FAQ(Products) Osaka Sanitary Co., Ltd.
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FAQ (Products)

Q What level of durability do the gaskets and packing have with regard to the flowing liquid?

A Refer to the following tables.
Even lines that use the conventional rubber packing are subject to contamination by shavings and other foreign matter and hence, there is a tendency to choose resin + cushioning rubber.

Q What is EHEDG?

A EHEDG stands for European Hygienic Engineering & Design Group.
It was inaugurated in 1989 with the participation of universities, hygiene organizations, food manufacturers, food-manufacturing equipment manufacturers, and other such institutions across the European nations who share the common goal of promoting hygiene in food-processing and packing. Their guidelines mostly contain details on the standards for the hygienic design of food-processing equipment and inspection methods, and the group also evaluates the efficacy of designs.

Q What is cavitation?

A Liquid contains saturated vapor pressure in relation to the temperature and turns into vapor internally when the pressure drops below this. This is known as saturation (boiling). Rapid changes in flow speed, the creation of vortexes, and obstacles in the flow channel, etc., within the unit result in the liquid turning to vapor and generating large numbers of bubbles if the pressure of the liquid falls below the saturated vapor pressure in localized areas, and these bubbles immediately implode. This is known as cavitation, which occurs most commonly at the impeller inlet in pumps. These air bubbles are moved by the current. Vibrations and noise can cause them to become unstable, resulting in reduced pumping levels or preventing pumping all together.

Q What conditions can be set to prevent cavitation?

A (1) In order to prevent cavitation and operate pumps safely, it is necessary for the absolute pressure directly in front of the pump inlet to be increased above the saturated vapor pressure to an equivalent of the [Required NPSH × (1 + α)]. The [NPSHav ≧ NPSHre (1 + α)] relationship must be maintained at all times within the operational range. Under normal circumstances, α ≧ 0.3 is used as the value of α (although NPSHre × 0.3 ≧ 0.5m). (2) For example, the NPSHre of the pump itself must be increased in addition to increasing the flow rate for the vortex pump capacity curve under normal circumstances, although the NPSHav determined by the plant must be conversely reduced. Consequently, as can be seen in Fig.1, the range to the left of point A where both NPSH curves intersect can be used, and the pump’s H-Q capacity must be lowered as shown by the dotted line because cavitation is generated in the area to the right of point A.
Relationship between NPSHav and NPSHre

Q What is NPSH?

A NPSH is an acronym for Net Positive Suction Head. It is used as a method of indicating pump suction conditions and suction capacity, and comes in two types: Available Net Positive Suction Head and Required Net Positive Suction Head.

(1)Available Net Positive Suction Head (NPSH Available)
An NPSH that is available for use from the viewpoint of equipment and that is determined in accordance with the suction pipes and plants regardless of the pump. It is a value that indicates with the use of a liquid column how much higher and safer the absolute pressure of liquid flowing through to the center of pump suction inlets is in comparison to the saturated vapor pressure related to the liquid’s temperature. Absolute pressure = Static pressure (pressure gauge reading) + Dynamic pressure (Speed head × density × gravitational acceleration)

(2)Required Net Positive Suction Head (NPSH Required)
The liquid that flows through to the vicinity of the impeller inlet temporarily loses pressure before it is applied by the impeller. The liquid column equivalent to this loss of pressure is known as NPSH, and this value is defined by JIS standards as “acquired from suction conditions when suction pressure gradually decreases during pump operations until the gross pump head has dropped by 3% (△H/H = 0.03) with regard to each discharge.”

Q What pump suction conditions are effective in preventing cavitation?

A It is necessary to increase the pump equipment plan and suction capacity when it is in use and to consider the following points in order to prevent cavitation.

(1)Lower the location of pump installation as far as possible, shorten the length of the suction pipe in order to minimize the suction head loss and lower the speed on the flow within the pipe, and set a sufficient NPSHav value.

(2)Make sure the design is planned so that the value is around NPSHav > 1.3 × NPSHre.

(3)Design the shape and dimensions of the suction water tank to prevent the occurrence of excessive drift and vortexes in the flow.

(4)Installing and operating pumps with more head than what suits actual circumstances will occasionally result in more water being discharged than planned, leading to cavitation if the water volume is not adjusted with a discharge valve.

(5)Avoid operations if the discharge volume is remarkably different from the planned volume, and note that the NPSH value will become larger in the low-head area if suction head fluctuations increase, which may result in cavitation.

(6)Water volume must not be adjusted with the valve on the suction pump under any circumstances.

Q Is it necessary to prime SE and SPL pumps?

A Yes. Liquid flow cannot be started unless the pumps have been primed. Even worse, the spindle seal will increase in temperature and burn if it is dry, which will result in damaged seals and leaks. The SPL models are fitted with automatic suction and must be primed.

Q We want to use valves that are used on lines before the filling machines but we are worried about foreign matter being mixed in. Are there any suitable valves?

A We recommend a diaphragm valve. The NBS diaphragm valves, for instance, do not use valve seat packing, so the spindle’s sliding parts do not come into contact with liquid.

Q Are there any valves available that will prevent liquid from accumulating at the point of use of the process water in pharmaceutical facilities?

A We recommend a T-type NBS diaphragm valve. Tees are not used at the point of use, so liquid cannot accumulate. We also have types with differing diameters available.

Q How should we carry out maintenance of pumps?

A Contact our sales liaison if you have any inquiries.

Q Do you sell sanitary tanks?

A : We design and suggest original tanks in accordance with the intended application.
Contact our sales liaison for further details.

Q We are intending to install a pig cleaner in our facilities. Do you have any suitable valves?

A We recommend a ball valve. These are full-bore valves that enable the pigs to pass through.
* Right-angled flow channels cannot be used with 3-way balls. Straight is the only available direction.
* Pigs are balls or unique parts produced by manufacturers that perfectly fit the inner diameters of pipes and are forced through the pipes with air pressure in order to recover residual liquid and for cleaning purposes.