Yokogawa has developed plugging diagnostics and impulse piping heating monitoring functions specifically for the EJX series pressure transmitters. This article provides a description of advanced diagnostic functions with digital communication over the FOUNDATION Fieldbus and HART protocols.

OOO Yokogawa Electric CIS, Moscow

Introduction

It is assumed that instrumentation should be equipped with diagnostic functions to prevent abnormal process conditions and, in addition, the possibility of their expansion should be provided. Diagnostic information based on various parameters of the physical process measured by the instruments and its further use allows the user to reduce the amount of routine maintenance and thus reduce maintenance costs. Instrumentation with advanced diagnostic functions enhances the control of process operations and reduces the cost of Maintenance (1).

Yokogawa's EJX series pressure transmitters diagnose plugging in the impulse piping used to transfer process pressure to the transmitter and monitor the condition of the impulse piping heating system at the connections to technological equipment. The first function, clogging detection in the impulse tubes, is based on the use of fluctuations in the pressure of the working medium that occur in the tubes. Another function, the control of the heating system of the impulse pipes, which is designed to prevent the medium in the pipes from cooling down, is based on the use of a temperature gradient corresponding to the thermal resistance inside the sensor. Unlike the self-diagnosis functions, these functions are referred to as the advanced diagnostic functions of the EJX series pressure transmitters. On fig. 1 shows the configuration of diagnostic functions.

Rice. one. Configuring Diagnostic Functions in EJX Series Instruments

In Yokogawa's dedicated technical reports (2), (3), experts can explore more detailed description the above functions and how they work.

Overview of Advanced Diagnostic Functions

Advanced diagnostic features for pressure transmitters in the EJX series, designed to measure differential, absolute, and overpressure, as well as temperatures, make it possible to detect abnormal process conditions by monitoring the state of the technological environment using special algorithms, which will be discussed later.

Blockage detection in impulse pipes

The pressure transmitters measure the pressure of the process fluid supplied to them through the impulse tubes. The impulse piping connecting the process outlets to the transmitter must accurately transmit process pressure. If, for example, gas accumulates in a liquid-filled tube during inflation or the channel becomes clogged, pressure fluctuations occur, it begins to be transmitted inaccurately, and the measurement error increases. So necessary condition accurate measurements is the possibility of using sensors with advanced functions for detecting clogging in the tubes by reducing the amplitude of pressure fluctuations when blocking impulse tubes, namely, by comparing the degree of attenuation of the amplitude of pressure fluctuations with the initial values ​​obtained by measuring pressure in normal conditions.

On fig. 2 shown typical installation impulse piping for the differential pressure transmitter and a schematic diagram showing the change in the amplitude of the pressure fluctuation under normal conditions and when blocked.

Rice. 2. Installation of impulse piping for the differential pressure transmitter and attenuation of the amplitude of pressure fluctuations

Monitoring the status of the impulse piping heating system

The desired temperature of the steam and heater, which maintains the temperature of the impulse tubes, is controlled by measuring the temperature of the flange, which is determined based on the temperatures of the capsule and sensor amplifier. On fig. 3 shows a typical design of the impulse tube heating system, consisting of a copper steam tube, an impulse tube and insulating material, and in fig. Figure 4 shows a graph from which the temperature of the flange can be estimated based on the temperatures of the capsule and amplifier.

Rice. 3. Impulse tube heating system

Rice. 4. Flange Temperature Estimation Based on Capsule and Amplifier Temperatures

Application of Advanced Diagnostic Functions in EJX Series Pressure Transmitters

EJX series pressure transmitters are capable of diagnosing blocked impulse piping on the side high pressure, on the side low pressure or on both sides. This is made possible by the use of a multi-parameter silicon resonant sensor that can simultaneously measure differential pressure, high-side static pressure, and low-side static pressure (4). Therefore, the pressure transmitters of the EJX series are designed not only for measuring differential pressure and level detection, but also for detecting clogging in impulse pipes on the pressure measuring side using the same measuring principle. With their help, you can control the temperature of the flange of any constructive form, since it is produced based on the temperatures of the capsule and amplifier.

