A “stuffing box” in the context of a marine diesel engine is not a component of the engine itself, but rather a critical part of the vessel’s propeller shaft sealing system. It is located where the propeller shaft passes through the hull, and its job is to prevent seawater from entering the vessel. It’s an essential item on any boat with an inboard engine, particularly those powered by a marine diesel.
Purpose and Operating Principle
The primary purpose of a stuffing box is to create a watertight seal where the propeller shaft exits the boat’s hull. As the propeller shaft rotates, driven by the diesel engine, this seal allows the shaft to turn freely while preventing the ingress of seawater. It also plays a dual role by providing lubrication and cooling to the shaft.
The operating principle is quite simple. The stuffing box consists of a housing that surrounds the shaft, into which special braided rope or other sealing material, known as packing, is inserted. A component called the gland is then tightened against the packing material, compressing it firmly around the shaft. This compression creates the watertight barrier. An ideal adjustment allows for a very slight amount of water to leak, typically a few drips per minute. This minor leakage is crucial as it lubricates and cools both the packing and the shaft, preventing excessive heat build-up and wear.
Main Components
A typical stuffing box is composed of several key parts:
- Housing: This is the main body of the stuffing box, a tube that is securely attached to the boat’s hull (often called the stern tube). The packing material is housed inside of it.
- Packing: This is the sealing material itself, a braided rope made from materials like flax or graphite, which is wrapped around the shaft.
- Gland: A metal collar or flange that is pushed against the packing to compress it.
- Locking Nut: The nut or nuts that are tightened to adjust the pressure applied by the gland on the packing.
Maintenance and Adjustment
Proper maintenance and adjustment are vital for the stuffing box’s longevity and to prevent damage.
Adjustment: As the shaft rotates, the stuffing box should leak a very small amount of water. If the leak stops completely or the box becomes hot to the touch, it indicates that the packing is too tight. Conversely, if there is a significant stream of water, the packing is too loose. To adjust, you should tighten the gland nuts in very small increments, usually about a quarter of a turn at a time, checking the leak rate after each adjustment.
Packing Replacement: Over time, the packing material hardens and loses its sealing ability. When it becomes difficult to maintain the correct drip rate even after tightening the gland, it’s time to replace the packing. This procedure often requires the boat to be out of the water. During replacement, all the old packing should be removed, and new packing should be installed in rings with the seams staggered to create an effective seal.
Remember, an overly tight stuffing box can cause excessive wear on the shaft and create unnecessary drag on the engine, while a loose one can lead to a dangerous amount of water entering the boat.
We offer an extensive range of marine engine brands and their associated spare parts, providing comprehensive solutions for both main propulsion and auxiliary power needs across diverse vessel types. Our supply capability covers various generations and models, ensuring support for a wide array of marine applications.
Featured Brands and Engine Series/Models:
SULZER:
- Two-Stroke Engines:
- RD/RND Series: RD68, RND76, RND76M, RND90, RND90M (Classic large-bore, low-speed engines, still in operation).
- RLA/RLB Series: RLA(B)56, RLA(B)66, RLA(B)76, RLB90 (Developed two-stroke designs).
- RTA/RT-Flex Series: RTA38, RTA48(T), RTA52, RTA58, RTA62, RTA72, RTA76, RTA84, RTA84M, RTA84C, RTA96 (Modern, fuel-efficient, electronically controlled two-stroke engines).
- Four-Stroke Engines:
- Z Series: ZL40/48, 16ZAV40S (Medium-speed engines).
- RF Series: RF44, RF56 (Often used for auxiliary power or generator sets).
- TAD Series: TAD36, TAD48 (For specific applications).
MAN (including pre and post-MAN B&W models):
- Two-Stroke Engines (KZ, KSZ, K, L, S, MC/MC-C, ME/ME-C): 40/54A, 52/90N, 57/80C, KZ57/80F, KSZ70/125, KSZ78/155, 90/160A, 52/55L, 58/64, 90/190C, L60/105E, 70/120E, 70/125C, L, KSZ78/155A, KSZ70/125B, L52/55A, 40/45 (A broad spectrum covering main propulsion and auxiliary engines).
B&W (Burmeister & Wain – prior to MAN B&W merger):
- MC/MCE Series: L35MC, L60MC, L80MC, L55GFCA, L80GFCA, L80GB, 74VT2BF, K62EF, K74EF, K84EF, K45GFC, K67GFK, K80GFK, K90GFS, 45HU, L70MC (Various generations of two-stroke diesel engines).
