Pump - Mono MS

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Mono MS pump.


Mono have been manufacturing pumps since 1935. The design is what's known as a progressive cavity pump, being a single helix rotor operating within a twin helix stator. In very simplistic terms it can be thought of as being similar to an Archimedean spiral pump.

Archimedean pump principal, similar to the progressive cavity pump. Source : Wikipedia













The MS pump has been in manufacture for at least 40 years and spare parts are still available. New these pumps retail at several hundred pounds but, although they don't appear frequently, they can be found second hand at reasonable prices on on-line auction sites.

The design is self priming and can be considered as a positive displacement pump. It is capable of pumping a large range of media including slurries and small entrained solids, although the latter will obviously induce premature ware. Different stator materials are available and the writer has had a viton stator pumping bio and vegetable oil in an MS pump for nearly five years at the time of writing with no noticeable adverse effects.


The pumps ability to pump viscous liquids makes it ideal for pumping WVO and semi-solid fats.


The Mono MS has the following specifications and performance:


  • power(kw) ... 0.18
  • Max. head ... 35.6m
  • Flow at 1450rpm ... 12.5 L/min @ 0 bar - 5.3 L/min @ 3.5 bar.
  • Max. suction head ... 8m (self priming)
  • Max operating temperature ... TBA
  • Inlet/Outlet connections … ¾” BSP, female
  • Body material ... cast iron
  • Rotor material ... stainless steel
  • Stator material ... synthetic nitrile rubber (standard) but others available including viton.
  • Weight ... 16kg (including motor)


Mono MS mechanical seal rebuild

The writers MS pump was found leaking so was dismantled. The problem was found to be a piece of landscaping fabric (used as a filter in the system). This seal differed from others in that there are no bellows. The static seal is made by an O ring located in the ceramic disc which seals it to the shaft.


After a few hours use, the seal started leaking again. The pump was dismantled and exactly the same problem found, tiny pieces of brass embedded in the graphite half of the seal.



During the last rebuild, a new gasket was made for the end cover.

A full size template was made for the gasket and can be down loaded in .pdf format below. Cut from a Corn Flakes packet or thick card and soak in vegetable oil or grease prior to assembly.

Click graphic for a full size pdf of the gasket. Allow time for the file to load, it's 1.3 Meg. Print without scaling, but as a check the OD of the gasket should be 140mm.




























See also Mono MS instruction manual

Julian (talk) 21:51, 10 May 2013 (BST)‎