HG/T 20510-2000 Instrument air supply design regulations (with clause explanation)
Some standard content:
Industry Standard of the People's Republic of China
Design Code for Instrument Air Supply System
Design Code for Instrument Air Supply SystemHG/T20510-2000
Main Editor: China Huatai Engineering Corporation
Approving Department: State Petroleum and Chemical Industry BureauImplementation Date: June 1, 2000
National Chemical Engineering Construction Standard Editing Center (formerly the Engineering Construction Standard Editing Center of the Ministry of Chemical Industry) 2001 Beijing
1 General Provisions
1.0.1 This regulation applies to the air supply design of measuring and control instruments in chemical plants. 1.0.2 The load of the instrument air supply system includes pneumatic instruments such as indicators, recorders, analyzers, signal converters, gas circuit solenoid valves, relays, transmitters, electric valve positioners, actuators, and air level gauges, air blowing method measurement air, positive pressure explosion-proof ventilation air, instrument repair workshop pneumatic instrument commissioning and maintenance air, instrument purge air, etc. 1.0.3 The instrument air source generally uses clean, dry compressed air. When necessary, nitrogen can be used as a temporary backup air source.
: 1.0.4 When implementing this regulation, it should also comply with the provisions of the relevant national standards in force. 195
Gas source quality requirements
2.0.1 The dew point of the gas source operating (online) pressure of the gas supply system should be at least 10℃ lower than the working environment or the local annual (seasonal) extreme minimum temperature in history. See Figure 2.0.1 for dew point conversion. 55
Dew point ℃ under atmospheric pressure
Dew point conversion chart
2.0.2 The selection of the inhalation position of the instrument air source should avoid inhaling flammable, explosive, toxic and corrosive gases (or steam). Industrial dust and atmospheric dust should also be avoided. 196
2.0.3 The gas source used for instrument air supply must be purified. After the purification device, at the outlet of the filter, the instrument air is required to have a dust particle size of no more than 3um. The dust content should be less than 1mg/m. 2.0.4 In the design of the instrument air source device, it is advisable to use an oil-free lubricated air compressor. The oil content in the instrument air sent by the air source device should be less than 10mg/m (8ppm (W)). 2.0.5 When an oil-lubricated air compressor is selected or the process compressed air source is directly used as the instrument air source, a high-efficiency oil remover must be equipped to control the oil content in the compressed air below the specified value, and corresponding filtering, drying devices and spare storage tanks must be equipped.
Air source device
Capacity of air source device
3.1.1 The design capacity of the air source device, that is, the gas production, should meet the needs of the gas-using instrument load explained in 1.0.2. The gas used for purging, pressurizing and replacing process pipelines and equipment is a non-instrument gas load and should not be supplied from this. 3.1.2 The total gas consumption of the instrument determines the design capacity of the gas source device. The total gas consumption of the instrument should be calculated in a summary manner.
You can also use a variety of simple methods to estimate the total gas consumption of the instrument, namely: 1
Summarize by the number of control valves, the gas consumption of each control valve is 1~2Nm*/h; the gas consumption of each pneumatic instrument in the control room is 0.5~1Nm2/h; the gas consumption of each pneumatic instrument on site is 1.0Nm/h; the number of air changes per hour for positive pressure ventilation explosion-proof cabinets is greater than 6 times. When calculating the gas consumption, this regulation refers to the standard state (101.33kPa, 0℃), but most of the instrument manuals refer to the operating state (gas supply pressure 140kPa, 20℃), and it must be converted at this time: Q=1.54Q.
Where Q is the gas consumption under the standard state, Nm/h; Q. - Gas consumption under the operating state, m/h. The capacity of the instrument gas source device is calculated according to formula (3.1.3): Q, = Q. [2 + (0. 1 ~ 0.3)]
Wherein, Q is the designed calculated capacity of the gas source device, Nm/h; Q is the total gas consumption of various instruments, Nm/h;
is the leakage coefficient of the gas supply network system.
3.2 Delivery pressure of the gas source device
According to the selection requirements of the pneumatic instrument in the design, the available gas source device limit pressure range is divided into the following 3.2.1
two levels:
500 ~ 800kPa (G)
300 ~ 500kPa (G)
The upper limit of the pressure is the delivery pressure of the gas source device under normal operating conditions. The specified lower limit of the pressure is the lowest pressure delivered by the gas source device. If it is lower than this specified value, there should be an audible and visual alarm and it should be handled as soon as possible. Safe gas supply
3.3.1 The backup unit gas supply is the main measure for safe gas supply. Once the working unit fails or stops working, the backup unit should be started and put into operation immediately. 3.3.2 For large-scale equipment or gas supply systems with high reliability requirements, in addition to the backup unit as a safe gas supply, a second gas source can also be set up. The second gas source can be automatically or semi-automatically put into operation. When the second gas source is put into operation, there should be an audible and visual alarm signal.
