Cracks drying

Control Plant potatoes early harvest early use heavy mulch to prevent cracked, dry soil, which exposes potato tubers to attack at harvest, destroy cull potatoes and infested vines before nightfall adult moths lay eggs on culls left out overnight. 

General hydrodynamic theory for liquid penetrant testing (PT) has been worked out in [1], Basic principles of the theory were described in details in [2,3], This theory enables, for example, to calculate the minimum crack s width that can be detected by prescribed product family (penetrant, excess penetrant remover and developer), when dry powder is used as the developer. One needs for that such characteristics as surface tension of penetrant a and some characteristics of developer s layer, thickness h, effective radius of pores and porosity TI. One more characteristic is the residual depth of defect s filling with penetrant before the application of a developer. The methods for experimental determination of these characteristics were worked out in [4]. 

Let us consider the calculation of sensitivity threshold in the case when the cracks are revealing by PT method. Constant distance H between crack s walls along the whole defect s depth is assumed for the simplicity. The calculation procedure depends on the dispersity of dry developer s powder [1]. Simple formula has to be used in the case when developer s effective radius of pores IC, which depends mainly on average particle s size, is smaller than crack s width H. One can use formula (1) when Re is small enough being less than the value corresponding maximum sensitivity (0,25 - 1 pm). For example. Re = 0,25 pm in the case when fine-dispersed magnesia oxide powder is used as the developer. In this case minimum crack s width H that can be detected at prescribed depth lo is calculated as... 

The case considered above corresponds to R < H. The calculation using formula (1) gives the next results. For example, consider the thickness of dry developer layer h = 20 pm. In the absence of sedimentation process our product family (penetrant and developer indicated above) could not detect the cracks with the depth lo < 1,33 mm of any widths. Nevertheless due to the sedimentation one can get the decrease of developer s thickness from h = 20 pm till h s 5 pm. As a result, our product family can ensure the detection of the cracks with H > 2,3 pm even with very small length lo = 0,4 mm. At the same time if lo = 1 mm, then the cracks with extremely small width H > 0,25 will be revealed. 

EUtration can be foUowed by dewatering, washing, and drying. In some appHcations, compression roUs or belts are used to close possible cracks in... 

The most common problem in the paint layers, which can have a wide variety of causes, is loss of adhesion. Upon drying of the medium, the paint layers develop shrinkage cracks. In itself, this is not a particularly worrisome phenomenon, but, if through any cause the adhesion between paint layers and ground or between ground and support is lost, the paint begins to flake. First the flakes cud up, and finally become completely detached and lost. 

Thermal drying has been studied in conjunction with a rail shipment of ca 1200 km from North Dakota to Illinois. Oil was appHed at 6-8 L/t to suppress dust loss, and cracks around the doors in the base of the cat were sealed to prevent ignition. Stable shipment and stockpiling were then possible (31). Thermal drying may be carried out to further reduce the moisture content as requited for briquetting or for mote efficient pulverizing and combustion. 

---