Sino-Inst offers a variety of Diaphragm Seal Pressure Transmitters for industrial pressure measurement. If you have any questions, please contact our sales engineers.

What are the application considerations for diaphragm seals?

The biggest advantage of the diaphragm pressure transmitter is that different diaphragm materials can be selected. According to different corrosion, media to achieve the best corrosion resistance. The commonly used diaphragm materials are SUS316L stainless steel. Tantalum, Hastelloy, Monel, Pure titanium, F4, etc. 

When choosing a diaphragm pressure transmitter, in addition to the correct choice of structure and range, the more important thing is to choose the material. The so-called reasonable is to consider its corrosion resistance, but also to consider the economy. For example, the corrosion resistance of the tantalum diaphragm and Hastelloy is excellent, but it is expensive. Only used in environments with high corrosivity and other cheap materials are not suitable.

The following table introduces several common corrosion-resistant materials that can be selected for corrosion media. For your reference.

Corrosive medium	Tin bronze (QSn6.5-0.4)	SUS316	Pure tantalum (Ta)	Monel (Ni70Cu30)	Hastelloy (HC)	Polytetrafluoroethylene (F4)
Sulfuric acid (H2SO4)	V	△	○	V	V	V
Nitric acid (HNO3)	╳	V	○	╳	V	V
Hydrochloric acid (HCI)	△	╳	○	╳	V	V
Phosphoric acid (H3PO4)	V	V	○	V	V	V
Acetic acid (CH3COOH)	V	V	○	V	○	V
Caustic soda (NaOH)	△	○	△	○	○	V
Soda ash (Na2CO3)	○	○	○	○	V	V
Baking soda (NaHCO3)	V	○	○	○	○	V
Chlorine (CI)	Dry: V	Dry: V	○	Dry: V	V	V
	Wet: ╳	Wet: ╳	Wet: ╳
Bromine (Br2)	Dry: △	Dry: ╳	○	Dry: ○	○	V
	Wet: ╳	Wet: △	Wet: ╳
Ammonia (NH3)	╳	V	╳	╳	○	V
Seawater (30% NaCI)	V	V	○	○	○	V

Extended reading: Common Pressure Sensor Applications

What is diaphragm seal pressure transmitter?

The diaphragm seal pressure transmitter is the flange type pressure transmitter. This type of pressure transmitter, assembling diaphragm seals to field transmitters for the purpose of measuring pressure, differential pressure, level, and flow.

What is a diaphragm seal?

A diaphragm seal has two primary tasks:

1. Separation of the measuring instrument from the process medium
2. Transfer of the pressure to the measuring instrument

You may like: Diaphragm pressure gauge

What is remote seal?

The remote seal is used to prevent the medium in the pipeline from directly entering the pressure sensor assembly in the pressure transmitter. It is connected to the transmitter by a capillary filled with fluid. As a result, they’re often used in refining, petrochemical, and chemical plants.

Extended reading: SI-703 Flush Diaphragm Pressure Sensor

What are the advantages of diaphragm seals?

Diaphragm seals offer the advantage that the “contact surface” between pressure medium and diaphragm is relatively large. Thus ensuring accurate pressure measurement, especially for very low pressures (< 600m bar). Furthermore, they can be easily dismounted, e.g. for cleaning or calibration purposes.

How do diaphragm seals work?

Basically, diaphragm seals are used in all pressure measurement processes to avoid direct contact between the measuring instrument and the medium during this process. In addition, if the measuring point cannot be installed or read because the measuring point is located in a hard-to-reach location, a diaphragm seal can also be used. In both cases, the applied pressure is transferred to the measuring instrument through the system fill fluid in the diaphragm seal housing.
The diaphragm of the seal can be made of different materials, such as stainless steel, Hastelloy, Monel, or tantalum. In addition, coatings with ECTFE, PFA, or gold can also be used.

We can provide the best diaphragm seal design, materials, system fill fluid, and accessories for each application. The combined configuration of the pressure measuring instrument and the diaphragm seal is mainly determined by the special application conditions of the diaphragm sealing system.

How does a diaphragm pressure sensor work?

When the diaphragm seal pressure transmitter is working, the high and low-pressure side isolation diaphragms and the filling liquid transfer the process pressure to the center filling liquid. The filling fluid in the center transmits the pressure to the sensing diaphragm in the center of the δ-chamber sensor. The sensing diaphragm is a tensioned elastic element and its displacement changes with the differential pressure. For GP gauge pressure transmitters, the atmospheric pressure is applied to the low-pressure side of the sensing diaphragm. AP absolute pressure transmitter, the low-pressure side always maintains a reference pressure. The maximum displacement of the sensing diaphragm is 0.004 inches (0.10 mm). The displacement is proportional to the pressure. The two capacitance fixed plates of the measuring diaphragm are linearly converted into a 2-wire current, voltage, or digital HART output signal of 4-20mADC by the amplifying circuit.

Extended reading: How to calibrate HART pressure transmitters

Rosemount 1199 Diaphragm Seal System

Rosemount 1199 remote transmission diaphragm system provides the world’s most extensive product variety and specifications to meet the requirements of various measurements and applications.

There are the following types of remote transmission differential pressure/level transmitters:
1) PFW flat type remote transmission device
2) RTW thread installation type remote transmission device
3) EFW inserted barrel remote transmission device
4) RFW flange mounted remote transmission device
5) SCW hygienic remote transmission device

The 1199 remote diaphragm can be assembled to Sino-Inst differential, gauge, and absolute pressure transmitters and liquid level transmitters.

We can learn more about the 1199 remote diaphragms.

Techincal Support

FAQ

Sino-Instrument is a pressure transmitters manufacturer in China.

We offer all types of Diaphragm Seal Pressure Transmitters. Like Direct Mounted, flange-mounted, single flange, double flange, Remote Diaphragm Seals, High Static, Digital Remote.

Most of our Diaphragm Seal Pressure Transmitters are used in oil, liquids, DP transmitter, flow measurement, level measurement (like the ultrasonic level measurement), density, and other process variables.

Diaphragm Seal Pressure Transmitters are generally available with three types of electrical output; millivolt, amplified voltage, and 4-20mA.

You can ensure product safety by selecting from certified suppliers, with ISO9001, ISO14001 certification. We will share more about instrument calibration, like the flow transmitter calibration.

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