If the second gas source is a nitrogen source, there should be no nitrogen accumulation at its leakage point or discharge point. 3.41
Determination of gas tank capacity
The gas source device should be equipped with a gas tank of sufficient capacity, and its volume is calculated according to formula (3.4.1): V = QstPo/ (Pi - P2)
- Tank volume, m;
Wherein V-
Q Gas source device gas supply design capacity, Nm/minPr--Normal operating pressure, kPa (A); P2--Minimum delivery pressure, kPa (A);
Po--Atmospheric pressure, usually Po=101.33, kPa (A);--Holding time, minutes min.
3.4.2 The holding time t should be determined according to the production scale, the complexity of the process flow and the design level of the safety interlock automatic protection system. If there are special requirements, the process professionals should propose a specific holding time t value; if there are no special requirements, the value can be taken within 5~20 minutes. 200
On-site instrument gas supply method
Single-line gas supply method
For gas supply points with dispersed layout or large fluctuation of gas consumption, single-line gas supply method should be adopted, as shown in Figure 4.1. 1
4.1.1. In order not to affect the gas consumption of adjacent loads, for gas consumption points with large fluctuation of gas consumption, the source should be taken from the gas source main pipe as much as possible.
Part number in the figure: 1 Gas source valve:
Filter;
3 Pressure reducing valve;
On-site pneumatic instrument.
Single-line gas supply piping system diagram
4.2 Branch-trunk gas supply
4.2.1For multiple instruments or densely arranged instruments, branch-trunk gas supply should be adopted, and the branch-trunk gas supply should be led to the air distributor or gas supply point. As shown in Figure 4.2.1. 201
Gas supply main pipe
Air distributor
Dry-branch gas supply system diagram
Ring gas supply
When the gas supply network supplies gas to the instruments of multiple devices, the gas supply network can be connected end to end to form a ring distribution pipe, as shown in Figure 4.3.1.
To area A
Gas source device
To area B
To area C
To area D
Ring gas supply piping system diagram
Gas supply to control room
Gas supply method
5.1.1 The total gas source of the control room should be installed in parallel with at least two or more groups of air filters and pressure reducing valves. When two groups are used, the capacity of each group is selected according to the total capacity; when three groups are used, the capacity of each group is selected according to 1/2 of the total capacity. See Figure 5.1.1 Piping diagram of the set valuer setting pressure reducing device. Figure 5.11 Piping diagram of the set valuer setting pressure reducing device Part numbers in the figure:
-pressure controller;
high-power safety valve;
-pneumatic set valuer;
high-power pressure reducing valve;
high-power air filter: www.bzxz.net
pressure gauge.
5.1.2 The control room should be equipped with monitoring and alarm instruments for the gas supply system. Usually there are pressure indicators and low-pressure alarms for the gas source main pipe.
5.1.3 If a second backup gas source is provided, the pressure indicator and low-pressure alarm for the second gas source should be provided. When the second gas source is put into operation, there should be sound and light signals. 5.1.4 A pressure controller and a safety discharge valve should be installed on the outlet side of the filter pressure reducing device. For a gas supply system with a gas supply pressure of 0.14MPa(G), the starting value is 0.16~0.2MPa(G). 203
5.2 Gas supply main pipe specifications
5.2.1 Gas supply main pipes are divided into two structural forms: integral and combined. If the main pipe is very long, it is more convenient to use a combined installation. The main pipe diameter is generally 40~50mm. The material is stainless steel and brass. When the main pipe is installed horizontally, its slope should be greater than 3/1000; and a drain valve should be installed at the lowest point on the downstream side. 5.3
Configuration of gas source valve
An instrument gas source valve should be installed on each gas supply branch. 5.3.2
The gas source valve should have a spare quantity of 10%~20%. 5.4
Piping behind the panel
The gas supply piping behind the panel should use 6×1 copper pipe or nylon single pipe. 6
Gas supply system pipeline
Pipeline laying
Gas supply pipeline should be laid overhead, not on the ground or underground. When laying the pipeline, avoid unsafe environments such as high temperature, 6.1.1
radioactive radiation, corrosion, strong vibration, and process pipelines or equipment material discharge ports. If it is difficult to avoid, appropriate measures should be taken to ensure personal and equipment safety. And meet the requirements of the "Instrument Piping and Wiring Design Regulations" (HG/T20512).
6.1.2 The laying of the main gas supply pipe and trunk pipe shall be designed and laid by the pipeline professionals according to the instrument gas supply conditions proposed by the automatic control professionals. When the gas source distributor is used, the gas source piping shall be laid to the air distributor by the pipeline professionals according to the requirements of the automatic control professionals.
Gas extraction on the pipeline
6.2.1 When the gas supply system needs to draw out the gas source from the main gas supply pipe or the pipe, the source extraction position shall be located above the horizontal pipeline, and according to the specific conditions of the engineering design, a gas source stop valve may be installed at the source extraction position. Whether to install a main valve on the trunk pipe shall be determined by the engineering design according to the specific conditions of the piping. 6.3 Sewage
6.3.1 When designing the piping of the gas supply system, sewage must be considered. Usually, a sewage valve is installed at the lowest point in a certain area where dirt is easy to accumulate.
6.4 Number of spare gas points
When designing the gas supply system, approximately 10%~20%6.4.17
of spare gas supply points should be reserved on the gas main, trunk or gas source distributor.
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