Piston Rod Stuffingbox / Diaphragm Gland

Piston Rod Stuffing Box is used in large 2 stroke marine diesel engine to have a sealing between under piston scavenge space and crankcase. It prevents sludge and scavenge air from under piston space to enter crankcase and avoids crankcase oil getting into under piston space.

It is fitted in a diaphragm between crankcase and scavenge space.

Stuffing Box consist of 3 parts:

1. 1 set of

Upper scraper ring - 4 segments of brass held together by garter spring [Removes sludge from piston rod.Sludge scraped goes into scavenge drain tank] +

Pack sealing ring - 4 segments of brass held together by garter spring

      2. 2 sets of

Cover sealing ring - 4 segments of brass held together by garter spring +

Pack sealing ring - 4 segments of brass held together by garter spring

[ seals air from under piston space going into crankcase]

     3. 4 sets of

Oil scraper ring - 3 segments of steel held together by garter spring which has has two replaceable cast iron lamellas slid on to it [sludge scraped is drained to stuffing box drain tank and it scrapes down crankcase oil back to crankcase]

*Stuffing box inside the engine

*Split stuffing box during overhaul

*Understanding stuffing box

Reasons for stuffing box performance deterioration:

• vertical scratches on piston rod - reduces sealing
• seal rings getting worn out
• garter spring tension reduces due to heating over the period of time
• drainways or grooves getting choked
• reduction in butt clearance

If butt clearance reduce more than 50% of the gap, should replace the rings at the earliest.If no spares are available then grinding of rings can be done temporarily in emergency cases.

Clearances taken during maintenance:

• Vertical clearance between ring and housing groove [ high clearance causes hammering of rings in housing while engine working]
• Ring end clearance / butt clearance [ less clearance results in ineffective sealing]
• Tension of springs are checked using length of the spring at different loads as mentioned in manual and free length of the spring as given in manual.