Packed glands or mechanical seals?

spongebob
10th May 2010, 09:05
Packed glands or mechanical seals?

As I look at the slowly increasing drip coming from the mechanical seal of my pool circulating pump I despair that there is not an old fashioned stuffing box to nip up occasionally instead of seeing it as an indication that the whole pump is stuffed and ready to throw away anyway.
Thinking back to the 50’s, I cannot remember any engine room pumps with mechanical seals, we were reliant on Messrs Walker, Chesterton or Turner Bros etc to provide us with the latest and greatest of roved asbestos based graphite impregnated gland packing material that ,by and large, did a creditable job.
It was a bit later in the sixties that the mechanical seal manufacturers made their play to convince and persuade us to change over in the interests of power efficiency, freedom from maintenance and durability but the costs were the biggest disadvantage as initially the seals were not cheap.
Ashore, pump manufacturers that I dealt with, KSB, Weir and Sulzer etc initially stuck with the packed gland option and proposed the seal as an optional extra
I recall the packing companies, already feeling the effects of the asbestos bogey, coming up with better and better types of gland packing but by the time I exited the industry 16 years ago the mechanical seal had made its mark.
Would it be fair to say that the biggest of all ship board glands, the stern gland, is about the only rotating shaft sealed by the old fashioned packing?
Just a glimmer of old times coming through.

Bob

WilliamH
10th May 2010, 09:12
I think the stern glands were some of the first to be fitted with mechanical seals, this became about with the introduction of oil filled tailshaft bearings. I can remember oil filled tailshaft bearings on ships built in the 1950's.

Doug Shaw
10th May 2010, 10:19
Bob

I don't think I ever sailed on a ship with a packed stern gland. All had oil-sealed stern tubes, I think (memory ain't wot it used to be).

Regards
Doug

Billieboy
10th May 2010, 10:59
Bob, packed stern glands went out in about 1968 on small diameter(10") shafts, and around 1975 on 24-30" shafts. The main culprits were "Sublime", and AEG(?) with stern tube seals on the propellor, and the super large reversible, "Glacier", stern bearing unit.

The former usually worked with VPP units with constant speed, unidirectional props, whilst the latter was fitted on larger fixed pitch props. Together with hydraulic prop hubs, they took the monkeys and three men off the tail end stages cutting costs and time for dockings.

chadburn
10th May 2010, 12:49
I have sailed on both like a lot of the older E.R. member's I would guess, preferred the mechanical seal on the stern gland but preferred the old stuffing box when it came to the pumps. Serpant A, Serpant C. or Greasy Hemp come to mind as well as "Pig's Tail's" which I still have in a tool box in the garage but have never used for well over 40yr's (but they might come in handy in the future if I find some big winkle's on the rock's at Staithes)(Thumb)

Billieboy
10th May 2010, 14:53
Talking gland packing, I was talking to a Walkers man in the Caribbean long ago, about, "valvasca", he said that the only place it was any good was on sugar cane rolling mill shaft seals! he advised, "Valcor", for Maneuvering valve glands, I used and advised, Valcor for the next thirty years, without any problems at all.

When it comes to BIG gland packing the biggest I ever used was on the Hydraulic accumulators on Cardiff and Barry docks, the packing was two inch square Tallow soaked hemp. The rams the Accumulators ran up and down on, were thirty six inch diameter, so one full turn, was a bit more than the full nine yards!

surfaceblow
10th May 2010, 15:08
One tanker I was on had packing on all of the Number 1 Salt Water Pumps like the Salt Water Service, and Main Circulating Pump and the Number 2 Salt Water Pumps had mechanical seals. We would use the pumps with packing glands while in Port and transiting most rivers. We found that even with the cyclone separators the sand and other grit would damage the mechanical seals. Most of the packing glands on the salt water pumps had the the sealing water lines removed and a grease cup was installed so when the gland started to drip a turn of the grease cup would stop the leak.

waldziu
10th May 2010, 16:10
This thread brings back mommories of the stern tube seals on my first ship the CA Destroyer Carysfort and as out side wrecker it was our job to refil the stern tube lubricators with Neox Grease. Which had the consistance of granite in cold weather and therfore the tin had to be place on a suitable unlaggedpipe or Vv to warm up so that one could get ones hand in and refill the screwdown lubricator. No problems in the tropics as one could almost pour it in. Modern war canoes had mecanical seals. Other Vvs had repackable glands. Half a twek with a ľAF and the jobs a goodun.

