The Dilemma of Tugs, Ships Fittings, and the SWL In Between

There has been a recent practice in pilotage of informing attending tugs of the SWL of the deck fittings they are made fast to. While I can appreciate the intention, and sharing information to develop a mutual understanding of the pilotage is very important, there are circumstances where too much information is more a hindrance than a help.

This article was originally going to be a post, but it exceeded the character limit, so I had to make it an article. As a result it doesn't contain as much information as I would normally like, along with photos and diagrams. So, please consider it an extended post, instead of a piece of academic rigour, but hopefully it gets my point across.

The initial problem is often determining what the SWL of the bitts are. I normally have a look at them while transiting the main deck on my way to the bridge, but this isn’t always possible. In many cases when I’ve asked the Master what the SWL of their bitts are, they’re either not sure what you’re asking for, or they will have to ask an officer on deck to have a look and wait patiently for the response. This ends up just wasting time as it serves as a distraction, stopping you from getting onto more important matters in the MPX. To avoid this I instead inform the Master of the bollard pull of tugs, which places the responsibility on them to tell me if that exceeds the SWL of the deck fittings. This issue has been mitigated somewhat lately as I’m starting to see more and more ships carry a mooring plan on the bridge with the deck fittings SWL and this be presented along with the Pilot Card.

But now that the SWL has been determined, what exactly does it mean? The SWL of mooring bitts are determined for a figure eight mooring configuration, with the tension working to compress the horns towards one another. How does that relate to towage? Some literature says the mooring SWL can be doubled for towage, some say it’s the same, for others it’s some value in between. We’re now seeing ships with a separate SWL for towage indicated, which almost makes things clearer. But how do you apply it? Which horn does the eye of the towage line go over - the one further from the lead as has been the typical practice, or the one closest as is the current thinking. Does the same apply when it’s the ship's line and the line is tied up on the bitts?

To further complicate matters, I’ve also seen bitts with an indicated towage SWL less than the mooring SWL. I have also seen deck fittings fail at loads less than their SWL.

So we have a numerical value, of which we are not sure how it applies, or how much faith we can put in it. We then pass that onto the attending tugs as an operational limit. What happens in the circumstances when we need more than that? I know of a number of situations where colleagues have asked for full tug power - say in gusting strong wind or a contingency - only to find the Tug Master has limited the line tension to the SWL of the bitts, and the ship has not responded as the Pilot intended. This is in no way a criticism of the Tug Master, who is operating in good faith, and most likely in accordance with their own procedures. Personally, if it was a choice between damaging port infrastructure or potentially damaging the deck fittings, I know which I would choose.

For me, I’d rather manage the loads on the deck fittings myself. If I have an 80 tonnes tug on 60 tonne bitts, then I don’t go over ? tug power - or better still I avoid situations where such forces are necessary. But if I'm in a situation where I need the tug to let out all the black smoke, they will do so without limit - remember it's a SWL, not a MBL. Passing a nebulous SWL to the Tug Master has the potential to add confusion, and may limit or hamper the tug's response in a situation when you need them most. The only exception is if the ships fittings have an extremely low SWL - say for example 24 tonnes. I will pass this onto the tugs to avoid potential damage from them snatching their lines or being too heavy handed. But I also clarify that if I need more than 24 tonnes, I will ask for it.

As I say to Masters who tell me that their SWL is less than the tug’s bollard pull ‘if we need more tug force than that, Captian, the bitts are the least of our worries’.