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세라믹 디젤 미립자 필터의 균열


EPOCH XT testing ceramic

Application
Detection of internal cracking in ceramic diesel particulate filters.

Background
The use of ceramic particulate filters is well established as a method for removing environmentally dangerous soot and similar particulates from diesel engine exhaust, especially for diesel engines used in trucks and buses. These filters have the form of large cylinders, approximately 100 mm to 300 mm (4 in. to 12 in.) in diameter and 150 mm to 350 mm (6 in. to 14 in.) high. They are commonly made of cordierite, silicon carbide, or ceramic in a fine honeycomb pattern. As the hot exhaust is forced through the porous filter under pressure, soot particles collect on the surfaces of the honeycomb channels where they then break down or oxidize due to heat.

These complex ceramic structures can potentially crack during manufacturing, handling, or in service, causing reduced performance or failure that can cause both environmental and engine damage. Ultrasonic testing can quickly and nondestructively detect internal cracking in both new and used ceramic filter elements. The technique usually requires access to only one end of the cylinder.

Equipment
This test can be performed with both conventional flaw detectors and phased array instruments Any of the Epoch-series flaw detectors (EPOCH LTCEPOCH 600, EPOCH 650 or Epoch 1000) can be used with a low frequency contact transducer such as an A601S-RB or V601-RB (500 KHz). The OmniScan SX can also be used with the aforementioned transducers. A soft polymer membrane on the face of the transducer is used to couple sound energy into the filter without the need for liquid couplants that could be difficult to remove. The Advanced Filter option (standard on the Epoch 1000) can be helpful for improving signal-to-noise when testing larger filters by improving the instrument's low frequency response. Phased array testing can be performed with the OmniScan or Epoch 1000 and 1.5 MHz probes such as the 1.5L16-A4.

Procedure
Using firm hand pressure, the transducer is coupled to the end of the filter. High frequency sound energy propagating as plate waves travels through the ceramic honeycomb, reflecting off the far end if there are no discontinuities. If there is a crack parallel to the end surface, an echo will be received ahead of the point on the display representing the far end of the filter. If there is a crack that is tilted with respect to the ends, there may be no direct reflection but the echo from the far end will disappear.
 

In the example below representing a setup with a flaw detector and an A601S-SB transducer, the left screen image represents a typical echo pattern from an undamaged filter. The peaks at the left side of that waveform represent reverberations of the outgoing sound pulse, and the echo at the right side represents the reflection from the far end. There should be no significant echoes in the zone in the middle that is marked by the red gate. The right screen image represents an echo pattern from a filter that is cracked just past its midpoint. The backwall echo to the right of the gate has disappeared because sound energy is no longer reflecting from the far wall. The transducer can be moved to as many points as desired on the face of the filter to check for cracks at other locations.

Typical Backwall Echo from Good Filter

Typical Backwall Echo from Good Filter

Typical Midwall Echoes from Cracked Filter

Typical Midwall Echoes from Cracked Filter

The specific instrument setup for each type of filter should be established through the use of a known good setup standard that is used to optimize the echo from the far end. By identifying the echo pattern from a good filter and looking for changes, a trained operator can quickly and reliably identify echo variations that correspond to internal cracks.

Phased Array Testing

OmniScan Testing

Phased Array can offer cross-sectional imaging of filters from either sectorial or linear scans. This can aid operator visualization of flaws. Automated testing has also been implemented using larger array probes and specialized fixturing.

Olympus IMS

이 애플리케이션에 사용되는 제품
OmniScan ™ X3 시리즈의 모든 결함 탐상기는 완전한 위상 배열 툴박스입니다. 혁신적인 TFM 및 고급 PA 기능은 강력한 소프트웨어 도구와 간단한 워크 플로우로 생산성을 향상시키는 동시에 결함을 확실하게 식별하는 데 도움이됩니다.
옴니스캔 PA는 수동 및 자동화 위상 배열 검사를 수행합니다. 모든 기능을 갖춘 A-스캔, B-스캔, S-스캔 및 C-스캔 디스플레이, 고급 실시간 데이터 처리를 제공합니다. 16:128, 16:16M, 16:64M, 32:32 및 32:128 요소로 구성 가능.
단일 그룹인 경량 옴니스캔 SX는 읽기 쉬운 8.4인치(21.3cm) 터치 스크린을 갖추고 있으며, 비용 효율적인 솔루션을 제공합니다. 옴니스캔 SX는 SX PA와 SX UT의 두 가지 모델로 제공됩니다. SX PA는 UT 전용 SX UT와 마찬가지로 P/E, P-C 또는 TOFD 검사를 위한 재래식 UT 채널을 장착한 16:64PR 장치입니다.
옴니스캔 MX2는 이제 UT 채널이 있는 새로운 위상 배열 모듈(PA2), TOFD(회절 비행 시간)에 사용할 수 있는 새로운 2채널 재래식 초음파 모듈(UT2) 및 성공적인 옴니스캔 MX2 플랫폼의 기능을 확장하는 새로운 소프트웨어 프로그램을 제공합니다.
EPOCH 650은 다양한 응용 분야에 대한 우수한 검사 성능과 유용성을 갖춘 재래식 초음파 결함 검출기입니다. 이 직관적이고 견고한 장비는 인기 있는 EPOCH 600 결함 탐상기 후속작이며 추가 기능을 갖추고 있습니다.
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