Advanced pressure sensor diagnostics are available on all models that support FOUNDATION Fieldbus and HART digital communication protocols. In table. Table 1 lists the EJX series pressure transmitter models and clogging detection options for each model.

Table 1. EJX Series Models and Applicable Clog Detection Objects

In table. Table 2 shows the characteristics of sensors with advanced diagnostic functions for the two digital communication protocols FOUNDATION Fieldbus and HART. The difference is observed in the purpose of the diagnostic alarm outputs, the number of alarm settings, etc.

Table 2. Characteristics of advanced diagnostic functions

Advanced Diagnostic Data Processing

On fig. 5 shows the sequence of actions performed when processing advanced diagnostic data, and in table. 3 shows the output parameters related to the respective diagnostics.

Rice. 5. Advanced Diagnostic Algorithm

Table 3 Diagnostic related output

Yokogawa's EJX series pressure transmitters detect plugging in impulse piping by detecting fluctuations in differential pressure, high-side static pressure, and low-side static pressure every 100ms or 135ms, and then statistically process the results based on the data. . For each diagnostic period, the following are important characteristics: the ratio of fluctuations in the nominal and diagnosed values, as well as the degree of blocking, determined on the basis of the correlation of pressure fluctuations. Note that the diagnostic period can be changed by means of a corresponding setting.

By monitoring the condition of the impulse piping heating system at 1 second intervals, the flange temperature is determined based on the temperatures of the capsule and amplifier and compared with the upper and lower thresholds, an appropriate assessment is made.

While the system is evaluating all the parameters, the required diagnostic parameters are selected and the resulting diagnostic result is output according to the alarm output setting.

When using the FOUNDATION Fieldbus communication protocol, diagnostic alarms are displayed not only in the status output value, but also in the function block analog input (AI) output. When using the HART communication protocol, the available outputs are not only cutoff and fallback analog signal 4-20 mA, but also a contact output.

Below is a description of the basic procedures for diagnosing plugged impulse piping and monitoring the condition of the impulse piping heating system.

Algorithm for diagnosing blockage of impulse tubes

The main step in the process of diagnosing clogged impulse pipes is monitoring pressure fluctuations. Lockout is determined by comparing the pressure swing values ​​of the current process with the nominal value corresponding to the operating state pressure. Basically, at high differential and static pressures, the fluctuation values ​​are also high, so the blockage detection process is stable. However, if the level or pressure of a highly viscous process medium with a viscosity index greater than 10 cSt is being measured, or the medium being measured is a gas, then it must be taken into account that the pressure fluctuation values ​​should not be high so that measurement error does not occur.

Blockage diagnostics are performed in the following sequence: setting the nominal values, simulating the situation with confirmation of the clogging detection, and real-life blocking detection. Simulation of a tube blockage situation is performed using a three-valve manifold or shut-off valve mounted on the impulse tubes.

In this case, the nominal values ​​of pressure fluctuations are quite large. A minimum pressure fluctuation value limit must be selected to perform diagnostics. Diagnostics will only be possible if the pressure fluctuation values ​​exceed the set minimum limit.

The diagnostic function parameters are configured using the Integrated Device Management Software Package PRM (Plant Resource Manager) and Versatile Device Management Wizard FieldMate developed by Yokogawa (5), (6).

Algorithm for monitoring the state of the impulse tube heating system

Since the flange temperature is determined based on the temperatures of the capsule and sensor amplifier, it is necessary to determine the appropriate factor to calculate it.

To do this, before performing the diagnostic procedure, it is necessary to heat the flange and measure its temperature. After that, the received coefficient is set in the device, as well as the alarm thresholds for high and low temperatures.

Alert Selection Algorithm

On fig. 6 shows a diagram for selecting alarms for pressure sensors with the type of communication using the HART protocol. The results of the blockage diagnostics and the flange temperature error are stored in the Diag Error parameter, and the output and display of the results are determined by the Diag Option.

Rice. 6. Alarm (for digital HART communication)

When using the FOUNDATION Fieldbus communication protocol, the diagnostic results are contained in the DIAG_ERR parameter, and the output data is determined by the DIAG_OPTION parameter.

