Water Pumps - Why Different?

[CGW]

1 hour ago, grollies said:

Jetting pumps (high volume/high pressure), like those used for filling pipelines, as you say, have a size larger on the suction side. I assume these are the types of pumps you used offshore?

 

To be honest I'm not sure what you mean by a "jetting pump"?  _-Different industry different terminology.

A very common pump in the offshore industry is a 75hp, with 6" x 4" suction/ discharge and a lot of smaller variants, mostly used for transferring fluids.

For larger volumes and higher pressures `1k to 10k or even up to 15k Psi, mud pumps or slush/cement pumps are used, these will generally be primed/charged by centrifugal pumps. A large mud pump would have ~12" suction line (per-charged with a Centrifugal pump) with a single 4" HP discharge line.

 

" Cavitation problems are rare nowadays with improved pump impeller design. It's usually a result of poor installation/suction restrictions and the pump trying to discharge more water than it can pull/is fed."

Exactly - we constantly battle space restrictions and end up with far from optimum piping arrangements, therefore it is important to make sure you do have adequate suction!

You also have to engineer, as I'm sure you know for worse case scenario, as when pumping from tanks when full,  making sure you can get the last foot out when near empty is two different scenarios.

 

Going back into retirement now - I'm boring myself! :)

Cheers

[sappersrest]

Pump choice for water......

A point to remember  you do need to specify the required the required flow i.e. m3/h  liters / minute etc.

Then the required head inc straight lengths of pipe , valves fittings etc. Friction loss tables and calculators are on the net now

The required flow velocity. usually 1.1  2.5 m/s 

The size of pipe etc.

Take this info to any good pump supplier or work it out for yourself  using the many online calculators  (using metric values)and then decide on the pump you require.

The supply of pumps is a very competitive market, many manufactures will be only to pleased to carry out these calculations for you

Just because your mate in the next field may be using a 1hp  pump it may not be the same for you.

In my experience pump problems are generally generally caused by 

Wrong choice of pump.no 1 cause

Bad installation . (please please when connecting a pump with different pipe connections i.e. 3 inch suction say to a 2 inch pump connection DO NOT USE CONCENTRIC  REDUCERS always use eccentric reducers with the flat part at the top) other wise you have sentenced  your poor pump to a very short life.

 

If you have to throttle back the delivery pipe work for whatever reason DO NOT USE BALLVALVES use a gate valve or a butterfly valve, the flow on ball valves are far to restrictive when throttled back.

 

 

[David B in Thailand]

I've been able to get prompt answers in English from Mitsubishi Water Pump Technical staff in Thailand. I've met two water pump technical engineers in Buriram. It might be worth the OP time to go in person and meet with a trained Mitsubishi representative in his area. The two bi lingual Mitsubishi Pump employees in this photo will be in Buriram April 3rd through April 9th and can explain features on any Mitsubishi water pump and work with authorized repair technicians for free warranty repairs or after warranty period repairs. There must be other water pump shops in Thailand that can provide factory support for customers who purchase Mitsubishi water pumps in English. 

[Artisi]

On ‎24‎/‎03‎/‎2017 at 6:48 AM, dbrenn said:

The noise is caused by the rear gearbox layshaft making contact with the flutter valve heatsink mounting bracket. It's normal and nothing to worry about.

you are kidding about the rear gearbox, aren't  you?

[Artisi]

On ‎26‎/‎03‎/‎2017 at 6:42 AM, Crossy said:

 

I'll put money on that being cavitation.

 

Sounds like classic cavitation - which is when the NPSHr is greater than NPSHa and seems to be backed up with your statement of throttling the discharge reducing the flowrate (lowering NPSHr) reduced the noise.  Obstructions in the suction line / well screen (if you have such a thing)  riser / inlet strainer / foot valve  restricts the flow, lowers the NPSHa and leads to cavitation (same as throttling an inlet pipe).

Anyone really interested in NPSHa / r  - let me know and I can offer up some engineering data for you. 

 

[Artisi]

To clarify the usual misunderstanding, cavitation is the sole result of the inlet pressure at the impeller eye being lower than the required pressure at the impeller eye,  nothing to do with air entrainment, gremlins',  long pipe lines (if correctly calculated for pressure drop) or the usual mumbo-jumbo offered up by many "experts".

If you are calculating for a 1 kw pump or a 1000 kw pump,  the same rules, principals, and requirements apply to ensure cavitation free operation.  

Edited March 31, 2017 by Artisi

[Artisi]

On ‎27‎/‎03‎/‎2017 at 0:57 PM, grollies said:

Ah, I now understand the bet! I can be a bit thick sometimes.

 

No, I do get what you mean. You're right about cross-sectional area on suction and discharge and gagging-in the discharge to get rid of cavitation. We're saying the same thing.

 

Cavitation problems are rare nowadays with improved pump impeller design. It's usually a result of poor installation/suction restrictions and the pump trying to discharge more water than it can pull/is fed.

 

My experience of low pressure/high volume pumps such as univacs is that they have same size suction and discharge pipes.

 

Jetting pumps (high volume/high pressure), like those used for filling pipelines, as you say, have a size larger on the suction side. I assume these are the types of pumps you used offshore?

 

Onshore and landfall oil & gas me, 25 years, ran a pipeline hydrotes company.

Please expand on "univacs" are you talking the old Sykes UK pump range? 

[grollies]

11 hours ago, Artisi said:

Please expand on "univacs" are you talking the old Sykes UK pump range? 

Yep, Andrew Sykes, SLD, Speedy Pumps, et al.

[Artisi]

2 hours ago, grollies said:

Yep, Andrew Sykes, SLD, Speedy Pumps, et al.

I worked for Sykes Australia (part owned by SLD)  and Sykes UK for approx 10 years in the late 60's to mid 70's before the demise of Sykes UK, the rest is now history. 

[kamalabob2]

This afternoon in Buriram I met a Mitsubishi Water Pump engineer who speaks English. He had quite a powerful demonstration booth at a Builders Merchant Home Garden Expo. They had several Mitsubishi water pumps on display and could answer questions I had regarding lift, water flow and electrical consumption. I would advise the OP to check with the better Mitsubishi Electric Water Pump dealer in his area.