This document describes the WISE Explosion Proof Pressure Switch and Differential Pressure Switch (Models P953 and P970), providing instructions for proper and safe operation, technical specifications, and maintenance guidelines.

Function Description

The device is a pressure and differential switch equipped with a micro switch. It functions as a controller that monitors incoming pressure against a set value. Upon reaching the set pressure, it provides an On/Off signal for process control, abnormality notification, or warning. Its pressure-resistant and explosion-proof structure allows for installation in hazardous and explosion-proof areas. The operating principle involves a diaphragm as the pressure measuring element. Displacement of the diaphragm due to pressure changes is transmitted via a rod to a lever, which then opens or closes the micro switch.

Important Technical Specifications

Main Specifications

Liquid Contact Part: ASTM A279 316L, ASTM A240 316L
Case: Cast Aluminium (ASTM B179 SC102A)
Painting: Silver
Repeatability: ± 1.0% of FULL SCALE
Working Temperature:
- Ambient: -40 to 65 ℃
- Fluid: Max. 100 ℃
No. of Contact Points: 1 X SPDT or 2 X SPDT (Independent Operation)

Electrical Properties

Rated Voltage	Resistance Load	Inductive Load	Withstand Voltage	Insulation Resistance
125V AC 15A	125V AC 15A	125V AC 15A	1500V AC, 50/60Hz One Minute (Between Each Terminal and Case)	100MΩ or More on 500VDC (Between Each Terminal and Case)
250V AC 15A	250V AC 15A	250V AC 15A
30V DC 2A	30V DC 2A	30V DC 1A
125V DC 0.5A	125V DC 0.5A	125V DC 0.5A
30V DC 2A	30V DC 2A	30V DC 1A	(Between Each Terminal and Case)	More on 100MΩ (Between Each Terminal and Case)
125V DC 0.5A	125V DC 0.5A	125V DC 0.05A

Measuring Pressure Range and Folded Terminal Gap (P953)

Adjustable Setting Range (bar)	Adjustable Setting Range (mmH2O (bar))	Dead Band (One SPDT Set Point)	Dead Band (Two SPDT Set Point)	Proof Range	Burst Range (bar)	Burst Range (MPa)
0.003~0.07	0.3~7	Within 5% of Adjustable Range	Within 10% of Adjustable Range	150% of Adjustable Range	35	3.5
0.027~0.15	2.7~15
0.045~0.3	4.5~30
0.075~0.5	7.5~50
0.09~0.6	9~60
0.12~0.8	12~80
0.15~1	15~100
0.3~2	30~200
0.45~3	45~300
0.9~6	90~600				70	7
1.5~10	1.5~1 MPa
2.25~15	0.225~1.5 MPa
3~20	0.3~2 MPa				170	17
4.5~30	0.45~3 MPa
7.5~50	0.75~5 MPa				200	20
8.5~70	0.85~7 MPa
10.5~100	1.05~10 MPa				400	40
15.5~150	1.55~15 MPa
20~200	2~20 MPa

Differential Pressure Range and Folded Terminal Gap (P970)

Adjustable Setting Range (kPa)	Adjustable Setting Range (MPa)	Static Working Pressure (MPa)	Proof Pressure (MPa)
1~15		0.1	0.15
15~25		0.1	0.15
25~35		0.1	0.15
35~50		0.1	0.15
	0.05~0.2	2	15
	0.2~0.4	2	15
	0.4~0.7	2	15
	0.7~1.5	4	20

Explosion Proof Grade

Type: 953 SERIES
Explosionproof Grade: Ex d IIC T6
Working Temperature: Tamb=-40 ℃ to +65 ℃
Warning Notice: Do not open when an explosive atmosphere may be present!

Usage Features

Process Control: Ideal for process control, abnormality notification, or warning based on On/Off signals when a set pressure is reached.
Hazardous Area Installation: Designed with a pressure-resistant and explosion-proof structure for safe installation in hazardous areas.
Stable Operation: Features a micro switch with snap action for stable opening and closing.
Simultaneous Indication and Switching: Suitable for applications requiring both pressure indication and switching functions.
Installation Guidelines:
- Store in a dry place, free from moisture, vibration, dust, or corrosive gases.
- Avoid temperatures exceeding specified limits and direct sunlight.
- Protect against lightning or vapor.
- Mount firmly using M5 bolts for panel or wall installation, or secure fittings.
- Use a flexible tube for the impulse line to prevent excessive force on the pressure gauge.
- When connecting to piping, use a designated spanner and avoid turning the product case itself.
Wiring Guidelines:
- Avoid imposing excessive force on the casing.
- Use plastic insulated or cabtyre cables appropriate for the load.
- Ensure firm terminal connections using M4 solderless terminals.
- Verify contact type before wiring.
- For conduit type, use waterproof sealing fittings.
- For cable gland type, use waterproof cable glands.
- A ground wire of at least 0.7 sq is required.

Maintenance Features

Operating Pressure: Commercial pressure should be maintained below 75% of the maximum graduation.
Pressure Limits: Do not exceed the allowable pressure limit or apply sudden pressure surges or drops.
Overpressure Protection: If pulsation or impact pressure is a risk, install overpressure protection devices like dampeners or gauge protectors.
Lubrication: Do not grease the operating parts within the pressure gauge.
Regular Inspection: Conduct inspections every 6 to 12 months to check contact operation.
Troubleshooting: If the indication instrument shows a significant error, remove it for inspection. Potential causes include wear, corrosion, external shock, vibration, or part damage, requiring adjustment or replacement.
Electrical Considerations:
- Adhere to standard rated current specifications (Section 5.1). If equipped with special micro software, allow for inrush current.
- Micro switch contact resistance may increase over time, especially in Si environments where SiO2 deposits can form. Ensure ventilation or a clean environment.
- For control sequence input, use an AC 110/220V buffer relay between the contact and the sequence to prevent contact disorder.
Safety Precaution: Always shut off power before opening or closing the cover for repair or inspection. Malfunctioning of the switch could ignite explosive gases within the gauge.

Wise P953 - Internal Apparatus

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