Graphical user interface (GUI) for advanced diagnostics

Device Type Manager (DTM) software FieldMate is equipped with a custom user interface, shown in fig. 7, with the help of which various parameters of the sensors are set and controlled. The GUI interface makes it easy to get a nominal value for diagnosing blockage and flange temperature coefficient, and makes it easy to select alarm protection.

Rice. 7. System interface example

The pressure fluctuation values ​​and the degree of blockage can be observed and controlled in the tabs of the windows (Device Viewer) of the FieldMate software. On fig. 8 shows examples of these tabs. Diagnostic data changes that occur when the valve is turned can be visualized during clogging modulation performed when setting up the blockage diagnostic.

Rice. eight. Examples of Diagnostic Information Screens and Changing Information in Device Viewer

Conclusion

Archiving of diagnostic information obtained as a result of using the devices described in the article and its further analysis allow for accurate diagnostics and control of technological processes. This is done by using EJX series pressure transmitters and Yokogawa's Integrated Device Management Software Package PRM (Plant Resource Manager).

Due to the recent increase in the volume of various operations of the technological process in production, instrumentation with advanced diagnostic functions is required to improve the functionality and accuracy of measurements. Yokogawa's products not only meet all of the above requirements, but also enable top-level solutions.

Teplopribor group of companies (GC) (Teplopribor, Prompribor, Teplokontrol, etc.)- these are devices and automation for measuring, controlling and regulating the parameters of technological processes (flow metering, heat control, heat metering, control of pressure, level, properties and concentration, etc.).

Products are shipped at the manufacturer's price as own production, and our partners - leading factories - manufacturers of instrumentation and control equipment, control equipment, systems and equipment for control technological processes- APCS (much is available in stock or can be manufactured and shipped as soon as possible).

Looped Perkins tube

Perkins tube is a steel loop impulse tube, designed for installation, protection of the device and selection of pressure of non-aggressive liquids, gases and steam. Perkins tube (loop impulse tube) is used for guard instrumentation (pressure gauge, sensor) from intense heat- overheating (by cooling the measured medium in the siphon), as well as to dampen water hammer(due to the compensating siphon loop, damping the pulsations of the water hammer). Perkins impulse tubes (straight and angled siphon elbows) are the most economical option for protecting and connecting pressure measuring instruments on all types of pipelines.

Perkins impulse loop tube cost depends on the material, design, thread type, etc.,
for example, the price of the basic version (straight, Steel 20, bottom for welding) - from 295 rubles *

Main Specifications of Perkens Loop Impulse Tubes

Design version:
- direct(for mounting on a horizontal pipeline)
- angular(for mounting on a vertical pipeline)
angular without a shoulder, with a shoulder in the direction of the loop or away from the loop.

Rated working pressure:
for St.20 up to 250bar (25MPa),
for 12X18H10T (stainless steel) up to 40 MPa.

Maximum working temperature up to 300C.

Diameter: Impulse tube 14x2mm, hinges usually 85mm (most common length 360mm).

Types of Perkins connection to the process / to the device:
- internal / external thread W-Z (nut/nipple)
- female / female thread W-W (nut / nut)
- for welding / thread (in / out)
Execution for welding is possible with reinforcement and without.

Thread type: pipe inch G1/2 or metric M20x1.5.

Material:
structural steel St.20 (painted or with anti-corrosion electroplated up to 200C), steel 09G2S or stainless steel 12X18H10T (up to 450C).

In the case when the temperature of the working medium exceeds 90 0 C, an impulse tube with a loop (siphon design) is used. Thanks to the use of a compensating loop, the devices are protected from pulsations of the measured medium, water hammer and overheating. Depending on the location of the pipeline, a straight or angular Perkins version is chosen.

Loop impulse (siphon) Perkins tubes are usually made of steels: St.20, 09G2S, 12X18H10T, 12X1MF, 10X17H13M2T. Options for connecting to the device: fitting / nut with various threads - M20x1.5; G1/2; NPT1/2; K1/2; R1/2 and others. Options for connection to the process: for welding, reinforcement for welding, fitting/nut with various threads — M20x1.5; G1/2; NPT1/2; K1/2; R1/2 and others.