- MC-C/ME-C Series: L50MC, S60MC, S70MC, K80MC, S80MC, K90MC-C, L67GFCA, L90GB (Electronically controlled and conventional two-stroke engines).
- VT2BF/EF Series: 50VT2BF, 62VT2BF, K84EF (Older models still in service).
MITSUBISHI:
- UEC/UET Series: UEC37L/LA/LS, UEC45HA, UEC60L/LA/LS, UEC45L/LA/LS, UET45/75C, UEC52/125H, UEC52L/LA/LS, UET45/80D, UEC52/90D, UEC(T)52/105D, UEC45/115H, UEC37/88H, UEC37H (Mitsubishi’s proprietary two-stroke and some four-stroke engine series).
PIELSTICK:
- PA Series: PA6, PC3, PC2-2, IHI PC2-5, PC4, PC2-6, PC4-2L, PC4-570, PA5 (High-speed, compact four-stroke engines, commonly used for generator sets or auxiliary propulsion).
AKASAKA:
- UET/UEC/DM/AH Series: UET45/80D, UEC52/105D, DM51SS, UEC 60/150H, UEC 60H, A31, A34, A37, A41, AH27, AH28, AH30, AH36, AH38, AH40, DM30, DM36, DM38, DM46, DM47 (A prevalent engine brand, particularly in Japanese-built vessels).
DEUTZ:
- RBV/TBD/BVM Series: RBV8M358, RBV8M540, RBV16M640, TBD620L6, BVM350, BVM540, BF6M716 (Various four-stroke medium- and high-speed diesel engines for auxiliary and smaller main propulsion applications).
HANSHIN:
- EL/LH/LU/LUN/LUD/LUS Series: EL30, EL32, EL35, EL40, EL44, LH28RG, LH31G, LU28(A,R,G), LU32, LU35, LU38, LU46(A), LU50, LU54, LUN28, LUN30, LUD32, LUD35, LUS38 (Another significant engine brand commonly found in Japanese vessels).
NIIGATA:
- MG/M Series: MG40X(EX), M34X, 6M28BF, TM31X (Medium-speed diesel engines, typically used in small and medium-sized vessels).
MAK:
- M/MU/AK/AKM Series: M332, M453AK, MU551AK, MU552AK, M601, MU452AK, 451AK, 6M453AK, 9M453C, 6M601C, 8M601 (Medium-speed four-stroke engines, widely used in various marine applications).
WARTSILA:
- 20/22/26/32/38/46/GD/TKR Series: 22, 32, 31, 26, 20S, 28, 38, 46, 32GD, 46GD, 14, TKR22, HFR-V32, NOHAB (Wärtsilä’s broad portfolio of medium- and high-speed diesel engines for main propulsion, auxiliary, and generator sets).
DAIHATSU:
- PS/PKT/DS/DL/DK/PL Series: PS-18, PS-22, PS-20, PS-26, PS-30, PKT-14, PKT-16, PKTD-16, DS-18, DS-22, DS-26, DS-28, DS-32, DL-14, DL-16, DL-19, DL-20, DL-22, DL-24, DL-26, DK-20, PL-24 (Compact and reliable engines primarily used for auxiliary power and generator sets).
CUMMINS:
- BT/CT/NT/KTA/QSK/QSM Series: 4BT3.9, 6BT(A)5.9, 6CT8.3, NT(A)855, N14, KTA19, KTA38, KTA50, QSK19, QSM11 (Robust and durable engines for marine auxiliary power, generator sets, and some smaller main propulsion applications).
CATERPILLAR:
- 3000/3100/3300/3400/3500/3600 Series & C Series: 3054, 3056, 3066, 3106, 3126, 3306, 3406, 3408, 3412, 3508, 3512, 3516, 3606, 3608, 3612, 3616, 3618, C1.5, C2.2, C7, C9, C10, C12, C15, C16, C18, C30, C32 (Reliable and widely used engines across a vast range of main propulsion, auxiliary, and generator set applications).
SCANIA:
- DI Series: DI 09, DI 13, DI 16 (High-performance diesel engines designed for marine applications, typically used as auxiliary and smaller main propulsion engines).
