Heavy-Duty Gate Valve

For gate valves with working pressures of up to about 800 psi for water supply.
All kidding aside, Velan offers a pretty wide range of valves and has a good reputation. They actually have an engineering staff that knows what they are talking about and should be competitive with other manufacturers of quality valves.
I've since been able to source suitable gate valves due to your help. However, I still have one problem. All the valves I've seen so far come with a rising stem and handwheel. In the open position the wheel may rise to almost 5 feet, for the 10-inch valves for example. Space is critical. The valves will be in chambers about 3 feet deep. Do valves of these sizes and pressure ratings come with non-rising stem and square wrench nuts?
From the original1GayeValve
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NFPA 85

To state whether a certain valve meets NFPA 85 criteria.  While we are busy ordering the standard, does anybody here know what the requirement would be for a 10" butterfly valve? 
sk the client about the criteria for which application.
The BOILER AND COMBUSTION SYSTEMS HAZARDS CODE mentions valves including dampers, scavanging, fuel / burner safety shutoff valves, barrier valves, charging valves, checks, dusttight valve in pulverized fuel, flow control, supervisory shutoff valves, vent control and vant valves.
Most topics apply with the installation, application arrangement, logic, etc. - not the valve design features.  Requirements address automated proof of closure features such as open/closed position feedback contacts,
From the originalgate valve

Relief Valve Slurry Application

Fluid will be bearing solids. Discharge is to atnosphere.
A spring loaded pinch valve would do but Red Valve limit their pressure to 150psi.
The rigs that these will be mounted on do not have compressed air.
(1) You could use the Red valve if you find a place 10M higher to mount it. Thereby subtracting enough head to get the internal pressure to less than 150 psi.
(2) An electrically controlled system: Pressure switch to monitor system pressure, solenoid valve, and a rack-and pinion actuator on a ball valve.  Drive the system with process water pressure.  Filter and regulate the water after the pressure switch.  If the water contains corrosives, the actuator and solenoid could be stainless steel.  Make the pressure switch normally closed, open to alarm.  Make the actuator on the ball valve "fail open" so on any loss of electrical supply, the relief opens and dumps pressure.
I did not suggest a pure electrically operated valve because electric actuators are so slow a damaging pressure spike may not be adressed.  A fast electric actuator on a small valve takes at least 6 seconds to stroke.  By then, the damage is probably done. 
From the originalgate valve

keep breaking gate valve stems

The crews are newly formed and do not have alot of experience. Just recently we have found 4 broken 24-inch gate valves. I suspect the crews are using a hydraulic operator and are setting the force of the operator too high.On a 24-inch gate valve, probably a Chapman installed in the early 1900s, what is the force that the hydraulic operator should be putting on the stem? The water utility I work for has purchased a couple of Wachs valve operating machines. A 24-inch transmission main is being cleaned and cement mortor lined. There were two 24-inch gate valves with broken 4-inch bypass valves. I had an operations crew go out and check all the valves on near the two broken valves. Typically all valves are supposed to be open. The crews went out and tried to close & open all the valves with the valve machine. In 2001 someone else had operated the valves and closed the valves with about 2500 pounds of force set on the machine. This year three more valves were broken with about 1300 pounds of force. We are petty sure the stems are breaking. I can not (do not know where to) find any information on how much force should be applid to the valves when operating them. I have not confirmed this, but I believe the stems are 2-inch diameter with acme threads made out forged bronze alloy.
From the originalgate valve

3-way valve converted to 2-way

To jerry-rig a 3-way valve to do 2-way operation? it seems to me that one would just need to disconnect the bypass leg and cap the open pipe connections.
A bit depending on type of valve you have (ball valve, plug or other) and liquid. Be aware of 'sticking' problems and/or adequate torque if the liquid have a dry-stuff content that could gather at the blinded port or if the liquid crystallizes when drying.
Normally, if the valve works well as a three-way, it should als work with a blocked port as two-way.
It provides a handy place for sludge to accumulate, and might trap high pressure to provide a "surprise" when the valve is serviced, but it will act as a 2-way in most cases.
Suggest you document that it is only temporary and keep a CYA file of who approved it.

From the originalgate valve

Valves for Lethal Service

Specifying valves for a oil centre.
For lethal gas, the ASME standard simply mentions that the valve should have enhanced stem seals.  No further definition or reference to any standards.
My opinion, ISO 15848 does not prove that the shaft seals will not leak once the gate valve is in the plant.  It is just an expensive, time consuming and overly complex lab. experiment that at best measures the permeability of the seal material.  It does let you know if the seal will remain tight after a thermal cycle.  But thats about it.
Once the valve is in the plant, outside factors will detemine if the shaft seal leaks.  Is the operator mounted properly or are there side loads on the valve shaft?  Is anyone monitoring for leaks and properly adjusting the packing load?  etc.  Do not rely on certificates from a lab. experiment as proof that a seal is going to remian tight in service.  Especially with lethal media.  You need to rely on experience and ensure you have the best seal possible for the application as proven through actual use in a plant.
From the originalgate valve

API trim 5 for steam service in API 600 gate valves

Using of trim 5 on gate vales in steam service. Is there a temperature you would recommend moving from other trims to trim 5. Is there a better trim than trim 5? When would galling be an issue, if at all? Does "clean" or "dirty" service affect the trim decision?
Typically I would recommend trim 5 more for reduced wear. If the valve is going to be operated frequently it's better to have trim 5, Also if the valve is in an area where it's a huge pain to service Trim 5 might be worth the upgrade.
In terms of valve wear reduction there isn't a much better material than stellite 6.
We use Trim 5 and Trim 8 in steam gate valves here in NYC as a standard. Where Trim 5 is full stellite and 8 is half stellite. Not all too much price difference, but the standard is Trim 8 for most manufacturers so delivery may be easier. If you need tighter longer lasting shut-off, where a gate valve is not a good option, we have moved to bubble tight ball valves.
By the way, the recommendation is not to use stellite for boiler feedwater containing Amines because they will leach the cobolt from the stellite and it comes apart.
From the originalgate valve