20 CAR § 880-1005 – Valves

(a)
1. (1) Each steam discharge outlet, except safety valve and superheater connections, shall be fitted with a stop valve located at an accessible point in the steam delivery line and as near the boiler nozzle as convenient and practicable.
2. (2) When such outlets are over two-inch pipe size, the valve or valves used on the connection shall be of the outside-screw-and-yoke rising-spindle type so as to indicate at a distance by the position of its spindle whether it is closed or open, and the wheel may be carried either on the yoke or attached to the spindle.
3. (3) A plug-cock type valve may be used provided the plug is held in place by a guard or gland, and it is equipped:
  1. (A) To indicate at a distance whether it is closed or open; and
  2. (B) With a slow-opening mechanism.
(b)
1. (1) If a shutoff valve is used between the boiler and its superheater connections, the safety valve capacity on the boiler must comply with the requirements of the ASME Pressure Vessel Code Section 1 PG-68, as adopted, no credit being taken for the safety valve on the superheater, and the superheater must be equipped with a safety valve capacity as required by the ASME Pressure Vessel Code, as adopted.
2. (2) In a separately fired superheater installation, a stop valve is not required at the inlet or the outlet of the superheater.
(c) All stop valves and the fittings between them and the boiler shall be equal at least to the requirements in the ASME code for the maximum allowable working pressure and the temperature in service and material used, subject to the provisions of the ASME code, and except where heavier construction is specifically required.
(d) Valves and fittings made of any material permitted by the ASME code, as adopted, for pressure ratings of one hundred pounds (100 lbs.) or more, and marked as required by the ASME code, as adopted, may be used for saturated steam service up to the rated pressure, except that in no case shall they be used for temperatures exceeding that permitted by the ASME code, as adopted.
(e) The nearest steam stop valve or valves to the superheater outlet shall have a pressure rating at least equal to the minimum set pressure of any safety valve on the boiler drum at the corresponding saturated steam temperature.
(f) The nearest stop valve or valves to the superheater outlet shall have a pressure rating at least equal to the minimum set pressure of any safety valve on the superheater and at the expected superheated steam temperature, or at least equal to eighty-five percent (85%) of the lowest set pressure of any safety valve on the boiler drum at the expected steam temperature of the superheater outlet, whichever is greater.
(g)
1. (1) When high-pressure boilers are connected to a common steam main, the steam connection from each boiler having a manhole opening shall be fitted with two (2) stop valves having an ample freeblow drain between them.
2. (2) The discharge of this drain shall be visible to the operator while manipulating the valve.
3. (3) The stop valves shall consist preferably of:
  1. (A) One (1) automatic nonreturn valve (set next to the boiler) and a second valve of the outside-screw-and-yoke type; or
  2. (B) Two (2) valves of the outside-screw-and-yoke type shall be used.
(h) When a second steam stop valve or valves is required, it shall have a pressure rating at least equal to that required for the expected steam temperature and pressure at the valve, or the pressure rating shall be not less than eighty-five percent (85%) of the lowest set pressure of any safety valve on the boiler drum and for the expected temperature of the steam at the valve, whichever is greater.
(i)
1. (1) When a stop valve is so located that the water can accumulate, ample drains shall be provided.
2. (2) All drain lines, including pipes, fittings, and valves, shall comply with the requirements for steam piping or water piping according to the service.