Inspection before the installation of vacuum pressure switches

The inspection of vacuum pressure switches before installation is a crucial step to ensure their normal operation and system safety. It requires detailed verification from multiple dimensions such as equipment integrity, compatibility, functional status, and environmental matching. The following are the specific inspection contents:

First, inspect the appearance and integrity of the equipment

Non-destructive inspection of appearance

Check whether there are cracks, deformations or scratches on the shell, especially on key parts such as the threaded interface and flange sealing surface. For instance, corrosion spots on stainless steel casings or dents and dents on aluminum alloy casings may lead to seal failure.

Seal integrity

Confirm that the O-rings, gaskets and other sealing parts are not aged, cracked or missing. If the seal is made of rubber, it is necessary to check whether its hardness meets the standard (such as Shore hardness 60±5).

Completeness of the attachment

Check whether the accessories such as the instruction manual, certificate of conformity, installation brackets and fixing bolts are complete. Some models may come with dedicated tools (such as pressure calibration adapters), which need to be confirmed together.

Second, technical parameters and compatibility verification

Range matching

Confirm that the switch range covers the system pressure range. For example, if the vacuum degree of the system needs to be controlled within -90 kpa to -10 kpa, the switch range should at least include -100 kpa to 0kPa.

Interface specification confirmation

Check whether the interface type (threaded, flange, quick insert, etc.) and size match the pipe. For example, G1/4 threads should use joints of the same specification, while flange connections need to verify the nominal diameter and pressure rating.

Verification of electrical parameters

Confirm that the parameters such as the voltage, current and contact capacity of the switch are compatible with the control system. For example, if the PLC output is DC24V, the switch needs to support this voltage and have sufficient contact capacity (such as AC250V/5A).

Verification of protection level

Select the protection level according to the installation environment. For example, a humid environment requires IP65 or above, and an explosive gas environment requires Ex d IIC T6 certification.

Third, functional pre-test

Mechanical action test

Verify whether the contacts of the switch can close/open normally when the set threshold (such as -80 kpa) is reached through manual pressurization or vacuuming equipment. For example, use a vacuum pump to evacuate air slowly and observe the changes in the indicator light or the signal of a multimeter.

Hysteresis test

Measure the pressure difference (hysteresis) when the switch operates and resets to ensure it meets the specifications (such as ±5kPa). Too little hysteresis may lead to frequent actions, while too much will affect the control accuracy.

Signal output verification

For electrical signal output type switches, it is necessary to connect an oscilloscope or data collector to check the linearity and stability of the output signal (such as 4-20mA). For example, within the range of -100 kpa to 0kPa, the output current should have a linear relationship with the pressure.

Fourth, environmental and installation condition inspection

Confirmation of installation location

Ensure that the installation location is convenient for operation and maintenance, and avoid high temperatures, strong vibrations or corrosive media. For example, at least 50mm of heat dissipation space should be reserved near the vacuum pump to avoid direct contact with the steam pipe.

Pipeline cleanliness inspection

Before installation, it is necessary to confirm that there are no impurities, oil stains or welding slag inside the pipeline. For high-precision applications (such as semiconductor equipment), it is recommended to use an endoscope to inspect the inner walls of the pipes.

Electrical connection preparation

Check whether the cable specifications meet the requirements (such as grounding of the shielding layer and sufficient wire diameter), and reserve sufficient length for later maintenance. For example, long-distance transmission requires the use of compensating cables or signal amplifiers.

Calibration and certification verification

Confirm whether the switch has undergone factory calibration and check the validity period of the calibration certificate. For high-reliability fields such as medical care and aviation, it is necessary to verify whether they comply with standards such as ISO 17025 or NADCAP.

Fifth, special inspection under special working conditions

Adaptability to corrosive media

If the medium contains acid, alkali or organic solvents, it is necessary to confirm whether the switch material (such as diaphragm, housing) is compatible. For instance, Hastelloy diaphragms are suitable for highly corrosive environments, while PTFE coatings can resist most chemical media.

Extreme temperature adaptability

Check whether the working temperature range of the switch covers the ambient temperature. For example, in a low-temperature environment of -40℃, it is necessary to confirm that the seals will not harden and fail. At a high temperature of 120℃, the temperature resistance performance of electronic components needs to be verified.

Explosion-proof and safety certification

In flammable and explosive places, it is necessary to confirm that the switch has explosion-proof certification (such as ATEX, IECEx), and check whether the grounding terminal meets the requirements. For example, the Ex d IIC T6 certification is applicable to the hydrogen environment.

Sixth, document and traceability management

Identification and traceability

Check whether the switch body is clearly marked with information such as model, range and serial number, and confirm that it is consistent with the certificate of conformity. For example, serial numbers can be used for subsequent quality traceability or maintenance record inquiries.

Verification of the operation manual

Confirm that the attached manual includes installation guidelines, wiring diagrams, troubleshooting, etc., and check whether the language version meets the requirements (such as bilingual in Chinese and English).

List of spare parts and vulnerable parts

If the project requires long-term maintenance, it is necessary to confirm the availability of spare parts (such as seals, contacts) and record the supplier information.