Ningbo Wanhua Polyurethanes Co. Ltd

Ningbo Wanhua Polyurethanes Co., Ltd is one of the fastest growing chemical companies for the production of polyurethanes in China. Established in 2005, Ningbo Wanhua currently produces 240,000 tons of diphenyl methane diisocyanate (MDI) annually. MDI is found in polyurethane products such as foam insulation, coatings, adhesives, and is widely used in construction, the automobile industry, and for the manufacturing of paint and footwear.

Ningbo Wanhua’s production process includes a series of advanced procedures involving continuous multi-level condensation reaction technology. Chlorobenzene is introduced as an additive in the company’s Aniline unit where the process of producing MDI takes place.

Chlorobenzene is a highly flammable, colorless liquid with an aromatic, almond-like odor. It does not occur naturally in the environment but is used in the manufacturing process.  It will partially dissolve in water, but readily evaporates into the air. Exposure to gas build-up can effect breathing and the central nervous system. Therefore, the volatile organic compound must be monitored closely due to its potential health and safety hazards.

 The original gas detection sensors were installed by an undisclosed company around the Aniline unit for LEL leak detection. Ningbo Wanhua officials soon decided that a higher level of protection was required to ensure personnel safety. The installed sensors could not detect in the ppm range; therefore, company officials deemed it necessary to upgrade the existing gas detection sensors with a more sensitive model with added features.

 Ningbo Wanhua’s requirements were for a high-performance, low maintenance, user-friendly system that accurately detects in the ppm range, with low drift and increased repeatability. A non-intrusive design with simple guided calibration, cost-effective pricing, durability, and longevity of the sensor life provided the added safety requirements for this application.

Following thorough investigation Ningbo Wanhua chose Detcon’s Model Series 700 sensors – a non-intrusive “Smart” sensor designed to detect and monitor a wide range gases – as its optimum solution.

Site engineer, Wang Chenfang selected a total of 20 sensors (10 Model PI-700s, and 10 Model DM-700s) to install strategically throughout the plant to provide a safe and productive operating environment for company personnel.

The Model PI-700 monitors VOC compound gases and has a range of 0-1ppm up to 0-5,000ppm.

The Model DM-700 monitors toxic gases and oxygen deficiency. The range for toxic gases is from 0-1ppm up to 0-10,000ppm, with ranges for oxygen measurement from 0-1% up to 0-25% by volume.

A primary feature of the Detcon Model Series 700 sensor is embedded intuitive software that easily guides the user through automatic calibration and configuration menus using a built in LED alphanumeric display. Chenfang said he personally likes the self-diagnostic features, which utilize a magnet to scroll through menus. This design, along with field replaceable sensor elements, met the company’s user-friendly requirements. 

“It is easy to conduct periodic maintenance and calibration. It is one of the simplest procedures,” Chenfang said. “We have managed to significantly cut down on man hours in the field trouble shooting for device errors.” 

Model 700 sensors are specifically designed for harsh and extreme locations. The superior level of environmental durability includes an electro-polished 316 stainless steel housing, multi-layered transient spike protection circuitry and 100% encapsulation of sensor electronics providing maximum protection from water and corrosion.

“The stainless steel transmitter housing is a plus point. I’m sure the effects of corrosion will be minimized and durability enhanced,” Chenfang said.

Detcon Model Series 700 is ATEX approved to II 2 G Ex d IIC area classification, is SIL 2 assessed, has the full CE Mark, and has North American approvals to Class 1, Div I, Groups B, C, D.