What is the difference between an ammonia pressure gauge and a stainless steel pressure gauge

Ammonia pressure gauge:

Ammonia pressure gauge refers to a direct indicator pressure gauge used to measure ammonia gas or liquid ammonia.

The elastic element (referring to the spring tube) of the ammonia pressure gauge is made of materials that can resist ammonia corrosion, and other parts should be able to resist ammonia corrosion or be plated with an ammonia-resistant coating.

A yellow horizontal line should be drawn under the instrument name on the dial of the ammonia pressure gauge.

Stainless steel pressure gauge:

The stainless steel pressure gauge uses direct contact joints and pressure-sensitive component materials, using icr18Ni9T, Ocr18Ni12Mo2Ti, and sus316. The structure is fully sealed. The stainless steel pressure gauge has strong resistance to corrosion of the measured medium and environmental corrosion. Stainless steel pressure gauges are suitable for highly corrosive media suitable for stainless steel component detection and harsh external corrosive environments. Stainless steel pressure gauges are widely used in petroleum, chemical, metallurgical and other industries.

Selection of stainless steel pressure gauge

1. Selection of wetted material for stainless steel pressure gauge:

At present, the commonly used stainless steel materials for wetted parts are as follows, and users can choose appropriate materials according to the corrosiveness of the measured medium.

(304, 316, 316L, Monel, titanium alloy)

2. Determination of accuracy level:

The accuracy grade of the stainless steel pressure gauge reflects the accuracy of how close the indicated value is to the true value when the gauge being checked is compared with the standard instrument.

The accuracy of the stainless steel pressure gauge = the absolute value of the maximum basic error of the tested gauge ÷ the upper limit of the measurement ratio × 100%.

The commonly used precision grade series of stainless steel pressure gauges are: 1.0 grade; 1.6 grade; 2.5 grade.

How to choose the accuracy grade of stainless steel pressure gauge

a. Habits or empirical methods:

Generally speaking, the accuracy level of pressure gauges is related to the outer diameter of the case. Pressure gauges with outer diameters of 50mm and 60mm generally have an accuracy of 2.5. Pressure gauges with an outer diameter of 100mm and 150mm generally have an accuracy of 1.6. class. Since stainless steel pressure gauges are mostly working gauges, the accuracy requirements of the pressure gauge are not high, so if the outer diameter of the pressure gauge is selected, the accuracy of the pressure gauge is basically determined.

b. Calculation method:

According to the requirements of production technology, economy and practicality, detection methods, etc., the accuracy level is calculated and determined according to the allowable error required by the minimum value of the measured pressure.

Accuracy level = absolute value of allowable error ÷ upper limit of measurement × 100%

3. Selection of range:

The range series of stainless steel pressure gauges are:

-0.1~0; -0.1~0.06; -0.1~0.15; -0.1~0.3; -0.1~0.5; -0.1~0.9; -0.1~1.5; -0.1~2.4; 0~0.16; 0~0.25; 0~ 0.4;0~0.6;0~1.0;0~1.6;0~2.5;0~4.0;0~6.0;0~10;0~16;0~25;0~40;0~60;0~100; 0~160Mpa.

Principle of range selection:

1. When measuring stable pressure, the maximum working pressure should not exceed 2/3 of the range.

2. When measuring the pulsating pressure, the maximum working pressure should not exceed 1/2 of the range

3. When measuring high pressure, the maximum working pressure should not exceed 3/5 of the range

4. For the pressure gauge below 1/3 of the range limit, due to the relatively large relative error, in order to ensure the accuracy of the measurement, the minimum working pressure should not be less than 1/3 of the range.

According to the above principles, after calculating a value based on the measured maximum pressure, select a value slightly larger than this value from the pressure gauge range series to be the selected range.

4. Dial diameter:

Shell nominal diameter (mm) series: Φ50, Φ60, Φ75, Φ100, Φ150;

In order to facilitate the operator to read the pressure gauge value, in general, the dial diameter of the pressure gauge should not be too small. If the stainless steel pressure gauge is installed higher or far away from the measuring site, it is best to choose a pressure gauge with a larger diameter.

5. Confirm the installation form:

The installation forms of stainless steel pressure gauges are as follows:

1) Direct installation with no edge in radial direction: Use the threaded interface of the meter to install directly on the equipment.

2) Installation on the rear side of the radial belt: use the rear side of the meter to fix it on the wall or equipment panel with bolts.

3) Radial belt front installation: Use the front of the meter to fix it on the equipment panel with bolts, and the meter is buried behind the panel.

4) Axial without edge direct installation: Use the threaded interface of the meter to directly install on the equipment.

5) Axial belt front installation: use the front of the meter to fix it on the equipment panel with bolts, and the meter is buried behind the panel.

6) Clamp installation: Use the clamp of the meter to fix it on the panel of the equipment, and the meter is buried behind the panel.

Users can choose a method suitable for equipment installation according to the above six installation forms.

6. Determination of thread specifications:

Stainless steel pressure gauge connection thread specifications mainly include: M14*1.5, M20*1.5, G1/4, G1/2, G3/8, NPT1/2, etc., and can also be produced according to user requirements.

7. Instructions for use and ordering:

1) When measuring the pressure of strong corrosive media or easy to crystallize and solid particles, stainless steel pressure gauges cannot be used. Corrosion-resistant diaphragm pressure gauges can be used.

2) Please specify the name, model, measuring range, accuracy grade and interface thread when ordering. Please specify for special requirements.