instructions for safety devices, approved by the owner of the vessel in the prescribed manner.
The results of checking the serviceability of safety devices and information about their settings are recorded in the shift log of the vessels by the persons performing the specified operations.
261. If it is necessary to control the liquid level in vessels that have an interface between media, level indicators are used.
In addition to level indicators, sound, light and other alarms and level locks are installed on vessels.
262. Liquid level indicators are installed in accordance with the manufacturer's instructions, while ensuring good visibility of this level.
263. On vessels heated by flame or hot gases, in which the liquid level may drop below the permissible level, at least two direct-acting level indicators are installed.
264. The design, number and installation locations of level indicators are determined by the developer of the vessel project.
265. The permissible upper and lower levels are marked on each liquid level indicator.
266. The upper and lower permissible levels of liquid in the vessel are established by the project developer. The height of the transparent liquid level indicator is at least 25 mm, respectively, lower than the lower and higher than the upper permissible liquid levels.
If it is necessary to install several height indicators, they are placed so that they ensure continuity of liquid level readings.
267. Level indicators are equipped with fittings (taps and valves) for disconnecting them from the vessel and purging them with the removal of the working medium to a safe place.
268. When used in level indicators as a transparent element of glass or mica, a protective device is provided to protect personnel from injury when they rupture.
The most common mistakes in using measuring and control instruments in. You will learn how to properly use shut-off valves, expansion tanks, etc. How to properly install diaphragms for fluid flow and much more.
The 20 most common mistakes made today and every day for the last 40 years:
1. Pressure drops across control valves are not calculated.
17. Excessive use of integral component (integration time too short) in temperature control loops.
The integral component does not distinguish the direction of change of the variable and only produces an effect when the process variable crosses the reference line, just like a 90-year-old car driver.
18. Insufficient use of differential component in temperature and pH control loops.
Turn off the differential component in such circuits and be the first to feel the joyful excitement of acceleration. Just don't turn off the trends - let them show new heights reached by an exothermic reaction or a steep titration curve.
19. Failure to use positioners in fast circuit valves.
This was a fad in the days of analogue controllers, pneumatic positioners, and Nyquist plots of ideal amplifiers and valves. Real world problems begin immediately after bench settings - high friction in the seal, shaft torsion, plunger friction when pressed against the seat. Therefore, failure to use the functionality and diagnostic capabilities of digital smart positioners is a crime and should be punished by forced guessing of the actual stem (shaft) position for each valve without a positioner. I’m sure this person will later agree that there is something more fun for an engineer.
20. Use of condensate accumulator in large and critical installations.
If several million dollars are spent on an important plant, why not pay it back and spend a little more on automating a hundred-dollar condensate trap? Installing a small vessel, level sensor and regulator will cost several thousand dollars. But they often save on this. Who cares that when the condensate trap is closed, the liquid overflows it and enters the heat exchanger, reducing the heat transfer area? Who will notice that the condensate trap is left open and steam is blowing into the condensate collection system? Since you never know what's really going on inside that little devil, you can always blame the problems on some other device. Going on site to the condensate trap with a wrench gives them the opportunity to physically warm up. Don't forget to stock up on calming tablets, as periodic overflow of condensation and steam blowing can cause motion sickness. Technologists and operators will certainly get sick to their stomachs, looking at the trends in the operating modes of their columns, evaporators and reactors, for which the authorities regretted spending another