Short-Set Vertical Turbine pumps

发布时间：2023/1/9 22:29:21 人气： [content:visits]

Short-Set Vertical Turbine pumps

Short-Set Vertical Turbine pumps are commonly used in all types of applications, from moving process water in industrial plants to providing flow for cooling towers at power plants, from pumping raw water for irrigation, to boosting water pressure in municipal pumping systems, and for virtually every other imaginable pumping application. Turbines are one of the most popular types of pumps for designers, end-users, installing Contractors, and distributors.

Assembly Drawing of a Standard Short-Set Vertical Turbine Pump

When we talk about Short-Set Vertical Turbine pumps bearings, it’s important to realize that in North America most vertical turbines only have sleeve bearings which are not designed to carry any thrust or weight. Instead, the pump shaft is rigidly coupled to the motor shaft, and the motor bearings are designed to handle the weight of the shaft and impellers, as well as the downthrust generated while the pump is in operation.

The Bowl Assembly

Short-Set Vertical Turbine pumps are often staged – that is, designed with more than one impeller. Each additional impeller increases the amount of head the pump can produce while the flow remains unchanged. For example, if a single-stage turbine (one with only one impeller) is designed to produce 1,000 Gallons per Minute (GPM) at 100 Feet Total Dynamic Head (Ft TDH), then adding a second identical stage will double the head the pump is capable of producing. So the two-stage unit would be capable of producing a flow of 1,000 GPM at 200 Ft TDH (100 Ft per stage).

When talking about Short-Set Vertical Turbine pumps with two-stages, we would say that it has a “two-stage bowl assembly”. The bowl assembly of a vertical turbine consists of the suction case or bell, the impellers, and the diffuser-style casings. All of the impellers are mounted onto a single bowl shaft which passes up through the middle of the diffusers in which the impellers are arranged. There is one diffuser for each impeller. Taken together, an impeller and a diffuser combine to form a stage.

Turbines may be designed for as much pressure and as many stages as the pump manufacturer designed the bowls to be capable of withstanding. To demonstrate this principle, let’s expand on the theoretical pump we just mentioned.

Let’s imagine that the pump manufacturer has designed the pump bowls to be capable of withstanding pressures up to 300 PSI (approximately 694 Ft TDH). While each bowl will produce 100 Ft at the rated flow of 1,000 GPM, we also need to be carefuly to consider other conditions and to avoid exceeding the pressure capability of the pump at all of those conditions. In our example, the pump will be starting and stopping against a closed valve. In this condition the pump will operate a “dead head” or “shutoff” – the pressure produced when the pump isn’t producing any flow. For the sake of example, lets say that for a single-stage shutoff head is 150 Ft. Based on those figures we can come up with the following table:

Stages	Head at Shutoff	Head at 1000 GPM
1	150	100
2	300	200
3	450	300
4	600	400
5	750	500

As you can see, with 5 stages the shutoff head will exceed the capabilities of our Short-Set Vertical Turbine pumps (694 Ft). So in this simplified example, we are limited to a 4-stage pump. In actual practice we would customize the impellers by trimming them, and in so doing we would be able to use a modified 5-stage pump that came very near the maximum limitation of 694 Ft TDH.

标签：Pump,vertical,Pumps,Turbine

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