Time-Based Factory Efficiency Analysis | I.C. Engine Assembly Line

Cold test stations are commonly arranged as sequential processes along a complete engine production line. The production line consists of several stations for engine building purposes, and before the engine exits the production line it passes through different validation and testing stations, such as leak testing stations, piston protrusion stations (known as torque to turn stations), and cold test stations. Each of these stations has a sequence of operation that is performed automatically or semi-automatic with the support of an operator. The waiting time until the engine finishes the operation in one station is called “cycle time”. The longer the cycle time the less efficient the production line. Cold testing stations are considered the most complicated and time-consuming, yet important test stations for engine and powertrain development. The lengthy cycle time affects the overall efficiency of the production line. This paper investigates the problem of the cycle time difference between consequent stations and its effect on the overall efficiency of the factory. New techniques and operations research methods are introduced aiming to recover from such a manufacturing obstacle. This research is investigating the limitations of a manufacturing operation standpoint. Each test station is treated as a block that simulates the actual station, and the overall factory workflow is described. Time-based equations governing block time, idling time, and utilization of the system are introduced, and the factory efficiencies are calculated and compared. After identifying the problem, a practical solution is explained.

Volume of saline (0.9% NaCl) solution required to reach maximum peristaltic pressure in cadaveric intact jejunal specimens from dogs of various sizes

OBJECTIVE To compare the volume of saline (0.9% NaCl) solution required to reach a maximum intraluminal peristaltic pressure of 25 mm Hg in dogs of various sizes. SAMPLES 25 grossly normal jejunal segments from 6 canine cadavers < 20 kg (small dogs) and 25 segments from 5 cadavers ≥ 20 kg (large dogs). PROCEDURES Jejunal specimens were obtained within 1.5 hours after euthanasia. Harvested tissue was transected into 12-cm-long segments, mesentery was trimmed, and each segment was measured from the antimesenteric to mesenteric serosal edges. A 10-cm segment was isolated with Doyen forceps, securing a pressure sleeve within the lumen. Intraluminal saline was infused, and the volume was recorded when a pressure of > 25 mm Hg was achieved. Data were analyzed only from specimens in which the pressure remained between 24 and 26 mm Hg for > 5 seconds. RESULTS Mean ± SD intestinal measurement for large dogs (17.82 ± 1.44 mm) was greater than that for small dogs (12.38 ± 1.38 mm) as was the volume of saline solution infused (17.56 ± 7.17 mL vs 3.28 ± 1.41 mL, respectively). The volume infused increased by 1.31 mL (95% CI, 1.08 to 1.18) for every 1-mm increase in intestinal measurement and by 1.06 mL (95% CI, 1.052 to 1.068) for every 1-kg increase in body weight. CONCLUSIONS AND CLINICAL RELEVANCE The volume of saline solution used for intestinal leak testing should be determined on the basis of patient intestinal measurement or body weight. In vivo studies are necessary to establish the optimal volume for intestinal leak testing.

Leak-Testing of an Endoscopic Aerosol Box for Preventing SARS-CoV-2 Infection during Upper Gastrointestinal Endoscopy

Objective: The SARS-CoV-2 virus has infected many healthcare professionals. Endoscopy is an aerosol-generating procedure and the endoscopy team is at risk of exposure and infection. We describe the leak-testing of an aerosol box that uses a glove-covering for the endoscope.Materials and Methods: An endoscopic aerosol box with a glove-covering over the endoscope was made for gastroscopy, EUS and ERCP procedures and was tested for leakage of aerosol/airborne particles. Fine particulate matter (PM) from burnt incense sticks was used as a model for viral aerosol. The leakage from the box was measured by comparing readings from 2 PM light-scattering sensors, one placed inside the box and the other just outside the glove opening in a sealed container. Negative pressure conditions were also used to see if this had any effect on the leakage.Results: The concentration levels of the particulate matter differed with different negative pressure conditions and movement of the endoscope through the glove. Very little leakage was seen with the endoscope stationary even with no negative pressure, at 2.4%, 0.17% and 0.07% for PM1, PM2.5 and PM10, respectively. The maximum leakage was 14% for PM1, 8.7% for PM2.5 and 2.6% for PM10 in the moving-endoscope condition and no negative pressure. This reduced to 6.2%, 1.3%and 0.37% respectively when suction was applied at full strength (negative pressure of -0.05 bar). Conclusion: The glove covering significantly reduced the passage of particles. The particulate leak was seen most with the smallest particles and reached 14% for PM1 without negative pressure. This reduced to 6.2% with maximum negative pressure using the wall suction.

Leak Testing

While the exercise of pressurizing a piping system and checking for leaks is sometimes called pressure testing, the Code refers to it as leak testing. The main purpose of the test is to demonstrate that the piping can confine fluid without leaking. When the piping is leak tested at pressures above the design pressure, the test also demonstrates that the piping is strong enough to withstand the pressure. For large bore piping where the pipe wall thickness is close to the minimum required by the Code, being strong enough to withstand the pressure is an important test. For small bore piping that typically has a significant amount of extra pipe wall thickness, being strong enough is not in question. Making sure that the piping is leak free is important for all piping systems.