Jim S
10th May 2010, 17:49
Does anyone remember the mechanical seals made by the United States Mechanical Packing Company? - The ones I remember were on pumps such as main condenser circulating pumps. They were in two halves and had a small lub oil filled lubricator. Generally very good if a bit fiddly to fit and seal.
Walker's Supetta (spelling?) was Weir packing of choice for the majority of their pumps.
I hope my memory is correct in that Weir Boiler Feed Pumps on the Tribal Class Frigates had mechanical seals but with the safeguard of an additional packed gland that was kept loosely packed. Never saw that elsewhere. On BP's Forties Field Oil Production Platforms the Weir Main Oil Line pumps had to change mechanical seal supplier after the oil wells started to produce water as well as oil.
The original seals were failing after less than two weeks in service. The replacement Flexibox Seals proved successful.

surfaceblow
10th May 2010, 18:48
I remember using various manufactures split mechanical seals for the larger pumps. My biggest problem with split seals was with keeping the sealing elements free of finger prints while trying to maneuver the pieces into the pump casings. There unusually was not a whole lot of room to angle the pieces into the stuffing box. Most of the pumps were not originally designed for mechanical seals.

Joe

eriskay
10th May 2010, 19:23
From seagoing experience in the 60s, in almost all cases it was packed glands and whilst both conventioanl seals and mechanic seals both had their good and bad points, I personally preferred the packed gland, finding it less fickle and more reliable.

In the desalination business, it was almost all mechanical seals and despite pre-flush and quenching services, and post-flushing, using pure distillate to remove any residual salts, we invariably experienced problems, especially at start-ups and shut-downs, although once 'up and away' the equipment was fairly reliable.

Problem with mechanical seals on large pumpsets (brine circulation), where shaft diameters could be of the order of 130-150 mm, was the exhorbitant cost of spares, or, worse still, replacements. Availability was also an issue, even the big names such as Crane might be offering a delivery of 5 or 6 months on certain specifications.

Satanic Mechanic
10th May 2010, 19:36
Has to be said I'll take mechanical seals any day of the week, they are maintenance free for years,

howardws
10th May 2010, 21:33
I joined the Caltex Brisbane in Europort as first trip cadet, in about 1962. The first time I went into the engine room the Second asked if I could pack a gland. I said "Yes" and he sent me to help the Fitter top up the packing on the stern gland. Not quite the size that I was used to!

chadburn
10th May 2010, 23:31
Does anyone remember the mechanical seals made by the United States Mechanical Packing Company? - The ones I remember were on pumps such as main condenser circulating pumps. They were in two halves and had a small lub oil filled lubricator. Generally very good if a bit fiddly to fit and seal.
Walker's Supetta (spelling?) was Weir packing of choice for the majority of their pumps.
I hope my memory is correct in that Weir Boiler Feed Pumps on the Tribal Class Frigates had mechanical seals but with the safeguard of an additional packed gland that was kept loosely packed. Never saw that elsewhere. On BP's Forties Field Oil Production Platforms the Weir Main Oil Line pumps had to change mechanical seal supplier after the oil wells started to produce water as well as oil.
The original seals were failing after less than two weeks in service. The replacement Flexibox Seals proved successful.

The United States Packing Co also made mechanical seals fot VTE piston rods the springs were a bally menace.(MAD)

spongebob
10th May 2010, 23:43
The first three replies made me think that I was the original dinosaur, sailing on ships with packed stern glands but I am now relieved to find that I am not.
I guess that mechanical seals would demand a better stern bearing than the old lignum vitae slotted systems or the later rubber cutlass systems as wear clearance in the stern tube plus heavy weather often resulted in a badly leaking gland after lateral shaft movement had hammered the packing.
This could lead to a situation such as described in my Mess Deck thread “Heavy weather”29/4/08.

Waldziu’s mention of the lubricated stern tubes of a naval ship reminds me of the old ex WW2 Loch class frigates with their white metalled stern tubes and spring loaded grease lubricators. They had a packed gland inboard but I cannot recall what prevented or even retarded the grease leakage into the sea on the outboard side. I do remember the foul stench when we pulled the bearing cages out for a refit, a mixture of sea water and grease and a few other bacterial elements that formed a brew that would out smell a sewer.

Bob