SENSOR PRESSURE GAS

[marcos_chagas20]

Dear, I need a sensor that performs pressure measurement of liquefied petroleum gas (cooking gas) in Brazil Pressure range 300 kpa up to 700kpa What is the sensor? Who can help me ? Can I use the MPX5700AP ??

email: marcos.chagas2009@hotmail.com

tel,: 5541999131855

[marcos_chagas20]

Hello Lisette, 

We recommend using Parker O-Lube silicone grease or DMS-T46 or T51. This type of grease is used by most of our customers without problems.  What volume of silicone grease should I apply and how? Can you help me in this process of how to apply silicone grease to the sensor? Thank you very much.

[lisettelozano]

Hello Marcos,

Our pressure sensors were made to be used in clean dry air only. Any other type of media (including LPG) will affect long term reliability and sensor’s performance as explained previously. If our customers decide to use our pressure sensors in other types of media than clean dry air, they will take all risks and responsibilities about the device in their applications and performance, as well that they are urged to conduct their own in-house evaluations and characterizations to determine if our devices are suitable for use in their non-clean dry air environment.

Have a great day,

Paulina

[lisettelozano]

Hello Marcos,

Unfortunately, and as mentioned previously, we can’t recommend using the MPX5700AP for such application with direct contact with corrosive gases or liquid substances might affect the sensor’s performance. This will affect long term reliability and will end up damaging the sensor. We can guarantee the proper functionality of the device in direct contact with clean dry air only.

As mentioned in the AN3728 Media Compatibility for Pressure Sensors, when a corrosive is introduced to the sensor that is not compatible, it has the potential to dissolve, or be absorbed by the gel and corrupt the die surface or lead to wire-bond breakage.

Please also refer to the AN936 for mounting techniques. You may also find useful the application notes  AN1950 for water level monitoring and AN1516 for liquid level control.

Again, NXP does not recommend the usage of the MPX5700AP sensor in direct contact with corrosive gases or liquid substances.  

Have a great day,

Paulina

[marcos_chagas20]

Hello Lisette, 

Below is the history of liquefied petroleum gas, which I wish to measure through MPX5700AP. It is not corrosive. It is not liquid.  Gasoline (in Brazil) or liquefied petroleum gas, contrary to popular belief, is not corrosive, polluting or toxic. ... Upon being exposed, this pressure is reduced, and the gas mixture returns to the gas phase, which is then used as fuel.  Liquefied Petroleum Gases are organic compounds, called hydrocarbons, made up of Carbon and Hydrogen. In the composition the Liquefied Petroleum Gas enters hydrocarbons of which the main ones are butane, propane, isobutane, propene and butene. The cooking gas is mainly composed of the propane and butane gases, plus the addition of a sulfur compound to give the scent that serves as a warning. Cooking gas is LPG (Liquefied Petroleum Gas), but this acronym can also mean Pressurized Liquid Gas. As explained above, I understand that I could use the sensor without a problem of corrosion, and without risk of explosion. What do you think ??
Thank you.

[lisettelozano]

Hello Marcos,

The MPX5700AP can measure from 0 to 700kPa, but please take into consideration that all of our pressure sensors were designed and are warranted to be used in clean dry air only. We recommend you to check our application note AN3728 Media Compatibility for Pressure Sensors which mention more about the media evaluations and risks. Our media compatibility disclaimer suggests that our customers are responsible for determining media compatibility in other environments than clean dry air.

I hope this information can be helpful.

Have a great day,

Paulina

-------------------------------------------------------------------------------
Note:
- If this post answers your question, please click the "Mark Correct" button. Thank you!

- We are following threads for 7 weeks after the last post, later replies are ignored
Please open a new thread and refer to the closed one, if you have a related question at a later point in time.
-------------------------------------------------------------------------------

[marcos_chagas20]

Dear, Thank you very much for the clarification. If you use to measure the pressure of liquefied petroleum gas (cooking gas) the MPX5700AP sensor is at risk of exploding. Or will it only be oxidized and will not measure the pressure of liquefied petroleum gas ?? Thank you.

[lisettelozano]

Hello Marcos,

Our devices are not compatible with petroleum-based media as per can’t be in direct contact with any other media than clean dry air since this could damage the protective gel and this could lead to out of specifications that we guarantee in the datasheet and affects lifetime and reliability. If the sensor is exposed to different media, after some working hours will fail.

However, a possible solution to interact our pressure sensors with other media is mentioned in the AN3728 page 2 Figure 2. This is by separating the media from the sensor by a column of clean dry air. Also, we recommend you check our application note AN936 with some tips for mounting techniques.

You may find also interesting the following application notes for the use of these devices in a liquid environment AN1950 and AN1516. The gel coating on the die should not come in contact with moisture as when wet, the gel can swell and cause unreliable readings.  The gel must remain intact as it protects the active surface of the die and wire bonds from oxidation.

Another possible solution to use our sensors in applications with other media than dry air will be by protecting the pressure sensor with silicon grease. We would recommend to use Parker O-lube silicone grease or DMS-T46 or T51. This type of grease is used by most of our customer without problems. In fact, the basic recommendations are to use a silicone oil (or preferably grease) with high viscosity and high molecular weight. In terms of contaminants, the silicon grease must be free of halogenures (Cl content < 50 ppm) to reduce the risk of bond pad corrosion. On the other hand, don't forget that whatever the material you will use, as soon as you put something on our gel you have a high probability to see some offset drift. This is coming from additional mechanical stress and/or gel swelling. The amount of gel and global mechanical design are usually also part of the offset drift.

Protecting pressure sensors with silicon grease is definitely the best way to use our products in harsh media. We don't have so much experience in how to implement this solution 'industrially'. The grease fill is done under vacuum to avoid air bubbles. Usually, an offset calibration is necessary because the grease brings some mechanical stress that may shift the offset value. This solution was tested and seems conclusive.

Please take in consideration that if you decide to use our sensor in your application you may perform the validation in the different media before the final product and assume total liability. Also, use of the device in any non-clean dry air environment will result in the warranty being voided. The same is true when modifying a device by adding silicon grease.

I hope this information can be helpful.

Have a great day,

Paulina

[marcos_chagas20]

Paulina,
Your response was very helpful. Thank you very much for your commitment and response. It was very enlightening. But I need to know how to proceed with the application of Parker O-Lube silicone grease or DMS-T46 or T51. Using this silicone grease inside the MPX5700ap sensor what is the risk of explosion with contact of the liquefied petroleum gas ??  Why using this procedure loses the NXP warranty for MPX5700AP sensor ??

thank you