- Butt welded
- Socket welded
- Bolted flange
- Bolted quick coupling
Elbows or ells :-Types of elbows
- Use standard available items wherever possible.
- Do not use miters unless directed to do so.
- Do not run piping under foundation.
- Do not run steam lines under oil lines, fire hazards may occur.
- Piping may have to go through concrete floors or walls. Establish these points of penetration as early as possible and inform the group connected (civil) to avoid cutting existing reinforcing bars.
- Include removable flanged spools to aid maintenance, especially at pumps, turbines, and other equipment that will have to be removed for overhaul.
- Steam lines, which are below grade in trenches provided with covers or (for short runs) sleeves.
- Take gas and vapor branch lines from tops of headers when it is necessary to reduce the chance of drawing off condensate or sediment, which may damage rotating equipment.
- Maintain vent lines at higher and drain lines at lower elevations.
Clearing and Access:-
- Process control during operation.
- Controlling services and utilities –steam, water, air, gas and oil.
- Isolating equipment or instruments, for maintenance.
- Discharging gas, vapor or liquid.
- Draining piping and equipment on shutdown.
- Emergency shutdown in the event of plant mishap or fire.
Which size valve to use:-
Where to place valves
- Preferably, place valves in lines from headers (on piperacks) in horizontal rather than vertical runs, so that lines can drain when the valves are closed.(in cold climates, water held in lines freeze and rupture the piping such lines should be traced.
- To avoid spooling unnecessary lengths of pipe, mount valves directly onto flanged equipment, if the flange is correctly pressured.
- A relief valve that discharges into a header should be placed higher than the header in order to drain into it.
- Locate heavy valves near suitable support points. Flanges should be not closer than 12 inches to the nearest support, so that installation is not hampered.
- For appearance, if practicable, keep centerlines of valves at the same height above floor, and in-line on plan view.
Operating access to valves
- Consider frequency of operation when locating manually-operated valves.
- Locate frequency-operated valves so they are accessible to an operator from grade or platform. Above this height and up to 20feet, use chain operation or extension stem. Over 20feet, consider a platform or remote operation.
Valves Operating Heights
- Infrequently used valves can be reached by a ladder –but consider alternatives.
- Do not locate valves on piperacks, unless unavoidable.
- Group valves which would be out of reach so that all can be operated by providing a plotform, if automatic operators are used.
- If a chain is used on a horizontally mounted valve, take the bottom of the loop to within 3feet of floor level for safety, and provide a hook near by to hold the chain out of the way.
- Do not use chain operators on screwed valves, or on any valve 1½ inches and smaller
- With lines handling dangerous materials it is better to place valves at a suitably low level above grade, floor, platform, etc., so that the operator does not have to reach above head height.
Access to valve in hazardous valves
- Locate main isolating valves where they can be reached in an emergency such as an an outbreak of fire or a plant mishap. Make sure that personnel will be able to reach valves easily by walkway or automobile.
- Locate manually-operated valves at the plant perimeter, or outside hazardous area.
- Ensure that automatic operators and their control lines will be protected from the effect of fire.
- Make use of brick or concrete walls as possible fire shields for valve stations.
- Inside a plant, place isolating valves in accessible positions to shut feed lines for equipment and processes having a fire risk.
- Consider the use of automatic valves in fire systems to release water, foam and other fire-fighting agents, responding to heat-fusible links, smoke detectors, etc., triggered by fire or undue rise in temperature –advice may be obtained from the insurer and the local fire department.
If there is no P&ID
- Provide valves at headers, pumps, equipment, etc., to ensure that the system will be pressure-tight for hydrostatic testing, and to allow equipment to be removed for maintenance without shutting down the system.
- Provide isolating valves at all small lines branching from header.
- Provide isolating valves at all instrument pressure points for removal of instruments under operating conditions.
- Provide valved drains on all tanks, vessels, etc., and other equipment which may contain or collect liquids.
- Protect sensitive equipment by using a fast-closing check valve to stop back flow before it can gather momentum.
- Consider butt-welding or ring-joint flanged valves for lines containing hazardous or searching fluids. Hydrogen is especially liable to leak.
- Provide sufficient valves to control flows.
- Consider providing a concrete pit (usually about 4ft x 4ft) for a valve which is to be located below grade.
- Consider use of temporary closures for positive shut-off.
- Provide a bypass if necessary for equipment which may be taken out of service.
- Provide a bypass around control stations if continuous flow is require. The bypass should be at least as large as the control valve, and is usually globe type, unless 6-inch or larger, when a gate valve is normally used.
- Provide an upstream isolating valve with a small-valved bypass to equipment, which may be subject to fracture if heat is too rapidly applied on opening the isolating valve. Typical use is in steam system to lessen the risk of fracture of such things as castings, vitreous vessels, etc.
- Consider providing large gate valves with a valved bypass to equalize pressure on either side of the disc to reduce effort needed to open the valve.