【Q&A】July 27, 2017

First, pass the cold fluid medium, then the hot fluid medium. First, open the outlet valve for drainage, then open the inlet valve to discharge a small amount of air from the heat exchanger. If the medium is toxic or corrosive, it should be discharged in a sealed manner.

First, a medium at a temperature close to room temperature is introduced, which helps to prevent excessive expansion or contraction of the heat exchanger material and thus maintains the stability of the equipment; afterward, another medium is added, which has the least impact on the heat exchanger.

Inject the cold medium first, then the hot medium, to prevent air blockage

●Open the drain valves on the tube and shell sides of the heat exchanger, drain all the liquid remaining, and then close them. Open the outlet valve for the cold medium. Open the inlet valve for the cold medium, and close the branch line valve at the same time. Once the cold medium is operating properly, slightly open the inlet valve for the hot medium to carry out preheating. After preheating is complete, fully open the heat medium outlet valve. Gradually open the hot medium inlet valve, while closing the hot medium branch valve, until the branch valve is fully closed and the inlet valve is fully open.

a) After the steam pressure test, ensure there are no leaks; then open the outlet water valve of the equipment fully, and subsequently open the inlet water valve. Before activation, a thorough inspection of the heat exchanger and its accessories is carried out to ensure that they are properly installed and meet the specified requirements. b) The heat exchanger may be put into service only after passing the pressure test; before commissioning, drain all water from the heat exchanger. c) First, open the cold stream outlet valve and the drain valve; then slowly open the inlet valve. After expelling all air and accumulated liquid, close the drain valve and the cold stream bypass valve, closing it completely. Be careful to prevent pressure buildup, while also monitoring any changes in the equipment. After the cold flow returns to normal, introduce hot fluid into the heat exchanger using the same method. d) After the flow rates of the cold and hot streams return to normal, issues such as dripping or leaking may occur due to changes in temperature and pressure. A comprehensive inspection must be conducted again; only when no problems are found can the system be deemed operational. Regular inspections should also be carried out periodically.

First, inject cold feed～then inject hot feed～drain the gas from the shell side during operation

First, apply the cold path; then, apply the hot path； Reason: To prevent vaporization in the cold circuit caused by feeding the hot circuit first and then the cold circuit.

1. Enable? a) If there is no leakage after the steam pressure test, fully open the water outlet valve of the equipment, and then open the water inlet valve. Before activation, a thorough inspection of the heat exchanger and its accessories is carried out to ensure that they are properly installed and meet the specified requirements. b) The heat exchanger may be put into service only after passing the pressure test; before commissioning, drain all water from the heat exchanger. c) First, open the cold stream outlet valve and the drain valve; then slowly open the inlet valve. After expelling all air and accumulated liquid, close the drain valve and the cold stream bypass valve, closing it completely. Be careful to prevent pressure buildup, while also monitoring any changes in the equipment. After the cold flow returns to normal, introduce hot fluid into the heat exchanger using the same method. d) After the flow rates of the cold and hot streams return to normal, issues such as dripping or leaking may occur due to changes in temperature and pressure. A comprehensive inspection must be conducted again; only when no problems are found can the system be deemed operational. Regular inspections should also be carried out periodically.

When starting up, the cold flow should be turned on first, followed by the hot flow; when shutting down, the process is reversed. This is done to allow the equipment to warm up gradually, thereby preventing it from breaking due to overheating or cooling, which could lead to leaks.

1. Commissioning of the heat exchanger: Preparatory work before commissioning: Wear personal protective equipment, including gloves and safety helmets； Use appropriate tools, including walkie-talkies, F-wrenches, and slip joints ； Issue a work order. Commissioning steps: (1) Pre-commissioning inspection: Check to ensure that all condensate water within the heat exchanger has been drained ； Check and confirm that the inlet and outlet blind flanges have been removed ； Check to confirm that all vent valves are closed ； Confirm that the pressure gauge, thermometer, and thermocouple are in use ； Check to ensure that the heat exchanger is properly grounded and that the anchor bolts are not loose ； Check to ensure that the nuts matching the flange and cylinder bolts are all installed, the bolts are fully tightened, and the connections are secure. (2) First, introduce the cold medium: Open the outlet vent valve first, then slowly open the cold medium inlet valve until it is fully open. Once an oil and gas odor is detected from the vent valve, reduce its opening degree; close it completely once oil is visible in the vent flow. After the heat exchanger is filled with the medium, open the outlet valve fully and close the bypass valve. (3) Introducing the heat medium later: Open the exhaust valve at the inlet side first, then slowly open the outlet valve for the heat medium until it is fully open. Once an oil and gas odor is detected from the exhaust valve, reduce its opening degree; close it completely once oil is visible in the exhaust stream. After the heat exchanger is filled with the medium, open the inlet valve fully and close the bypass valve. (4) Inspection after operation: Check whether the temperature and pressure are ； Check for leaks at the static seal points ； Check whether the traffic is normal.