The efficiency of using a siphon device to control steam pressure is ensured by the effect of condensation of cooled steam in the kinks of the siphon.

Additional Information

Selective pressure device- this is a mounting element with the help of which the connection of instrumentation and automation equipment to pipelines, gas ducts, air ducts, process equipment, communications, etc. is carried out.
The simplest pressure selection device is the assembly of a siphon impulse tube with a shut-off device (cock, valve or valve).

Auxiliary equipment and protective and mounting fittings for installation, proper operation and protection of pressure control devices (pressure gauges, vacuum gauges, pressure vacuum gauges, sensors-relays, converters, etc.).

Mounting and supply fittings for pressure gauges, vacuum gauges and combined pressure and vacuum gauges:
1. Mounting fittings: selective devices - OS: bosses (weld-in adapters), straight and angled bends (including Perkens loop tubes) or copper and steel impulse tubes (lines).
2. Pressure gauge valves (up to 16/25 bar) or valves/valve blocks (over 2.5 MPa), pressure and safety valves.
3. Gaskets / seals copper, fluoroplastic, paranitic, rubber, etc.
4. Adapters M20/12 - G1/2/G1/4 (external/internal thread), couplings, barrels (material steel, brass, stainless steel).
5. KMCH - a set of mounting parts (usually: mounting flange (rear or front), bracket, bracket, fasteners).
6. HRC - a set of connecting parts (usually: flanges, fittings, nuts-M20x1.5 / G1 / 2, nipples (steel, stainless steel), fasteners, seals).

Protective separation devices:
1. Protective devices: dampers (absorbers of water hammer pulsations, yuza), coolers (radiators), membrane separators RM, capillary lines and connecting sleeves mod-55004.
2. Protective covers. Installation in special insulating fireproof moisture-proof cabinets and covers, the use of special heaters.

Spare Parts and Accessories - Spare Parts:
1. Indicator of working pressure (arrow-yabednik).
2. Liquids for filling the “Device-Separator Membrane-Connecting Sleeve” system, the type of liquid is selected depending on the temperature and type of medium being controlled (for example, for food production etc.)..
3. Spare parts and accessories - spare parts and accessories (mechanisms, arrows, dial / scales, etc.).

Copyright © 2015-2018 all rights and text reserved,
the text is encrypted, copying is tracked and prosecuted; auth.-FMV ;.
Official website of Teplopribor Group of Companies - production and sale of instrumentation and automation: Pressure control devices (pressure transducers (sensors), relays, pressure gauges, differential pressure gauges, pressure gauges), additional equipment and mounting and shut-off valves for them (selective devices, impulse tubes (lines), taps / valves, etc.). See technical description/characteristics, price list (wholesale price), catalogue, order form (how to choose, order and buy) selected devices, etc. Perkens at the manufacturer's price, check the availability in a warehouse in Moscow or the production time. Delivery / shipment of shopping malls (Business Lines and others) throughout the territory of the Russian Federation.

Price: from 295 rubles.

Availability in stock: In stock*

* At the warehouse in Moscow, loop (siphon) Perkins impulse tubes (straight or angled) are available only in the standard (basic) version; in the absence of special designs, the planned production time will be 10-15 working days, or inexpensive analogues available in stock can be offered.

All prices for loop (siphon) Perkins impulse tubes (straight or angled) are indicated in rubles (see the general price list) excluding tax (VAT = 18%), additional cost. options and equipment, packaging, shipping and / or delivery costs, based on a wholesale order (for large wholesale lots and for project orders, the price is formed individually, based on the size of the lot, the agreements reached and the address of the object).

ATTENTION! Be careful when choosing a supplier - on Russian market shut-off and control valves and selected devices pressure, there are cheap low-quality Perkins loop impulse tubes: analogues, fakes and illiquid assets, devoid of proper service, guarantees; therefore, perhaps even having a lower price than original products.

