1、最小流量:在正常情况下,泵不允许在Qmin线以左范围内运行。泵短时间内允许小流量运行,最小流量为0.05倍设计点流量,但不超过5分钟,任何更长时间运行都将造成泵内过热。不管怎样,在这种小流量情况下,会影响泵的结构和系统,导致扬程的变化。如果泵在系统中运行,而系统的净扬程是总扬程的主要部分,或并联运行,或考虑到变转速运行,那么这种扬程的变化是不可忽视的。
2、最大流量:工作极限由NPSHR决定,而NPSHA必须大于NPSHR一个余量值。
3、扬程和性能参数适用于P为1.Okg/dm³和粘度不大于20mm²/S介质,如密度不足1.0,功率是ρ的倍数:
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bearings,
the correct oil level must be verified at regular.
7). If the flexible coupling elements
begin to show signs of wear, they should be replaced in due time.
8). If the liquid for sealing, cooling
and lubricating is taken from an external source, the pressure must be 1.0 to 2.0 bar
higher than at the suction nozzle.
The gland packing(if the pump is fitted with one) should drip slightly during operation.
The gland should only be gently tightened.
3. Stopping
1) . While stopping the pump running,
first turn off the brake valve on the discharge pipe passage way.
2). Close the auxiliary connections. The
shaft seal in pumps where the liquid is fed in under vacuum must also be
lubricated with sealing liquid during standstill.
3). In the event of frost and/or
prolonged shutdowns, the pump and if applicable the cooling chambers must be
drained or otherwise protected against freezing.
4). Pumps handling liquids posing health
hazards must be drecontaminated. When draining the edium see to it that there
is no risk to persons or the environment.
Explanations
a. Minimum flow:
In normal service the pumps should not
be operated to the left of the line indicating Qmin. Lower flows, up to 0.05×Qoptimum, are permissible for short periods of up
to 5 minutes. Any longer operation will cause overheating within the pump.
However, at these lower flows the influence of the system as well as the pump
configuration may cause the pump head to vary. Such head variations are
significant if the pump is to operate in a system where the static head is a
major portion of the total head or parallel or variable speed operation is to
be considered.
b. Maximum flow
The limit of operation is given by the
NPSHR characteristic with the
indicated margins relative toNPSHA.
c. The total heads and the performance
characteristics refer to mediums compressed with p = 1.0 kg/dm³ and kinematic viscosity
up to 20mm²/s. If the density is not 1.0, the
performance characteristics are to be multiplied by ρ.
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