Spec Check Issue 6: Long-Coupled and Close-Coupled Pumpsets
Welcome to Issue 6 of Spec Check! Today we discuss long-coupled vs close-coupled pumpsets.
This discussion paper is about the benefits of close coupled pump sets as compared to the conventional long coupled pumpsets. It has been long standing convention in the HVAC market to supply long coupled pumpsets for chilled and condenser water reticulation. Long coupled refers to the method of mounting a Bareshaft BPO pumps on a bases and coupling it to a separate motor with a spacer coupling. Close coupled refers to the design of an intermediate yoke which allows the pumps to have a direct connection to a standard metric frame flanged electric motor. Traditionally these pumps were always more expensive than the conventional long coupled pumpsets due to the greater volumes of Bareshaft pumps made for the world market.
The long coupled pumpset has been challenged in recent years with increasing preference by site managers and contractors to utilise work methods such as pre-fabs and pre-packaged products that minimise site labour and its associated risks.
The main advantages of the close coupled configuration are:
- Compact design saving space in your plantroom – approx. 30% reduced floor space.
- Back pull out Feature is retained with the close coupled pumps – repairs and inspections can still be performed without dislodging pipework.
- BakerBloc close coupled pumps still utilise standard metric frame motors, which are readily available in multiple brands across the country minimising downtime in the event of motor failure.
- Once delivered to site and installed there is no need to have the coupling alignment checked thus allowing your site manager to continue with the flushing, start up and commissioning of the system without having to coordinate the pump technician thus streamlining the whole operation.
- Close coupled pumps enable smaller inertia bases giving cost savings of base as well as less concrete required – less carbon footprint.
- Reduced maintenance-two bearings instead of four.
THINGS TO WATCH
There are two main pitfalls to look out for when assessing the use of close coupled options.
- Are the offered pumps fitted with standard metric frame motors? The BakerBloc design passes this test. (some motor pumps are factory fitted with a motor produced by the pump manufacturer that is unique to the pump resulting in expensive replacement)
- Is the base design such that the Back Pull Out feature is not compromised? Does the base design/length allow for the easy sliding back of the motor for servicing?
MAINTENANCE – DOES IT MATTER?
For larger motor sizes maintenance can still be a streamline operation if forethought is given to the placement of overhead fixture for installing a block & tackle when servicing is required. The easiest and most cost effective way to specify the installation of a Dynaset as supplied by Ramset. These are an internally threaded insert that requires predrilling a 16 or 20mm hole (depending on Dynaset Model) in the concrete slab. The most common servicing task in the life of a pump is the replacement of the seal. This can be a one man operation for any size pump if the above matter is considered. Visit http://www.ramset.com.au/product/detail/83/Dynaset-Drop-in-Anchors we would recommend an anchorage point for pump sizes 22kW and greater.
HOW TO SPECIFY
We suggest you incorporate the following clauses into your specification:
All close coupled pumps are approved on this project shall have standard metric frame IEC electric motors fitted. Motors that are not interchangeable with readily available brands such as WEG, Teco, CMG, will not be accepted. Extended baseplates to be sufficient length beyond the rear of the electric motor to allow motor and pump element to be withdrawn sufficiently to allow service work on the pump to remove motor from off baseplate. The back pull out design shall not be compromised in any way.
Motors shall be 3 phase T.E.F.C suitable for indoor/outdoor installation [Retain the correct item for this project] motor speed 24/48 [retain the correct item for this project] revs per second.
Pump construction shall be cast iron casing, bronze impeller and stainless steel shaft with mechanical seal fitted suitable for the liquid being pumped. Pump connections to be flanged for all connections 40mm and greater.
Installation considerations to be adhered to by the contractor:
Gauge tapings/sockets or binder points to be installed on both sides of the pump to allow for future pressure drop readings across the pump. Isolation valves to be installed on both sides of the pump to allow for isolating the pump from the system during Hydrostatic testing and for future servicing.
For pumps with motor sizes 22kw and greater an anchorage point shall be fitted to the ceiling immediately above the pump motor eyebolt. (Dynaset from Ramset or similar. Must be of sufficient load to take the weight of the motor) in the case of multiple pumps side by side contractor shall include the installation of an I Beam or similar for the client to be able to fit their own gantry block and tackle for future servicing and or replacement. It is mechanical contractors’ responsibility to ensure there is clear air space about the pump units – impede the easy removal of the pumping / motors for future servicing or replacement.
In addition to any automatic air release valves fitted, there must also be isolation valves at high point that can be manually opened to quickly discharge air from the system. These should be not less than 20mm. on systems that have an excess of 300meters of piping, we suggest a 20mm valve (gate of ball) to be fitted at the first elbow above the pump on the discharge side.
Got more questions? Get them answered here.