Live tap of water main on an extremely busy street 3

[Twinkle Star]

The City is going to perform a live 8" x 8" tapping sleeve and valve next month on a very busy street. I am concerned about the safety of the City Employees working on a live tap. Could someone please help me with any suggestions on safety aspect that will need to be considered or taken? I want to make sure we as general contractor take all necessary precautions. Please help.

 

[r13]

Adequate construction warning signs, traffic aids/flag persons, excavation safety setup per OSHA requirement (slop protection if deeper than 4', personal PPE, access and escape from excavation), make sure the water flow is cutoff, may require lock box procedure.

 

[Twinkle Star]

Hello, thank you for your input. What is a lock box procedure? How to make sure water flow is cut off? I am new to all this. So please bear with my questions.

 

[r13]

Since you are working with the city and their employees, they knew the requirement and procedures. Just keep it on your to-do/check list, ask and remind them during the coordination meetings. (I believe they need to close some valves that have live water to the pipe/valve under construction, similar to home project - turn off the source for branch works. In industry project, the closed valves need to be "locked" with detailed tag, so nobody will incidentally turn them on before completion of the job. The proper term should be "lockout-tagout procedure")

 

[oldestguy]

My opinion is that any city of any worth already has proper safety rules and equipment. If you are working for the city, just follow them. If you are not working for the city this is not-going to get any attention other than giving you a not so good reputation.

 

[Ron]

Live taps are common. Municipalities do them routinely.

 

[LittleInch]

It's a little surprising this hasn't been done before or a procedure established, but a properly run construction HAZID I think would be very useful to identify, assess and then mitigate the risks that the HAZID team can think of.

Something like this

https://www.contractorsunlimited.co.uk/toolbox/hazid.shtml

You face some clear risks here being traffic collision and impact, water filling the excavation as well as the usual handling issues and excavation collapse / supports / means of escape, asphyxiation etc.

If this is a live main then there is a risk of major water flow if it all goes horribly wrong.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[r13]

Twinkle Star,

As a young construction professional, you could be challenged in many ways. Be prepared, know the job, listen before talk, and ask instead of questioning, if you see something done the other way. Familiar with OSHA regulation and construction practice are very important for success. I wish you have a good start.

 

[coloeng]

With the exception of adequate traffic control/safety measures and trench safety there should be no concern with an experienced crew doing a live tap on an existing main. This is done all the time. The procedure is: 1)install the tap saddle on the main; 2)bolt a valve on to the tap saddle; 3)attach a tapping machine to the valve; 4)ensure the valve is in the open position; 5)drill the hole in the main with the tapping machine; 6)withdraw the drill portion of the tapping machine back through the valve; 7)close the valve; 8)disconnect the tapping machine from the valve. Your tap is substantially complete. The tapping machine is designed to be water tight when it is doing the tap, so no reason to shutoff the water in the existing main.

 

[r13]

I agree most of city crews are well trained and doing it in a daily base. But, flooded street/basement and injured workers are not rare event either. Do not interfere with the crews' way of handling, but keep eyes open on the work to ensure the safety of everybody, include yourself.

Unless there is direct involvement of city engineer(s)/technical personnel, you maybe duty bound to represent the city. Check it out.

 

[IRstuff]

Too many workers die because shoring was inadequate from shortchanging due to tight schedules.

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert!

https://www.youtube.com/watch?v=BKorP55Aqvg

faq731-376 forum1529 Entire Forum list

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[r13]

I inspected a bridge crane that had derailed, the impact damaged the end truck, the platform stair and railing. Before leave, I reminded the crew to setup temporary platform with railing for work safety. The advice went into deft ear, as I wasn't the plant safety guy. The first thing the next day I was told, the repair crew manager had fell 100' to the ground and pronounced dead at the scene. We'd been friend for quite a while, he left his wife, kids behind ....

 

[LittleInch]

A full size tee (8" x 8") isn't that common though and I wasn't sure if it is actually feasible. - "The City is going to perform a live 8" x 8" tapping sleeve "

This implies the cutter is taking away 50% of the existing pipe.

An 8" x 6" I thought was the biggest you can do.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[jgailla]

LittleInch is right. You can't do an 8" tap on an 8" line. What I've done in the past is do a 6" tap and then use a reducer to go from 6" to 8". There's some additional head loss through the reducer, so it needs to be analyzed and the pipe may need to be upsized to provide proper pressure at the required flow. Since 8" is usually the minimum required for fire water, I've always had sufficient capacity even with the restriction.

 

[r13]

Soil guy do water works

 

[oldestguy]

There is no room here for sarcasm.

 

[r13]

No sarcasm intended, joking, amazing, and some admiration.

 

[FacEngrPE]

I do not think I would so a hot tap this way, but "Split T" tapping saddles are on the market that are designed for full size taps. These are installed by welding then together, and then they are welded to the carrier pipe.

.
Source T. D. Williamson Inc, TDW Tapping Fittings catalog.

You could verify fitting was designed for the installation arrangement and has an appropriate pressure rating. Reviewing the OEM guidance is worthwhile.

This job clearly needs a job safety plan, as indicated above, but except for the size on size tapping sleeve seems routine for a skilled crew. The biggest risk is that the skilled crew will sometimes take unwise shortcuts because it worked before.

If you have the opportunity to take the OSHA outreach classes (or similar), you will have the opportunity to see a bunch of eyeopening workplace safety failures.

https://www.osha.com/courses/outreach.html

 

[Ron]

@retired13.....jgailla started in geotechnical and materials, then expanded his horizons in broad civil practice. Sharp engineer.

 

[r13]

Ron,

Agree. Always envy people excel in multi fields, especially engineering.