Auxiliary fittings for pressure measuring instruments include such a device as a Perkins tube, otherwise called an impulse tube for a pressure gauge or a loop tube. It is designed to reliably protect the device from possible fluctuations in the measurement environment and from excessive heating. With the help of a tube, the temperature at the point of contact of the device with the system decreases. In addition, the tube serves as an adapter from the pressure gauge to the pipeline.

Condensate accumulates in the cavity of the impulse tube, preventing the measured high-temperature medium from entering the middle of the pressure gauge. When putting the line into operation, it is necessary to make sure that there is coolant in the steel tube.

The Perkins loop tube is used in the measurement of liquids and gaseous substances, which are not strong reagents. In this capacity and as an intermediary between devices and pipelines, the impulse tube is the most economically profitable option connections. The operation of such a tube can extend the life of the measuring instrument for many years. The best way to connect this type of fitting to the pipeline system is the use of a threaded connection. In some cases, the connection is carried out by welding. Impulse tubes are made from various grades of stainless steel. If it becomes necessary to install pressure sensors, then Perkins copper tubes are used for their installation.

The impulse tube, which has an angled design, is used to install a measuring device on it and connect it to impulse systems. Sometimes these tubes are made of brass. Straight loop tubes are used in the same cases. The general purpose of this additional equipment consists in damping oscillations and pulsations in the medium being measured and preventing pressure gauge heating.

On the pages of the Soyuzpribor LLC online store you will find pressure sampling devices, connecting sleeves, various adapters for pressure gauges, frames, dampers, bosses and other types of additional equipment.

Connecting sleeve

To create normal temperature conditions, the connection of the diaphragm seal with measuring instrument must be carried out either through a connecting sleeve or through a supply pipe, which is installed by the user between the pressure tap and the separator.

Pneumatic measuring pressure transducers GSP are always connected to the separator by means of a sleeve.

Displacement is allowed when mounting a separator with a connecting sleeve in height, while taking into account the installation error of the measuring device with an upper measurement limit of up to 1 MPa, determined by the hydraulic pressure of the separation liquid column in the connecting sleeve.

The standard connecting sleeve, model 55004, has a length of 2.5 meters when unfolded.

damping device

The damping device is resistant to ambient temperature from minus 55 to plus 70 °C, at relative humidity from 30 to 80% over the entire temperature range, and is also resistant to relative humidity of 95% at 35 °C (for U version) and relative humidity up to 100% at a temperature of 35 °C (for version T).

Valve block

Valve blocks BK are intended for connection to the lines with the measured medium of devices for measuring excess and vacuum pressure. Blocks allow you to cut off devices from the lines without depressurizing the medium being measured, check the zero value of the readings of the devices or purge the impulse lines. For oxygen pressure measurement lines, degreasing of parts in contact with the measured medium is carried out and the designation “K” is put.

Adapters and couplings (bosses)

Coupling and adapter for pressure gauges or thermometers are connecting (connecting) fittings used in systems (pipelines) for transportation gaseous media and liquids of low viscosity and non-crystallizing character. In essence, these products are additional (auxiliary) equipment.

The impulse tube is used for pressure relief, connecting impulse lines to flow and pressure regulators. In addition, this is another inexpensive options solutions for high medium temperatures. Each meter of impulse tube lowers the temperature of the medium by about 80 degrees. Usually steel or copper impulse tubes are used. One end of the impulse tube, connected to the pressure source, has the most convenient thread for mounting G1/2, and the other end, connected to the transmitter or regulator, has a thread that matches the thread of the equipment.

For example: for ease of installation of pressure sensors, the AQUA-KIP company offers an impulse tube (copper) with threaded internal and external connections any length. Copper tube withstands pressure up to 87 bar and at the same time easily bends, which allows you to effortlessly and additional tool lay it in place from the pressure tap to the device.

Specifications:

Copper tube: 10x1

Pressure (max): 87 bar (30 bar for threaded fittings)

Temperature: -25+210 C

Process and device connection thread: G1/2, G1/4, G3/8 (please specify internal or external on request)

The price is for impulse tube 1 meter long and with G1/2 thread.

Length: 1 meter